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ssss1 Schematic of a dry bean seed.

Source: Adapted from Georges (1982).

The intact seed coat (botanically termed the testa) has an important function in protecting the legume from damage due to water absorption and microbial contamination. This is particularly important during harvest and storage. The seed coat consists of 7.7% of the total dry weight in the mature bean with a protein content of 5% (dry‐wt basis) (Powrie et al. 1960; Kigel et al. 2015). Slow darkening or nondarkening seed coats are more desired in the market because they are perceived to be fresh, high‐quality beans (Erfatpour et al. 2021).

The major components in the seed coat structure of legumes include the waxy cuticle layer, the palisade cell layer, the hourglass cells, and the thick cell‐walled parenchyma. These structures are presented in ssss1. These structures have been identified using scanning electron microscopy (SEM) in white beans, navy, pinto, and adzuki beans (Sefa‐Dedeh and Stanley 1979b; Swanson et al. 1985), cowpeas (Sefa‐Dedeh and Stanley 1979a), and broad/faba beans (McEwen et al. 1974).