Research Of Crux Technology On Preparing Bifidobacteria High-activity Concentrated Yoghourt Starter

Bifidobacteria as a typical probiotics, its function of increasing the health have been admitted, Dairy products with bifidobacteria had been a bioengineering products of 21 century. With the improvement of people's health consciousness, the study and development on functional dairy product will become heat issues and consume fashion in dairy products domain. With the rapidly development of fermented dairy product, It's of significant for promoting the industrial process of Lactic acid bacteria starter, improving development of fermented dairy product;In this paper, it has isolated strains and optimization collocation for fine Bifidobacteria. Studied on the technology of bifidobacteria single and mixed with lactobacillus fermenting milk.The cheap enrichment medium suited for industrial processing and freeze-drying protectant were screened. The technology of enrichment culture for bifidobacteria, cell concentration, lyophilization were studied. The suitable conditions for bifidobacteria during the process of freeze-drying were explored initially. High efficiency concentrated bifidobacteria freeze-drying culture were prepared. And the fermentative activity of the freeze-drying starter in milk were examined.In this paper,the scale culture of bifidobacteria were explored and analysed.The growth, fermentation, livabitily of cold storage,postacidification,freeze-drying resistance of four different Bifidobacteria strains were studied. Two special strains of Bbm and Blm were obtained.Inoculation, the ration of saccharose initial pH, fermented temperature,oxygen-resistant etc factors were studied on the effect of fermentation. On the basic of above,by orthogonal experiment optimizing the technology parameters of bifidobacteria mixed with lactobacillus fermented milk. The results indicated: the optimal technology of bifidobacteria single fermented was as follows: addition of 4% saccharose in milk medium,inoculation 3%(the viable number 5×l0⁷cfu/mL), initial pH of medium 6.5,fermented temperature 39℃, fermented with oxygen;The single bifidobacteria optimal technology was adopted to fermented milk ,the curd time for Bbm or Blm are in 5h, the viable number of both reach l×10⁹cfu/mL, pH about 5.0.The optimal technology of mixing bifidobacteria with Lactobacillus together fermented was as follows: addition of 4% saccharose in milk medium, the overall inoculation 3%,the ration of strains (Lb-DR:St-3: Bbm or Blm)equals 1:1:1.the initial pH 7.0,fermented temperature 39℃,fermented with oxygen;The mixed bifidobacteria fermentation optimal technology was adopted to fermented milk,the curd time for Bbm or Blm are at 3h20min, the viable number of overall reach over 1×10⁹ cfu/mL, pH about 5.0.Jerusalem artichoke juice medium, tomato juice medium, carrot juice medium and wort medium which are apt to gain and separate are obtained by cell growth experimented. The effects of nutritional medium on freezeing resistance of bifidobacteria were studied, The results shows: tomato juice medium is the medium of freezeing resistance, tomato juice medium inoculated with bifidobacteria cultivated at 37℃ for 12h and The highest survival rate after freeze were.71.81%.Sterilization mode, liquid volume in flask, initial pH, fermented temperature, inoculation, fed-batch factors were studied on the effect of culturing in 500mL flask about bifidobacteria. On the basic of above, by orthogonal experiment optimizing the technology parameters.The results indicated: Inoculated with 0.1% in 400mL medium, the initial pH 7.00 and cultivated at 37℃ for 12h, the viable number reach above l×l0⁹cfu/mL.In the Study of the effect of centrifuging force and time on the loss rates of bifidobacteria, The optimum centrifugal factor on cell concentration were decided: The harvesting rate of Blm living cells reached the highest when centrifugated at 9000 r for 5¹0min or at 4000r for 20min, while 4000 r 10min or 7500r 5¹0min for Bbm.The effects of culture condition and nutritional medium on resistant freeze of Bifidobacteria. were studied, The results shows: Cultivated at 37℃, cell gaining at the end of logarithm and beginning of stable, pH in protectant at 6.5⁷.0,Added glycerin 0.01% and VE 0.01%,can dramatically increase the freeze-drying survival rate of Bifidobacteria.The effect of freeze-drying resistance about nutritive ingredients were studied.The result showed: 13 protective agents including skimmed milk,a-trehalose significantly raised up cell survival rate on freeze-drying. Five compound protective agent's prescription were screened out. The number of living cells was 1011 cfu/g after lyophilination. The highest survival rate of Blm was 66.75% and Bbm 74.36%.Storage experiments show: Different Sealed- preservation(vacuum, air) and storage temperature (4℃,RT)have no effect on the cell survival rate of 33^# lyophilizated products, stored for 360d, the living cell number was still over 10¹⁰cfu/g, and the reduced number didn't amount to one log rank.By examining the activity of freeze-drying cultures in milk, the result indicates: The fermentation nature of the mixed freeze-drying cultures prepared by 33^#kinds of compound protectant is better;Inoculated with 0.01% and cultivated at 39℃, fermented with oxygen, the curd time are 6h, the viable number reach above 1×10⁹cfu/mL, pH is about 5.0.Liquid volume in flask were3000mL and 3500mL in 5L fermenter, Inoculated with 0.1%, the initial pH 6.86 and cultivated at 37℃ by the lowest pace (100r/min) churning up for 12h, the viable number reach above 1×l0⁹cfu/mL.