The following are the main raw materials of cheese: milk, which is recognized as a good nutritional product. It takes about 1kg milk to make1kg cheese, so cheese is also called "milk gold". Cheese contains not only high-quality protein, but also trace mineral elements such as sugar, organic acids, calcium, phosphorus, sodium, potassium and magnesium, and nutrients such as iron, zinc, fat-soluble vitamin A, carotene and water-soluble vitamins B 1, B2, B6, B 12, nicotinic acid, pantothenic acid and biotin (table/kloc-). Every 65,438+000g of soft cheese can provide 35% to 40% of protein for an adult, while every 65,438+000g of hard cheese can provide 50% to 60%. Because whey (whey protein with high physiological titer) needs to be removed in cheese making, the biological value of cheese is lower than that of whole milk protein, but higher than that of pure casein. In some new processes, such as ultrafiltration, cheese can be produced without discharging whey, which improves the protein nutritional value of cheese. In addition, Maillard reaction does not occur in cheese production, so the essential amino acids of cheese can be kept to 9 1% ~ 97% of the original milk content. Making cheese requires microbial fermentation. Under the decomposition of chymosin and protease in microorganisms, protein forms small molecular substances such as amino acids, peptides, peptides and peptones, which are easy to digest, and the protein digestibility reaches 96% ~ 98%. It is also reported that casein in milk gradually degrades into peptides and amino acids during cheese ripening. Some amino acids can be further degraded under the catalysis of bacterial decarboxylase. γ -aminobutyric acid is decarboxylated from glutamic acid, so many cheeses contain γ-GABA. γ-GABA is a functional factor, which has the functions of lowering blood pressure, anticonvulsant, relieving pain, improving brain function, calming, promoting long-term memory, activating renal function and liver function. Fat not only gives cheese a good flavor and delicate taste, but also provides a part of energy needed by human body, and its digestibility in the body is 88% ~ 94%. In addition, the cholesterol content related to fat content in cheese is also low, usually 0 ~ 100 mg/ 100 kg. In cheese production, most lactose is excreted with whey, and the rest is converted into lactic acid by fermentation, so cheese is one of the optional nutritional foods for lactose intolerance and diabetes.

Cheese contains essential minerals such as calcium, phosphorus, magnesium and sodium. Due to the need of cheese processing technology, calcium ions will be added to increase the content of calcium, which is easy to be absorbed by the human body. Every 100g soft cheese can meet the daily calcium requirement of 30% ~ 40% and the daily phosphorus requirement of 12% ~ 20%. Every 100g of hard cheese can completely meet people's daily calcium demand and 40% ~ 50% daily phosphorus demand. Different kinds of cheese contain different amounts of sodium chloride. In recent years, because people realize that high concentration of Na+ is related to some hypertension diseases, some manufacturers try to replace NaCl with magnesium chloride and KCl, but the taste is still insufficient. Table 2 is the average value of trace elements contained in ordinary cheese.

In the process of making cheese, casein in milk coagulates and whey is discharged, so cheese contains more fat-soluble vitamins, while most water-soluble vitamins are discharged with whey; In the process of cheese ripening, vitamin B, nicotinic acid, folic acid, biotin and so on can be synthesized due to the action of various enzymes and microorganisms. The content of vitamin C is so small that it can be ignored.