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Sucrose content in soybean seeds is desired to be high because as a sweetness-imparting component, it helps in wider acceptance of soy-derived food products. Conversely, galactosyl derivatives of sucrose, that is, raffinose and stachyose, which are flatulence-inducing components, need to be in low concentration in soybean seeds not only for augmenting utilization of the crop in food uses but also for delivering soy meal with improved metabolizable energy for monogastric animals. In the present study, analysis of 148 soybean genotypes for sucrose and total raffinose family oligosaccharides (RFOs) contents revealed a higher variation (4.80-fold) for sucrose than for RFOs content (2.63-fold). High-performance liquid chromatography analyses revealed ranges of 0.64-2.53 and 2.09-7.1 mmol/100 g for raffinose and stachyose contents, respectively. As information concerning the environmental effects on the sucrose and RFOs content in soybean seeds is not available, we also investigated a set of seven genotypes raised at widely different geographical locations for these quality traits. Sucrose content was found to be significantly higher at cooler location (Palampur); however, differences observed for raffinose and stachyose contents across the growing locations were genotype-dependent. The results suggest that soybean genotypes grown at cooler locations may be better suited for processing soy food products with improved taste and flavor.

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Immature seeds of soybean are becoming increasingly popular as a snack/vegetable to harness the health benefits of soybean. They are shelled from the immature pods picked from the mother plant at different reproductive stages. Information concerning changes in antioxidant constituents and antioxidant capacity during reproductive phases of soybean seeds is scarce. The aim of the present study was to determine whether immature seeds picked at different reproductive stages differ in tocopherol, isoflavone, total phenolic contents, free radical scavenging activity, and total antioxidative capacity. Seeds shelled from the soybean pods picked at three reproductive stages (R5, R6, and R7) as well as at full maturity were subjected to high-performance liquid chromatography analyses for tocopherol and isoflavone contents. Significantly higher values (P<0.05) were observed for tocopherols and isoflavones in immature seeds picked at late reproductive stages. At the first reproductive stage, that is, R5 stage, delta-tocopherol was the predominant form of tocopherol, whereas in subsequent reproductive stages as well as at complete maturity stage, the gamma-isomer contributed maximum proportion to the total tocopherol content. Genistein was, in general, the major form of isoflavone at all reproductive stages. Reduction in free radical scavenging activity, total antioxidant capacity, and total phenolic content in late-picked seeds concomitant with increased concentration of tocopherol and isoflavone isomers was observed. The results show that bioactive constituents other than isoflavones and tocopherols may decline with the advancement of maturity.

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Three Indian soybean genotypes, namely, Kalitur, Hara soya and NRC37 with black, green and yellow colored seed coat respectively were gamma irradiated at a dose of 0.5, 2.0, and 5.0 kGy. The total isoflavones and total phenol content (TPC) in all the genotypes increased significantly at a dose of 0.5 and 2 kGy respectively. The anthocyanin content was high in Kalitur, while other genotypes showed no detectable amounts of it. The hydroxyl radical scavenging activity (HRSA), DPPH free radical scavenging activity (FRSA) and total antioxidant power (TAP) were highest in Kalitur with black seed coat color. However, maximum enhancement in antioxidant properties was found in NRC37 with yellow followed by Hara soya with green seed coat color at a dose of 0.5 and 2.0 kGy. It was also observed that the 3 soybean genotypes showed an increase in antioxidant constituents and antioxidative properties at lower doses of 0.5 and 2.0 kGy while, the antioxidant effects of soy seeds were either decreased or remained constant at a higher dose of 5.0 kGy. It is suggested that mild gamma irradiation enhanced the antioxidant constituents and, hence, antioxidant potential of soybean seeds.

Plant seed oils, including soybean seed oil, represent the major source of naturally derived tocopherols, the antioxidant molecules that act as free radical quenchers preventing lipid peroxidation in biological systems and vegetable oil products. All four isomers of tocopherols, i.e. α, β, γ, δ tocopherols that exist in nature are found in soybean seeds. The biological activity and the contribution of these isomers in improving the oxidative stability of vegetable oil are in reverse order. Because of the nutritive value and the importance for oil stability, enhancement of tocopherol content, through breeding programs, in soybean seeds has become a new and an important objective. Genotypic variability, which is the basis of every breeding program, is scarcely reported for tocopherol content and profile in soybean seeds. In the present investigation, the tocopherol content and profile in seed samples of 66 genotypes of Indian soybean were determined. The ratios observed between the lowest and the highest values for α, β, γ, δ, total tocopherol content were 1:13.6, 1:10.4, 1:7.5, 1:9.1, 1:7.9, respectively. The mean contents for α, β, γ, δ and total tocopherols were 269, 40, 855, 241 and 1,405 μg/g of oil, respectively. Total tocopherol content was the highest in ‘Co Soya2’ followed by ‘Ankur’. Concentration of α‐tocopherol was the highest (27%) in ‘Ankur’ followed by ‘MACS124’ (26%) whereas gamma tocopherol concentration was the highest (69%) in ‘VLS1’ and ‘PK327’ followed by ‘MACS13’ (67%). In view of the fact that levels of unsaturated fatty acids, apart from tocopherols, also determine the oxidative stability of vegetable oils, the relationship of four isomers of tocopherols with each other as well as with different unsaturated fatty acids and oil content was also investigated in the present study. All the four isomers of tocopherols exhibited highly significant correlations with each other (p < 0.001) whereas γ‐tocopherol and total tocopherol content showed a significant relationship with linoleic acid (p < 0.05).

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