Lecture 3

Lecture 3 - FST 1 – Main topics – Lecture 03 Food...

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Unformatted text preview: FST 1 – Main topics – Lecture 03 Food Composition Refers to the chemicals food is made of, not food ingredients (flour, eggs, sugar, etc). Food components: Nutrients plus many minor components, such as color compounds, flavor compounds, many others. Nutrients: chemical substances in food that provide: - energy - materials to build and maintain the body Macronutrients: needed in gram quantities Micronutrients: needed in milligram or microgram quantities. There are 6 classes of nutrients: Carbohydrates, Lipids, Proteins, Vitamins, Minerals, and Water. Nutrients that provide energy: Carbohydrates: 4 kcal/g Lipids: 9 kcal/g Proteins: 4 kcal/g Calorie is a unit of measure for the energy in foods. It is measured using a bomb calorimeter. One calorie is the amount of heat it takes to raise the temperature of 1 gram of water by 1ºC. One kilocalorie is the amount of heat it takes to raise the temperature of 1000 grams of water by 1ºC. 1 kcal or Calorie = 1,000 cal The International System of Units (ISU) uses the joule (J) as unit of energy. 1 kcal = 4.184kJ Water is a vital nutrient. Our body contains ~60% water. Among the functions of water in the body are: ‐ solvent; component of body fluids; reaction medium; temperature regulation; ‐ vehicle for transporting nutrients to cells, and to remove waste products, etc. Chemically water is H2O; it is a polar molecule. It forms hydrogen bonds with other water molecules. Ice melting and water vaporization involve hydrogen bonds breaking (see McGee p.792‐4). Minerals Chemical elements that the body uses to ‐ promote chemical reactions; ‐ form body structures, such as Ca (bones), Fe (blood). Vitamins have diverse functions in the body: ‐ help regulate and support chemical reactions in the body; ‐ are required in very small amounts in the diet. Lack of vitamins in the diet can have widespread effects. There are 13 vitamins, and they are classified as: ‐ Fat soluble vitamins: A, D, E, and K ‐ Water soluble: B vitamins, C No single food is a good source of ALL vitamins. It is important to eat a variety of foods. Examples of a fat soluble and a water soluble vitamin: Vitamin A is found only in foods of animal origin (beef liver, chicken liver, fish, fortified milk, etc). Plant foods contain provitamin A (precursors of vitamin A) carotenoids. Carotenoids are natural pigments with colors varying from yellow to orange to red; they give color to carrots, tomatoes, etc. Some carotenoids ‐ such as beta‐carotene and alpha‐carotene‐ can be converted to vitamin A in the body. Beta‐carotene is the carotenoid with the highest provitamin A activity. Vitamin C. Some good sources are: citrus fruits, green peppers, kiwi, strawberries, etc. Deficiency of vitamin C causes scurvy; disease characterized by bleeding gums, loose teeth, and weakness, among many other symptoms. In the past it afflicted many people on long sea voyages. Today it is rare in developed countries. Vitamins in foods – losses Water soluble vitamins ‐ extracted in water / leaching ‐ some are sensitive to heat or light Fat soluble vitamins ‐ insoluble in water ‐ stable at cooking temperatures Readings 1. McGee p.792‐4 (Water) 2. McGee p.786‐7 (Microwaving) Note: Alcohol is not an essential nutrient, but it also supplies energy: ~ 7 kcal/g ...
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This note was uploaded on 08/16/2011 for the course FST 001 taught by Professor Charlesf.shoemaker during the Winter '10 term at UC Davis.

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