Study On Fermentation Strains And Storage Stability Of Koumiss

L.helveticus H9,L.casei Zhang,L.plantarum P-8 three strains of lactic acid bacteria and S.cerevisiae QH2-2 one strain of yeast bacteria,which have excellent probiotic properties,are used in this present study.The fresh horse milk in Xilinhaote was fermented with single bacteria and compound bacteria,and then the indexes(pH,TA,living bacteria number,sensory evaluation,protein and fat)were compared and analyzed.The best fermentation conditions,the best strain combination and the strain proportion be selected.In order to get stable koumiss fermented by pure strain,the formula of stabilizer was optimized by response surface methodology on the basis of single factor experiment.The pH,TA,viable count and organization condition of the koumiss were measured at low temperature(4?)and room temperature(25?).The results showed that the optimum temperature of koumiss fermented by pure lactic acid bacteria was 37?.L.helveticus H9 and L.plantarum P-8 could ferment the koumiss by single bacteria.Under the condition of 30?,fermented 9h,the best combination was L.helveticus H9: L.plantarum P-8: L.casei Zhang: S.cerevisiae QH2-2(1:1:2:1).The acidity of mixed bacteria fermentation was greater than single bacteria and shortened the fermentation time,improved the tissue state and taste of the koumiss.The combination of S.cerevisiae QH2-2 was more close to the traditional koumiss in the taste and flavor.The content of protein was 2.03~2.70g/100 mL and fat was 1.68~2.13g/100 mL,in fermented koumiss by pure lactic acid bacteria,which was close to that of traditional koumiss.High fat pectin,propylene glycol alginate(PGA)and soybean polysaccharide were selected as stabilizers for koumiss,and the single factor test was carried out by the centrifugal precipitation rate,viscosity and sensory evaluation.The result of single factor test is the optimum dosage of high fat pectin was 0.10%,the optimum dosage of PGA was 0.06%,and the optimal dosage of soybean polysaccharide was 0.15%.The response surface method was used to optimize the addition of high fat pectin,PGA and soybean polysaccharides.The proportion of the best compound stabilizer was as follows: the addition of high fat pectin was 0.08g/100 mL,the addition of PGA was 0.06g/100 mL,and the amount of soybean polysaccharide was 0.12g/100 mL.According to the formula,the koumiss has the best sensory evaluation and good stability.Under 4? low temperature,the number of lactic acid bacteria and yeast maximum in 3 days,the number of living bacteria was in the stable period,and the number of living bacteria decreased obviously at 14-28 days.Under 25? room temperature,the number of living bacteria in the koumiss decreased obviously and the physical state changed in 3 days,part of the whey was precipitated.Therefore,it is best to drink koumiss at 4? low temperature for 14 days,at 25? room temperature to drink koumiss within 3 days.Compared with the koumiss without stabilizer,the koumiss with stabilizer significantly improved the whey precipitation and flocculation.