chemistry for changing times 12 th edition hill and kolb chapter 17 food: molecular gastronomy john...
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Chemistry for Changing Times12th Edition
Hill and Kolb
Chapter 17Food:
Molecular GastronomyJohn Singer
Jackson Community College, Jackson, MI© 2010 Pearson Prentice Hall, Inc.
© 2010 Pearson Prentice Hall, Inc.
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The Food We Eat
Foods are chemicals. They include carbohydrates, fats, and proteins, along with water, vitamins, minerals, and fiber.
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Carbohydrates in the Diet
The monosaccharides glucose (dextrose) and fructose, and the disaccharide sucrose are the most common dietary sugars.
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Carbohydrates in the Diet
Digestion and Metabolism of Carbohydrates
Glucose and fructose are absorbed directly into the bloodstream.
Sucrose is hydrolyzed into glucose and fructose.
Sucrose + H2O → Glucose + Fructose
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Carbohydrates in the DietLactose, found in milk, is hydrolyzed to glucose and galactose.
Lactose + H2O → Glucose + GalactoseSome people lack the enzyme necessary to hydrolyze lactose. This is known as lactose intolerance.
Galactose is converted to glucose during metabolism. Some babies lack the enzyme (galactosemia) necessary for this conversion and require a synthetic formula for proper nutrition.
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Carbohydrates in the DietComplex Carbohydrates
Starch and cellulose starch are polymers of glucose connected by alpha linkages; most animals and humans possess the enzymes necessary to hydrolyze starch to glucose that can then serve as a source of energy. Carbohydrates such as starch produce 4 kcal of energy per gram.Cellulose is a polymer of glucose connected by beta linkages; most animals and humans lack the enzymes necessary to hydrolyze cellulose, and it serves as a source of roughage or dietary fiber.
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Carbohydrates in the Diet
Glycogen is the means by which animals store glucose. It is a highly branched polymer of alpha glucose and is sometimes known as animal starch. Excess glycogen is stored as fat.
Some bacteria found in the gut of termites and digestive tract of grazing animals can hydrolyze cellulose to glucose and these animals can use cellulose as a source of food.
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Fats and Cholesterol
Fats are esters of fatty acids and glycerol. Some fat is metabolized for energy and produces 9 kcal of energy per gram. Some is used for cell membranes.
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Fats and Cholesterol
Digestion and Metabolism of Fats
Fats are digested in the small intestine. Enzymes called lipases hydrolyze triacylglycerols into mono and diacyl glycerols, fatty acids, and glycerol.
Fats are stored in the body in adipose tissue in locations called fat deposits. Fat deposits are located around major organs beneath the skin.
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Fats and Cholesterol
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Fats and Cholesterol
Dietary fats and cholesterol have been implicated in arteriosclerosis and cardiovascular disease. Deposits form on the inner walls of arteries called plaque.
Normal Artery Hardened Artery
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Fats and CholesterolPlaques that clog arteries are rich in cholesterol. Cholesterol is a fat-like steroid molecule that is common to animal tissue. Cholesterol is carried in the blood by lipoproteins. Lipoproteins are classified according to their density. Very-low-density lipoproteins (VLDLs) transport triglycerides. Low-density lipoproteins (LDLs) carry cholesterol from the liver to the blood and are responsible for the formation of plaques. LDLs are the so-called “bad” cholesterol. High-density lipoproteins (HDLs) carry the cholesterol to the liver and are the so-called “good” cholesterol.
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Fats and Cholesterol
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Fats and Cholesterol
Diets high in saturated fats and trans fats have been linked to high LDL levels in blood. It is recommended that one limits the amount of saturated fat and trans fat in the diet.
Trans fats are formed when unsaturated fats are hydrogenated in order to make margarines or more solid fats.
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Fats and Cholesterol
Saturated vs. Cis- vs. Trans-Unsaturated Fats
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ProteinsProteins are digested into individual amino acids. These amino acids are used to synthesize proteins for growth and repair of tissue.
The body can synthesize all but nine amino acids necessary for protein synthesis. These nine amino acids are called essential amino acids and include: isoleucine, lysine, phenylalanine, tryptophan, leucine, methionine, threonine, and valine.
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Proteins
Complete proteins contain all the essential amino acids needed for growth and repair of tissue. Lean meat, milk, fish, eggs, and cheese contain complete proteins.
The human body requires about 0.8 g of protein per kg of body weight. Protein deficiency can lead to retarded growth and development, discoloration of the skin and hair, and swollen abdomen.
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Minerals: Inorganic Chemicals and Life
Dietary minerals are the inorganic substances necessary for life.
Bulk structural elements and macrominerals make up more than 99% of all atoms in the human body.
Trace elements and ultratrace elements make up the rest.
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Minerals: Inorganic Chemicals and Life
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Minerals: Inorganic Chemicals and Life
Lack of dietary minerals can have serious consequences. Lack of iodine in the diet can lead to thyroid goiters.
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Vitamins
Vitamins are organic compounds that are essential in the diet. Vitamins do not include proteins, fats, carbohydrates, and minerals. Vitamins can be classified as either fat-soluble or water-soluble.
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Vitamins
Fat-Soluble Vitamins
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Vitamins
Water-Soluble Vitamins
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Vitamins
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VitaminsVitamin deficiency can be serious.
(a) Softened bones due to deficiency of vitamin
D.
(b) Pellagra due to deficiency of niacin.
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Other Essentials: Fiber and Water
Dietary Fiber
Fiber may be soluble or insoluble. Insoluble fiber is mostly cellulose, whereas soluble fiber is mostly gums and pectins. Fiber has a number of benefits. It helps to maintain proper colon function and may help to control blood sugar and lower cholesterol levels.
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Other Essentials: Fiber and Water
Water
Water is an essential part of our diet. Actually, most of what we ingest is water. In addition, we require 1-1.5 L of water daily.
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Starvation and Fasting
Starvation is the total deprivation of food. It takes less than one day for the body to deplete itself of glycogen stores. After the glycogen is depleted, the body will then metabolize the fat reserves. Fat metabolism leads to ketosis as ketone bodies are released into the blood and urine. This can lead to acidosis as the blood pH drops. Body proteins will also be metabolized and eventually muscle proteins will be metabolized.
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Starvation and Fasting
Ketone Bodies
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Starvation and Fasting
Malnutrition can also occur due to eating too much processed food. Processing of food removes much of the nutritional value and fiber. It is ironic that people in developed nations experience obesity and poor nutrition while living in a land of food abundance.
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Food Additives
Food additives are substances other than basic food stuffs added to food as a result of production, processing, packaging, or storage.
Sugar, salt, corn syrup, citric acid, baking soda, vegetable colors, mustard, and pepper make up more than 98% of all additives by weight.
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Food Additives
Additives that Improve NutritionKI: Added to salt to prevent goiter.
Vitamin B1: Added to polished rice.Vitamin C: Added to fruit juice and other beverages.Vitamin D: Added to milk to prevent rickets.Vitamin A: Added to margarine to match nutritional value of butter.
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Food Additives
Flavoring Agents
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Food Additives
Artificial Sweeteners
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Food AdditivesArtificial Sweeteners
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Food AdditivesFlavor EnhancersA popular flavor enhancer is monosodium glutamate (MSG).
Excess MSG can be harmful. It has been shown to cause birth defects if eaten in large amounts by pregnant women.
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Food AdditivesSpoilage inhibitors: Antimicrobials prevent spoilage from molds, yeasts, or bacteria. Propionic acid, sorbic acid, benzoic acid, and their salts can be used.
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Food Additives
Spoilage Inhibitors
Sodium nitrate (NaNO2) is used to cure meats and gives the pink color to ham, hot dogs, bacon, and bologna. However, stomach acid converts the nitrite ion to nitrous acid, which can then react with amines to form nitrosoamines, which are known carcinogens.
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Food Additives
Antioxidants: BHA and BHT
Foods that contain fats can turn rancid due to the formation of free radicals. Antioxidants react with free radicals, preventing their chain reaction formation. Antioxidants include butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tert-butylhydroquinone, and propyl gallate.
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Food Additives
Antioxidants
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Food Additives
Food Colors
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Food Additives
Food Colors
Some food colors such as FD & C Orange No. 1 have been banned by the FDA. Others have been found to be carcinogens. Even so, they present little risk since they are used in such small amounts.
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Food Additives
Nanoscience in Foods
Nanoscience and nanotechnology involve the production and use of materials at the nanometer scale.
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Food Additives
Nanofoods are being explored which contain nanocapsules that can change color, flavor, and texture of foods.
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Food Additives
Nanopackaging is being developed to improve the shelf life of food by employing nanoparticles in films that block out or remove harmful gases, such as carbon dioxide or oxygen, that spoil food.
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Food Additives
Nanosecurity devices are being developed for both pathogen and contaminant detection.
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Poisons in Our FoodCarcinogens
Foods contain both natural and added carcinogens. Scientists estimate that we consume natural carcinogens at 10,000 times the rate of synthetic carcinogens.
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Poisons in Our Food
Incidental AdditivesIncidental additives get into food accidentally during production, processing, packaging, or storage. About 10,000 incidental additives end up in our food. Some have been causes of concern, including Alar (its breakdown product is dimethylhydrazine, a suspected carcinogen), PCBs, PBBs, antibiotics, DES, etc.
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A World without Food Additives
Food additives are likely a necessary part of a modern society. Each year in the U.S., there are 76 million illnesses, including 5,000 deaths due to bacteria, viruses, and parasites in food. Few, if any, deaths are associated with the use of intentional food additives.