Rheological and thermal properties in relation to molecular structure of New Zealand sweetpotato starch

New Zealand sweetpotatoes (kumara) (Ipomoea batatas) represent under-utilized genetic resources for sweetpotato quality. In this report, starches from 7 New Zealand sweetpotato varieties with commercial significance were studied for swelling power, water solubility, rheological properties, gelatinization and retrogradation. Diversity in these physicochemical properties has been recorded among the starches. Pearson correlation analysis showed that some of the internal unit chain parameters of amylopectin such as the quantity of fingerprint B-chain and length of B-chains are significantly related with the swelling and gelation properties of the starch. Multiple structural/compositional factors contribute to the rheological and thermal behaviours of the starches. Some of the sweetpotato starches had certain rather similar physical properties as compared to maize and potato starches (1 genotype each) employed for comparison. This suggests that these sweetpotato starches may replace maize/potato starches for specific applications.