I. Introduction: Development and development of lactic acid bacteria beverage 2.2 Main experimental materials: Development and development of lactic acid bacteria beverage 3.3 Screening of the starter and determination of the culture conditions:
Lactic acid bacteria beverage is a fermented milk-containing beverage with rich nutritional value and unique flavor, which is made from fresh milk or milk powder, fermented by Lactobacillus bulgaricus and Streptococcus thermophilus, and then added with other auxiliary materials. Due to the fermentation of lactic acid bacteria, the lactose in cow's milk is decomposed into galactose and lactic acid, and some proteins are decomposed into small peptide chains and amino acids, so that the nutrients of milk are more digestible and absorbed, suitable for patients with lactose intolerance. It can also improve the utilization rate of calcium, phosphorus and the like in the human body. At the same time, lactic acid bacteria also have functions such as improving intestinal bacteria, regulating gastrointestinal function, preventing aging, beauty and beauty, and enhancing immunity.
Compared with fermented yoghurt, lactic acid bacteria beverage has a refreshing taste and variable flavor and low cost. Compared with blended yoghurt drink, it has a sweet and sour taste, has the unique flavor of fermented milk and the health care effect of lactic acid bacteria, and has great market potential and Advantages.
Second, the main experimental materials and test analysis methods:
2.1 Lactic acid bacteria and its starter:
Lactobacillus bulgaricus, Streptococcus thermophilus.
The cultivation of lactic acid bacteria starter is indicated: 
Fresh milk, white sugar, aspartame, xanthan gum, sodium alginate, guar gum, phosphate, citric acid, sodium citrate, lactic acid.
2.3 Experimental main instruments and equipment:
PL302 electronic balance (0.1 g); AL204 electronic balance (0.001 g);
H.HB11 type electrothermal constant temperature incubator; SPX-250B type biochemical incubator; SWCF2FD type clean workbench;
LS-C50L type autoclave; Delvo-X-PRESCTM antibiotic tester;
DELTA320 acidity meter; 752 type UV-visible spectrophotometer;
NDJ-4 rotary viscometer; centrifuge; colloid mill; high pressure homogenizer;
2.4 Experimental analysis method:
(1) Antibiotic test (antibiotic tester or another 100ml milk emulsion sterilization, inoculation, fermentation test)
(2) PH value measurement method: (measurement by acidity meter)
(3) Determination of titration acidity (take 10 ml sample, dilute with 20 ml of distilled water, add 0.5% phenolphthalein indicator 0.5 ml, titrate to 0.1% with 0.1 ml/L NAOH solution, multiply the number of NAOH consumed by 10 by 10, That is to titrate the acidity, consume 1ml for 10T).
(4) Determination of lactic acid bacteria (refer to GB/T4789.35 test method).
(5) Precipitation analysis: Accurately add 10 ml of the prepared beverage in a graduated centrifuge tube, then centrifuge in a 4000r/min centrifuge for 10 minutes, measure the depth of the top layer, and discard the upper solution to accurately weigh the sediment. , the amount of precipitation is:
Precipitation rate (%) = precipitate (g) / 10 ml of drink (g) × 100%
Third, the experimental content and points:
3.1 experimental design
(1) Standardize the fresh milk after testing, then sterilize and cool, inoculate and ferment to make yoghurt, then add yoghurt and white sugar, compound stabilizer according to different proportions (orthogonal experiment), add softened water to prepare beverage and homogenize, and determine the basic formula of the product. [Then then determine the acidity of the yogurt fermentation and the acidity of the product according to the flavor requirements of the product; finally, the screening test of the stabilizer, determine the amount of the composite stabilizer, and finally determine the best formula of the product] Several basic points are: 1 strain screening 2 product sugar acid ratio adjustment 3 product stability is established 4 different product flavor optimization.
3.2 Experimental route:
The yogurt starter is mixed and fermented with Streptococcus thermophilus and Bulgarian bacillus. Due to the different metabolites of the two bacteria, the optimum growth temperature is different. When the fermentation is mixed, the determination of the culture temperature and the mixing ratio has a significant effect on the formation of the flavor component.
According to the characteristics of the two bacteria and the flavor component requirements of the lactic acid bacteria beverage, we selected different ratios for the test and concluded that the strains with medium and low viscosity, strong acidification, strong aroma, and the ratio of streptococcus to lactobacillus were selected. : 2 is the best.
3.4 Determination of sweet and sour ratio of beverage products:
The determination of the sweet and sour ratio of the beverage product not only improves the flavor of the lactic acid bacteria product, but also enables the flavor of the yogurt product to be better released.
After comparative experiments, the total sugar content was determined to be 13%. Considering the cost factor, some sugar was removed by sweetener; the product acidity was controlled at pH 3.7-3.9; the product formed a good taste.
3.5 Product stability:
The dispersed particle protein in the lactic acid bacteria beverage is easy to coagulate and precipitate. 80% of the milk protein is casein, which is a polymer ampholyte. In the process of compounding, the protein is agglomerated and precipitated at pH 3.5-3.9. The stabilizer forms a protective colloid as a polymer and prevents aggregation and precipitation of protein particles. Therefore, in the production of yogurt drinks, the selection of stabilizers is very important.
If the stabilizer is not properly selected, the product will precipitate, stratify or become a tofu flower. Therefore, based on the single factor test, we consider the cost factor to three factors, CMC-NA, PGA, and sodium citrate. The three-level orthogonal test determined the optimal combination of three factors: CMC-NA 0.4%; PGA 0.15%; sodium citrate 0.04%.
IV. Conclusion:
(1) Yogurt starter has certain influence on product and product flavor. Different strains used in the same strain have different flavor and tissue state of fermentation products. In the production of lactic acid bacteria beverage, acid production is required to be relatively fast. A strain that produces low-yield, high-yield flavors. Finally, the streptococci were determined: the lactobacillus was 3:2, the culture temperature was 43 ° C, and the fermentation end acidity was 95-1000 T.
(2) Lactic acid bacteria beverage fermented milk 38%, total sugar content 13%, PH3.7-3.9, acidity 0.4-0.5%, product sweet and sour than palatable.
(3) The best combination of stabilizers is: CMC-NA 0.4%; PGA 0.15%; sodium citrate 0.04%.
(4) The main technical indicators of lactic acid bacteria beverage products are: protein ≥1.0%; lactic acid bacteria ≥100,000 cfu/ml.
Development and development of lactic acid bacteria beverage