Production and nutritive value of soybeans

Soybean world production has been increasing at a rate of 5.2% per year (average yield is around 1,400 kg/ha). This production has been solely used for oil extraction and the protein meal obtained for animal rations, but lately it is being used for human consumption. Brazil, the third largest producer, has had a yearly rate of production increase of 32% in the last years. Average yields in Brazil are still low (around 1,500 kg/ha), but in experimental results, yields over 3,000 kg/ha have been obtained. Some problems needstill to be solved, such as obtention of adapted varieties, soil fertility, adequate agronomic practices, damage by insects and diseases. Protein and oil contents are highly negative correlated, they are genetically controlled and can also be influenced by environmental conditions and agronomic practices. To breed for high protein (above 48%) enhances a decrease in oil and yield, but new varieties containing 43% protein and with a good yielding capacity have been developed lately. Methionine content varies from 1.0 to 1.6% g/16g N; there is a correlation of 0.56 to 0.58 between methionine in the protein and protein in the seed. Particular attention has been given to toxic factors such as trypsin inhibitors, whose action is related to the availability or utilization of methionine; this effect, however, can be eliminated by heat.