Comparative Study of Two Cowpea (Vigna unguiculata L. Walp) Varieties: Biochemical and Phytochemical Composition, Glycemic Index and Glycemic Load

Abstract

Cowpea is a nutrient-dense legume with potential relevance to diets characterised by high carbohydrate intake. The aim of this study was to conduct a comparative assessment of the nutritional value of two cowpea varieties in order to determine the Glycaemic Index (GI) and Glycaemic Load (GL) in apparently healthy subjects. This was an experimental study including 18 adult subjects who consumed a test food each day, calculated to provide 50 g of available carbohydrate (anhydrous glucose, white and red cowpea). GI and GL were determined using the standard method. The nutritional composition of white and red cowpea in terms of protein, lipid, fibre, starch, amylopectin and amylose contents ranged from 25.37 to 24.34 g; 1.78 to 1.73 g; 6.33 to 4.78 g; 64.19% to 64.96%; 22.59 to 23.11%; and 41.07 to 42.37%, respectively. Total polyphenol, flavonoid and antioxidant activity contents ranged from 143.95 to 156.89 mg GAE/100 g DM, from 14.49 to 14.30 mg QE/100 g DM, and from 15.87 to 45.34%, respectively. Both cowpea varieties exhibited low GI and GL values, but the GI and GL of white cowpea were markedly lower than those of red cowpea. GI and GL were 25.29% and 5.72 g for white cowpea, and 29.86% and 7.17 g for red cowpea. Both cowpea varieties showed good nutritional potential together with a low glycaemic index and glycaemic load. These findings demonstrate compositional differences between the varieties while confirming their low acute glycaemic responses in the apparently healthy adults studied.