Cowpea storage under nitrogen‐modified atmosphere at different temperatures: Impact on grain structure, cooking quality, in vitro starch digestibility, and phenolic extractability

Abstract

Cowpeas were stored for 12 months under a nitrogen-modified atmosphere at 15, 20, and 25°C. Cowpeas analyzed immediately, without subjection to the storage period, constituted the initial sample. Long-term storage promoted changes in the cooking characteristics of the cowpeas as a result of a rigidized cotyledon structure. Hardened cowpeas exhibited lower percentages of starch hydrolysis. Even under nitrogen-modified storage, the higher temperatures of 20 and 25°C favored the structural alterations that hampered the enzymatic digestion of starch. The changes were minimal at 15°C, indicating that the combination of a nitrogen-modified atmosphere and the indicated temperature not only most accurately maintained the coat color, but also provided the best glucose release results. The storage period and the cooking procedure reduced the free phenolic and proanthocyanidin content of the cowpeas, regardless of the applied storage conditions. Increases in the extractability of bound phenolics were observed, regardless of the storage conditions. Practical applications Results of the present study contribute to the understanding of the effects of the storage conditions on the cooking and nutritional quality of cowpeas and may help the cowpea production chain to adopt proper technologies in order to guarantee a constant supply of high-quality cowpeas to consumers from the developed and developing countries. The color, physicochemical properties, and starch digestibility were considered in the determination of the quality of stored cowpeas.