The power of fermentation: the contribution of production technology to the nutritional value of cheese

Cheese is one of people's favorite dairy products and can be divided into natural cheese and processed cheese.

Natural cheese is a dairy product made by adding specific strains of bacteria to cow's milk or goat's milk, cream, skimmed or partially skimmed milk, or buttermilk for pre-fermentation, then adding rennet to coagulate the casein, cutting the curd and removing the whey; it is then further squeezed, salted, and matured, and then made through processes such as film dipping, wrapping, and packaging.

Processed cheese is another type of dairy product made from natural cheese. Compared with pure cow's milk, milk powder and other dairy products, the fermentation process improves the nutritional value of cheese, and the nutrients it contains have obvious functional characteristics and health benefits.

Lactic acid bacteria fermentation to ensure intestinal health

The starter culture commonly used in natural cheese is usually made of a mixture of several bacteria, among which there is a symbiotic relationship between two or more strains in the starter culture, whether it is mesophilic or thermophilic. The lactic acid bacteria in the starter culture not only produce lactic acid, but also produce aromatic substances and carbon dioxide, which is necessary for the formation of cavities in perforated cheese and small-pore cheese. Another important function of these lactic acid bacteria is to inhibit the growth and proliferation of bacteria remaining after pasteurization and re-contamination bacteria by producing acid.

The lactic acid bacteria commonly used in cheese starter cultures are a type of probiotics. They and their metabolites have health benefits for the human body, are beneficial to maintaining the stability and balance of normal intestinal flora, and prevent constipation and diarrhea. Some probiotics have probiotic functions such as lowering serum cholesterol. Studies have found that lactic acid bacteria strains isolated from natural cheese can absorb cholesterol during their growth and integrate cholesterol into the bacterial cell membrane, or adsorb cholesterol to the surface of bacterial cells, thereby inhibiting intestinal cholesterol absorption.

Small molecule protein, easier to digest

Compared with other dairy products, cheese can provide the largest amount of protein for the human body. As a source of high-quality protein, cheese contains all kinds of essential amino acids for the human body in sufficient amounts. Casein is the main protein component in cheese, while the content of water-soluble whey protein and lactoglobulin is relatively small (the content is related to the amount of whey excretion).

The coagulation method and maturity of cheese processing will have a direct impact on the protein composition of the product. In enzyme-coagulated cheese, casein molecules combine with one or two Ca2+ to form a paracasein-Ca2+ complex. Under the action of lactic acid produced by the starter, a part of the complex dissociates and releases free paracasein, and Ca2+ combines with lactic acid to form calcium lactate. In the maturation stage, paracasein molecules are hydrolyzed to form water-soluble small molecular nitrogen-containing compounds, thus forming a soft, elastic and easily digestible cheese product.

Protein hydrolysis releases more soluble calcium

Cheese contains many important minerals such as calcium, phosphorus, and magnesium. The calcium in cheese is as important as the calcium in cow's milk: every 100 grams of soft cheese can meet 30% to 40% of a person's daily calcium requirement; every 100 grams of hard cheese can fully meet the daily calcium requirement.

Cheese is also a good source of biosynthetic calcium: during the cheese-making process, milk protein coagulates under the action of rennet to form a network structure. During the cheese ripening process, this structure continues to disintegrate under the action of residual rennet. The insoluble calcium in the casein bundles is also released with the hydrolysis of protein to form soluble calcium, which is very beneficial for digestion and absorption.

Studies have shown that milk calcium can inhibit the absorption of fat and bile acid, increase fecal fat excretion and the conversion of calcium-induced cholesterol into bile acid, thereby potentially lowering blood lipid levels in the human body.

The coagulation process enriches fat-soluble vitamins, and the ripening process synthesizes vitamin B

Since most of the milk fat remains in the curd of cheese, most of the fat-soluble vitamins also enter the curd. On the contrary, most of the water-soluble vitamins are discharged along with the whey during the curd production process (whey drainage process). Therefore, cheese is rich in fat-soluble vitamins, such as vitamin A, vitamin E and vitamin K.

During the cheese ripening process (ripening process), vitamin B can also be produced under the synthesis of microorganisms. For example, in Swiss cheese, a higher concentration of vitamin B12 can be obtained due to the action of propionic acid bacteria. Generally, most cheeses are rich in vitamins A, B2, B12 and folic acid, and vitamin C is almost negligible.

Ripe cheese is lactose-free and is suitable for people with lactose intolerance.

In mature cheese, the content of carbohydrates (mainly lactose) is relatively small. The reason is that a large amount of lactose has been discharged from the cheese system with whey, while the small amount of lactose remaining in the curd is converted into lactic acid and other organic acids under the action of microorganisms. Therefore, most varieties of cheese are dairy products suitable for people with lactose intolerance.

In summary, cheese is a food with high nutritional value made from fermented milk. Compared with raw milk, cheese contains lactic acid bacteria, is rich in fat-soluble vitamins, has a higher protein absorption rate, and is suitable for people with lactose intolerance. As Chinese residents' pursuit of health continues to increase, it is believed that cheese products with excellent quality will be favored by more consumers.

When choosing cheese products, you will feel more at ease if you choose a brand that is independently developed, produced, and has strict quality control.

References

1. Li Xiaodong. Dairy Technology[M]. Beijing: Science Press, 2011.

2. Chen Lijun. Dairy Science and Technology[M]. Beijing: Light Industry Press, 2007.

3. Zhang Lanwei, Gu Ruixia, Kong Baohua, et al. Milk and Dairy Products Technology. Beijing: China Agriculture Press, 2006.

4. Guo Benheng. Cheese. Beijing: Chemical Industry Press, 2004.

5. Ji Tiebo, Cui Yurong. Dairy Microbiology. Beijing: Light Industry Press, 2006.

6. Wang Moyi, Yin Junling, Liu Xiaoming, et al. Effect of calcium addition on cheddar cheese quality[J]. Food and Fermentation Industries, 2017, 43(3):144-150.

Author: Sun Changyan | PhD/Senior Engineer, Harbin University of Science and Technology

Reviewer Yu Huanling | Professor of Capital Medical University

Reviewer Xu Weisheng | PhD/Associate Researcher, Institute of Nutrition and Health, Chinese Center for Disease Control and Prevention

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Source: China Good Nutrition