An engineering, microbiological and sensory study of yogurt from soymilk.

摘要

The current literature on soymilk yogurt is reviewed. Methods of measurement of biomass, carbohydrate and fat content of the milk are discussed.;Biomass, product and substrate concentrations were measured for mixed culture fermentations of Lactobacillus bulgaricus and Streptococcus thermophilus in soymilk. The methodologies used to make these measurements were checked and evaluated in this study.;To increase stachyose consumption during yogurt preparation, fortification of soymilk was delayed until 2.5 hours had passed in the soymilk fermentation process. The method of fortifier addition "in the middle" or "delayed fermentation" of the fermentation is discussed. Also discussed, is variation of the type of fortifiers added to the fermenting soymilk.;After adjusting the inocula in soymilk for 168 hours, the typical bovine milk yogurt bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus, consumed 0.08 g/100 ml of stachyose sugar (desirable) in soymilk during fermentation. However, preparation of the inocula on nonfat dry milk powder yielded bacteria which displayed oligosaccharide formation (undesirable) during fermentation of soymilk.;Dannon yogurt and soymilk yogurt made by fortification with 25% fructose solution, Carnation evaporated milk or nonfat dry milk were evaluated by a trained taste panel for attributes of sweet, sour and beany flavor and for viscosity. In addition, analytical measurements were made for total sugar concentration in the soy-yogurts using HPLC, for viscosity with a Brookfield viscometer and for acid formation using pH. Sour and sweet flavors displayed no relation between analytical and sensory measurements. Viscosity showed high linear relationship between analytical and sensory measurements.;Gas phase head space analysis of CO