The Impact On The Characters Of Yogurt By Replacing Milk Protein With Soy Protein

Soy protein is resourceful and cheap. More importantly, it was full of nutrition and hashealth-promoting functional–properties. Soy proteins was used to substitute for milk proteinsto prepare yogurt in this paper. Thereby making the fullest use of soy proteins and improvingnutritional value and reducing cost of making yogurt. Therefore, it could possibly be used torelieve the problem of milk shortage in our country.Soy protein concentrate (SPC) and soy protein isolate (SPI) were used as rawmaterial.Flavor, rheological, sensory and chemical properties for yogurts whose milk proteinhad been replaced by soy protein were determined.10%,20%,30%,40%,50%,60%,70%(pro,w/w) milk protein of yogurts were replaced by soy protein respectively. And thecontent of protein was kept at2.8%(w/w) constantly. The study showed that compared withyogurt, the pH after7h fermentation of yogurt whose70%milk protein had been replaced bySPC increased from4.23to4.82, and acidity decreased from71.5°T to37°T; the waterholding capacity increased from51.85%to67.53%, brightness decreased from84.92to81.72.Compared with yogurt, The pH after7h fermentation of yogurt whose70%milk protein hasbeen replaced by SPI increased from4.23to4.53, and acidity decreased from71.5°T to49°T;water holding capacity increased from51.85%to64.11%, brightness decreased from84.92to83.81.Results showed that, the content of hexanal, whose mainly contributes to beany flavor,was significantly decreased when double-protein milk was fermented by lactic acid. Yogurtswhose milk protein had been replaced by SPC have few beany flavor components comparedwith Yogurts whose milk protein had been replaced by SPI. Yogurt whose70%milk proteinhad been replaced by SPC contain Isoflavone0.74mg/100g (dry weight) and has no saponin;compared with yogurt conjugated lipid increased0.07%and non-protein nitrogen increased0.1%. Yogurt whose70%milk protein has been replaced by SPI contain Isoflavone38.77mg/100g (dry weight), saponin21.03mg/100g (dry weight); compared with yogurtconjugated lipid increased0.21%and non-protein nitrogen content has no change. The resultsof sensory evaluation show that the yogurts whose30%milk protein has been replaced bySPC is great.