【正文】 uch as riboflavin and B12, and minerals such as calcium, zinc and magnesium. These days, they are available with a range of fat contents. Nutrient content in 100g Human milk Cow milk Sheep milk Water Protein Fat CHO En (kj) 272 226 247 Ca(mg) 30 104 82 P(mg) 13 73 98 Fe(mg) VA 11 24 84 B1 B2 Milk product Milk has been derived from many types of mammals and put to different uses over the centuries. This has resulted in the development of a number of milk products. These include butter, cheese, cream and yogurt. Cream is made by separating the fat and solids from milk. It is a fatinwater emulsion. When whipping or double cream is whipped it changes from a liquid to a foam. This is due to the partial denaturation of the proteins, which stabilise the mixture by trapping air. Cheese can be classified in a number of ways, for example by the place where it is produced or the method of production. Generally it is posed of milk solids, including some water and other ingredients. An enzyme called rennin is used to clot the milk and produce the milk solids (casein curd) and liquid (whey) which is drained off. The different kinds of cheese result from different methods of production and raw ingredients. Yogurt is milk which has been coagulated and soured by lactic acid. The lactic acid is produced by the addition of harmless bacteria. Butter is a waterinoil emulsion made from cream. Its position is controlled by law: * milk fat, at least 80% but less than 90% * dry nonfat milk material, no more than 2% * water, no more than 16% 7. Fish Composition The structure of muscle in fish is made up from segments of short fibres which give fish its characteristic flaky texture. These segments are separated by sheets of fine connective tissue. This substance is very fragile and is easily converted to gelatine. The bination of short muscle fibres and gelatine gives fish its tenderness, and is the reason why overcooking will result in fish falling apart. Characteristic Fat content: Oily fish have more than 5% fat in their flesh, eg sardine and salmon. White fish have less than 5% fat in their flesh, eg cod and halibut. Nutrition Protein： 1520% Fat： % Vitamins： A、 D、 E、 B2 Minerals： Ca、 Se 8. Eggs As an egg gets older, several changes occur: water moves from the white to the yolk the yolk structure weakens the egg white bees thinner the air space increases bacteria may enter through the shell a ‘bad egg’ smell occurs due to the production of hydrogen sulphide and related pounds An egg is made up from 3 main parts: the shell, white and yolk. Characteristic (1) Coagulation: When eggs are heated, the protein in the white and yolk starts to coagulate. This means that the liquid egg bees firmer. As heating continues the egg eventually bees solid. Boiled, poached, fried and scrambled eggs all demonstrate this process. The coagulation of eggs makes them suitable for a variety of functions. (2) Emulsification: Egg yolk contains lecithin which acts a an emulsifier. It can be used to stabilise emulsions. Adding egg yolk to a mixture of oil and water prevents the two liquids from separating. An example of this is mayonnaise which is an emulsion of oil and vinegar, held together by egg yolk. Industrially manufactured mayonnaise uses pasteurised egg (which has been heat treated to destroy potentially harmful microanisms), rather than raw egg, to ensure safety. (3) Foaming: Whisking egg white incorporates air and produces a foam a relatively stable mass of bubbles. If left to stand, the foam will gradually collapse, but when heated the foam bees permanent, eg meringue. Whole egg incorporates air less well, but gives sponge cakes a light texture. Nutrition Protein： 1113% Fat： 915% yolk:3033% VB、 A、 D、 E、 K、 C Minerals： % P60% Ca13% Fe、 S、 Mg、 K、 Na 食物蛋白質 生物價 （ BV） 蛋白質功效比 （ PER） 凈蛋白利用率 （ NPU） 全蛋 100 94 牛奶 91 82 酪蛋白 77 76 乳清蛋白 104 92 牛肉 80 73 馬鈴薯 71 大豆蛋白 74 61 稻米蛋白 59 57 雞蛋蛋白質與其他食物蛋白質質量比較