Comparative nutritive value of various staple foods

A population successful in an ecological niche must have a dietary pattern that provides the minimum requirements of all 40-45 essential nutrients, in addition to the energy sources-carbohydrates, fat, and protein. Cereal pro duction and its contribution to diets in developing countries exceed that o f legumes and roots, tubers, plantains and bananas. Legumes are highest in protein and is rich in lysine but deficient in cystine and methionine. Cere als are intermediate in protein content; their protein is rich in cystine a nd methionine but deficient in lysine. Thus cereal-legume diets have a bett er amino acid balance than either diet alone, as shown by the high protein quality of most composite diets. Storage proteins are prolamin and glutelin in cereal endosperm, but globulin in legume cotyledon, occurring as prolam in protein body (PB) in cereals and globulin PB in legumes. Glutelin PB occ urs in rice endosperm. Roots, tubers, plantains and bananas are high in moi sture, hence, poor in protein content and other nutrients and have a poor p ostharvest shelf life. Potato protein has a balanced amino acid composition . Antinutrition factors for protein include protease (trypsin) inhibitor, t annins, and phytate. Digestible energy correlates with true protein digestibility and increases with processing. Starch occurs as partially crystalline storage granules. T he amylose content of starch correlates negatively with glycemic index and positively with resistant starch, a component of soluble dietary fiber. In some cases, starch gelatinization temperature correlates negatively with gl ycemic index and positively with resistant starch. Antinutrition factors fo r starch include amylase inhibitor, tannins, and phytate. Flatulence factor s include galactose-containing oligosaccharides, which are particularly hig h in legumes, Soluble a-glucans of oat and barley have hypocholesterolemic activity. Legumes are generally energy-dense due to their high fat content, particula rly peanut and soybean. The unsaponifiable matter of rice oil has hypochole sterolemic activity. Some varieties of root crops have cyanogenic glycoside s that release HCN on hydrolysis, causing death to consumers. Others have s aponins and tannins that contribute to a bitter taste. Staple foods are a m ajor source of vitamins and minerals due to the large amount consumed. Breeding efforts in the 1960s and 1970s attempted to improve the protein co ntent and limiting amino acid (lysine content in cereals and cystine and me thionine in legumes) in staple foods, both of which require more energy to produce. CGIAR recently launched a project to increase the micronutrient de nsity of selected crops, particularly vitamin A, iron, and zinc, although m ineral absorption from a vegetable sourer is poor. The low phytate mutant o f cereals may improve protein digestibility, glycemic index, and mineral ab sorption. Rice mutant lacking lipoxygenase 3 and a lower polyunsaturated fa tty acid content may reduce fat rancidity and maintain the essential fatty acid level of food during storage, as in soybean. The adoption of GATT-WTO in most countries, the accompanying emphasis on va lue-added food products, and the popularization of functional foods and nut raceuticals in developed countries will have an impact on the properties an d nutritive value of food products in developing countries in the 2000s.