Effect of cowpea (Vigna unguiculata) processing methods on flatus causing oligosaccharides

Oligosaccharide contents of 5 cowpea varieties were studied in raw and processed samples. The average content of the oligosaccharides in whole raw cowpea were raffinose 1.19g/100g and stachyose 3.88g/100g with no varietal difference in the levels of raffinose. Stachyose levels showed difference due to variety. Dehulling resulted in a mean reduction of 30.25% for raffinose and 26.80% for stachyose while cold water soaking for 16hrs gave a mean reduction of 40.34% for raffinose and 35.29% for stachyose. Cooking for 40mins was sufficient to reduce the mean raffinose and stachyose contents to 47.06% and 36.85% respectively. Mean reduction of 47.90% for raffinose and 47.16% for stachyose were obtained when the cowpea was processed into bean cake. Cooking with potash reduced the mean raffinose level by 68.90% and 61.34% for stachyose. Hot water (80 degrees C) soaking for 4 hrs brought about a mean decrease of over 80% for both raffinose and stachyose. Processing time and treatment (processing method) affected the levels of the oligosaccharides more than variety. (C) 2000 Elsevier Science Inc.