Effects of different processing methods on the functional, nutritional, and physicochemical profiles of cowpea leaf powder

Indigenous fruits and vegetables can improve food security and biodiversity. However, their use is hindered by perishability, seasonal availability, cooking losses, lack of nutritional composition data, and connections to low socioeconomic status. This study aimed to process cowpea leaves into powder and determine the effect of five home-cooking methods on their protein, functional, physicochemical, and heavy metal profiles. Cowpea leaves were boiled, blanched, steamed, sous-vide cooked, and stir-fried, at 5, 10, and 15 min before dehydration at 60°C. Cowpea leaves contain protein up to 20 g/100 g. The leaves are rich in calcium, potassium, and zinc, providing up to 70% of the adult recommended dietary allowance for calcium and potassium per 100 g of powder. Cowpea leaf powder exhibited good water/oil absorption and rehydration capacities. Sous-vide and steamed cowpea leaves provided an overall superior nutritional profile (p ≤ 0.05). Heavy metals in the cowpea leaf powders were below the WHO permissible limits except for aluminum and high arsenic levels. This study demonstrated that cowpea leaf powders could be potentially incorporated into foods to improve functional properties and nutrient intake.