Hypoglycemic effect of biscuits containing water-soluble polysaccharides from wild yam (Dioscorea hispida Dennts) or lesser yam (Dioscorea esculenta) tubers and alginate

To determine the hypoglycemic effects on biscuits supplemented with single or mixture of hydrocolloids, crude water soluble polysaccharides (WSP) extracted from tubers of either wild yam (CWY) or lesser yam (CLY) and commercial alginate powder (ALG) were used. Five different types of hydrocolloid mixture were prepared, namely CWY, CLY, ALG, mixtures of CWY and ALG (CWY/ALG) and CLY and ALG (CLY/ALG) at a ratio of 1:1. The biscuits (BIS) formula were incorporated with 2.5% of these hydrocolloid mixtures and biscuit without addition of hydrocolloid (NON-BIS) was used as control. A meal tolerance test (MTT) was carried out by feeding each biscuit to alloxan-induced hyperglycemia rats respectively, and the blood glucose levels were monitored for the first 120 min. A long term antihyperglycemic effect was monitored weekly for their blood glucose levels and changes in body weight for 4 weeks, followed by the determination of the short chain fatty acids (SCFAs) profile from the caecum digesta at the end of feeding treatment. As a comparison, standard feed was respectively fed to a group of hyperglycemia rats (HYP-STD) and a group of normal rats (NOM-STD). The MTT results indicated that all hydrocolloid containing biscuits affected the absorption of glucose into the blood and were able to maintain it at a normal level. ALG-BIS was the most effective, followed by CWY/ALG-BIS, CLY/ALG-BIS, CWY-BIS and CLY-BIS. After 4 weeks, the glucose blood levels were significantly reduced, showing a pattern of reduction similar to that of the MTT. The magnitude of reduction was as follows: 57% (ALG-BIS), 50% (CWY/ALG-BIS), 49% (CLY/ALG-BIS), 39% (CWY-BIS), 35% (CLY-BIS) and 2% (NON-BIS) respectively. The hyperglycemic rats fed with biscuits gained about 7-11% in body weight and opposite results were found on hyperglycemic rats fed with standard feed. Despite the variation in composition, the order of concentration of the SCFAs was similar, i.e. acetic acid propionic acid butyric acid. It may be concluded that biscuits added with WSP, extracted from tubers of either wild or lesser yam, or their mixtures with alginate, have significant hypoglycemic effects.