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GETTING TO KNOW FOODS
Good cooking starts with a good understanding of its raw materials, the foods we cook.
We’re all familiar with the foods that we regularly buy and eat, and the more we cook, the better we get to know them and the way they behave. But foods have histories and inner qualities that aren’t obvious from our everyday encounters with them, and that determine their value and behavior. The more fully we know our foods, the better we can choose them and cook with them.
I first encountered the inner world of foods decades ago as a student, when I headed to an unfamiliar section of the library and found shelf after shelf devoted to the science of food and agriculture. I browsed in them, and at first was startled and amused by what I saw: photographs taken through the microscope of meat fibers and the way they shrank as they cooked, microbes growing in yogurt and cheese, the oil droplets jammed against each other in a bit of mayonnaise, gossamer-thin gluten heets in bread dough. But soon I was mesmerized. And though I’d stopped studying science years earlier, I found myself drawn into what was going on behind these scenes, into the nature and behavior of the protein and starch and fat molecules that they were constructed from. It was thrilling to begin to understand why meats get juicy when cooked just right and dry when overcooked, why milk thickens into yogurt and cheeses have so many textures and flavors, why well-formed bread dough feels almost alive to the touch.
The language and ideas of science are less familiar than our foods are, and I know that their strangeness can be off-putting. Try to put up with them anyhow, and don’t worry about the details. Just start by knowing that there are details, and that they can help you understand cooking and cook better. Then, when a question comes up, when you really want to know more, use the brief explanation in this book as an entry point to the world of details that’s out there to explore.
WHAT FOODS ARE
Foods are complex, dynamic, and fragile materials.
Most foods come originally from living plants and animals, which are nature’s most intricate and active creations. Some—fresh fruits and vegetables, fresh eggs, shellfish from the tank, yogurt—are still alive when we buy them.
Living things are fragile. They thrive in the right conditions, die and decay in the wrong ones. Their tissues can be damaged by physical pressure, by excessive heat or cold, by too little fresh air or too much, and by microbes that start consuming them for food before we can.
Most foods are produced on farms or ranches or in factories far distant from our kitchens. Before we can buy them, they have been raised, harvested, prepared and packaged, transported to the market, unpacked, and displayed—and require careful temperature control and gentle handling throughout to minimize their deterioration.
Our food plants and animals have been bred and selected over thousands of years and come in countless different varieties, each with its own advantages and disadvantages.
The quality of a food is a general measure of how well it fulfills its potential for providing nourishment and the pleasures of flavor, texture, and appearance.
Food quality depends on many factors. These include the variety of plant or animal the food comes from, how that plant or animal lives, and how the food is handled in its progress from farm to plate.
HOW FOODS ARE PRODUCED
Cooks today can choose foods from a wide and sometimes confusing range of production systems.
Most foods are produced in “conventional” large-scale industrial systems that are designed to minimize production costs and food prices, and maximize shelf life. Conventional foods are produced and shipped from sources all over the world, wherever labor and other costs are low enough to offset the costs of transportation.
Most meats come from farm animals raised largely or entirely indoors, with little living space, on manufactured feeds that often include materials the animal wouldn’t normally eat (fish meal, rendered animal remains and waste), antibiotics to stimulate growth and control disease, and sometimes with growth-stimulating hormones.
Most fruits, vegetables, grains, and cooking oils come from plants grown with industrial fertilizers, herbicides, and pesticides. Some crops have been genetically modified with modern DNA technology, which may reduce herbicide and pesticide use.
Most fish and shellfish are produced in aquaculture, the water- animal version of intensive meat production, in confinement and on formulated feeds. Some fish and shellfish are still harvested from the wild.
Most prepared foods are made from conventional ingredients, and usually include texture stabilizers, natural or artificial flavor con centrates, and preservatives. They’re industrial approximations of the original kitchen product, designed to minimize price and maximize shelf life.
Conventional systems have important drawbacks. Conventional agriculture and meat production, and aquaculture, can cause damage to the environment, the spread of antibiotic-resistant bacteria, and unnecessary animal suffering. Harvesting wild fish and shellfish has depleted many populations to dangerously low levels.
Alternative production systems attempt to remedy various drawbacks of conventional systems. Many foods are now advertised or certified to have been produced:
• organically, without the use of industrial fertilizers or pesticides, genetically modified crops, or most industrial additives, and with minimal use of antibiotics;
• sustainably, without damaging effects on the local or global environments, or on wild populations;
• humanely, with consideration for the quality of life of farm animals;
• fairly, with farmers in developing countries receiving a good price;
• selectively, without the use of genetically modified crops, certain hormones or antibiotics or feeds, or preservatives or other additives; or with the use of high-quality or heritage varieties;
• locally, with fewer resources spent on transportation.
Food production terminology is neither precise nor tightly regulated. The terms are loose at best, and because some justify higher prices, they may be used to mislead or deceive.
Be skeptical about alternative production claims, but not cynical. All food choices, even casual ones, influence the agriculture and food industries and the people who work in them, and have a cumulative impact on the world’s soils, waters, and air.
Good cooking calls for good ingredients. Cooking can mask the defects of mediocre or poor ingredients, but it can’t make the best foods with them.
Foods land in our shopping carts with a history. Their genetic background, their variety or breed, and everything they go through from farm to display case influence their quality and what we can do with them.
Think about your priorities and choose foods consciously. If production practices and their consequences matter to you, then check the credentials of the suppliers and buy accordingly.
No particular production method is a guarantee of food quality. Both conventional and alternative foods can be mistreated or spoiled during the harvest or later handling.
Learn to read the signs of quality in the foods you shop for. The chapters in this book describe what to look for in each food.
Check the ingredient lists on prepared foods to know what you’re really buying.
Care for the foods you buy to preserve their quality. A long hot car ride from the store can cause damage as much as mishandling at any other stage.
INSIDE FOODS: FOOD CHEMICALS
As with all material things, including our bodies, foods are composed of countless invisibly small structures called molecules. We eat so that food molecules will become our body’s molecules.
Molecules come in various families or kinds, and we call those kinds chemicals. Many chemical names—proteins, enzymes, carbohydrates, saturated and unsaturated fats—are familiar from nutrition guidelines and packaged food labels. They’re becoming common cooking terms because they can help cooks understand what their methods are actually doing to change foods.
The major chemical building blocks of foods are water, proteins, carbohydrates, and fats. These chemicals, and the changes they undergo during cooking, create the structures and textures of our foods.
Water is the primary chemical in fresh foods of all kinds, and a major ingredient in most cooked dishes. The cells of all living things are essentially bags of water in which the other molecules are suspended and do their work.
Water is what makes foods seem moist. Its loss is what can make them seem unpleasantly dry or pleasantly crisp.
Water is also an important cooking medium. We cook many foods in hot water, or in the watery fluids from other foods.
Water can be acid, alkaline, or neutral—neither acid nor alkaline. Acidity and alkalinity affect the reactions of other food molecules and are important factors in cooking. Acid liquids include fruit juices and vinegar, and taste sour. Alkaline ingredients include many city tap waters, baking soda, and egg whites, and taste flat.
The boiling point of water is an important cooking landmark. It’s instantly recognizable as bubbling turbulence, and it marks a specific temperature, 212°F/100°C at sea level (lower temperatures at high altitudes), that is hot enough to kill microbes, firm meats and fish, and soften vegetables.
The boiling point of water is an important cooking limitation. It is too low to develop the rich flavors of roasting and frying, which develop increasingly quickly above 250°F/120°C.
Water in foods can slow their cooking. When foods are heated in the hot dry air of an oven or barbecue, their surface moisture evaporates and cools them.
Proteins are the main building blocks in meats and fish, eggs, and dairy products.
Proteins are the sensitive food chemicals, easily changed by heat and by acidity, and the reason that meats and fish are tricky to cook well.
Picture proteins as separate long threads, more or less folded up, crowded together in a watery world.
Proteins coagulate when the temperature rises to 100 to 140°F / 40 to 60°C and the threads unfold and stick to each other, forming a solid mass of stuck threads with water pockets trapped in between. This is why heating causes meat and fish flesh to get firm and liquid eggs to solidify.
Coagulated proteins dry out when they are cooked hotter than their coagulation point and stick more tightly to each other. This is why meat and fish flesh quickly get hard and dry, why eggs get rubbery, and why precise temperature control helps cook these foods just right.
Acidity can also cause proteins to coagulate, even at low temperatures. This is why acid-producing bacteria set milk into yogurt and an acid marinade firms and whitens pieces of fish in ceviche.
Enzymes are active proteins: proteins that change other chemicals around them, and so change food qualities. Meat enzymes make meats tender and more flavorful. Some fish enzymes turn fish mushy and unpleasantly fishy. Enzymes in fruits and vegetables cause discoloration and destroy vitamins.
Cooking inactivates enzymes and prevents them from changing foods further, because like other proteins they’re sensitive to heat and acids.
Gelatin is the exceptional insensitive protein. Instead of its molecules staying separate at low temperatures and sticking together irreversibly at high temperatures, they cluster together to form a solid gel when cool, melt when heated, and can be repeatedly gelled and melted.
Carbohydrates are the main building blocks in foods from plants: vegetables, fruits, grains, and so on.
Sugars and starches are carbohydrates that plants use to store energy, and that we can digest, absorb, and use for energy.
Fiber is the common name for the other carbohydrates that plants use to build the walls of their cells, and that we can’t digest and absorb well. They include pectins, gums, and cellulose.
Carbohydrates are not as sensitive and easily changed as proteins. When heated, most of them simply absorb water and dissolve. This is why ordinary cooking softens plant foods, and why precise temperature control is not important in cooking most of them.
Carbohydrates are also extracted from plants and used as purified ingredients.
Sugars contribute sweetness to foods. In large amounts they also create a thick body—as in syrups—or a creamy or brittle solidity, as in candies.
Starch is a bland carbohydrate, the main chemical in grain flours and also sold in pure form. Starch molecules are long threads, and plants pack them into dense granules, the familiar powdery particles of cornstarch and other pure starches. When cooked in liquid, the granules absorb water and release the long threads, creating thick body in sauces and solid structure in baked goods. Starches from different sources—wheat, corn, potato, arrowroot, tapioca—have special qualities that suit them to different cooking uses.
Pectin is a bland carbohydrate whose long molecules thicken jams and jellies.
Agar, xanthan gum, guar gum, and locust bean gum are bland carbohydrates from seaweed, microbes, and seeds whose long molecules are also used to thicken and stabilize sauces, ice creams, and gluten-free baked goods.
Fats and oils are chemicals in which animals and plants store energy. They’re commonly extracted and used as purified ingredients. Unlike proteins and carbohydrates, they are fluids, and provide a delicious moistness to foods. Unlike water, they can be easily heated to temperatures far above water’s boiling point, and help create the characteristic flavors of roasting and frying. They also carry aromas better than water, and help flavors linger in the mouth during eating.
Fat and oil name different versions of the same chemical.
Fats are solid at room temperature and melt into a liquid beginning around body temperature. They come mainly from meats, and include butterfat and lard.
Oils are already liquid at room temperature, and solidify only when chilled. They’re mainly extracted from seeds—canola, soy, corn, peanut—and from the olive fruit.
Food fats and oils are mixtures of different chemical fats.
Saturated fats are fats that tend to be solid at room temperature and resistant to staling, thanks to the rigid structure of their molecules.
Unsaturated fats are fats that tend to be liquid at room temperature and prone to staling and off flavors, thanks to the flexible structure of their molecules.
Hydrogenated fats are unsaturated fats that have been chemically modified to make them saturated, more solid and resistant to staling.
Trans fats are unusual unsaturated fats that behave like saturated fats. Small amounts occur naturally in butter, beef, and lamb; large amounts occur in hydrogenated oils and shortenings. They’re unhealthful and are being eliminated from manufactured foods.
Omega-3 fats are highly unsaturated fats found mainly in seafood and in walnuts and canola oil. They appear to be especially healthful and are being added to many foods.
Meat fats are solid at room temperature because they have a high proportion of saturated fats. Poultry fats and pork fat (lard) are softer than beef and lamb fat because they contain more unsaturated fats.
Vegetable and fish oils are liquid at room temperature because they contain a high proportion of unsaturated fats.
Oils and melted fats don’t mix with water unless they’re helped by other ingredients. When combined, they form temporarily separate droplets. Fats and oils are less dense than water, so their droplets rise to form a layer above the water.
Emulsions are creamy mixtures of oil and water with droplets of one suspended in the other. Added egg yolk and other ingredients can coat the droplets and make a stable mixture that feels thicker than water or oil alone.
Food texture or consistency is what a food feels like in the mouth: how hard or soft it is, and how it feels as we chew it, move it around, and swallow it. Texture is created by the main food building blocks, and by how the cook handles them.
Most cooking problems involve texture, not flavor.
Liquid foods may be thin and watery or thick and velvety, smooth or rough or lumpy, oily or creamy.
Solid foods may be hard or soft, moist or dry, chewy or tender, leathery or crisp.
Most pleasant textures result when the building blocks are evenly integrated with each other, and in the right proportions. Unpleasant textures result when the building blocks are segregated from each other or fall out of balance.
Meats, fish, eggs, and custards are tender and moist when moderate heat causes their proteins to bind loosely to each other and to water. They become tough and dry or curdled when excess heat causes the proteins to bind tightly to each other and squeeze water out.
Vegetables are tender and moist when brief near-boiling heat causes their cell wall carbohydrates and starch to bind less tightly to themselves, and to absorb water. They become mushy when prolonged heat causes the plant cells to lose their structure and fall apart.
Breads, cakes, and pastries are pleasantly firm when their carbohydrates have absorbed the right amount of moisture, too dry or too soft otherwise.
Sauces are smooth when starches or fats or proteins are evenly dispersed in the sauce liquid. When these ingredients are not evenly dispersed, sauces are lumpy or curdled or oily.
Bird skins and bread crusts are crisp when they’ve had all their water cooked out of them and the solid structures have no flexibility; as they reabsorb moisture and gain slight flexibility, they become leathery.
To understand texture changes, try to picture in your mind what is happening to the food’s building blocks as you cook.
Flavors are the major source of our pleasure in eating. They come from specific chemicals in foods, usually present in tiny amounts, which we are able to sense with our taste and smell receptors.
Good cooks hone their ability to analyze food flavors, recognize how they can be improved, and make adjustments.
Flavor is a combination of taste and smell. We sense taste on the tongue, and smell, or aroma, in the nose.
There are five basic tastes.
• Saltiness comes mainly from sodium chloride, in foods and added in the form of salt crystals.
• Sourness comes from acids of several kinds, especially citric and malic acids in fruits, acetic acid in vinegar, and lactic acid in fermented foods such as yogurt and cheese, cured sausages, and sauerkraut. Acids stimulate saliva flow and contribute to the mouthwatering quality of foods and drinks.
• Sweetness comes mainly from various kinds of sugars found in plants and in milk. There are many different chemical sugars, all with names ending in -ose. Table-sugar sucrose is sweeter than corn-syrup glucose and milk-sugar lactose, but less sweet than honey’s main sugar, fructose.
• Savoriness, also called by the Japanese term umami, is the brothy, round, mouthfilling taste caused by monosodium glutamate (MSG) and a few other chemicals. It’s strong in meat stocks, soy sauce, aged cheeses, mushrooms, and tomatoes.
• Bitterness is the characteristic taste of chemicals that some plants make to deter animals from eating them. This is why it takes getting used to, and why not all people enjoy it. Bitterness is strong in chicories, brussels sprouts, and mustard greens, and an important part of coffee, tea, chocolate, and beer flavors. Added salt greatly diminishes bitterness.
Pungency and astringency are other important mouth sensations. Pungency is the heat and bite of black and chilli peppers, ginger, raw garlic and onion, and mustard, wasabi, watercress, and arugula. Astringency is the drying, rough effect caused by tannins in strong black tea or red wine.
There are hundreds of different aromas in foods. Aromas are what individualize foods and give them their specific flavor identities. All fruits have sweet and sour tastes, but only apples smell like apples, peaches like peaches.
There are many different aroma qualities in foods, which may smell not just fruity, meaty, fishy, eggy, nutty, or spicy, but also flowery, grassy, earthy, woody, smoky, leathery, and barnyardy.
Food aromas are always mixtures of aroma chemicals. Like chords in music, food aromas are an integrated combination of several individual chemical notes. Coriander seed and ginger share a lemony note in their spiciness; ripe banana has a note of clove.
When we combine ingredients in cooking, we create new aroma mixtures. Herbs and spices give us dozens of notes to fill out the flavor harmony of a dish.
Heat changes food flavors. Cooking gives meats and fish stronger flavors than they had when raw. It makes onions and garlic milder, cabbage stronger. Mustard greens lose their pungency and gain bitterness.
Cooking can add new flavors to foods. Frying in oil or fat creates a characteristic flavor from changes in the fat molecules.
High heat or prolonged heat creates especially delicious “browned” flavors. When a food turns brown in the frying pan or oven, or on the grill, it’s a sign that heat has caused flavorless proteins and carbohydrates to react together to form hundreds of taste and aroma molecules. The browning reactions are most productive at temperatures above the boiling point of water, so foods brown best when heat dries out their surfaces.
To season a food is to balance and adjust its flavors to give the greatest possible pleasure to the people who will eat it.
Good seasoning is the cook’s responsibility. It can’t be specified in a recipe, because ingredients and cooking procedures are too variable.
People perceive flavors differently. This is a matter of inescapable biology, not arbitrary preference. People inherit different sets of chemical receptors, and may be hypersensitive to some tastes or smells, completely blind to others. Some people are born with more taste buds than others. And everyone’s overall sensitivity to taste and smell declines in later life.
A good cook allows for differences in flavor perception. Discuss them openly to learn whether you’re especially sensitive or insensitive to particular flavors, and then take that self-knowledge into account when you season foods. Don’t be offended when people ask to season your food for themselves.
Tastes provide the foundation of flavor, and aromas are its free-form superstructure. To season a food is to balance its basic tastes and fill out its aromatic possibilities.
Always check the seasoning toward the end of cooking. Food flavors evolve during the cooking process. Flavor integration or “melding” is desirable, but often involves the loss of appealing flavor notes.
Season foods while they’re at serving temperature. Flavor perception is strongly affected by temperature. Saltiness, bitterness, and most aromas are accentuated in hot food.
To season a food, taste it actively. Ask yourself questions such as these:
• Is there enough salt to avoid blandness?
• Would the acid of some lemon juice or vinegar make the flavor brighter and more mouthwatering? Acidity is especially undervalued as a general flavor booster and balancer.
• Is there enough savoriness or sweetness to carry the aroma?
• Would some pungency from pepper add a desirable edge?
• Have desirable aromas faded away or become masked? Should they be revived by adding a fresh round of those aromatics? Should the aroma be filled out with a complementary herb or spice, or butter, or grassy olive oil?