The Effect Of Fermentation Characteristics Of Lactic Acid Bacteria On The Quality Of Fermented Mixed Buffalo Milk

Buffalo milk is a feature of high-quality resources in southern China,with high nutritional value and great potential for development.Buffalo milk has many many technical problems in the processing and product development,because buffalo milk with high solid content,protein,fat and mineral content and it has different characteristics in the process from Holstein cow,such as:poor thermal stability and acid gel hardness is too high,etc.So screening of lactic acid bacteria with good fermentum characteristics,and study on it influence quality of mixture of buffalo milk and Holstein milk has important practical significance.The main results concluded as follows:(1)The results showed that the maximal difference of acid production rate of L978 was 18.46 °T/h and the minimum difference of strain V9 was 1.78 ° T/h.S393 is a viscose filamentous strain,and its fermentum skim milk has a length of 15.37cm.The strains were divided into the strain with rapid acid production rate(L978,S393,k01 and LH100)and the strain stable acid production rate(Y450L,XPL,V9,S937 and k01)according to the change of acid production rate after the growth retardation.Results The strains were homolactic fermentum(Y450L,k01,S393 and S937)and heterolactic fermentum(L978,XPL,V9 and LH100)according to the metabolic type,and the acid producing rate,metabolic type and viscose were selected.S393,Y450,L978,XPL and S937 were the experimental strains.(2)Study on the effect of different fermenting strains on the quality of mixed fermented milk,5 strains of different fermenting strains were selected to ferment mixed milk of different proportions.Through texture profile analysis(TPA),laser confocal microscopy(LSCM)And their micro structure and volatile constituents were determined by SPEM GC/MS.The results showed that the hardness and chewiness of the mixed milk of S937 were significantly lower than those of the other four strains(P<0.05),and the cohesiveness and adhesiveness of the mixed milk is significantly higher than those of the others(P<0.05).The results showed that hardness and chewiness of the fermented mixture of S393 and L978is significantly higher than the fermented mixture of Y450L and XPL(P<0.05);Hardness,elasticity,stickiness and chewiness decreased significantly with the addition of buffalo milk(P<0.05).With the decrease of buffalo milk content in the mixed milk,the number of pores in the fermented milk sample increased and the pore size became smaller,and the gel structure was compact.S937 fermented milk samples had the lowest volatile species,only 26 species,while the S393 fermented milk samples had a maximum of 36 volatile substances.The relative percentage of the volatile substances in mixed milk samples was found to be the same The relative abundance of the volatiles in the fermented S393 and Y450L strains was similar,and the relative abundance of the volatiles in the samples fermented by L978 and XPL were similar,but both of them were different due to the specific strains Acid production rate of different and different.(3)The changes of water-holding capacity of mixed fermented milk during storage were studied and the relationship between the fermented milk and texture was analyzed.The hydrogen proton density of fermented mixed milk samples during storage was determined by LF-NMR.It is found that the hydrogen proton density of homolactic fermentum is higher than that of stable acid-producing strain Y450L,Among them,the variation range of hydrogen proton of S3 93 fermented skimmedHasten milk was 336.74,and the maximal variation range of Y450L mixed milk containing 50%buffalo milk is 1907.41.The heterolactic fermentum L978 had a good water-holding capacity during the storage period.The proton change rate of the fermented pure skim milk was 608.96,while that of the stable acid-producing strain XPL The maximum variation of milk was 2128.72.The water-holding capacity of the mixed milk fermented with each strain decreased first and then decreased with the decrease of buffalo water content.The ropy strain had a good effect on the water-holding capacity of the fermented milk during the storage period,and the hydrogen proton change of the fermented milk was only 272.45.The hardness of fermented milk samples increased with the storage time,and the hardness has maximum value of S393 fermented milk is 1.968N at 21d.Y450L and XPL had a smaller change in hardness than the strains S393 and L978.The cohesiveness of the mixed-milk samples of the ropy strains changed a lot during the storage period.The elasticity of the fermented mixed milk samples decreased with the storage time,and the elasticity of the pure skim milk of S937 was 34.64mm at 21d.In addition,during the storage period,the change of the strain with rapid acid production rate S393 and L978 was greater than that of the smooth fermentum of the the strain stable acid production rate strain,while the viscosity of the fermentum mixture was affected by the protein content and protein Structural effects.It was found that the hardness and hydrogen proton density of fermented mixed milk were negatively correlated with the hydrogen proton density,and the correlation of the mixed milk with the amount of buffalo milk added in the mixed milk Decreased.