ABSTRACT
The effects of natural fermentation on the stability or shelf life of adhesives produced from starch of two cassava varieties (Manihot utilissima and Manihot palmate) were studied. It was observed that the HCN content of the Manihot utilissima reduced from 35.74±0.11 mg/kg for unfermented starch sample to 6.93±0.25 mg/kg after 5 days of fermentation (p = 0.037), while the sample’s pH increased from 4.60±0.05 to 6.89±00 respectively. However, the reduction in HCN concentration and corresponding increase in pH for manihot palmate were only marginal, as the concentration of HCN in the starch reduced from 2.49±0.12 to 0.89±0.26 while the pH increased from 6.02±0.04 to 6.35±0.05 after five days of fermentation. The viscosity test conducted at room temperature for a period of 30 days to determine the stability or shelf of the produced adhesives show that adhesives produced from unfermented Manihot utilissima starch sample as well as samples of that cassava variety fermented for only 1 day have longer shelf-life as exemplified by the relative stable low viscosity of the adhesive over the 30 days test period with a highly significant effect, (p = 0.018). The drying time of Manihot utilissima was significantly high at 7.1±0.01 minutes (p = 0.041) and remained relatively stable for the 30 days storage time. The results therefore show that the higher the cassava starch acidity the lower its viscosity, the higher its drying time and the longer its shelf-life.