Effect of retort processing on the conversion of soybean isoflavones and Soyasaponins in flexible pouches

Abstract This study investigated the effects of retort processing on the conversion of bioactive components in soybeans, including isoflavones and soyasaponins, by analyzing their decomposition and metabolic intermediates. The experiment included four soybean samples: soaked soybeans (SS), retort-processed soaked soybeans (RSS), soaked + boiled soybeans (SBS), and retort-processed soaked + boiled soybeans (RSBS). Retort processing significantly increased the content of isoflavone glycosides (genistin, daidzin, glycitin) and group B soyasaponins in soaked soybeans and boiled soybeans after soaking ( p < 0.05). Specifically, in the RSS group, retort processing increased genistin content by 104.6% (from 88.85 µg/g to 181.77 µg/g), followed by daidzin (from 92.27 µg/g to 174.64 µg/g) and glycitin (from 133.20 µg/g to 216.83 µg/g). In the SBS group, retort processing showed the highest increase in genistin, followed by daidzin and glycitin. Further, retort processing increased soyasaponin I, II, and III in RSS and RSBS groups. These changes suggest results of the conversion of malonyl-isoflavone glycosides and DDMP-conjugated soyasaponins among soybean bioactive compounds to isoflavone glycosides and group B soyasaponins, respectively, during retort processing. Meanwhile, changes in the contents of isoflavone aglycones (genistein, daidzein, glycitein) and soyasapogenol B were not significant, likely because the retort process failed to decompose sugar moieties of isoflavone and soyasaponin glycosides fully. These results suggest that the retort process may play an important role in promoting the creation of intermediates in the decomposition process from soybean isoflavones and soyasaponins. Graphical Abstract