College of Food Science and Technology, Nanjing Agricultural University, Nanjing, PR China.
J Sci Food Agric. 2019 Jan 30;99(2):861-867. doi: 10.1002/jsfa.9256. Epub 2018 Oct 3.
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.
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.
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.
乳酸菌发酵使豆浆形成类似酸奶的产品，同时伴有蛋白质酸性凝固。目前尚不清楚发酵过程中大豆蛋白的凝固是否会影响摄入后的蛋白质消化率。本研究采用体外胃肠消化（GIS）法，对不同 pH 值（6.0、5.7、5.4 和 5.1）的豆浆（pH 6.3）和大豆酸奶（SY）进行了对比研究。
乳酸发酵使豆浆的 pH 值逐渐降低至 330.0 min 时的 5.1。pH 值的降低导致体积加权平均直径 D[4,3]和 D[v,90]分别从 0.81 µm 增加到 97 µm 和 1.82 µm 增加到 273 µm。在 pH 值为 6.0 至 5.7 之间，大部分蛋白质的溶解度下降。GIS 的应用使 SY 样品，尤其是 SY-5.7、SY-5.4 和 SY-5.1，显示出主要峰约为 10 µm 的颗粒，并且与豆浆相比，可溶性蛋白质含量也较低，减少百分比分别为 18%、28%和 43%。GIS 过程中大豆蛋白的裂解模式几乎不受样品 pH 值的影响。然而，在 SY-5.7、SY-5.4 和 SY-5.1 中，33.9 kDa 处的条带数量较少。
本研究结果表明，乳酸发酵改变了大豆蛋白的消化率。随着蛋白质凝固过程的进行，SY-5.7、5.4 和 5.1 的生物可利用蛋白质含量低于豆浆。 © 2018 化学工业协会。
