Effect of drying method and variety on quality of cassava starch extracts

Cassava tubers are main sources of calories and dietary fibre for Nigerians. Cassava tubers are highly perishable and need to be processed immediately after harvest. Cassava can be used for human consumption, livestock feed or industrial purposes. Cassava starch is one of the main industrial products of cassava processing. The long drying times for cassava starch production during sun drying have necessitated the need for alternative drying methods. However, the quality of the starch obtained from these alternative drying methods needs to be investigated. Starch was produced from four different varieties (TME 1, TMS 30572, TMS 01/1235 and TMS 01/1181) of cassava using two drying methods (sun and oven drying at 40o C). The physical (yield and moisture content), functional (water binding capacity, swelling power and solubility) and pasting properties of the starch produced were investigated. The moisture content varied from 9.24 to 10.48%, with oven dried TME 1 having the lowest values and sun dried TMS 01/1181 having the highest value. The yield of starch obtained from drying the four varieties using the two drying methods increased from 458.5 to 687.2g per kg of cassava tuber. The water binding capacity, swelling power and solubility increased from 97.97 to 99.83 g water/g sample, 11.69–14.19 g/ml and 10.20 – 12.96% (g soluble solids/ g DM of whole starch sample) respectively, for the different varieties dried using the two drying methods. Peak viscosity, trough, break down, final viscosity, peak time and pasting temperature values for the four cassava varieties were in the range of 335.76–619.89 RVU, 135.67–192.35 RVU, 199.38–433.99 RVU, 196.01–257.72 RVU, 3.23–3.91 min and 70.05–72.95oC, respectively for the two drying methods. The values obtained from the cassava varieties considered were generally significantly different (except colour) which shows significant effect of cassava variety used on starch properties. Also, cassava starch samples dried at lower temperature have better functional and pasting properties. This indicates that alternative drying methods should be used at temperatures lower than 40oC in order to obtain products of high quality.