Effect of processing, fermentation, and aging treatment to content and profile of phenolic compounds in soybean seed, soy curd and soy paste

This study reports the effect of processing, fermentation, and aging treatment on the content and profile of 43 phenolic compounds in soybean seeds, soy curd (tofu), and soy paste (ChungGukJang, CGJ). Mean content of phenolic compounds was ranked as soybean seed = CGJ aged for 3 days (CGJ-3D) = CGJ aged for 6 days (CGJ-6D) > tofu (P < 0.0001). Low percent recovery (47.1%) of phenolic compounds in tofu was due to heating (boiling), leaching in water, filtering, coagulation, and whey exclusion during tofu making. Aging period did not affect the mean contents of 43 phenolic compounds in the CGJ, whereas it affected the phenolic acids contents in the CGJ (P < 0.01). Benzoic, ferulic, chlorogenic, gentisic, protocatechuic, or beta-Resorculic acid was major phenolic compounds in soybean seeds, tofu, CGJ-3D, or CGJ-6D. Especially, the CGJ-3D contained large amounts of isoflavone aglucons and phenolic acids compared to soybean seeds or tofu. (C) 2011 Elsevier Ltd. All rights reserved.