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Does lactic fermentation influence soy yogurt protein digestibility: a comparative study between soymilk and soy yogurt at different pH
Author(s) -
Rui Xin,
Zhang Qiuqin,
Huang Jin,
Li Wei,
Chen Xiaohong,
Jiang Mei,
Dong Mingsheng
Publication year - 2018
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.9256
Subject(s) - food science , fermentation , chemistry , soy protein , lactic acid , digestion (alchemy) , bacteria , chromatography , biology , genetics
BACKGROUND Lactic acid bacteria fermentation allows soymilk to form a yogurt‐like product accompanied by protein acidic coagulation. It is not known whether the coagulation of soy protein during fermentation influences protein digestibility when ingested. In the present study, soymilk (pH 6.3) and soy yogurt (SY) at different pH (6.0, 5.7, 5.4 and 5.1) were subjected to in vitro gastrointestinal digestion (GIS) and a comparison study was conducted. RESULTS Lactic fermentation allowed the pH of soymilk to reduce gradually to 5.1 in 330.0 min. A decline in pH resulted in the volume‐weighted mean diameters D [4,3] and D [ v ,90] increasing from 0.81 to 97 µm and 1.82 to 273 µm, respectively. Predominant proteins lost their solubility between pH 6.0 and 5.7. Application of GIS allowed SY samples, especially SY‐5.7, SY‐5.4 and SY‐5.1, to reveal particles with a predominant peak at approximately 10 µm and also lower soluble proteins compared to soymilk, with reduction percentages of 18%, 28% and 43%. The cleavage pattern of soy protein during GIS was scarcely affected by the sample pH. However, a lower quantity of the band at 33.9 kDa was found in SY‐5.7, SY‐5.4 and SY‐5.1. CONCLUSION The results of the present study demonstrate that lactic fermentation altered soy protein digestibility. With the process of protein coagulation, SY‐5.7, 5.4 and 5.1 had a lower bioaccessible protein content compared to that of soymilk. © 2018 Society of Chemical Industry