Effect of soaking and ionising radiation on various antinutritional factors of seeds from different species of an unconventional legume, Sesbania and a common legume, green gram (Vigna radiata)

Seeds of three different species of Sesbania (Sesbania aculeata, S. rostrata and S. cannabina) and one species of Vigna (Vigna radiata) were gamma-irradiated at dose levels of 2, 4 and 6 kGy after aqueous soaking and the effects of the irradiation on the proximate composition, various antinutrients and viscosity were studied. Crude protein, crude lipid, crude fibre, ash, nitrogen free extract (NFE) and energy value did not differ appreciably between raw seeds and those soaked and irradiated after soaking, for all the samples. When compared with respective raw and soaked seed materials, irradiation significantly (P < 0.05) increased the total phenolic contents. No significant effect was observed on the reduction of phytic acid and canavanine contents, whereas approximately 50% reduction of lectin activity was observed at the highest dose of irradiation (6 kGy) in different Sesbania spp. On the other hand, non protein amino acid, canavanine and lectin activities against cattle blood erythrocytes were not detected in raw, soaked, or soaked followed by irradiated seeds of V. radiata. The highest radiation dose level of 6 kGy in S. aculeata and S. rostrata and 4 and 6 kGy in S. cannabina and V. radiata were significantly effective (P < 0.05) in reducing saponin content. Among the various Sesbania and V. radiata seed samples, irradiation at 2-6 kGy in S. aculeata significantly (P < 0.05) reduced the trypsin inhibitor activity in a nondose-dependent manner when compared with raw and soaked samples. Particularly, the irradiation at a dose level of 6 kGy significantly (P < 0.05) reduced viscosities of different spp. of Sesbania and V. radiata seed samples and this might be due to the depolymerisation of non-starch polysaccharides (NSPs). (C) 2002 Elsevier Science Ltd. All rights reserved.