Effect of soaking, autoclaving and repeated boiling on oligosaccharides in cowpea.

Oligosaccharides in beans are known to be the major cause of flatulence associated with beans consumption. The effects of soaking, autoclaving and repeated boiling on the oligosaccharide levels in ten cowpea varieties were studied. The oligosaccharides were extracted in 70% aqueous ethanol and separated by thin layer chromatography(TLC) method.The quantitation was done using the spectrophotometer. The results showed that, the total oligosaccharide content varies among the cowpea varieties; 0.197 -0.918g/100g. IT93K-596 had the lowest oligosaccharide content (0.197g/100g) and IT94K-410-2 the highest (0.918g/100g). Autoclaving, soaking and repeated boiling had a reductive effect on the total oligosaccharides content in the cowpeas used. Autoclaving reduced raffinose level by 23-68%, stachyose level by 12-81% and total oligosaccharides level by 23-74%. Repeated boiling reduced the raffinose level by 23-61%; stachyose, 20-58% and total oligosaccharide by 15-55%. The loss of raffinose and stachyose after soaking ranged from 18.2-53.6% and 20.4-75.1% respectively and the total oligosaccharide loss, 25.1-63.9%. These treatments are therefore recommended for oligosaccharide reduction in cowpeas however their efficiency is variety dependent. These processing methods promise improved utilization or consumption of cowpea in the sense of curbing flatulence associated with beans meal.