Studies On The Development And Stabilizati-On Mechanism Of Soymilk Beverage Fermen-Ted By Lactobacillus Acidophilus

Soymilk is a traditional,cheap and accessible product in China.As a result of the impact of traditional eating habits,people failed to realize its benefits.And the beany flavour also weakens its availability for a lot of consumers.To develope a soymilk beverage fermented by lactic acid bacteria can not only solve the problem of taste but also take the advantage of soybean nutrition.Moreover,it can provide regions lack of milk with inexpensive but high-quality vegetable protein functional beverages.Therefore,the development of soymilk beverage fermented by lactic acid bacteria is of great significance.Fermented soymilk beverage has the problem of instability caused by suspended fat and proteins sedimentation and so on.The optimum additives formulation and technology parameters were investigated by orthogonal regression test,response surface and ridge analysis,the result was showed as follow:composite emulsifier (monoglycerides:sucrose esters=2:1,HLB=8) 0.15%,CMC 0.24%, pectin 0.11%,sucrose 6%,sodium citrate 0.1%,sodium tripolyphosphate 0.13%,pH4.0 and homogenization pressure 25MPa.The developed fermented soymilk beverage was aivory-white, palatable and smooth emulsion,including 1.15%protein,0.72%crude fat,9.52%total solid,0.64%ash content.It was also showed 55.52°T acidity,19.11cP viscosity and 0.26μm particle diameter.17 kinds of amino acids,6 kinds of fatty acid and more than 20 kinds of characteristic flavors were detected.The product had a good physical stability and the living Lactobacillus acidophilus number maintained 3.38×10~6cfu/mL after 30 days storage under 4℃.The soybean protein was measured by SDS-PAGE and zeta-potential instrument.The results were showed as follow: molecular weight of soybean protein was mainly distributed in the areas of 77.08KDa,35.79KDa,34.69KDa,29.87KDa,while a few in the areas between 10 and 20KDa.The pH of isoelectric point was pH4.5.The effect of pH and concentration of polysaccharide(HMP/CMC) on the particle diameter,zeta-potential and sedimentation in HMP (CMC)-fermented soymilk were studied.During pH3.8～4.4,bridge flocculation happened between HMP and soybean protein with 0%～0.2% HMP added.Fermented soymilk with 0.3%HMP only could be stable at pH4.4 while the one with more than 0.3%HMP could be stable.With 0.3%～0.7%HMP,the particle diameter increased as function of concentration,zeta-potential stayed between -8～-25mv and sedimentation was less than 1.2%.The critical value of HMP concentration was 0.4%.During pH3.8～4.4,the zeta-potential of the fermented soymilk with 0～0.2%CMC stayed between 0～-20mv and sedimentation was as high as 30%.The one with 0.3%CMC became unstable while zeta-potential reached-14mv and particle diameter gone up to 22.58 after 3 days storage.lThe left ones with 0.4%～0.7%CMC got zeta-potential below -20mv,particle diameter 0.26μm and sedimentation below 1.0%.The critical value of CMC concentration was 0.4%.