Development stage, storage temperature and storage duration influence phytonutrient content in cowpea (Vigna unguiculata L. Walp.)

Abstract

Cowpea (Vigna unguiculata) plays an important role in sustainable food security and livelihood improvement in Sub-Saharan Africa (SSA). The crop is rich in phytonutrients and minerals, which are key in solving malnutrition and hunger crisis, a major challenge in SSA. However, physiological status, storage temperature and duration affect phytonutrient levels and postharvest life of the leafy vegetable. Despite the significant importance of cowpeas, the maturity and postharvest storage effects on quality of the leafy vegetable remains unrevealed. The aim of this study was to analyze the dynamics of phytonutrients in cowpea leaves during development under field conditions in Kenya and in storage. The total carbohydrates (glucose, fructose, sucrose and starch) were highest at 90 d after planting (105.9 ± 2.5 g kg-1) compared to 30, 60 and 120 d. The total Phenolics (Gallic acid equivalents) increased gradually with age up to 12.0 ± 0.2 g kg-1 by 120 d. Catechin equivalent flavonoids, trolox equivalent antioxidants (TEA) and chlorophyll were highest in concentrations at 60 d after planting with 8.0 ± 0.5 g kg-1, 26.19 ± 0.5 g kg-1 and 5.7 ± 0.4 g kg-1, respectively. Quercetin equivalent flavonoids and total carotenoids did not show significant changes with age, while mineral concentration dynamics were specific for each element. Storage of cowpea leaves at room temperature (50–55 % relative humidity) led to a stronger decline of phytonutrients after 4 d, but mostly they remained stable at cold storage (5 °C). Results of this study highlight the importance of developmental stage at harvest, storage conditions and duration for the optimal availability of phytonutrients in freshly consumed leaves and for postharvest management strategies.

A review of the contribution of cowpea leaves to food and nutrition security in East Africa

“…TA B L E 3 Nutritional composition of cowpea vegetables (mg/100g dry weight) in which the phytochemicals strongly declined at 4 days (Kirigia et al, 2018). Most of the farmers of cowpea leaves still rely on traditional techniques for handling the vegetables along the value chain resulting in greater losses (Gogo et al, 2018).…”

“…reported postharvest losses exceeding half of the production quantity of cowpea leaves and other AIVs among some of the farmers in Kenya. Storage conditions based on their temperature affect the physicochemical attributes of cowpea leaves in terms of antioxidant properties, nutritional quality, color, and texture(Kirigia, Winkelmann, Kasili, & Mibus, 2018;Natabirwa, Mukiibi, Zziwa, & Kabirizi, 2016). The quality of cowpea leaves deteriorates with storage.…”

Development and challenges of green food in China

“…Food possibly spoils in warehouse as a consequences of pest attack and biological changes (respiration and rancidity development). Decay of food depends on composition, humidity and temperature of storage [66,67] . In warehouse, for successful storage of roots, tubers and other foods, it is necessary always to select high quality products with no physical damage or pest attack.…”

Investigation on morphology and physiology of potted rose grown with light from microwave-plasma and high-pressure sodium lamps

“…with 1.5 mL ethanol (80% v/v). Primary soluble sugars (glucose and fructose) were determined enzymatically according to Zhao et al (2010) with slight modifications as described by Kirigia et al (2018).…”