Optimization of germination time and heat treatments for enhanced availability of minerals from leguminous sprouts

Germinated legumes are highly nutritious food especially for their enhanced iron bioavailability primarily because of reduction of phytates and increase in ascorbic acid with an advancement of germination period. Length of germination time followed by different heat treatments affect the nutritive value of leguminous sprouts. To optimize germination time and heat treatments for enhanced availability of iron from leguminous sprouts, three legumes namely, mungbean, chickpea and cowpea were germinated for three time periods followed by cooking of sprouts by two cooking methods ie. pressure cooking and microwaving. Optimized germination time for mungbean was 12, 16 and 20 h; 36, 48 and 60 h for chickpea and 16, 20 and 24 h for cowpea. Germination process increased ascorbic acid significantly in all the three legumes, the values being 8.24 to 8.87 mg/100 g in mungbean, 9.34 to 9.85 mg/100 g in chickpea and 9.12 to 9.68 mg/100 g in cowpea. Soaking and germination significantly reduced the phytin phosphorus in all the three legumes, the percent reduction being 5.3 to 16.1% during soaking and 25.7 to 46.4% during germination. The reduction in phytin phosphorus after pressure cooking was 9.6% in mungbean, 18.4% in chickpea and 6.1% in cowpea. The corresponding values during microwaving were 8.4, 19.7 and 4.5%. Mineral bioavailability as predicted by phytate:iron enhanced significantly with an increase in germination time. Further reduction i.e. 0.9 to 16.3% was observed in three legumes after the two heat treatments. The study concluded that the longer germination periods ie. 20 h for mungbean, 60 h for chickpea and 24 h for cowpea followed by pressure cooking for optimized time were suitable in terms of better iron availability.