Cultured Milk Processing Technology

Cultured milk processing involves fermenting milk with specific bacterial cultures to produce various dairy products like yogurt, lactic acid bacteria fermented beverages, kefir, and sour cream. These products are valued for their distinctive flavors, textures, and nutritional benefits, including probiotics.

Cultured milk also called lactic acid bacteria fermented beverage, it is a dairy product with certain nutritional value and unique flavor prepared from fresh milk or milk powder as raw material, fermented by Streptococcus thermophilus and Bulgaricus and other starter agents. It mainly includes two categories: live bacteria type and bactericidal type. The live lactic acid bacteria fermented beverage has a pure and refreshing taste, contains active lactic acid bacteria, has high nutritional value, can adjust intestinal absorption, and has functions such as beauty and health care.

The capacity of cultured milk processing plants is from 500L/H to 10000L/H, according to different culture bacteria can produce different end products.

The cultured milk production process involves milk reception or milk reconstitution, milk standardization, milk homogenization, degassing, pasteurization and cooling, starter culture adding, fermentation, flavoring, filling and packing.

1. The raw and auxiliary materials of cultured milk(lactic acid bacteria fermented beverages) mainly include dairy products, white sugar, coffee, cocoa, chocolate, etc. Dairy products mainly refer to raw milk, skimmed milk powder, whole milk powder or condensed milk. Sugars are mainly sucrose, glucose, fructose syrup, lactose, etc. Fruit and vegetable juice mainly includes concentrated and NFC fruit and vegetable juice, fruit and vegetable juice with pulp, the commonly used fruits are orange juice, strawberry juice, apple juice, pineapple juice, carrot juice, etc. Cocoa powder and chocolate: The fat content of cocoa powder is 10%-25%, which is easy to disperse in water, and the fat content of chocolate is more than 50%, which is difficult to disperse in water.
2. Sweeteners: sweeteners used in lactic acid bacteria fermented beverages include acesulfame potassium, aspartame, fructooligosaccharides, etc.
3. Acidity regulators: Acidity regulators include sour agents and alkaline agents. Alkaline agents mainly include sodium carbonate, sodium bicarbonate, etc., whose main function is to adjust the pH of beverages.
4. Emulsifiers: Compound emulsifiers are generally used in production. Commonly used emulsifiers are glycerol monostearate and sucrose fatty acid esters.
5. Stabilizers: Stabilizers commonly used in lactic acid bacteria fermented beverages include agar, carrageenan, pectin, xanthan gum, gellan gum and modified starch.
6. Preservatives: mainly includes benzoic acid and sodium salt, sorbic acid and potassium salt.
7. Flavor agent: including milk flavor, lactic acid flavor, coffee flavor, cocoa flavor, chocolate flavor, etc.
8. Enzyme preparation: mainly lactase, which is used to hydrolyze lactose in milk into glucose and galactose to make lactic acid bacteria beverages for lactose intolerance.
9. Antioxidant: It is beneficial to prevent oxidation and maintain the color and flavor of beverages, such as ascorbic acid, sodium erythorbate, vitamin E, etc.
10. Starter: Starter can promote the acidification of milk. Commonly used starter are Streptococcus and Lactobacillus.

The process of cultured milk fermented lactic acid bacteria beverage with fresh milk as raw material is shown in the following diagram:

1. Milk powder reconstitution or fresh milk receiving: dissolve the milk powder with about half of the purified water at about 50°C, and let the reconstituted milk stand for 30 minutes when the milk powder is completely dissolved.
2. Adjustment of raw milk components before fermentation: use milk powder, whey powder or protein powder to adjust the non-fat milk solids content in milk to 15%-18%.
3. Degassing, homogenizing and pasteurizing: degas the product before homogenizing, otherwise the homogenizing head will be easily damaged when the product is homogenizing. During homogenization, the temperature is 70-75°C and the pressure is 20Mpa; the sterilization conditions are 90-95°C and 5min.
4. Lactic acid bacteria strains adding: The most commonly used strains in production are the mixed strains of Streptococcus hygrothermal and Bulgaricus, the ratio is 1:1, and the inoculation amount is 3%.
5. Lactic acid bacteria fermentation: keep a constant temperature during fermentation and carry out in a constant temperature. fermentation tank. In order to obtain a higher viscosity product, a suitable pump should be used to transport the yogurt.
6. Ingredients formulation: After the fermentation is completed, the manufacturer can prepare and mix yogurt, sugar, fruit juice, stabilizer, sour agent, spices, etc. according to their own formula in the blending tank.
7. Sterilization: After the ingredients are finished mixing, degas and homogenize the material, the homogenization pressure is 20Mpa, and the sterilization process is 95-105℃ holding for 30S or 110℃ holding for 4S. If the beverage is filled into bottles, 98 ℃, 20-30min in container sterilization will be needed.

Unstable taste (thin taste, sweet or sour taste, astringent)

The main reasons for the unstable taste are inaccurate dosing during ingredients feeding, water entering the material before and after sterilization and filling, continuous acid production by lactic acid bacteria due to improper cold chain in the sales process. The main solution is that various ingredients need to be accurately weighed and dosed. When adding to the mixing tank, load cells and flow meters should be used to ensure accuracy. Reasonable process parameters are used during sterilization and filling.

Stratification and Precipitation

The protein particles dispersed in lactic acid bacteria fermented beverages are very unstable and easy to aggregate and precipitate. The control measures are mainly to finely homogenize the material, add sucrose to improve the viscosity of the material, and also choose an acid-resistant stabilizer, such as pectin, to increase the stability of the material.

Beverage Browning

Decomposed protein amino acids in lactic fermented beverages react with sugars to form brown pigments. Factors that affect browning are temperature, pH, sugar and amino acid types. The control measures are to adopt a reasonable sterilization process, the heating time of the material should not be too long, and the product should be stored in a dark and ventilated place.