A Comparative Study of the Syneresis of Yam Starches and other Modified Starches

The syneresis of starch gels from 19 yam cultivars (belonging to 4 Dioscorea species and complex of species) and 5 modified starches were studied during refrigeration (4°C) and freezing (-20°C). Syneresis of starch gels evolved on refrigeration at the onset from zero and remained constant between 20% to 60% after 8 weeks of storage for all the yam species. The cultivars Daminangba (Dioscorea alata) and Assawa (Dioscorea cayenensis) were the most refrigeration-resistant. During freezing, syneresis of yam gels evolved from zero and remained constant in the 56 - 70% interval for the D. alata, 35 - 70% for the D. cayenensis-rotundata complex, and 37 - 55% for D. dumetorum and D. esculenta. The Kpokpokpo (D. cayenensis-rotundata) was the most freeze-resistant cultivar. The resistance during refrigeration of Daminangba and Assawa, as well as the freeze resistance of Kpokpokpo were in all cases less than those of Amioca and Colflo 67, the best modified commercial starches. Treatment of yam gels with appropriate doses of hydrophilic ingredients might be necessary to reduce their syneresis to acceptable levels. KEY WORDS: Syneresis, Refrigeration, Freezing, Stability, Yam starch. The Journal of Food Technology in Africa Volume 7 No.1, 2002, pp. 4-8