Mutation Breeding Strain Of High Conversion Ratio Of Reducing Sugar In Solidified Honey-skimmed Milk Acidophilus Milk

Soidified honey-skimmed milk acidophilus milk is a fully new yoghourt whose materials are honey and skimmed-milk and fermented to lactic acid by lactobacilli.Casein in skimmed milk will be denatured during fermentation.Besides of intrinsic nutrition and flavor of common yoghourt,this new yoghourt also possesses of exceptive faint scent of honey. Soidified honey-skimmed milk acidophilus milk is a dairy products with good developmental future.Through mutating two acidophilus milk production strains (Lactobacillus delbrukeii subsp.bulgaricus and Streptococcus salivarius subsp.thermophillus),two high conversion ratio of reducing sugar mutant strains Lb-20M-5 and St-20M-18were obtained. Conversion ratio of reducing sugar were 31.96%和33.15%,and increased 35.54 % and 31.55% respectively compare of the lactobacilli before mutation.The mutant strains have choiceness geneticstability.Conversion ratio of reducing sugar reflects transformation of lactic acid. This paper studied how fermentation time and temperature and initial fermentation liquid pH effected the conversion ratio of reducing sugar in honey acidophilus milk. Single factor and orthogonal experiment design methods were applied to determine the optimum fermentation parameter i.e.fermentation time 42°C,fermentation temperature 4h and initial pH 6.8 in the essential condition of the 8% for honey,10% for skimmed-milk and 2% mixed inoculation that the proportion of two lactobacilli1:1. Conversion ratio of reducing sugar was 36.18%and increased 32.72% compare of the lactobacilli before mutation. The quality of the acidophilus milk fermented by the mutatant strains with honey and skimmed-milk were all right,and the o mutatant strains have achieved the requirement standard of acidophilus milk GB19302-2003.