Value addition and influence of succinylation levels on the quality of wild yam ( Discorea villosa) starch

Background: Recent increase in demand for starch in food applications has called for research into other new sources. Dioscorea villosa is an underutilized wild yam starch source and its starch was isolated and succinylated at 0, 3, 6, 9 and 12% (0-12% succinic anhydride: 88-100% starch) using standard procedures. The degree of substitution, chemical composition, functional properties, anti-nutritional factors, pasting properties, atomic spectra and α-amylase and α-glucosidase activities of the samples were determined using standard methods. The data obtained were analysed using ANOVA.

Results: The percentage succinyl content and degree of substitution increased from 0-10.45% and 0-0.19% respectively. The amylose, amylopectin, α-amylase and α-glucosidase activities varied from 49.88-59.70%, 40.29-50.11%, 0.17-0.96 and 0.62-10.07 respectively. The phytate, tannin, oxalate and saponin contents ranged from 0.08-0.13 mg g-1, 0.04-0.08 mg g-1, 0.21-0.31 mg g-1 and 0.18-0.26 mg g-1 respectively. The peak viscosity, trough, break down, final viscosity, set back, peak time and pasting temperature values ranged from 94.32-274.69 RVU, 83.50-197.50 RVU, 7.94-81.28 RVU, 113.69-367.39 RVU, 30.14-173.89 RVU, 5.30-6.94 min, and 84.78-94.70 °C respectively.

Conclusion: Isolation and subsequent succinylation improved the wild yam starch quality and reduced its anti-nutritional factors. Succinylation at 9% had the best functional and pasting properties, therefore making it suitable as a potential emulsifier, fat replacer to prevent obesity and stabilizer in food applications. Its limited enzyme activities make it desirable in the production of slowly digestible food products, such as snacks for diabetic patients.