· It is a macro nutrient and so can be stored in the body.
· 1g of protein provides 17kJ (4kcal).
· Of the 20 amino acids commonly found in proteins, 8 are essential/indispensable in the diet. An additional one must be supplied in the diets of rapidly growing infants. The non essential (indispensable) amino acids can be synthesised in the body by converting one amino acid into another within the body cells.
· When protein foods are eaten, the proteins are hydrolysed during digestion to produce amino acids. After absorption, the amino acids are transported by the blood to the cells. In the cells, the amino acids recombine and proteins are formed.
· Functions in the body: growth and repair/maintenance of cells; formation of enzymes, anti bodies and some hormones; formation of red blood cells.
· Excess: used for energy
· Deficiency - not common in UK except for some cases of anaemia. In Africa and Far East: kwashiorkor - wasting of muscles, retarded growth, anaemia, distended abdomen caused by oedema. It is common amongst young children after weaning. Dried skinned milk is one of the most useful foods for the treatment of kwashiorkor. PEM (Protein-Energy Malnutrition) is used to cover the whole range of conditions from protein deficiency at the one extreme to energy deficiency at the other.
· Novel (or new) Sources of Protein: the following have been developed because they are low in saturated fat and can be used as a healthier alternative to meat:
> Textured Vegetable Protein (TVP): The protein from certain oilseeds can be used to make textured products which can be used to replace, or partly replace, meat in a wide variety of dishes. The seeds most frequently used are soya beans as they are a good source of protein. Soya-bean meal can be used to manufacture a product with a meat-like texture, known as Textured Vegetable Protein (TVP). The protein is extracted by adding an alkali and fibres are formed by extruding the protein through fine nozzles or spinerettes. The fibres are combined with fat, a protein binder, colours and flavours. The product is similar to cooked meat and can be frozen, canned or dehydrated. TVP is used in catering, particularly in industrial canteens and the school meals service.
> Single Cell Protein: Micro organisms have a high protein content and contain useful quantities of vitamins. Quorn is a novel protein food or meat substitute which is made from a microscopic type of fungus and therefore described as a mycoprotein. It is grown in a fermenter and "harvested", then heat processed, flavoured and sliced or shredded. Quorn can be used as a substitute for meat in home-cooking and is used in manufactured foods such as pies and curries. It is used extensively in vegetarian and vegan cooking.
Physical and Chemical Structure of Protein
· Contains the elements hydrogen, oxgen, carbon and nitrogen. Some also contain phosphorus and sulphur.