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

Authors: BORBI, MAKAFUI - Michigan State University; WEATHERSPOON, LORRAINE - Michigan State University; Wiesinger, Jason; JASKSON, JOSE - Michigan State University; Glahn, Raymond; BOURQUIN, LESLIE - Michigan State University; DOLAN, KIRK - Michigan State University

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2024
Publication Date: 11/12/2024
Citation: Borbi, M., Weatherspoon, L., Wiesinger, J.A., Jaskson, J., Glahn, R.P., Bourquin, L., Dolan, K. 2024. Effects of different processing methods on the functional, nutritional, and physicochemical profiles of cowpea leaf powder. Journal of Food Science. Vol. 89, Issue 12, pp. 8715-8729. https://doi.org/10.1111/1750-3841.17569.
DOI: https://doi.org/10.1111/1750-3841.17569

Interpretive Summary: Indigenous fruits and vegetables are a valuable source of fresh food, but their use is hindered by seasonal availability and perishability. In addition, their nutritional compositions and health benefits are largely unknown, especially after cooking and processing. Cowpea leaves are an indigenous food in many parts of West Africa, and can be consumed freshly cooked, or dried and milled into a powder for long term storage. The aim of this study was to process cowpea leaves into powder and determine the effect of five home-cooking methods on their protein, functional, physicochemical, mineral 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 60oC. Cowpea leaves contain up to 20% protein, and are a rich of source 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. However, the heavy metals aluminum and arsenic where in high concentrations, mostly likely from the milling process and soil contamination. If processing measures can be controlled to minimize heavy metal contamination, cowpea leaf powders could be potentially incorporated into foods to improve functional properties and nutrient intake.

Technical Abstract: 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 60oC. 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.