Preliminary Study On Aroma Generation Of Fermented Soymilk By Lactobacillus Plantarum

The nutrition and health-care function of fermented soymilk earned consumers' favor. However, the industrialization of fermented soymilk was limited because of its beany flavor. In the present study, the fermentation characteristics of fermented soymilk was analyzed. The relationship between the flavor compounds and odor indexs of fermented soymilk was also investigated. The results provide idea and theorical data for commerization of fermented soymilk.After the flavor and sensory evaluation of fermented soymilk by 102 strains of Lactobacillus plantarum, higher flavor and odor index score strains of L.plantarum IMAU60042, L. plantarum P8, and lower score strains of L. plantarum IMAU30118, L. plantarum IMAU60051 were enrolled as our study. The four strains of Lactobacillus plantarum were involved in fermented soymilk with an inoculation of 2.0×107cfu/mL, and then the products with fermentation final pH 4.5 were stored at 4℃for 14d. Fermented samples were collected at 0d, 1d, 7d and 14d for determination of viable counts, pH, titratable acidity(TA), viscosity, syneresis and free amino nitrogen.The flavor substances of fermented soymilk during storage were determined by GC-MS.As a result,1) The viable counts of L. plantarum IMAU60042 and L. plantarum P8 in fermented soymilk were above 3.39×10~8cfu/mL. The TA of soymilk fermented by L. plantarum IMAU60042 and L. plantarum P8 went up to 87.36°T or73.40°T, respectively. The average viscosity and syneresis rates of soymilk fermented by L. plantarum IMAU60042 and L. plantarum P8 with better fermentation characteristics were 1358.67cp or 1161.00cp and 13.17% or 15.84%, respectively. For another two strains, the viable counts of soymilk fermented by L. plantarum IMAU30118 and L. plantarum IMAU60051 were lower than 1.70×10~8cfu/mL.Weak acid production, the TA of soymilk fermented by L. plantarum IMAU30118 and L. plantarum IMAU60051 were less than 65.81°T. The average viscosity and syneresis rates of soymilk fermented by L. plantarum IMAU30118 and L. plantarum IMAU60051 with worse fermentation characteristics were 774.00cp or 770.00cp and 18.36% or 20.00%, respectively.2) Thirty-nine volatile flavor compounds were detected in fermented soymilk and they respectively belonged to alcohols(13), aldehydes(6), ketones(8), benzene compounds(2), acids(7), esters (2) and hydrocarbon compounds(1).3) Soymilk fermented respectively by L. plantarum IMAU60042 and L. plantarum P8 was of bean pleasure flavor and moderate sour taste which were associated with the presence of diacetyl, 2-butanone, 2-hydroxyl-3-pentanone, acetaldehyde, acetic acid, pentanoic acid and acetone. Soymilk fermented respectively by L. plantarum IMAU30118 and L. plantarum IMAU60051 was of smelly, abnormal and beany flavor with low bean pleasure flavor which were associated with the presence of hexanol, hexanal, 2-pentylfuran, 1-octen-3-ol, benzaldehyde, acetaldehyde and acetic acid.4) Acetic acid and acetaldehyde were also the main flavor substances of soymilk fermented and their ratio also had effect on the flavor of fermneted soymilk.