Nutritional value of Vigna unguiculata (L.) Walp. accessions with different seed color

Background. Cowpea Vigna unguiculata (L.) Walp. has long been a cultivated crop in Africa, Southeast Asia, and the Americas. Cowpea seeds are renowned for their delicious flavor and high protein, carbohydrate, macro- and micronutrient content, and bioactive compounds. The crop is known for its antioxidant, anticarcinogenic and antibacterial properties. Food products made from cowpea seeds have nutritional value and are a staple in the diets of health-conscious individuals. The aim of the work was to determine the nutritional value of seeds of V. unguiculata accessions from the VIR collection of different ecogeographical origin, having different colors of the seed coat. Materials and methods. Thirty-nine accessions from the VIR collection were chosen for the study. The content of nutritious and bioactive compounds, i.e. protein, starch, anthocyanins, carotenoids, β-carotene and chlorophylls was determined. The variation of the anthocyanin content was revealed depending on the seed color. The amount of anthocyanins in seeds was determined by spectrophotometry, of protein by Kjeldahl, and starch by Evers. Chlorophyll, carotenoids and beta-carotene were determined spectrophotometrically. Results. The range of variation of the anthocyanins content in seeds is quite wide from 1.8 mg% to 404.4 mg%. The highest values were noted in black seeds (124.3-404.4 mg%). The content of total protein was within 18.8-30.5%, the range of starch variation was 42.6-57.1%, the content of chlorophylls a and b ranged from 0.13 to 3.7 mg%, and carotenoids and β-carotene were found in minimal quantities of 0.07-0.72 mg% and 0.01-0.14 mg%, respectively. Conclusion. In our experiment, the anthocyanin content of seeds influenced the color of the seed coat, but did not affect the protein, starch, carotenoid, and β-carotene levels. A significant association was also observed between the carotenoid content of seeds and the ecogeographical origin of the accession. A positive correlation (r>0.8) was found between the chlorophyll and β-carotene content, and between β-carotene and carotenoids, while a negative correlation was found between the starch and protein content (r= –0.81). The accessions k-1738 ‘Sibirski Razmer’ (Russia) and k-567 (India) demonstrated the best nutritional value for the complex of traits studied.

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