Effect of Cooking on Isoflavones, Phenolic Acids, and Antioxidant Activity in Sprouts of Prosoy Soybean (Glycine max)

Abstract

Soy sprouts possess health benefits and is required to be cooked before consumption. The effects of cooking on the phenolic components and antioxidant properties of soy sprouts with different germination days were investigated. A food-grade cultivar Prosoy with a high protein content was germinated for 1, 2, 3, 5, and 7 d and cooked till palatable for 20, 20, 5, 5, and 7 min, respectively. Total phenolic content (TPC), total flavonoids content (TFC), condensed tannins content (CTC), individual phenolic acids, isoflavones, DPPH, ferric-reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC) of raw and cooked sprouts were measured. Cooking caused significant losses in phenolic content and antioxidant activities, and maximum loss was on day 3 > 5 > 7, including TPC (32%, 23%, and 15%), TFC (50%, 44%, and 20%), CTC (73%, 47%, and 12%), DPPH (31%, 15%, and 5%), FRAP (34%, 25%, and 1%), and ORAC (34%, 22%, 32%), respectively. Cooking caused significant losses in most individual phenolic acid, benzoic group, cinnamic group, total phenolic composition, individual isoflavones, and total isoflavones. The losses of phenolic acids such as gallic, protocatechuic, hydroxybenzoic, syringic, chlorogenic, or sinapic acids during cooking were not compensated by the increases in trihydroxybenzoic, vanillic or coumaric acids on certain days of germination. Cooking caused minimal changes in phenolic acid composition of day 1 and 2 sprouts compared to 3, 5, and 7 d sprouts.

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“…In fact, isoflavones consist of two forms, aglycone forms and conjugated forms including glucoside type, acetylgucoside type, and malonyglucoside type. Approximate isoflavone contents of soybean and its products from various experiment researches are shown in Table (Zhu, Hettiarachchy, Horax, & Chen, ; Ishihara, Singh, Chung, & Tam, ; Baiano, Terracone, Gambacorta, & La Notte, ; Chan et al., ; Cvejic, Tepavcevic, Bursac, Miladinovic, & Malencic, ; Oh, Hwang, & Lim, ; Ma & Huang, ; Chen & Chang, ; Xu, Bin, & Xu, ; Kumari & Chang, ; Szymczak et al., ; Morales‐de La Pena, Martin‐Belloso, & Welti‐Chanes, ; Lee, Hwang, Son, & Cho, ; Niyibituronsa et al., ). Although the amount of aglycone form was little in natural food, it could be elevated greatly after fermentation.…”

“…The data of germinated soybeans were obtained from Zhu et al. (); Chen & Chang () and Kumari & Chang ().…”

“…. (2015) and Kumari & Chang (2016). g The data of cooked soybean sprouts were obtained from Kumari & Chang (2016).…”

“…(2015) and Kumari & Chang (2016). g The data of cooked soybean sprouts were obtained from Kumari & Chang (2016). The soybean sprouts were cooked by boiling in tap water for different times (20 min for 1 and 2-day germinated sprouts, 5 min for 3 and 5 day sprouts and 7 min for 7-day germinated sprouts).…”

“…l The data of fermented soybean products (soybean paste, sauce, sufu, miso, douchi) were obtained from Xu et al (2015). & Xu, 2015;Kumari & Chang, 2016;Szymczak et al, 2017; Morales-de La Pena, Martin-Belloso, & Welti-Chanes, 2018; Lee, Hwang, Son, & Cho, 2019;Niyibituronsa et al, 2019). Although the amount of aglycone form was little in natural food, it could be elevated greatly after fermentation.…”