Functional and pasting properties of cassava and sweet potato starch mixtures
Starch is an important carbohydrate contained in staple foods such as potato, wheat, maize, rice, and cassava. Native starches, irrespective of their source, are undesirable for industrial applications because of their inability to withstand processing conditions such as extreme temperature, diverse pH and freeze-thaw variation. In order to improve on the desirable functional properties, native starches are often modified. The functional and pasting properties of cassava starch and sweet potato starch mixtures at different ratios were investigated. Starches from four different cassava genotypes (‘Adehye’, AFS048, ‘Bankye Botan’ and OFF146) and one local sweet potato were used for the study. The swelling volume and swelling power of ‘Adehye’ and AFS048 starches decreased as the proportion of added sweet potato starch increased. The pasting and peak temperatures of cassava-sweet potato starch mixtures increased with higher proportions of sweet potato starch. However, peak viscosity and paste stabilities did not show any clear pattern. Ease of cooking of the starch was prolonged up to a ratio of 50:50 cassava-sweet potato starch mixture. The set back viscosity was improved for all the cassava varieties at a ratio of 20 per cent cassava starch to 80 per cent sweet potato starch. Overall results indicated that cassava and sweet potato starch mixtures could be employed industrially, where high pasting temperatures and low setback viscosity are required.