What is the application of lactic acid bacteria in the food industry?

Lactic acid bacteria is a kind of bacteria that can produce a lot of lactic acid by fermentation and use of sugar substances. It is a kind of bacteria that is beneficial to human body. Lactic acid bacteria fermentation can produce a large number of organic acids, alcohols and various amino acids and other metabolites, which has physiological effects such as inhibiting spoilage bacteria, improving digestibility and preventing cancer.
The application of lactic acid bacteria has a long history, but the real scientific research and utilization began in the middle of the 19th century. Nowadays, people have realized the physiological function of lactic acid bacteria, and lactic acid bacteria fermentation has been widely used in food processing.
Types of lactic acid bacteria

The morphology of lactic acid bacteria is mainly classified into two categories: spherical and rod-shaped. According to the biochemical classification, lactic acid bacteria can be divided into five genera: Lactococcus, Streptococcus, Leuconostoc, Bifidobacterium and Pediococcus. Each genus has many species, and some species also include several subspecies. Lactic acid bacteria of Lactobacillus genus are generally elongated culm, most of which are arranged in chain shape.
The main applications in the fermentation industry are: homofermentable lactobacillus, such as Lactobacillus deli, Lactobacillus bulgaricus, Lactobacillus Swiss, Lactobacillus acidophilus and Lactobacillus casei; Heterofermentative lactobacillus, such as Lactobacillus brevis and Lactobacillus fermentans.
Streptococcus lactic acid bacteria are generally arranged in short or long chains, are spore free Gram-positive bacteria, facultative anaerobic. The main ones commonly used in production are: lactic streptococcus, butanedione lactic streptococcus, cheese streptococcus and lactococcus thermophilus. Leuconostoc are mostly arranged in circular or oval chains, often found in fruits and vegetables, and can grow in high concentrations of sugary foods.
Physiological function of lactic acid bacteria
1, nutritional effects of food raw materials after lactic acid bacteria fermentation, can make protein, fat and sugar decomposition into the body more easily absorbed pre-digestion state, but also can increase the content of soluble calcium, phosphorus, iron and some B vitamins, improve its digestion and absorption performance and nutritional value.
2, enhance immunity Lactic acid bacteria can enhance immunity, manifested in two aspects: first, affect the non-specific immune response, enhance the activity of mononuclear phagocytes, polymorphonuclear leukocytes, stimulate the secretion of reactive oxygen species, lysosomal enzymes and mononuclear factors; The second is to stimulate specific immune responses, such as strengthening the levels of IgA, IgM and IgG on the mucosal surface and in serum, promoting the proliferation of T and B lymphocytes, and strengthening the body’s immunity.
3. Improving blood lipids At present, the research on the effects of lactic acid bacteria on blood lipids is not very mature, but a large number of animal experiments have shown that organic acids, special enzyme systems, bacterial surface components and lactic acid metabolism in the body can improve blood lipids. Acetate, propionate and lactate in organic acids can regulate the metabolism of fat, and play a certain role in reducing plasma TC(total cholesterol) and LDL(triglyceride) and increasing high-density lipoprotein HDL
4, antibacterial and intestinal action After the Lactobacillus enters the human body, it will multiply in the intestine, produce lactic acid, acetic acid and some antibacterial substances, so that the pH value and REDOX potential of the intestine are reduced, which can inhibit the growth and reproduction of pathogenic bacteria and bacteria harmful to human health, and can play the role of antibacterial and disease prevention. At the same time, the massive growth and reproduction of lactic acid bacteria also maintained the balance of intestinal flora and played a role in intestinal whole.
Application of lactic acid fermentation in food processing
1, the application of dairy products processing Dairy products are the most widely used lactic acid bacteria fermentation, is also the most mature field. The main products are yogurt, cream and cheese.
Yogurt production
Yogurt is a product made from fresh milk or milk powder which is fermented by lactic acid bacteria. After the raw milk is heated for sterilization (generally 90℃ for 30min) and homogenization, it is reduced to the appropriate temperature, sugar and stabilizer are added to stir evenly, and lactic acid bacteria starter is inoculated at the appropriate temperature for fermentation. After the fermentation is completed, it is placed in a cold storage at about 4 ° C to cool and mature, and the finished sour milk is obtained. The lactic acid bacteria used in the production of sour milk mainly belong to Lactobacillus, Streptococcus, and bifidobacterium.
The production of cream is a dairy product made from the thin cream obtained after centrifugal separation of milk, which is pasteurized, cooled, matured, fermented by lactic acid bacteria, stirred and pressed. According to different fermentation methods, cream can be divided into natural fermented cream and artificial fermented cream. Naturally fermented cream is made by natural fermentation of microorganisms in milk. Artificial fermented cream is made by sterilizing thin cream and then adding a pure culture starter to ferment it.
Cheese production Cheese refers to raw milk after sterilization, cooling, adding an appropriate amount of lactic acid bacteria starter fermentation, so that protein (mainly casein) solidified, excluding whey, the clot pressed into a block made of products. Lactic acid starter for the production of cheese, which varies with the type of cheese.
2, the application in the processing of vegetable protein drinks is currently mainly used in the production of sour soy milk and peanut lactic acid fermented yogurt. Due to the limited milk resources, the cost of yogurt is high, and sour soy milk and peanut lactic acid fermented yogurt can be used as a substitute for yogurt to provide people with a large amount of high-quality protein, therefore, the development of sour soy milk and peanut lactic acid fermented yogurt has great economic and social benefits.
Alcoholic fermented milk beverage The starter culture of this milk beverage is divided by lactic acid bacteria, and yeast. Yeast itself contains a complete variety of amino acids, fermentation produces important flavor substances, forming a unique hop aroma; At the same time, yeast can produce a variety of water-soluble vitamins, which further improves the nutritional value of fermented milk.
Lactic acid bacteria use lactose fermentation to produce lactic acid, which reduces the pH of fermented milk and increases the coagulability of fermented milk. Milk wine is a new type of fermented milk drink, rich in nutrients and unique in taste. The carbon dioxide, ethanol and aromatic substances produced by the fermentation of the bacterial mixture give the milk its foaming and sour taste.
3. Application in vegetable deep processing The application of lactic acid fermentation in vegetable deep processing was originally limited to the production of pickled cabbage. In recent years, with the development of food science, lactic acid fermentation has also been used in the production of vegetable lactic acid fermentation drinks. Among many vegetable processing methods, the use of lactic acid bacteria to process vegetables has a long history in China, and has a wide application prospect.
In the 1960s, foreign countries began to use artificial inoculation of lactic acid bacteria pure culture, which can make lactic acid bacteria in the fermentation process at the beginning of the dominant, inhibit the abnormal fermentation caused by harmful bacteria, thus shortening the fermentation cycle, vitamins are not destroyed, the product flavor pure, crisp fresh, good color, acidity, pure natural, especially suitable for raw food. The fermentation industry of pure lactic acid bacteria started late in China. At present, it is mainly limited to the fermentation of dairy products, vegetable lactic acid fermentation foods are mainly pickles, sauerkraut and vegetable juice drinks, and pickles have formed large-scale production in the south.
4. The application in meat production improves the color and flavor of meat products
Lactic acid bacteria not only have the relevant enzyme systems produced by general micro-matter, but also produce some special enzyme systems, which can improve the flavor of products and promote the maturity of fermented meat products. In addition, the lactic acid produced by fermentation not only denatures part of the muscle protein and forms a gelatinous tissue, but also improves the hardness, elasticity and slicing of meat products.
Reducing the production of TMARine and reducing the residue of cucurbitate If Lactobacillus acidophilus of Lactobacillus is added to meat products, the residual amount of nitrite can be greatly reduced and the generation of carcinogenic substances – nitrosamines can be reduced. Therefore, the application of a small amount of nitrite as hair color agent combined with the preservative effect of lactostreptococcin can reduce the amount of nitrite.
Inhibit the growth of putrefying bacteria and extend the shelf life of meat because lactic acid bacteria use carbohydrates, such as glucose, to produce a lot of lactic acid, and these lactic acid in meat and meat products can prevent the growth of putrefying bacteria, improve the tissue structure and appearance. The use of lactic acid and sodium chloride treatment of fresh meat can reduce the water activity of fresh meat, thus preventing microbial growth and extending shelf life. If added in emulsified meat products, cooked ham, roast beef whole meat products, can extend the product shelf life.