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Lee et al. (1983) produced fractionated navy beans with a 90% cotyledon yield, which was further milled and air classified to yield a fine protein component (32% w/w; containing > 40% protein and 31% starch) and a coarse starch fraction (55% w/w; containing > 67% starch and 16% protein). These results were indicative of the general distribution of protein and starch within the cotyledon portion of the beans.

ssss1 SEMs showing structural components of dry navy bean: (a) seed cotyledon cells and (b) Starch granules embedded with a protein matrix (CW = cell wall, M = middle lamella, P = protein bodies, S = starch granules, P = protein).

Source: Original images by author, M.A. Uebersax.

The embryo is a relatively small portion of the seed mass (typically < 2%) but has a dramatic influence on seed quality. This biologically active component of mature seeds possesses high levels of enzymatic activity that are readily activated by optimum moisture and temperature conditions. The mobilization and oxidization of lipids high in unsaturated fatty acids produce highly oxidized off‐flavors. High temperatures (> 130°F) that may occur during even mildly adverse storage conditions will result in embryo damage with irreversible loss of seed vitality. It is commonly recognized that precursors of the germination process are initiated during ambient water‐soaking conditions. Thus, traditional overnight cold‐water soaking of beans activates many complex embryonic catabolic enzymes associated with seed spouting (e.g., proteases, amylases, pectinases, cellulases and phytases) and, therefore, enhances the water‐hydrating and water‐holding capacity of the bean.