The effect of processing on in vitro protein and starch digestibility and predictive glycaemic index of five Vigna unguiculata (cowpea) cultivars

Abstract

In this study, the effects of thermal processing on in vitro starch and protein digestibility in five different Vigna unguiculata cultivars were evaluated along with the predicted glycaemic index of each cultivar in its raw and processed form. Starch analysis was divided into total starch (TS), rapidly digestible starch (RDS) and resistant starch (RS). Samples were also analysed from a nutritional perspective and their correlations evaluated. Results showed that thermal processing reduced nutrient contents while increasing the protein digestibility. A significant increase was found in the RDS of processed samples (6.21 - 6.75%) in comparison to the raw samples (1.89 - 2.18%). Low glycaemic indices were also obtained in the raw samples and remained within the category of a low glycaemic index food even after thermal processing, suggesting cowpea could elicit low postprandial increases in blood glucose levels subsequent to processing.

Keywords

• cowpea
• glycaemic index
• protein digestibility
• Vigna unguiculata