Study On Propagation Culture Of LAB And Processing Of DVS Yogurt Starters

Consumers and scientific researchers pay more attention to the fermented goods for their nutritious and joyful taste with the development of dairy industry. Researchers presently study on DVS yogurt starter. It is significance to enhance competion power of domestic yogurt starter cultures and will promote dairy industry.Discussing:multiplication culture conditions of the Lactobacillus plantarum, thalli concentration and separation technics, vacuum freeze drying process parameters. Sifting and optimizing efficiently LAB propagation medium, freeze-drying protectant and preparing high quality DVS yogurt starter cultures.Firstly, adopting vacuum freeze drying Lactobacillus plantarum powder as trial microorganism bought from SICC (Southwest Center Of Industrial Culture Collection In China). Activated and several times culture to pure-blood and inoculated to vary mediums. Select the proliferate results best MRS medium as the basic medium in the initial stage of this research ultimately and lay foundation for the next concentration culture.Regulate broth acidity timely by adding buffers agents to restrain Lactobacillus plantarum'autolyze'. Create a well growing environment and lessen the natural mortality rate , effectively. The results indicated:added 2% buffer I can stabilize the broth.Drew the corresponding curves by running after for 30 hours according to pH value,OD value and the amount of live LAB for the sake of finding out their growth status and rhythm.LAB growth curves changed after adding buffer agent. Adding 2% buffer I 2h before LAB cultured 15h and started to 'autolyze', once every 2h. Viable count and protracted corresponding growth curve measured. Results indicated:the time LAB viable count most varied from 15h to 18h and made its exponential phase prolong 3h after adding buffer agent.Accelerated growth by superadding growth factor for gaining abundant LAB. Added cane sugar,milk sugar,dextrose and fruit sugar as its carbon sources. Peptone,beef extract,yeast extract and tryptone as its nitrogen sources. Cap fungus fruit,tomato juice,carrot juice and potato juice as its vegetable juice ordered to offer mineral and vitamine.Determined appropriate growth factor and better basic medium prescription by single-factor and orthogonal experiment.Results indicated, cane sugar, yeast extract and potato juice feed it better, the viable count increased from 6.88×1010cfu/ml to 1.58×1011cfu/ml.Adopted centrifugation method to concentrate and separate the broth. The more reason centrifuge condition is:centrifuge temperature 0℃,centrifuge speed 3000rpm,centrifuge 10min. Achieved rational ooze rate and viable count according to this centrifuge mean, taken cost into account too.Freeze drying to gain freeze-dry powder after concentrating and separating the LAB broth. Add buffer agent to avoid the LAB to die in the freeze-drying process. Adopted conventional freeze-drying protectants to carry through orthogonal experiment:glycerol,tween 80 and monosodium glutamate:buffer protectants functioning after adding in broth.The viable count reach to 2.69×1011cfu/ml according to the additive amount:tween 80 0.5ml/L,glycerol 0.5ml/L,monosodium glutamate 5g/L.