STORING AND COOKING 48 49 Preservation CHEMICAL PRESERVATIVES Preservation in action Different preservation methods work in differing but often complementary ways. Each strategy guards against some or most of the threats, though few can protect against all of them. Pasteurization (heating food to destroy harmful microbes) is a safety measure that also preserves food. SSAMLTOINKGINAGND KEY Sunlight PICK Oxidation DRYING LING Enzymes Microbes/ FREEZING bacteria CHILLING Slowed ANNING Stopped FOOD PASTEURIZING C HOW LONG CAN TINNED FOOD LAST? In theory, canned food should last indefinitely. In 1974, cans recovered from the Bertrand, a steamer that sank in the Missouri River in 1865, were found to be edible. (Airtight conStTaiOneRrI,NkeGpt in darkness)
Chilling HOW LONG CAN and freezing FOOD STAY FROZEN? By extending the life of perishable foods—making it possible Bacterial growth should be to store them for long periods and transport them across great halted indefinitely in frozen distances—refrigeration and freezing have transformed the food food, but the food’s quality economy and broadened our diets. deteriorates as freezing breaks or weakens cells, changing texture and flavor. Refrigerator Gas travels Freezing suitability casing insulates through freezer and fridge, Vegetables that hold water, such as cold lettuce and cabbage, get mushy when Why do we freeze food? lowering the thawed. When the water in their cells Liquid quickly turns temperature freezes, ice crystals puncture the cell to cool vapor walls, breaking the food’s structure. At low enough temperatures the chemical Meat and fish can be frozen because Expansion device their cells are flexible. expands liquid and and biochemical processes that cause food converts it to gas spoilage effectively halt. Freezing water also removes the liquid essential to many Cell wall Water biochemical processes. Plant cell Animal cell The wall surrounding The membrane a plant cell is rigid surrounding an animal and inflexible. cell is soft and flexible. Cooling gas Why do we chill food? Cell wall condenses breached into liquid Degradation and spoilage of food and drink is the result of chemical and biochemical processes caused by free radicals, internal Water freezes Water freezes enzymes, and microbes. Temperature affects As the water in As the water in the the rate of these procesess, and chilling food the cell turns to ice, cell turns to ice, the slows them down. it expands and membrane stretches ruptures the cell wall. to accommodate it.
CHEESE BANANA Hot, compressed When chilled, enzymes in Contents gas loses heat leak out bananas break down cells Compressed gas from pump travels Carbonated drinks and cause browning through pipes at retain their fizz MILK Cell releases contents Cell retains contents rear of fridge As the ice thaws, As the ice thaws, the because carbon Milk the cell contents intact cell membrane spoilage are released through contracts, keeping all dioxide bubbles CHICKEN delayed the ruptured wall. of its contents inside. have less energy by chilling SODA BROCCOLIto escapeChilling chicken at when chilled about 39ºF (4ºC) delays bacterial growth PUMP How fridges work TOMATOE THE FRIDGE IS THE Gas compressed by MOST COMMON a pump loses heat Broccoli kept close to 32ºF (0ºC) will Tomatoes lose flavor APPLIANCE. IN THE STORING AND COOKING through pipes at the retain all its vitamin C for 7 days below 45ºF (7ºC) US, 99.5 PERCENT Chilling and freezing rear of the fridge. As OF KITCHENS HAVE it cools, it condenses to A FRIDGE. liquid, but then reaches an expansion device, where it turns to gas again. This evaporation cools it rapidly before it enters the freezer or fridge, where it chills the food before returning to the pump. Importance of thawing Cooked surface Frozen interior HISTORY OF REFRIGERATION Frozen food is best and most STEAK As early as 1000 bce, the Chinese ICE 50 51 safely thawed by leaving it in the Cooking meat from frozen were cutting blocks of ice to use ICE BOX refrigerator, sitting it in cold water, It is best to avoid cooking meat from as food-cooling aids, and this or using a “defrost” microwave frozen. If the insides of the meat was the most important form setting. It is important to thaw remain uncooked, there is a risk that of cooling technology for the food all the way through prior any bacteria in the meat that would next 2,800 years. Refrigerated to cooking, otherwise there is an have been killed by cooking will remain. ships appeared in the late increased chance of undercooking 1800s, while the first domestic the inside, while overcooking fridges appeared in 1911. the outside—particularly when frying and grilling.
Fermentation Used across the globe throughout history, fermentation is a simple form of food preservation requiring no heat or artificial energy source. In the absence of oxygen, microbes can convert sugars into acids, alcohol, and gas. Why do we ferment foods? Fermented cabbage Sauerkraut, originating from Europe, is As microbes such as Lactobacillus thrive in an one of the most popular preparations oxgen-free environment, their success suppresses of fermented cabbage. the growth of spoilage microbes, generating preservative by-products and interesting flavors. 2 Teasing out the sugar Fermentation microbes are often the same as the Salt helps to draw water and ones found in our gut, so eating fermented cell contents (including sugars) out of food can be a good way to top up gut flora. the plant cells, so that the fermenting microbes can get to work. 1 Salted and soaked Water and sugars drawn Salt is applied as a brine, out of cells by salt cutting off oxygen supply to competing microbes. The cabbage must be kept below the surface. SALTY WATER WATER SUGAR Salt SHREDDED IN THE 1700S FERMENTED CABBAGE CABBAGE WAS USED BY SAILORS TO COMBAT VITAMIN C DEFICIENCY AND SCURVY Other foods that are fermented Fermented milk CHEESE Milk has a very short YOGURT In addition to helping to preserve foods, fermentation shelf-life, but fermented CRÈME FRAÎCHE can leaven dough through generating gas, and produce dairy products can last browning reactions, adding color and flavor. Different for months. These range methods of fermentation are used in breadmaking; from yogurt and crème alcoholic drinks and vinegar production; making fraiche, fermented for yogurts and cheeses; pickling fruit and vegetables; just a few hours, to curing meats; making soy and fish sauces; softening large cheeses prepared olives and removing their bitterness; and producing over many months. chocolate from cocoa beans. MILK
STORING AND COOKING 52 53 Fermentation 3 Fermentation ICELANDIC DELICACY A succession of fermenting microbes consumes the sugars, generating a complex mixture of alcohols, Pre-industrial societies used acids, and flavor compounds. Fermentation also helps fermentation to prevent spoilage to retain the nutritional value of the cabbage. The of fish, resulting in delicacies of layer of carbon dioxide gas protects vitamin C from strong odor and flavor. Iceland’s oxidation, while B vitamins are produced. Hákarl is Greenland shark that has been gutted and beheaded, buried in a sandy pit and left to ferment for six to 12 weeks before being wind-dried, shaved, and cut into small pieces. Flavor compounds Bubbles of HÁKARL are released carbon dioxide Microbes 4 Fermented result consume sugar The delicious and nutritious FLAVOR sauerkraut is tart and crunchy. Yeast COMPOUND growth is limited by the process, but a little growth is acceptable and even MICROBE generates a distinct, flowery aroma. SUGAR SAUERKRAUT Fermented soy MISO Fermented cucumber CUCUMBER PICKLE Soybeans have high SOY SAUCE Cucumbers are turned into POI levels of protein and oil, pickles using lactic acid which can be extracted TEMPEH bacteria and brine with as a kind of milk. This is five to eight percent salt fermented in a similar concentration. fashion to milk and with outcomes as equally Fermented taro root diverse—from the thick Rich in starch but toxic miso paste used for when raw, taro are used in soups and seasoning Hawaii to make poi, a to tempeh, a cultured fermented preparation rich soybean cake. in flavorful volatile acids. SOY TARO ROOT
Raw foods VITAMI NC NC Raw food appeals to many because cooking 23% RAW can damage or lower levels of vitamins and minerals. There is a growing trend for raw 6% BOILED food diets, but eating raw foods does not 31⁄2 oz (100g) always mean maximum nutrient intake. of CARROTS Best raw foods 31⁄2 oz (100g) Carrot of KALE When carrots are boiled, Vitamin C and flavonoids (see p.110) are vitamin C levels decline examples of beneficial nutrients that are precipitously since this particularly vulnerable to heat. The type of vitamin dissolves best raw foods are likely to be those (is soluble) in boiling water with high levels of these fragile and is then poured away. nutrients. For instance, green, leafy vegetables (see pp.112–13) VITAMI are rich in vitamin C and other antioxidants to help the plant 200% RAW deal with the damaging effect of sunlight. Raw foods do not tend to 89% BOILED raise blood sugar levels (see p.141) since they contain fewer simple sugars. KEY Raw Kale A percentage of your daily Cooked This leafy vegetable is rich in vitamin need of certain vitamins C. The large surface-area-to-volume and minerals can be ratio of kale and other leafy greens measured in raw and makes them particularly vulnerable cooked portions of food. to nutrient loss in boiling water. RAW FOODISM DOES COOKING Raw foodism is a typically vegan practice Vitamin Vitamin Selenium “KILL” FOOD? of eating about 70-100 percent uncooked B12 D food. Claimed effects range from weight There are a few plant loss to curing diabetes and cancer. It is Zinc Iron Omega-3 enzymes that remain active based on beliefs that “live foods” have fatty acids in the stomach, but digestion natural energy, and on misconceptions changes their shape and they about the role of plant enzymes in NUTRIENTS MISSING FROM become inactive. They are digestion. For instance, some plant A RAW FOOD DIET enzymes do help digest certain kinds of not “alive” in the protein, but most plant enzymes will be strictest sense. broken down by stomach acid. However, certain nutrients are missing from a purely raw food diet.
STORING AND COOKING 54 55 Raw food A SPECIAL CASE CANNED TOMATOES Lycopene is a beneficial carotenoid pigment 4oz (112g) ONE found in tomatoes. Heat weakens plant cell MACKEREL walls and makes the cell contents more FILLET accessible for digestion. Lycopene in tomato cells is released during the heating stage of the canning process. A can of tomatoes contains over four times the lycopene of the same amount of raw tomatoes. V 51% RAW IRON 30% DRIED ITAMIN B3 30% RAW Mackerel (81⁄2oz, 240g) Vitamin B3 levels are higher in raw compared 2% CANNED to dried mackerel. This is (101⁄2oz, 296g, ) because as mackerel dries, oxygen reacts with BOWL OF vitamin B3, depleting its COCONUT MILK levels within the fish. Coconut milk Iron levels within freshly squeezed coconut milk are higher because the addition of water during the canning process dilutes the milk. Limitations of raw foods RAW FOODS WHAT HAPPENS Brassicas People on raw food diets can experience If eaten in excessive amounts, brassicas such as broccoli nutritional deficiencies and even food Green potatoes and kale contain goitrogens—substances that can poisoning. Many cooking processes can interfere with hormone production in the thyroid gland. actually enhance the nutritional value of Fava beans foods. We cook food for safety, practical Salad bars Green parts and sprouts in potatoes contain solanine, a reasons, or even just to improve flavors toxic alkaloid, which if eaten can cause bouts of nausea (see pp.60–61, 64–65). Raw foods can pose or diarrhea. risks to health—through toxins in food that do not get broken down and pathogens Also known as broad beans, these contain alkaloids that that are not killed. can cause a condition, known as favism, in which your red blood cells deteriorate. Many disease outbreaks E. coli, Salmonella, and Staphylococcus have been linked to improperly washed raw vegetables at salad bars.
Food processing IS RAW MILK SAFE TO DRINK? “Processed” has become a dirty word in today’s food culture, but the definition of a processed food can vary Bacteria in raw milk can greatly. Very few foods do not undergo some degree cause food poisoning. of processing, much of which is absolutely essential. Pasteurization is a very Sometimes, though, we can take processing too far. important process that kills harmful bacteria, What is food processing? which makes milk Processing is generally defined as any change that is made to food or safe to drink. drink to alter its quality or shelf life. After harvesting crops and slaughtering livestock, methods of preservation are often put in place so food can be available at a later date. In addition to preservation, we change foods from their natural state for three main reasons: to make food edible, to improve its nutrition, and to make food safer to eat. GRAIN VITAMIN B1 VITAMIN B2 JUICE VITAMIN B12 Heated VITAMIN B3 Rollers IRON grind grain into flour Vitamins and FLOUR minerals Cooled BREAD WHITE RICE WHITE PASTA PASTEURIZED JUICE Safety Edibility Improved nutrition Drinks such as juice and milk are Processing is necessary to make some Food can be enriched in the factory sometimes required to be processed foods edible. The edible parts of grain with extra nutrients. In grain products, in order to make them safe to drink. are extracted and then ground into flour, this is carried out because refining, Pasteurization is a process of heating which is processed further, by forming which makes white rice from brown, and cooling that kills harmful bacteria. dough and baking, into bread. removes many nutrients, which must then be replaced—sometimes by law.
STORING AND COOKING 56 57 Food processing HIDDEN INGREDIENTS CORN SYRUP TOMATO PASTE Many highly processed foods are high in added sugar, salt, fat, and low in dietary fiber—with the aim of improving their taste and palatability, and to make them last longer. If levels of these ingredients are high, some authorities require food producers to highlight them on the packaging (see p.43). However, in some countries it is possible to avoid drawing attention to unhealthy or unpopular ingredients by listing complex constituents such as tomato paste or corn syrup (themselves processed from many parts) singly, without an analytical breakdown. 1 Reconstitution How potato snacks are made Potatoes are cooked, mashed, The journey from potato to reconstituted snack dehydrated, and milled into flour. can be a long and convoluted one. A range of Starches from corn and wheat may be changes are made to a simple potato to make it look almost unrecognizable—and taste completely different. added, and the resulting flour is mixed. Processed starch 2 Extrusion 3 Frying added to milled flour A dough is made with The half-cooked the flour and squeezed through potato snacks are dried and passed through a continuous shaped nozzles at high pressure frying machine to assure rapid, to create partially cooked, shaped snacks. even cooking. Mashed, half- Potato Potato snack cooked potato flour deep-fried in oil Highly processed foods Half-cooked snack shaped by nozzle When we think of processed foods, we are probably thinking of highly 4 Flavoring The cooked chips are shaken processed foods, such as chips, snacks, and chocolate – in which the main ingredients have themselves been free of excess oil, sprayed or dusted with flavorings, salt, and other milled, refined, cooked, or otherwise significantly additives, and finally packaged altered in ways we cannot do in the kitchen. Highly for distribution. processed foods are almost always high in calories, Flavorings, salt, and sugar, and fats, and low in nutrients and fiber. additives sprinkled onto chips WITHOUT PROCESSING 50–60 PERCENT OF FRESH FOOD COULD BE LOST AFTER HARVEST
Main chemical additives Preservatives Sweeteners Additives are classed into several main groups according These prevent spoilage These alternatives to sugars to their role, for example, as sweeteners, flavorings, or and prolong shelf life by preservatives. In most countries, all these additives must slowing the growth of include aspartame and pass strict safety regulations before they are allowed in microbes and retarding saccharine. They are used food, although an additive approved in one country to reduce calories, since may not necessarily be approved in another. natural chemical they are either much lower reactions that would 5 PERCENT OF THE otherwise make food in calories than sugar, WORLD’S POPULATION HAS unpleasant or inedible. or can be used in very A SENSITIVITY TO ONE OR MORE FOOD ADDITIVES small amounts. Nutrients Stabilizers Antioxidants These replace vitamins and These prevent emulsions These are chemicals minerals destroyed during (foods such as mayonnaise) that inhibit oxidation. processing, or enrich foods from separating into their They are used to delay with nutrients they do not oily and watery constituents browning and decay caused after they have been mixed, by oxidation, prolonging contain naturally. helping to maintain the shelf life. Ascorbic acid (vitamin C) is a commonly food’s texture and consistency. used example. Additives WHAT IS A BATTLE BUTTIE? Additives are found in a wide variety of processed foods. They are crucial in extending the shelf life The US Army developed of foods, replacing lost nutrients, preserving appealing a sandwich that will not textures, and adding taste and color. become stale for at least two years. This is due to a packet of Not all bad iron filings in each sandwich bag that absorbs the oxygen Additives can include natural and artificial substances, although the dividing line between them is fuzzy. Some of the additives are natural that microbes need substances that have been used since ancient times for enhancing or to grow. preserving food—sodium chloride (common salt), for example. Newer additives are tested extensively before being approved for use.
Emulsifiers Flavorings Colors Emulsions are mixtures of Artificial or natural These are used to add liquids that do not normally mix, flavorings are added to or improve colors lost such as oil and water. Emulsifiers replace or enhance in processing or to add promote such mixing in foods— natural flavors lost in in mayonnaise, for example. processing. Taste and color to white or smell are closely linked, dull-looking foods in so many flavorings also order to make them have smell components. look fresher and more attractive. Acidity regulators Anti-caking agents Leavening agents These are used to control the These help to prevent These are added to doughs acid–alkaline balance (pH) of powdered or granulated foods (such as flour and salt) and batters to help them food for taste (acid foods from absorbing moisture and rise by promoting the taste “sharp” or sour; alkaline ones, bitter), and to inhibit clumping together. production of gas (usually carbon dioxide); a common the growth of microbes so that food remains safe to eat example is baking soda. when it has a long shelf life. What’s in a burger? BURGER BUN TASTE BUD TICKLER PICKLES There may be more than CHEESE The savory umami flavor comes mainly you think. Even a 100 from the amino acid glutamic acid, and an percent meat patty may BURGER PATTY artificial preparation of this acid— have stabilizers to make KETCHUP monosodium glutamate (MSG)—is widely sure the meat keeps its used as a flavor enhancer, especially in shape while cooking and BURGER BUN Asian dishes. In the 1960s, MSG was linked flavorings such as salt, to symptoms such as migraines and pepper, and onion powder. palpitations, but later studies The bun and toppings showed that MSG does not may also have additives, cause health problems, to help prevent the except in a few people growth of microbes and who have a specific keep them fresh-looking. sensitivity to it.
Cooking BAK LLING GRI Heat produces chemical and physical Grilling (applying dry heat from below) changes in food, making it softer, more is probably the earliest method of cooking, digestible, and causing the food to release since it can be done with an open fire. Grilling nutrients. However, sometimes nutrients are with a heat source above the food is called broiling. Grilling imparts very high temperatures to foods, enabling browning reactions, but there is a risk of charring. degraded when certain foods are cooked. Food surface GRILL closest to Why do we cook food? Infrared light heat source carries heat Some scientists think that the discovery of cooking cooks first to food (see pp.8–9) was a key trigger in our evolution. Cooking improves and generates new flavors, ING/RAOnAoSvTenINtrGansfers heat, from a gas aromas, and textures. One such example is a browning reaction, in which sugars in food lose flame or electric element to the food water when heated, producing flavor. Raw foods are often tough, fibrous, difficult to chew, and hard for digestive processes to attack. Unless mainly by convection, as hot air circulates in cooked, many food components cannot be the oven. Direct infrared radiation from the broken down by our digestive system. Also, oven’s hot walls also heats the food. cooking helps to kill or suppress pathogens Hot air OVEN and renders many toxins inactive. circulating ING Steaming transfers heat to food Infrared radiation through air convection (as in baking), STEAM but also through condensation of vapor. Just as it takes a lot of energy to convert water into steam, so steam gives up a lot of heat energy as it condenses back into water as it reaches and moistens the food. Steam delivers PAN BOILING Boiling is one of the most efficient heat to food methods of cooking, since all of the food Water gives is in direct contact with the heat transfer off steam medium (water). Browning reactions are not triggered because of the constant presence of water. Convection currents in water carry heat from source to food PAN A GLOWING COAL RADIATES 40 TIMES MORE HEAT ENERGY THAN THE EQUIVALENT AREA OF AN OVEN WALL
FRYING STORING AND COOKING 60 61 Cooking Oil can reach higher temperatures than water, and in shallow frying it is used to HOW MICROWAVES WORK conduct heat directly from the source (pan base) to food. This means browning reactions happen A microwave has a transmitter that sends out waves of quicker. In this method all of the immersed food around 5in (12cm) in length. They are shorter than radio surface is in contact with the heat transfer medium (oil). waves, but longer than infrared waves from grills and ovens. A turntable rotates the food to ensure all parts are cooked. Bottom surface of food Heat from flame cooks first transferred to food Microwaves Wave guide through pan bounce off reflective wall Transmitter, or PAN “magnetron” Food Turntable Deep frying uses convective heat WAVINMGicrowaves agitate the water in transfer, but since the medium (oil) can reach a much higher temperature than foods, generating heat and thereby water, food can be cooked much more quickly cooking the food. It may seem as though than frying and browning reactions happen faster. microwaves heat foods from the inside out but DEEP FRYING they tend to heat all molecules at the same time. MICRO However, microwaves will cook the wet interior Convection currents in of dry-cased foods (such as pie) more quickly. oil carry heat from Oil reaches temperatures source to food above 212ºF (100ºC) Agitated water molecules Microwave—a wave with a generate heat frequency of around 2,450MHz PAN MICROWAVE Fast and slow cooking Oven wall during roasting 2,000°F/1,100°C 480°F/250°C 2,900°F/1,600°C Cooking quickly can minimize damage to easily degraded nutrients, and can seal the Coal in a barbeque outside of meat or fish to limit moisture loss, but it is harder to heat food evenly and the Gas flame in a grill interior is likely to remain undercooked. Slow cooking heats through more evenly but can degrade nutrients and dry out food. Turning up the heat Flame grilling and barbecuing are better for thin foods with high surface area to volume ratios, since this raises the likelihood that food will be cooked through.
104ºF (40ºC) 122–140ºF (55–60ºC) 149–167ºF (65–75ºC) RAW STEAK PROTEIN Juices may be reddish Oxygen leaves meat in color but it is not Protein blood—it is some of Meat turns gray-brown chains the red pigment as myoglobin changes shape begin to (myoglobin) leaking out unravel 1 Proteins change 2 Juices leak out 3 Oxygen leaves Water begins to escape from Collagen sheaths around muscle Myoglobin, which gives raw unraveling protein chains in steak and fibers contract, squeezing cells so that and rare meat its red color (see collects within cells. Under gentle heat, the water they have accumulated pp.68–69), changes shape. This means muscle fibers within a steak begin to oozes out. Fiber-weakening enzymes the meat loses its color as myoglobin relax and unfold, while the meat’s own reach high levels of activity but then can no longer hold on to oxygen, enzymes actively break them down. change shape and stop working. fading from red to pink to gray-brown. How food cooks At the molecular level, cooking involves a complex series of interactions between heat, water, and individual food components, and between the components themselves. When cooking, DO FOODS LOSE NUTRIENTS WHEN the perfect balance between temperature, time, and the desired change in chemistry must be achieved. COOKED? What happens when food cooks? Some foods lose a portion of vitamins when cooked. In Food, especially meat, is composed of molecules similar to ours— others, the chemical reactions proteins and fats. Plants mostly comprise of carbohydrates. Heating and release of nutrients while these molecules changes their nature, causing some to combine into new molecules, others to break down into smaller ones, and some to cooking can improve degrade. When heated, large molecules in food, such as enzymes, their nutritional change shape and stop working. Water is a crucial factor: dry cooking value. causes water to evaporate; wet cooking can have the opposite effect, causing food to absorb water, as with rice or pasta.
STORING AND COOKING 62 63 How food cooks 167–194ºF (70–90ºC) 230–239ºF (110–115ºC) 266–284ºF (130–140ºC) COOKED STEAK BURNED STEAK Meat shrinks; becomes PROTEIN tough and fibrous from loss of juices and fluids Sugar Amino acids combines recombine Water evaporates to create as steam with new protein protein chain Carcinogenic compound 4 Water boils off 5 Maillard reaction 6 Surface chars Collagen begins to break down At the meat’s surface nearest If meat is exposed to high and liquefy. In a pan-fried steak, water the heat source, where water has temperatures, such as those from coals evaporates, and it becomes dense and boiled away, Maillard reactions take or flames on a barbeque, or left to cook dry. In wet-cooked meat (such as in a place—combining amino acids and for too long, combustion reactions will stew) the collagen melts, so the meat sugars that turn the meat brown and take place that produce carcinogenic remains succulent and juicy. provide it with aromas and flavor. compounds (see pp.68–69). The story of steak Cooking vegetables 1 Pectin Many changes happen at the molecular Long chains of level to steak meat as its temperature Vegetables are composed linked sugars (carbohydrates) rises and cooking progresses from one mainly of carbohydrates, which hold vegetables such as extreme to the other. are generally much tougher and carrots together—making more heat resistant than them tough and fibrous. COOKING WITH A proteins. The cell walls of plants PRESSURE COOKER in particular are hard to break Pectin molecule IS EQUIVALENT TO down, although heat will COOKING WITH AN weaken them, allowing water 2 Bonds broken OPEN PAN 3.6 MILES from inside the cells to leak out. When heat is (5.8 KM) BELOW Vegetables turn tender when applied to pectin chains, SEA LEVEL boiled because pectin (a type of they dissolve at boiling carbohydrate), which sticks cells point, making carrots tender. together like bricks with mortar, dissolves at boiling point. Sugars break apart Blending cooked vegetables when heated will eventually break down cell walls altogether—this is how vegetable puree is made.
Safe Preventing contamination cooking At home, you can reduce the risk of contamination either by rinsing and washing to As well as transforming food’s flavours remove the dangerous microbes or cooking and and textures, cooking makes it safe to heating to kill them with elevated temperatures. eat by destroying toxins and killing microbes, though if not done properly, WASHING FRUIT AND it risks making food less safe. Importance of rinsing VEGET Fruit, vegetables, and salad can be ABLES contaminated with Listeria and norovirus, especially if grown with certain types of fertilizer, or if prepared by someone with poor hygiene. Contamination Contaminants confined to the surface of plant foods can be washed away, which is preferable Your skin and immune system protect you from harmful to peeling, as the outer layers are organisms, but if they enter your body via your food, often the most nutritious. they may cause food poisoning. Unfortunately, the scale and complexity of modern food production greatly Water increase the risk of contamination. From farming to processing and distribution, contamination can happen Bacteria Listeria at any point in the food production chain. The most washed common threats are the bacteria Salmonella, E. coli, off leafy Campylobacter, and Listeria, the parasite trichinosis, greens and the viruses hepatitis E, hepatitis A, and norovirus. Norovirus Killing bacteria WASHING LEAFY GREENS Bacteria can be robust and persistent, but few living things survive being heated to extreme temperatures. WASHING SILVERWARE AND SURFACES Heat disrupts chemical bonds and drives off water, causing the bacteria’s cell components to break down, What washing kills their enzymes to change shape and lose their function, A major source of food contamination is and their cell walls to breach. As each species of poor kitchen hygiene. Work surfaces and bacterium has a different composition, they have varying implements can spread germs easily. Soap or levels of tolerance to heating. disinfectant kills bacteria, but dirty cloths can SALMONELLA LISTERIA harbor germs. 158ºF (70°C) 165ºF (74°C) LOW HIGH Campylobacter TRICHINOSIS E. COLI Bacteria 136ºF (58°C) 154ºF (68°C) removed by soap Safe temperatures E. coli You can remove bacteria from your food by making sure it WASHING reaches certain temperatures. For example, to kill E. coli you UTENSILS need to make sure that the center of the food reaches at least 154ºF (68°C); for Listeria it needs to reach 165ºF (74°C).
STORING AND COOKING 64 65 Safe cooking YOUR KITCHEN SINK MAY CONTAIN 100,000 TIMES MORE GERMS THAN YOUR BATHROOM Appropriate cooking COOKI SHOULD I WASH NG MEAT CORRECTLY RAW CHICKEN? There is a high chance of the surface of a piece of meat being contaminated. It is hard for microbes to enter the Washing chicken may interior of red meat, so just the outside needs cooking. splash bacteria, such as Because poultry is more easily penetrated by bacteria, Campylobacter, off the chicken it needs to be cooked all the way through. and onto surrounding Bacteria only on surfaces where they outer surface of meat may proliferate. Campylobacter Salmonella Heat penetrates COOKING meat thoroughly CHICKEN Heat REHEATING RICE COOKING BEEF STEAK Illness associated with reheated rice is called “fried-rice syndrome,” REHEATING LEFTOV ER FOOD heat and is caused by the bacteria Bacillus cereus. Spores in freshly Sufficient cooked rice that sits at room Leftovers can be safe to eat. First, limit temperature will grow into bacteria, microbial contamination by taking leftovers which release toxins that cause away from the heat source so it can cool vomiting and diarrhea. Reheating quickly. Hot leftovers in the fridge can raise the rice might kill the bacteria, but their temperature of surrounding spores may survive. chilled foods, initiating Bacteria live microbial growth within BACILLUS CEREUS throughout leftovers them. Stirring reheated BOWL OF foods from the microwave REHEATED will help spread the heat and kill any RICE leftover bacteria. Heat Clostridium REHEATING MEALS
TYPES OF FOOD
Red meat Meat has played a central role in human nutrition for at least 2 million years. In the modern world, meat— especially red meat—has accounted for an increasingly high proportion of our diet, with consequences for obesity, cardiovascular health, and cancer rates. Myoglobin and cytochromes What makes red meat red? MUSC LE TISSUE Meat usually refers to muscle, however, the term can also encompass organ meats. Red meat gets most of its color from iron-containing myoglobin, a richly pigmented protein that provides cells with oxygen, similar to hemoglobin in red blood cells. Energy is supplied to muscle by fats, which are broken down by cytochromes— a type of protein in muscle fibers that is also red. WHY CAN MEAT Muscle fiber SOMETIMES TASTE Muscle fiber METALLIC? In muscles that are constantly at work—such as leg muscles— Very lean cuts of red meat there are lots of myoglobin and lack flavorsome fat, which cytochromes, which provide the contributes to the typical beef muscle fibers with all the oxygen taste. This can accentuate the and energy, respectively, that metallic flavor from the high they need to function. quantities of iron in red meat, BOWEL CANCER RISK especially muscle meat and liver. Although some large-scale studies have implied that that consumption of red meat (particularly chargrilled or barbecued) correlates with a risk of colorectal (bowel) cancers, the association is weak. Furthermore, the reason for a link is unclear, and may be because fatty red meat contributes to obesity (a high BMI is associated with a risk of colorectal cancer), rather than the ingested fat itself. An analysis of 27 independent studies found no clear patterns of a direct relationship between higher red meat intake and increased risk of cancers.
TYPES OF FOOD 68 69 Red meat Red meat and nutrition Red meat is a complete protein source, providing all of the essential amino acids that our bodies cannot create. It is also a rich source of iron and B vitamins. Significant health concerns remain, however. The red meat we consume tends to be high in fat—the higher the fat content, the greater the flavor and tenderness of the meat. Higher fat content means a greater number of calories, more saturated fats, and the health risks associated with them. CA M RE FATTY CH CE ACIDS PHEASANT D BLOOD CELLS LL CONSTITUENTS Enzyme breaks MUSCL fats down to fatty acids E CELL The body needs iron to make We need the amino acids provided AMINO oxygen-carrying hemoglobin by meat to construct the proteins ACIDS in the blood, as well as that make up our cells, including Enzyme breaks Enzyme breaks myoglobin in our their membranes and all proteins down glycogen down own muscles. the cell machinery. to amino acids to glucose USCLES OLESTEROL Producing flavor GLUCOSE Hanging is common for any wild-caught meat, including gamebirds such as pheasant. Enzymes within cells start to attack other cell components. Proteins are The fat-burning nature of red broken down into savory Our own muscle fibers are built muscle means that red meat is amino acids, glycogen into from protein that we can only high in saturated fats and sweet glucose, and fats into make if we get the right balance aromatic fatty acids. cholesterol, which can affect and supply of amino acids our cardiovascular health in our diet. (see pp.214–15). RCINOGENS Hanging meat Carcinogens are naturally found SINCE 1961, Meat should be hung after in many foods, but in such small GLOBAL PORK slaughtering to prevent excessive quantities that they are offset CONSUMPTION toughness. Meat cut immediately HAS INCREASED on slaughtering will be very tender, by other nutrients. Smoking BY 336 PERCENT but within hours muscles contract or charring meat can also irreversibly. To minimize these produce carcinogens. effects, carcasses are hung in such a way that the muscles are stretched by gravity. Longer hanging periods (such as a week) allow enzymes in the meat’s own muscles to get to work tenderizing and producing flavors.
White meat White meats include chicken, turkey, duck, and pigeon—some definitions include veal, piglet, rabbit, certain game birds, and frog. The different function and physiology of white meat gives it unique characteristics of flavor and nutritional value, which in turn have led to an explosion in global production and consumption of poultry. What makes white meat white? Myoglobin and EN BREAST cytochromes White muscles are specialized for short bursts of intense (oxygen-carrying action (they are full of what are known as “fast-twitch pigments) fibers”). They burn glycogen (made of linked glucose molecules) and can work without oxygen for brief periods, CHICK although they must rest in between bursts of activity. Muscle fiber This means they have less oxygen-carrying pigments Light meat (red pigments that deliver oxygen to muscle) White muscle cells do not need as than red meat. Chicken legs, which always rich a bloody supply as red muscle support the body, will have slightly more red cells, so they contain less oxygen- pigments, giving dark meat. Also, these carrying red pigments—making redder muscle fibers have their own white meat lighter in color. fat supply, making dark meat more flavorful. UPSIDE-DOWN ROASTING In Western cultures, there is a chef’s trick to Fat from back roasting chickens and turkeys—place them drips into meat breast-down in the oven. This is because most of the bird’s fat is HEAT located on its back, so when placed upside down and cooked, the fat trickles into the bird’s meat—providing a rich flavor and moist texture. If cooked breast upward, the flavorsome fat just pools at the bottom of the pan and is wasted!
TYPES OF FOOD 70 71 White meat Pasture-raised or caged chickens? VITAMIN E OMEGA-3 FA Nutritionists argue that there is a nutritional difference between hens raised inside in cages and those allowed to roam and feed outside in pastures. Pasture-raised chickens have a different diet, a more active foraging strategy, and lower stress levels than caged, barn-raised, or free-range chickens (see pp.232–33). There is evidence that this not only improves the amount of essential fatty acids and vitamins in the meat, but also reduces the levels of unhealthy fatty acids. OMEGA-6 FATTY ACID ATURATED FATTY ACID TTY ACIDS SS S -32.9% -51.9% +90.8% +406.8% Nutritional differences KEY IN THE US, TURKEY According to a study comparing Caged chickens CONSUMPTION pasture-raised and caged HAS DOUBLED IN chicken, the pasture-raised Pasture-raised THE PAST 25 YEARS poultry had less omega-6 fatty chickens acids and more beneficial omega-3 (especially when fed on soybeans), less fat overall (including saturated fat), and much more vitamin E. RESTORATIVE PROPERTIES OF CHICKEN SOUP DOES TURKEY MAKE YOU DROWSY? In several cultures, most notably in Ashkenazi Jews, chicken soup has long No, not at all—this is a myth been described as particularly effective that stems from the fact that against colds. One study was conducted there is an amino acid called in which blood samples of those who ate tryptophan found in turkey chicken soup and had a cold were analyzed. The study found that chicken soup did that is used to create the have anti-inflammatory and decongestant sleep-inducing hormone properties that eased symptoms such as runny noses, as well as promoting good melatonin. digestion, boosting fluid intake, and providing healthy nutrients.
Cuts of meat Fat within muscle The nutrition, taste, texture, nutrition, and even the cooking method of a piece Fatty meat takes of meat is ultimately determined by its longer to cook original location on the animal’s body— and how active that part was in life. Taste and texture STEWING Each cut encompasses a different set of muscles on the Muscle animal. The guiding principle behind evaluating different fiber cuts of meat is that more active muscles (such as those found on the legs) have thicker fibers and more Fatty meat CHUCK STEAK connective tissue, and so will have tougher and chewier meat. More active muscle will Fattier cuts of meat can benefit from slow cooking also have more fat, however, and so may to render down their fat. Globules of fat are be more flavorsome. Butchers divide most scattered in-between muscle fibers that would animals into a broadly similar set of cuts, have provided the muscle with energy (see p.68). with the same terminology applying to cows, sheep, goats, and pigs—the CHUCK French have the most types of cut RIB EYE when it comes to beef. TONGUE CHEEK NECK Connective tissue Tough meat CUFOTSRFERLEOGM takes longer to become tender RIBS BRISKET BRISKET BRAISING Muscle fiber Tough meat BRISKET MEAT Cuts from the breast, such as brisket, have higher levels of connective tissue that supported much of the animal’s weight when it was alive. Brisket is cooked for longer and often in liquid to dissolve the connective tissue and make the meat less tough.
TYPES OF FOOD 72 73 Cuts of meat Muscle fiber OFFAL Lean tender meat Offal (the internal organs of an animal, not including can be cooked in muscle or bone) comes in many forms, and each organ has its own distinctive flavor and texture. Offal a shorter time generally has more connective tissue and tends to need slow, thorough cooking; livers are a popular FRYING exception. A lot of offal and organ meat has high levels of nutrients and essential fatty acids, and low levels of harmful fat. For instance, liver and kidney can be particularly high in iron and folate (vitamin B9). Lean meat SIRLOIN STEAK Kidney Tongue Less active muscles such as those found in sirloin cuts need less of an embedded energy supply and so will have less fat or no fat at all; hence they are known as lean, or tender, cuts. Heart Liver Feet RUMP 45HOURS IS SIRLOIN THE MAXIMUM TIME IT CAN TAKE TO COOK PIGS’ FEET—AFTER TAIL WHICH EVEN THE BONE IS EDIBLE CUHTINS DFRLOEGM FLANK LEG WHY CAN’T WE EAT RAW MEAT? It is thought that our teeth and stomachs evolved to be better at digesting the more easily available nutrients in safer, cooked meat, but we are able to eat very fresh raw beef (like steak tartare).
Processed meats Grinding Surfaces are the risk zones Since ancient times, meat has been processed to extend for meat contamination, and its lifespan and to add flavors and aromas that can only grinding radically increases be produced through the unique biochemical processes meat’s surface area. Producers involved—resulting in a wide range of products. therefore ensure any bacteria are killed by blanching the Why do we alter meat? Meat mixtures meat (very briefly heating and Meat mixtures were cooling it) before grinding. Meat is metabolically active. It is fragile on the cellular traditionally a way to level and rich in moisture and nutrients, so it is at high maximize use of every GROUND MEAT risk of rapid spoiling. Spoiling includes fats going part of a valuable animal rancid (oxidizing), and growth of microbes from animal carcass so that nothing hides and intestines if they contaminated the meat went to waste. Today, during butchering. Processing meat helps to delay or meat mixtures are halt spoilage and generates complex and interesting thought of as cheaper, flavors and textures. It can also mean turning whole lower quality products, meat into ground and reconstituted forms, sometimes often with negative known as meat mixtures. These bring their own health impacts. culinary possibilities, but also their own health risks. THERE IS A 42 PER- CENT HIGHER RISK OF DEVELOPING HEART DISEASE FOR EVERY HOT DOG YOU EAT PER DAY Methods of preservation MEAT MEAT Dead ANTIOXIDANT bacteria Curing encompasses a range of preservation techniques, including CARCINOGEN SALT the traditional methods of smoking ANTIMICROBIAL and salting (which can often be Moisture drawn out used together). In modern times, Smoking preservative chemicals such as Smoke contains antimicrobial and Salting of surrounding meat potassium nitrate are also used. antioxidant compounds and helps to Bacteria in the meat process it into prevent fat from going rancid. However, Adding salt to meat draws water out of cells, nitrite, which reacts with oxygen in smoke also contains carcinogenic depriving microbes of the moisture they the meat to form nitric oxide. This (cancer-causing) compounds. need to thrive. High salt levels cause protein binds with the iron in the meat to filaments to spread out so that they no longer prevent oxygen from affecting fat scatter light, making meat translucent. and making it rancid. Meat gains a rosy color and a piquant flavor.
Sausage-making Mechanically reconstituting 74 75 To make sausages, chopped meat Most reconstituted ham is made and usually some filler, such as by pressing together pieces of Injections of salty water bread crumbs and spices, are pork (not necessarily muscle Many bacon and ham stuffed into tubes traditionally meat) that have been blasted off products are injected with made from animal intestines. the bone by jets of high-pressure a solution of water, sugars, The fat in sausages keeps them water. This is just one method of preservatives, flavorings, and from drying out when cooking. what they call “mechanical additives to bulk them out recovery” of meat. and save money. Some bacon strips are 50 percent water. High-pressure water blasts meat off bone Different parts Different parts of meat results Solution injected of meat in in ham’s patchy color into bacon sausage results in mottled color Meat flecks pressed together into ham slices SAUSAGES RECONSTITUTED HAM BACON WHY DOES PRESERVATIVE HEALTH CONCERNS RECONSTITUTED HAM HAVE A RIND OF FAT? Nitrite has been a popular preservative for the flavor and color it adds to meat, and is Manufacturers of re-formed often used in salamis. It is especially good ham often add a coating of fat to at delaying the growth of bacteria that produce toxins that cause botulism. give an illusion of authenticity However, nitrite can react with amino to their product, as if it has acids in the meat to produce been cut directly off carcinogenic compounds called the carcass! nitrosamines. Although there is little hard evidence that nitrites in cured meats increase cancer risk, its use is now often carefully regulated.
Meat substitutes Consumers prize meat for its flavor, texture, and 1 Fungus, glucose, nutritional value, but many are concerned by the and minerals added negative health, environmental, and ethical impacts A starter culture of the fungus Fusarium of meat consumption and production. One solution is added to a fermentation tank. It needs to these problems is the use of increasingly popular food to metabolize into protein, so meat substitutes. sterilized glucose syrup is added to the tank, along with trace minerals. Trace minerals added HOW MYCOPROTEIN IS MADE Glucose added Starter culture of fungi added 5 Mycoprotein grows For about six weeks the mycoprotein continues to cycle around the fermenter and grow. Eventually, it 4 Cooling down collects in a chamber and The rapid growth of the fungus, and its constant metabolism, is then harvested. generate lots of heat. Coils of cooling water help to maintain the optimum temperature for fungal growth. Oxygen Nitrogen 2 Ammonia and air added MYCOPROTEIN COLLECTS Fungal growth is boosted by adding nitrate from ammonia and oxygen from air. These gases are bubbled through the mixture to help mix it. COOLING SYSTEM Using meat substitutes HEAT DRYING AND TREATMENT CHILLING Although meat substitutes might seem like a modern trend related to 6 Finished products health benefits, they have actually Harvested mycoprotein been popular since ancient times is heated to neutralize harmful SAUSAGE through cultural and religious substances, spun in a centrifuge SLICES prohibitions against meat. For to dry, and is then chilled. The example, tofu was created in ancient mixture is also treated to make China by vegetarian Buddhists. Today it more closely resemble muscle the primary sources of meat substitute fibers, flavored, and shaped are soy-based products, gluten-based into meatlike products, such HARVESTED products from grains, the use of other as sausages or slices. MYCOPROTEIN protein sources such as nuts, and, as shown here, the controlled growth of mycoproteins from fungi.
TYPES OF FOOD 76 77 Meat substitutes IN 10TH CENTURY Versatility of soy CHINA, TOFU WAS COMMONLY KNOWN Soy is rich in proteins and oils, which makes AS “SMALL MUTTON” it an extremely useful base for meat substitutes. Fermenting the soy releases its rich cargo of 3 Waste gases nutrients and these can then be processed in The air and ammonia similar fashion to milk and dairy products. Many different soya products have been developed. bubbled through the mixture, Gases along with waste gases released produced by the metabolism of the fungus, are extracted from the fermenting vessel. Tofu Thousand layers tofu Tofu, or bean curd, is made by A process of freezing then curdling soy milk to produce thawing tofu creates a product curds, which are then broken with a spongy network that down to release water and resembles many layers. pressed into blocks. Mycoprotein (fungus) starts to grow SOYBEANS Textured vegetable protein Tofu skin Made from the by-products of Heating soy milk creates a thin soy-bean oil processing, but solid skin that traps oil. textured vegetable protein Fibrous and chewy, it is dried as sheets is a versatile meat or sticks. alternative. IS MYCOPROTEIN VEGAN? Although pure mycoprotein probably would be vegan, most marketed products are not because they use egg white as a binder and milk ingredients during processing.
OMEGA 3 FATS (PERCENTAGE BY WEIGHT) 0 0.5 1.0 1.5 2.0 1.0 2.5 1.6 1.6 2.0 2.1 HERRING SALMON MACKEREL BLUEFIN TUNA TROUT Oily fish 184 BILLION TONS One of the richest known sources TOTAL GLOBAL FISH of vital omega-3 fats, oily fish have PRODUCTION IN 2014 oil throughout their tissues and more oil overall than white fish. They tend to be warmer-water species or more active fish, such as trout, tuna, and salmon. Oily fish and white fish SASHIMI Fish are high in protein, rich in nutrients such as iodine, calcium, and Fish sashimi, thin slices of raw fish B and D vitamins, and low in cholesterol. Fish are often divided into oily prepared Japanese-style, is popular (or fatty) and white fish. Oily fish have more fat than white fish and are worldwide. However, because the particularly rich in omega-3 fatty acids (see pp.28–29), notably EPA and fish is raw, there is the risk that it DHA. These two omega-3s can be made in the human body from another may be contaminated with omega-3, alpha linolenic acid (ALA), but only in small amounts—so EPA parasites or microbes, and the fish and DHA are best obtained from the diet. White fish have less fat than oily fish. They also contain omega-3s, but less than oily fish. must therefore come from high-grade sources and be Fish prepared carefully. The largest single source of wild food in the human diet as well as the product of a rapidly growing branch of farming, fish are a source of important nutrients such as protein and omega-3 fatty acids.
0.2 0.3 TYPES OF FOOD 78 79 0.4 Fish 0 0.5 0.5 1.0 FLOUNDER HALIBUT 0.6 1.5 SNAPPER 2.0 COD 2.5 CATFISH KEY Oily fish Fat under skin Fat between White fish muscle blocks Omega-3 fats (% by weight) High fat concentration Dark Where’s the fat? in dark muscle muscle In fish, fat is generally stored White in thin layers under the skin White fish Spine muscle and between muscle blocks. White fish have less oil and omega-3s than oily It is also present in strips of fish, and the oil tends to be concentrated in the Gut cavity WHITE FISH dark muscle that run along liver rather than throughout their body tissues. White the body. These strips are White fish include all flatfish, such as halibut muscle larger and fattier in oily fish and flounder, as well as some cold-water OILY FISH and smaller and less fatty ocean fish, such as cod, monkfish, and mullet. in white fish. Concentration of toxins Volcano MERCURY Factory Mine The ocean is the ultimate repository FOOD CHAIN of much of the pollution generated HEAVY by natural and manmade sources. METALS Pollutants that are not readily broken down naturally, such as Large Tuna Mackerel mercury, heavy metals, and shark Krill persistent organic pollutants (POPs, see pp.202–03), may be present in HIGH LEVEL MEDIUM LEVEL LOW LEVEL low levels in small prey animals but OF MERCURY OF MERCURY OF MERCURY accumulate through the food chain, becoming concentrated in top predators, such as sharks. Toxins in the food chain Persistent pollutants become concentrated as they move up the food chain. Sharks, swordfish, and other top predators may contain dangerous levels of these pollutants.
Shellfish WHY DOES COOKING CRUSTACEANS Colossal heaps of discarded shells at prehistoric sites attest to the historic importance of shellfish in the TURN THEM RED? human diet, and today this diverse group of aquatic organisms is still a valuable source of nutrition. The shells of crustaceans contain carotenoid pigments The value of shellfish linked to proteins. Cooking alters the proteins, releasing Shellfish—crustaceans such as crabs and shrimp, and mollusks such as oysters and octopus—are a superfood category all of their own, being an the reddish-colored excellent source of lean protein. They are also rich in B vitamins, iodine, carotenoids. and calcium. From a flavor point of view, seafood is rich in tasty amino acids, such as glycine, which tastes sweet, and umami (savory) glutamate. APHRODISIACS ABOUT ONE-THIRD OF THE WARM-WATER Raw oysters have a historic SHRIMP HARVEST reputation as an aphrodisiac, and IS FARMED RATHER 20% there is some evidence that this THAN FROM reputation may be justified. They WILD STOCKS are high in zinc, which aids male fertility, and have also been found to contain amino acids that can trigger the release of sex hormones in men and women. 15% PERCENTAGE OF FAT, BY WEIGHT High protein, low fat Compared to the meat of land animals, most crustaceans and mollusks offer high protein for little fat. Their meat protein also offers a contrast in texture with land-animal red meat, because it is white muscle packaged with high levels of the 10% protein collagen, making it firm and moist. In contrast, red Crab meat contains a similar proportion meat contains high levels of the protein myoglobin, which give the meat its red color, and lower levels of collagen. of protein and fat to shrimp Scallops have little fat 5% but also a fairly small amount of protein OYSTER SCALLOP SQUID CRAB SHRIMP 20% 0 15% 10% PERCENTAGE OF PROTEIN, BY WEIGHT
TYPES OF FOOD 80 81 Shellfish When to eat shellfish Toxic algae Nontoxic KEY algae Safe Many types of shellfish are best High levels of Dangerous avoided at certain times of the year, algal toxins Lower levels for a number of reasons. First, many of algal toxins Seasonal toxicity species breed in the summer and The summer months expend their energy reserves during SPRING SUMMER FALL WINTER are often the worst this period, becoming meager and for toxic blooms of less tasty. Second, summer is also algae and for harmful the period when toxin levels are microorganisms, highest. The best period for eating which proliferate in many shellfish is during the winter warmer waters and months, when they are fattening up in can accumulate in preparation for the breeding season filter feeders, such and when toxin levels are low. as many mollusks and crustaceans. LAMB Lamb has a high Shellfish poisoning percentage of fat in relation to protein Many shellfish feed by filtering out food particles from the water. BEEF However, they also trap toxins and microbes, which may build up and, if enough contaminated shellfish are eaten, may cause poisoning. The toxins are not destroyed by cooking. Symptoms of the main types of shellfish poisoning are outlined below. CHICKEN Paralytic shellfish poisoning Numbness and tingling, loss Octopus meat is one of coordination, difficulty of the best sources of speaking, nausea, vomiting. May be fatal. low-fat protein Amnesiac shellfish poisoning Memory problems, which LOBSTER OCTOPUS may be long term, or even permanent brain damage. 25% 30% May be fatal. PERCENTAGE OF PROTEIN, BY WEIGHT Neurotoxic shellfish poisoning Nausea, vomiting, slurred speech. No known fatalities. Diarrheal shellfish poisoning Diarrhea, nausea, vomiting, abdominal pain. No known fatalities.
Eggs SHELL After a decade or more in the shadow of a EGG W HITE health scare in the developed world, eggs are reemerging as what many consider to Inside chicken eggs be the perfect food. Handy self-contained Eggs provide an almost perfect packages of healthy protein, eggs are rich balance of proteins, along with in almost every desirable nutrient. omega-6 fatty acids, and the antioxidants zeaxanthin and Nutrition powerhouse EGG INGREDIENTS lutein. In fact, they contain every Icon sizes show total nutritionally essential vitamin The egg white, or albumen, amount of each nutrient. and mineral with the exceptions contains 90 percent of an egg’s of vitamins C and B3 (niacin). water and half of its protein. The 0.1–9 mcg most plentiful protein in egg white 0.01–9.9 mg YOLK is ovalbumin. Accounting for around one-third of the mass of 10 mg–0.9 g MAGNESIUM the egg is the yolk, which contains half the egg’s overall protein, 1–5 g VITAMIN A three-quarters of the calories, and all the iron, thiamin (vitamin B1), Rich in protein, FAT VITAMIN D fat, cholesterol, and vitamins A, D, but low in fat and ZINC E, and K. In fact, eggs are one of VITAMIN K the few food sources of vitamin D. cholesterol, egg Also present in the egg yolk are white is extremely essential fatty acids. useful in cooking The yolk contains SELENIUM the vast majority of the egg’s rich load of vitamins, minerals, and other trace nutrients PROTEIN EGGS AS EMULSIFIERS POTASSIUM IRON VITAMIN E Emulsifiers blend substances that are unmixable, such as oil and water. The result is an emulsion—tiny droplets of one substance suspended in the other. Egg proteins can create emulsions useful in cooking, such as mayonnaise, which is an emulsion of oil in vinegar or lemon juice. MAYONNAISE Water-loving PROTEIN IN CLOSE-UP part of egg Oil protein Vinegar faces the water-based Oil-loving part of egg fluid outside protein surrounds and isolates a tiny droplet
TYPES OF FOOD 82 83 Eggs Cooking eggs RAW EGG Eggs are versatile cooking 179 ingredients, but the quality of an Curled THE NUMBER OF egg diminishes over time, partly protein EGGS PER PERSON because the shell is highly porous, AVAILABLE FOR allowing moisture to escape. As an In a raw, unbeaten egg, the protein chains CONSUMPTION egg dehydrates, it becomes more are folded and curled up, enabling GLOBALLY alkaline, which makes the egg them to remain separate, self- IN 2014 white runnier and the membrane contained units suspended around the yolk weaker. Freshness, in water; the egg therefore, is essential in making the remains liquid. best fried and poached eggs. BEATING EGGS BAKING EGGS Eggs have proteins that harden when heated or beaten, resulting in Trapped air a range of useful cooking effects. bubble COOKING EGGS Uncurled Uncurled Air bubble protein with protein expands cross-links Whisking or beating eggs is another way The scaffolding provided by long, to put energy into the system. As with interlinked egg proteins helps to give Heating gives energy to the protein chains, which shake themselves out into heating, the protein chains acquire cake mixtures structural integrity, energy and unravel and interlink, allowing the trapped air bubbles long chains that can cross-link. Cross- linked protein assemblages cause trapping bubbles of air to to expand without breaking the egg to harden and form a foam. or bursting open. become opaque. WHAT’S THE A BAD REPUTATION DIFFERENCE BETWEEN WHITE AND BROWN EGGS? In recent years, eggs have experienced bad press, but most concerns are The color of a chicken egg in unfounded. For instance, egg yolk is no way reflects differences in high in cholesterol, but contrary to what taste or nutritional value. It is scientists once thought, dietary cholesterol does not greatly affect blood cholesterol merely determined by the levels. Salmonella contamination, which has breed of the hen that hit the headlines in some countries, is in fact produced it. the main risk in eating eggs, but the risk is now very low thanks to hen vaccination. Vulnerable people (such as the elderly) can further lower the risk of becoming ill by cooking or pasteurization of their eggs.
Milk and lactose DOES MILK REALLY HELP WITH Humans are unique among mammals in continuing to consume milk after infancy, but our ability to cope—to a greater or lesser BRITTLE BONES? degree—with the milk-sugar (lactose) opens up for us a delicious and nutritious world of dairy products. Milk is rich in calcium and phosphate—two minerals that help to contribute to healthy bones. For those who can’t tolerate milk, other foods can supply these important minerals. HEATING Most harmful bacteria killed by heat 0.7% VITAMINS AND MINERALS COWS’ MILK 3.4% PROTEIN 3.7% FAT 4.8% LACTOSE 87.4% WATER COOLING Cooling stops the milk from caramelizing What’s in milk? How pasteurization works Milk evolved as a starter food for mammalian infants, providing a rich, dense source of nutrients In the 1860s the French chemist Louis including sugars and fats for energy, and protein, Pasteur investigated microbial activity in fats, minerals, and vitamins for building and growing food and developed a heat treatment that bodies. Babies can survive for months on milk alone, and killed potentially harmful microbes without adults almost can, although milk is lacking in vitamin B12, significantly affecting flavor. This process vitamin C, fiber, and iron. The milk of different species tends is applied to milk to make it safe to drink. to contain the same nutrients but in different proportions.
Diversity of dairy products The varied composition of milk gives it great value, both as a food source in its own right and as the base for a wonderful range of dairy products, both fermented and unfermented. Processing is important for milk products with medium-to-long shelf life, because even pasteurized milk contains high levels of bacteria and will spoil quickly. How cream is made CENTRIFUGAL CREAM REINDEER MILK IS ONE Cream forms naturally in fresh, untreated SEPARATOR OF THE RICHEST MILKS milk, because it is an emulsion that will AVAILABLE: 17 PERCENT FAT separate under gravity. In industrial AND 11 PERCENT PROTEIN production, a centrifugal separator will spin milk at high speeds in order to separate the cream. How ice cream is made LACTOSE TOLERANCE Milk is not simply frozen—if it were, the fat and protein would coagulate. Instead, FREEZING ICE CREAM Bovine milk-drinking is a behavior that has it is frozen and spun at the same time in become widespread relatively late in human order to force air into the mixture. This evolution, and so the genes that make it freezes the ice crystals at a steady rate, possible are unevenly distributed among producing a smooth, consistent texture. world populations. In most people, the level of lactase, the enzyme that allows us to digest How condensed milk is made lactose, decreases rapidly after infancy, so that TYPES OF FOOD Boiling milk to evaporate half its adults can become lactose intolerant. However, Milk and lactose water leaves behind condensed milk. in some parts of the world, especially in Its shelf life is prolonged as spoilage Scandinavia, populations have evolved to microbes cannot survive with much continue making lactase into adulthood. of the water removed. Sugar is often added to improve taste. WATER CONDENSED Lactose tolerant Lactose intolerant EVAPORATED MILK How powdered milk is made SPRAY-DRIED SCANDINAVIA 98% CHINA 8% 84 85 Continuing to evaporate the water POWDERED LACTOSE TOLERANT LACTOSE TOLERANT until about 90 percent is lost results MILK in a highly concentrated syrup, which is then freeze-dried or spray-dried by scattering tiny droplets into hot air. Powdered milk is proof against microbial attack but can go rancid.
Yogurt and IS THERE ANOTHER live cultures WAY TO BOOST GUT FLORA? Milk contains agents of extraordinary People with digestive problems transformation—bacteria that can produce a due to too few microbes in the galaxy of fermentation products that improve nutrition. The same microbes that produce gut can gain those essential yogurt may also benefit your gut, promoting bacteria by undergoing a fecal a healthy balance and diversity of gut flora. transplant. Feces of someone with rich gut flora are liquidized What is yogurt? and inserted into the colon Yogurt is curdled (separated) milk. The fat droplets that are usually of the patient. dispersed within milk have been captured by unraveled protein chains, creating the thicker, clumpier composition of yogurt. This change in structure is caused by bacteria (such as Lactobacillus) that acidify the milk. Yogurt was probably first made by accident – today, it is produced on a large scale using industrial methods. 1 Incubated milk KEY 2 Yogurt is made Milk thickens Initially the milk is boiled to Bacteria Lactose is fermented into into yogurt Lactose sugar lactic acid by the bacteria. This concentrate proteins. The milk is Protein causes protein chains to unravel Lactic acid then allowed to cool partially and Fat provides bacteria are introduced to begin and mesh together, capturing sour taste some fats and water—and also fermentation—they begin to provides the sour taste of yogurt. consume the sugar lactose. Lactic acid is Fat globules released from form bacteria fermenting lactose sugar Protein uncurls due to release of lactic acid
TYPES OF FOOD 86 87 Yogurt and live cultures Do live cultures survive digestion? YOGURT WITH Live culture LIVE CULTURE survives digestion Live cultures in both yogurts and probiotic supplements are carefully selected and tested to in the stomach ensure they do survive the acidic conditions of our stomach. Some supplements are even coated STOMACH in substances that protect them until they reach the alkaline conditions of the small intestine. Probiotic foods PROBIOTIC BENEFICIAL EFFECTS IN YOGURT Probiotic (pro meaning “for,” biotic meaning Lactobacillus Studies suggest it may reduce the risk of developing “life”) are bacteria that, when eaten, can live rhamnosus allergies, aid in weight loss in obese women, treat on in our gut and become part of our gut Lactococcus severe gastroenteritis in children, and reduce risk flora—a community of beneficial microbes lactis of rhinovirus infections in unborn infants. (see p.25). Some bacteria in yogurt, such as Lactobacillus bifidobacteria (also present in the infant gut plantarum Studies suggest that this species may aid in treatment and gained from breast milk), Lactobacillus Lactobacillus of antibiotic-associated diarrhea, produce an fermentum, L. casei, and L. acidophilus, all acidophilus antibacterial and potentially anti-tumor compound, colonize the human gut, helping to suppress Bifidobacterium and protect against an infection that causes diarrhea. bad bacteria by outcompeting them and bifidum making the gut environment unfavorable Bifidobacterium Studies suggest it may prevent endotoxin (toxins in for them, shielding the intestinal wall, and animalis lactis bacteria) production, has antifungal properties, and producing antibiotics. They also suppress can reduce symptoms of irritable bowel syndrome. immunity and reduce inflammation, help to reduce cholesterol (see p.25), and even This is commonly used against common causes of suppress carcinogens. travelers’ diarrhea. Studies suggest it may help reduce the hospital stay of children with severe diarrhea and THE 100 TRILLION shows antifungal properties. BACTERIA IN YOUR GUT OUTNUMBER This is one of the first bacteria to colonize the infant THE CELLS OF YOUR gut after delivery. Studies suggest it may reduce the BODY BY 10 TO 1 hospital stay of children with severe diarrhea; and it helps with reducing cholesterol levels. Studies suggest this strain may help treat a type of constipation in adults, reduce microbes in dental plaque, reduce the risk of upper respiratory illness, and reduce total cholesterol. TRAVELING LIVE CULTURES KEFIR GRAINS Kefir is a mildly alcoholic, yogurtlike drink made from fermented milk in eastern Europe, the Caucasus, and other regions. It is made using remarkable cultures known as “grains” (but they are not grains), which look like small cauliflower florets and combine live microbes with dairy proteins, fats, and sugars. These have been passed down through families and communities, and carried great distances by migrants. Starter cultures for many other traditional dairy fermentations have similarly been carried by migrants to new homes across the world.
Cheese MILK A single form of processing can lead to an astonishing profusion of products, as with the transformation ACID AND HEAT of milk into cheese. Cheese can take RENNETRAenNneDt (CanULTURE In cheeses like thousands of forms, from soft and paneer and queso sinuous to rock hard and pungent. enzyme produced in fresco, rennet and calves’ stomachs) and cultures are not used. How cheese is made starter bacteria are added. Instead, acid and heat are They act on the milk’s used to coagulate the milk. Milk has a short shelf life. Turning it into casein protein, curdling it. D S cheese is a way of concentrating and preserving its nutritious value, mainly by removing water that supports spoilage CURDS Queso fresco microbes. Curdling the milk makes it possible to remove much of its water, When casein while salting and acidifying the pressed protein molecules have their curds helps preserve them further. The ends clipped by the enzymes in result is a solid mix of protein and fat, rennet, they can bond to one another with milk and microbe enzymes roped in and coagulate, trapping water and fat droplets in a mesh to give a gel, known as curds. to break down the contents into flavor- Curdling WATERY Casein proteins filled fragments. is driven WHEY in milk are by the active the only ones THERE ARE AT LEAST enzymes acted on by 400 COMPOUNDS in rennet the enzymes THAT CAN AFFECT BRINED SOLID CURD WASHMEDedAiumN-DorPRESSE THE FLAVOUR OF CHEESE Salt inhibits the semi-hard cheeses like microbes that cause Edam and Gouda are made Variety of cheese spoilage, firms protein by washing curds in water to The type of cheese produced from milk depends on structure, and adds flavor. remove acidity and calcium, how it is processed; the use and degree of pressing, Brining the whole cheese then pressing or “knitting” drying, washing, or cooking; whether mold is added, produces cheese such as and length of aging. The protein and fat content of them together. the milk itself (and the animal it came from) also feta or halloumi. determine the kinds of cheese that it can become. Halloumi Edam
DOES CHEESE STRETCHED MICROBES HEATED GIVE YOU NIGHTMARES? Curds soaked Microbes are For harder There is no hard evidence in hot water, then added at different cheeses more of the that this is true, but high fat stretched by kneading and stages in cheese watery whey is forced out content meals can disturb pulling, produce a fibrous or production, depending on of the curds by heating. stringy cheese. Some, like the desired outcome. The longer it lasts, the digestion and thus sleep, mozarella, are eaten fresh. which might lead to a higher drier the cheese. Mozzarella chance of remembering EDDARHEaDrdA, dNryD PRES dreams. AGED cheeses are made by GRASS-FED CHEESE Ripening or CH cutting curd into small SED affinage of a cheese loaves that are stacked, Grass-fed cheese is made with milk from is an art of its own. cows fed only on grass. It is naturally rich Provolone is aged after milled, and pressed in vitamin K and calcium, and higher in stretching to develop (“cheddaring”). conjugated linoleic acid—a type of fatty acid associated with a wide variety of its flavor. health benefits, including immune and inflammatory system support, improved Provolone Red TYPES OF FOOD bone mass, improved blood sugar Cheese regulation, reduced body fat, reduced SURFACE RIPENED INTERNALLY RIPENELDeicester risk of heart attack, and maintenance of lean body mass. Working inward Blue molds from the cheese surface such as Penicillium VITAMIN K FATTY where they form a rind, white roqueforti grow in small cavities CALCIUM ACID molds such as Penicillium in the cheese, produced by camemberti break down proteins piercing. They break down milk fats and cause calcium phosphate ions into shorter molecules, to produce 88 89 to migrate from the center, distinctive blue-cheese flavors. liquefying the cheese. Pierced cheese Rind Camembert Stilton
Starchy foods Although they can be rather tasteless and bland, starchy foods, such as potatoes, yams, rice, wheat, and pulses, are a primary staple of most people’s diets, providing a large proportion of energy requirements as well as other nutrients, such as protein and fiber. Types of starchy foods What is starch? Starch is used by plants to store energy, either in Starch is a carbohydrate formed from long chains the plant cells themselves for short-term storage, of identical glucose units linked together. There are or in roots, tubers, fruits, or seeds for long-term two types of starch: amylose, made of straight chains storage. It is these long-term stores that are the of glucose molecules, and amylopectin, made of starchy foods we are familiar with—potatoes and branching chains. The relative proportions of amylose rice, for example. However, starchy foods also and amylopectin in a starchy food affects how quickly include processed foods, such as flour, bread, it is digested and, therefore, its glycemic index. noodles, and pasta. Most authorities recommend that starchy foods make up the main source of Straight chain Branched chain carbohydrate in our diets. of glucose of glucose Rice is the seed of a grass AMYLOSE AMYLOPECTIN LONG-GRAIN RIC The potato plant is a POTATO type of nightshade E AMYLOPECTIN AMYLOPECTIN 80% 79% AMYLOSE AMYLOSE 20% 21% Grains Tubers Rice, wheat, oats, barley, and Potatoes, yams, sweet potatoes, other grains are high in starch, and other tuberous vegetables especially when the parts with get their distinctive cooked more fiber and protein—the textures from their starch germ and bran—are removed. granules. When raw, the starch Grain starches typically consist is packed into hard granules, of 15–28 percent amylose, but when heated, the granules although short-grain rice has soak up water, swell, and turn almost none, which is why it into a gel, giving a tender but becomes sticky when cooked. dry texture.
TYPES OF FOOD 90 91 Starchy foods BLOOD GLUCOSE LEVEL HIGH GI Blood glucose rises Glycemic index and falls dramatically Glycemic index (GI) is a measure of how quickly Blood glucose a carbohydrate-containing food raises your blood rises steadily but sugar level when that food is eaten by itself. remains low Carbohydrates that are digested quickly and cause a rapid increase have a high GI; examples include LOW GI sugar and starchy foods with a lot of amylopectin, such as potatoes and white rice. Amylopectin is HOURS 1 2 more easily digested than amylose, as it has more chain ends for enzymes to work on. But a food’s Blood glucose levels GI by itself is not a good indicator of whether that Foods with a high glycemic index (GI) produce a large, rapid rise food is healthy; for example, chips have a lower GI in blood sugar followed by a similarly rapid fall, leaving us feeling than boiled potatoes but are very high in fat. hungry. Low GI foods do not cause this “sugar spike,” but produce a slower, smaller increase, followed by a gradual decrease. GLOBALLY, EACH In botanical terms, PERSON EATS AN bananas are berries AVERAGE OF 73LB (33KG) OF POTATOES A YEAR BANANA Peas are the fruits PEAS of the annual plant Pisum sativum AMYLOPECTIN AMYLOPECTIN 66% 70–75% AMYLOSE AMYLOSE 33% 25–30% Legumes and pulses Fruit Peas, beans, and pulses tend to Designed to attract animals that have a higher proportion of amylose will spread the seeds, fruits build in their starch content than other up starch stores, which break starchy foods. Amylose is smaller down into sugars when the fruit than amylopectin so the individual ripens. A dramatic example is amylose chains can pack more tightly the banana (though commercial than amylopectin chains can. As a varieties do not have seeds). result, more cooking is needed to It changes from 70–80 percent separate the chains and soften starch when green to less than these vegetables. 1 percent starch when ripe.
Grains MINERALS PHYTOCH Grains are the most important food Bran EMICALS group globally in terms of supplying An outer coating of tough, calories and nutrients for the majority fibrous material, the bran is rich FIBER of the world’s population. in fiber, minerals, B vitamins, and phenolic phytochemicals (which Types of grain form part of the seed’s Also known as cereals, grains are the edible defense system). seeds of plants of the grass family. The grains we eat most commonly, either by B VITAMI MINS NS themselves or as ingredients in other foods, are rice, wheat, corn, oats, ENDOSPERM BRAN PROTEIN CARBOHY barley, rye, and millet. Amaranth, buckwheat, and quinoa are also Endosperm DRATE commonly thought of as grains, The endosperm, or kernel, although botanically they of a grain is rich in starch, and FATS are not related to true significant amounts of proteins, grains. Nutritionally, fats, and B vitamins, although the all of them are high in amounts vary according to the carbohydrate, much of it as complex, slow- type of grain. release starches. B VITA Anatomy of a grain Grains are seeds, designed GERM to protect and nurture embryonic plants. They consist of three main MINERALS PHYTOCH elements: the germ (the plant embryo), the endosperm (the EMICALS energy store), and the bran (the protective outer layer). Many of the most valuable nutrients are in the germ and bran, which are removed during refining. WHOLE GRAIN VS. REFINED GRAIN Germ The germ is the most Whole grains contain all parts Endosperm Endosperm nutritionally rich and flavorful PROTEINS of the grain. Refined grains, Bran part of a grain, containing large Germ amounts of fats, proteins, vitamins, minerals, and phytochemicals. REFINED GRAIN such as white rice and white B VITAMIN flour, have had the bran and germ removed. Refining may also S VITAMIN A FATS involve bleaching to make the grain whiter. After refining, grains may be enriched to add back nutrients previously removed. WHOLE GRAIN
TYPES OF FOOD 92 93 Grains 100,000 ENERGY SOURCE THE NUMBER OF DISTINCT Globally, we get far more of our VARIETIES OF RICE calories from grains than from any other type of food: overall, they Types of rice provide more than half of the total calories we humans eat. Around 60 Rice is the largest source of calories for humans worldwide. On percent of the calories eaten by people average, it contributes about 21 percent of the total calorie intake in developing countries come directly of every person on the planet, although there are large regional from grains. In the developed world, variations. For example, in southeast Asian countries such as the figure is about 30 percent, Vietnam and Cambodia, rice provides up to 80 percent of the although many more of the total calories eaten by each person. There are two main subspecies: calories consumed come indirectly japonica and indica, with javanica being a subtype of japonica. from grains via the feed eaten by animals we then eat. Oils, fats, sugars Other foods Grains 19.1% 2.8% 51% Japonica Indica Javanica Roots and Fruits, vegetables, Meat, fish, Originating in China Long-grain indica rice Grown mainly in tubers pulses, nuts 8.2% milk, eggs but now grown in many is grown in lowland highland tropical zones 5.3% 13.5% temperate and subtropical tropical and subtropical in Indonesia and the regions, japonica rice is regions. It has a high Philippines, javanica rice, short-grain and has a low amylose content so like japonica, has a low amylose content (see p.90). takes longer to cook. amylose content. Nutrient content of grains WHITE RICE Carbohydrate 80% 7% 65% Overall, whole grains are a good source of calories, carbohydrates, fiber, proteins, B vitamins, and AMARANTH Protein phytochemicals. Most grains contain about 70–75 0.7% percent carbohydrate, 4–18 percent fiber, 10–15 percent protein, and 1–5 percent fat. However, Fat there is a lot of variation between the different grains in their specific nutrient content, as shown Carbohydrate by white rice and amaranth. 14% Amaranth vs white rice Protein Compared with most other grains, amaranth 7% contains relatively little carbohydrate but lots of fat, whereas white rice is high in Fat carbohydrate and low in fat.
Bread Unleavened bread Consisting at its most basic of a cooked Developed before leavening, and still popular mixture of flour and water—often with in many forms today, unleavened breads were salt added, and sometimes with yeast a natural development of the use of cereals to or a raising agent, such as baking make porridge or grain mash. They were made soda—bread is one of the oldest types simply by baking the porridge or mash without of prepared food and remains an using any raising agents, producing a flat bread. important staple even today. UNLEAVENED BREAD ORIGIN Making leavened bread Tortilla Latin America Johnnycake North America Leavened bread is made with a raising agent—most Souri North Africa commonly yeast—that causes the dough to develop Pita Greece bubbles of gas, expand, and rise. Mixing flour and Baladi Egypt water causes proteins in the flour to form a network of Bouri Saudi Arabia gluten (see pp.98–99) in the dough. The yeast ferments Matzoh Middle East the starch and sugars in the dough into alcohol and Lavash Middle East carbon dioxide gas, which gets trapped in the gluten Chapati India network. When the fermented dough is baked, the heat Roti India drives off the alcohol and carbon dioxide, leaving the familar spongelike structure of bread. Salt Gluten proteins Air bubble Strengthened STARCH gluten network STARCH ENZYME Loose MALTOSE network of gluten 1 Mixing ingredients 2 Kneading the dough proteins Flour, water, salt, and yeast are mixed to form Kneading the dough makes the gluten dough. When mixed with water, the gluten proteins in network stronger. It also incorporates air into the flour form a loose network. The starch in the flour is broken down to maltose (a sugar) by enzymes in the flour. the dough, producing small bubbles that get trapped in the gluten network.
TYPES OF FOOD 94 95 Bread Sourdough bread Wild yeast DON’T BURN IT! The first leavened breads were Bacteria Acrylamide is a cancer-causing probably sourdoughs—breads process chemical produced when bread made with a starter culture maltose and other starchy foods, such as consisting of wild yeasts and potatoes, are cooked at high specific bacteria. The wild yeasts SOURDOUGH temperature and start to brown. cannot process the maltose sugar CULTURE The amount of acrylamide can be in the dough; this is done instead minimized by cooking food to the by the bacteria, which produce Commercially lightest acceptable color. lactic acid as a byproduct. As a cultured yeast result, the bread has a slightly BURNED acidic, sour flavor, but it is can process TOAST generally more flavorful, denser, maltose and longer lasting than other types of leavened bread. YEAST CULTURE THE FIRST PRESLICED, WRAPPED BREAD WAS PRODUCED IN 1928, BY US INVENTOR OTTO ROHWEDDER Alcohol evaporated Gas bubbles out by heat of baking expand MALTOSE ALCOHOL Sugar combines with protein CRUST GLUCOSE YEAST Yeast “burns” Amino acids glucose recombine to create new protein chain CARBON DIOXIDE 3 Fermenting 4 Baking After kneading, the dough is left to ferment. Baking causes the alcohol to evaporate, In this process, the yeast produces enzymes that convert the maltose sugar into the simpler sugar, drives off the carbon dioxide, and causes the bubbles to expand and interlock, forming a glucose. The yeast then “burns” this glucose for spongy texture. On the surface, Maillard energy, producing carbon dioxide gas and alcohol. The gas helps to enlarge the air bubbles in the reactions occur (see p.63), combining amino acids and sugars to form a brown crust. dough, making it rise.
Noodles SHOULD I COOK MY and pasta PASTA AL DENTE? Pasta cooked al dente—firm to Noodles have a long history in east Asia, where the bite—is broken down in the they are a staple food in many countries. Pasta, body more slowly than pasta a specific type of noodle, is a traditional Italian cooked until it is soft. As a result, staple but has become popular worldwide. it releases sugar more slowly and so has a lower glycemic What is the difference? NOODLES index, which may reduce spikes in blood sugar. Noodles—sheets, ribbons, and other shapes of cooked dough—may be made from various PASTA flours. The flour is mixed with water, eggs, or both to create the dough, which is then shaped and cooked. Pasta is a type of wheat noodle made specifically from durum wheat flour, which can be made into complex shapes because of its high gluten content (see p.98). Flour varieties BUCKWHEAT RICE FLOUR MUNG BEAN DURUM WHEAT Many types of flour are FLOUR FLOUR FLOUR used to make noodles, including flour from unusual sources, such as roots of the kudzu plant, mung beans, and corms of the konjac plant (all native to Asia). Of the types shown here, all are gluten-free except for wheat and durum wheat flour. POTATO FLOUR KUDZU FLOUR KONJAC FLOUR WHEAT FLOUR How instant 1 Preparing dough 2 Cooking and cooling 3 Dehydrating noodles are made Flour, water, salt, and The raw noodles are Water is removed cooked by steaming for a The key stage in making kansui (an alkaline liquid) are few minutes, then cooled by air drying or frying instant noodles is the middle kneaded to make dough, which is and the resulting instant one. Cooking then cooling rolled then cut into thin noodles. to harden them. noodles are then packaged. raw noodles makes them more absorbent than Sheet Noodles being Instant normal noodles. This of dough steamed noodles means that they retain more water and so have a Raw shorter cooking time when noodles being prepared for eating.
TYPES OF FOOD 96 97 Noodles and pasta ORATIVE LONG RIBBON DEC T CUTSPAGHETTI FARFALLE CONCHIGLIE VERMICELLI ANGEL HAIR RUOTE Pasta shapes RADIATORI FUSILLI Pasta shapes and patterns FETTUCCINI combine aesthetics, function, CANELLONI and culture. Some shapes and types are associated with specific regions, such as penne with Campania in southern Italy, and farfalle with Lombardy in northwest Italy. Some shapes are particularly suitable for holding sauces: shell-shaped conchiglie, for instance, are good for thick meat or cream sauces and can even be stuffed. TAGLIATELLE MACARONI LINGUINI LASAGNE PENNE RIGATONI SHOR BRONZE-DIE PASTA Bronze die 15.8 Pasta shapes are made by Rough-surfaced MILLION TONS (14.3 pressing the dough through pasta shape MILLION METRIC TONS) perforated plates called dies. OF PASTA ARE PRODUCED Dies made of bronze are WORLDWIDE EVERY YEAR prized because they have a rough surface that imparts a coarseness to the pasta that is good for holding sauces; bronze-die pasta also cooks more quickly.
Gluten GLIADIN MOLECULE Found in many grains, including wheat, gluten is a vital ingredient in a huge range of breads, pasta, and other dough products. However, some people are sensitive to gluten and suffer health problems when they eat it. What is gluten? Gluten is an enormous composite protein—the largest known—that consists of a strong, stretchy mesh of smaller proteins linked by molecular bonds. These smaller proteins are glutenin, which has a long, chainlike shape, and gliadins, which are shorter and round. The glutenin is what gives gluten its elasticity, whereas the gliadins give it strength. It is this combination of stretchiness and strength, together with its meshlike structure that can trap bubbles of gas, that makes gluten important in bread-making (see pp.94–95). GLUTEN IS THERE GLUTEN- LEIN MOLECU Glutenin FREE WHEAT? molecules STRETCHED GLUTEN can uncoil if No, all wheat contains gluten. stretched, However, there is a type of giving gluten its stretchiness wheat starch that is gluten-free. It is made by thoroughly Molecular bond forms washing wheat flour between gliadin and with water to remove glutenin molecules, the gluten. helping to create a molecular mesh MOLECULAR BOND Structure of gluten Gluten is a resilient, rubbery substance that forms when glutenin and gliadin molecules in flour are mixed with water; this happens when making dough, for example. The molecules bond together to form a mesh that can trap bubbles of gas—as occurs when dough is kneaded. Because the mesh is stretchy, the gas bubbles can expand without breaking it.
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