The following points highlight the top six food products with nutritive value. The food products are: 1. Milk 2. Egg 3. Meat 4. Fish 5. Vegetable Foods 6. Alcohol.
Nutritive Value: Food Product # 1. Milk:
a. Milk is nearest to a perfect and complete food.
b. It contains not only protein, fat and carbohydrate but also minerals and vitamins.
c. The chief proteins are caseinogen and lactalbumin. Caseinogen is a phosphoprotein. Caseinogen is associated with calcium as calcium caseinogenate. Small amounts of other proteins are also present.
d. Milk fat is in the form of a very fine emulsion. It contains all saturated fatty acids as well as unsaturated fatty acids.
e. The carbohydrate of milk is lactose which is less sweet than sucrose.
f. It is rich in calcium, potassium, sodium, chlorine and phosphorus. The iron content is very low which is insufficient for baby.
g. It is rich in vitamin A and vitamin B, and good in vitamin B, and nicotinic acid but poor in C and D.
h. Milk kept on un-sterilised becomes sour due to formation of lactic acid from lactose by bacteria present in milk and this lactic acid is sufficient to precipitate (curdle) the caseinogen.
i. When milk comes in contact with rennin or proteolytic enzymes, it becomes clotted.
j. The protein of milk neutralizes gastric HCl to allow clotting.
k. The percentage composition of milk of different species is given below:
l. Condensed milk is prepared by the removal of water by evaporation in vacuo. Vitamins A and B are preserved. Dried milk is prepared by passing a film of milk over hot rollers or spraying milk into hot air to evaporate water.
Nutritive Value: Food Product # 2. Egg:
a. The hen’s egg contains about 30% yolk, 59% white and 11% shell. The chemical composition of duck’s egg is similar to that of hen’s egg.
b. The white contains proteins and salts. The greater part of the protein is ovalbumin. The other proteins are conalbumin, ovoglobulin and ovomucoid (a glycoprotein). The pale yellow colour is due to riboflavin. The white contains 10.7% protein, 0.1% fat and 1.4% carbohydrate.
c. The yolk contains 51% water, 15% protein, 33% fat of which 4% cholesterol, and 1% mineral. The proteins are vitellin (a phosphoprotein) and livetin (a globulin). The minerals are calcium, iron and phosphate. The yolk is rich in vitamins A, B1, B2 and D but not C. The other B group vitamins and E are also present.
Nutritive Value: Food Product # 3. Meat:
a. Meat contains about 22% protein and B group vitamins but does not contain vitamins A, C or D.
b. Nearly all the carbohydrates disappear during hanging, and lactic acid as well as acid phosphates are formed. These acids convert collagen to gelatin when the meat is cooked. In boiling, there is the loss of salts, gelatin and extractives. During roasting this loss is reduced.
c. The flavour of meat is due to the organic substances extracted from meat by boiling water.
Nutritive Value: Food Product # 4. Fish:
a. Fish is free from carbohydrate just like meat. The fat content ranges from a trace to 5%. It is fair source of B group vitamins. Fatty fish contains some vitamins A and D.
b. Large fish is rich in phosphorus but deficient in calcium. Small fish eaten with bones are good sources of calcium.
c. It contains 22% protein, 1.4% fat, 75% water. The dried fish may contain about 5% carbohydrate because of the use of flour.
Nutritive Value: Food Product # 5. Vegetable Foods:
a. The crude cereals (wheat, rice, barley, rye, maize, and oats) contain 11% protein, 70% carbohydrate, 0.5% to 8% fat, 11% water and 2% minerals. Oatmeal is the richest in protein and fat—rice is the poorest.
b. The main proteins of cereals are glutelins and gliadins. Small amounts of albumins and globulins are generally present.
c. The fats contain considerable amounts of olein to make them liquid at ordinary temperatures.
d. The carbohydrate is almost completely starch in the form of grains covered by a thin membrane of cellulose. Small amounts of sugar are also often present in cereals.
e. The abundant mineral elements are calcium and phosphate. The phosphate is partly in the form of phytic acid (inositol hexaphosphate) which interferes the absorption of calcium. Some cereals (wheat and rye) contain the enzyme phytase which hydrolyzes phytic acid and reduces the anti-calcifying effect.
f. There is a great loss of vitamins B and E, and mineral elements, especially Ca, P and Fe in the roller milled white flour. Carotene and ribotlavin are lost by chemical blenching.
a. The dried pulses (peas, beans, lentils etc.), contain large amounts of protein. The main protein is a globulin called legumin. The dried pulses contain 20-25% protein, 11% water, less than 2% fat.
b. The soya bean contains high protein, high fat and low carbohydrate. Soya bean oil is used for frying “fish and chips”.
c. The dried pulses are the good sources of many B group vitamins and minerals but deficient in vitamins A, D, B12 and C.
a. Nuts contain high protein and fat but low carbohydrate. The protein content is slightly lower than that of dried pulses.
b. They can be used for the preparation of milk substances which can be fed to infants over 6 months of age and to young children of some areas where milk is not available in sufficient amounts.
D. Roots and Tubers:
a. The most important tuber used in this country is the potato, sweet potato. These are the chief sources of starch. These can substitute sugar and cereals and are the valuable sources of iron and vitamin C.
New potatoes contain about 28 mg vit. C. per 100 gm. but on storage 5 mg vit. C per 100 gm. is reduced.
b. The common roots (carrots, beetroots, turnips) are almost free from starch. Their caloric value is completely due to sugars (sucrose, fructose and glucose). Carrots, the richest in sugars, are the sources of carotene. Roots contain valuable salts but negligible protein and fat. Arrowroot contains traces of protein and salts.
E. Green Leafy Vegetable:
a. Green leafy vegetables are rich in carotenes.
b. They are good sources of calcium, riboflavin, folic acid and vitamin C.
c. They are the cheapest among the protective foods.
d. Yellow pumpkin is a fair source of carotene.
a. Fresh fruits are the protective foods. Their energy value is due to sugars and starch. The protein and fat are usually less than 0.5%. Many fruits contain pentose’s and pectins.
b. Tartaric acid, malic acid and citric acid are present in fruits.
c. Cooking destroys vitamin C and makes fruits more digestible by softening the cellulose.
d. Some fruits, notably the banana, contains starch as well as sugar. It has high protein content.
e. The carbohydrate of dates is all sugar, not starch. The protein content is low (2%).
G. Tea, Coffee, Cocoa:
a. The black tea sold consists of the leaves of young shoots of the tea plant which are fermented and dried by heat. It has negligible caloric value. It has a stimulant and a diuretic effect. Strong tea disturbs gastric digestion due to tannic acid.
b. Coffee is the roasted seed of coffea arabica. The odour is due to an oil, caffeol, formed when the beans are roasted. It has little caloric value. It contains caffeine and tannic acid. It cannot be regarded as food unless taken with milk and sugar.
c. The seeds are obtained from the pods of the cocoa tree after fermentation and roasting. They contain 50% fat. Cocoa as beverage is of little importance. It becomes nourishing when taken with milk and sugar. Chocolate consists of ground cocoa nibs mixed with sugar. Starch and flavouring are frequently added.
Nutritive Value: Food Product # 6. Alcohol:
a. Alcohol has an energy value of 7 calories per gram. Hence, it has been admitted as food. Its consumption is restricted due to its pharmacological action. It is consumed in the form of wines, spirits or liquors.
b. Beers are the fermented product of malt and contain 4-8% alcohol. It has small amount of protein and some sugar.
c. Wines are the products of fermentation of fruit juices (usually grapes). The alcohol content is 10-20% and sugar 0.1 -4%. They contain large amount of organic acids (tartaric, malic, succinic, etc.).
d. Spirits are the distillation product of many fermented products. Whisky is a distilled beer and brandy is a distilled wine. They are practically free from sugar. The alcoholic content is 30-50%.
e. Liquors are alcohol sweetened with cane sugar and flavoured with essences. The sugar content is 30% and alcohol is 35- 55%.