EFFECT OF BOILING TREATMENTS ON BIOCHEMICAL CONSTITUENTS OF VEGETABLE-TYPE SOYBEAN

Abstract

Immature seeds of four vegetable-type soybean genotypes were subjected to boiling under pressure (5 min) and at atmospheric pressure (10 min) to assess the two boiling treatments in minimizing the losses of biochemical attributes viz. isoflavones, vitamin C, sucrose and reducing the undesirable factors viz. trypsin inhibitor, lipoxygenases, raffinose and stachyose. Boiling under pressure caused significantly higher (P < 0.05) decline for daidzein and glycitein compared with the boiling at atmospheric pressure. Similarly, boiling under pressure caused significantly (P < 0.05) less vitamin C loss and higher decline of sucrose. Conversely, genistein increased because of both the boiling treatments. Both the boiling treatments equally deactivated lipoxygenases, while the boiling at atmospheric pressure was more effective in reducing trypsin inhibitor. Raffinose and stachyose was either not detected or present in negligible levels in raw seeds. Results suggest that the boiling of vegetable soybean at atmospheric pressure may be preferred to the boiling under pressure. PRACTICAL APPLICATION Immature green seeds of vegetable soybean are subjected to boiling treatment prior to consumption or storage. The information regarding the changes in the levels of biochemical constituents of vegetable soybean after boiling treatment is very limited. In the present investigation, the effects of boiling treatment under pressure and at atmospheric pressure on the levels of isoflavones, vitamin C, sucrose, lipoxygenases, trypsin inhibitor, flatulence factors of immature seeds were studied. Though there was less loss for vitamin C content because of boiling under pressure and both the boiling treatments were found equally effective for inactivating lipoxygenases, the boiling applied at atmospheric pressure appeared comparatively superior as it resulted in less isoflavones and sucrose losses and higher trypsin inhibitor reduction. The study is of practical significance for vegetable soybean industry, which requires blanched immature seeds with high levels of taste and nutraceutical components and minimum concentration of antinutritional factors for canning.