Application of lysozyme in food industry

Lysozyme is an effective antibacterial agent discovered by Fleming in 1922. It is a biological enzyme composed of hydrolytic enzymes supplemented with protective agents. Also known as mucopeptide N-acetylmuramoyl hydrolase, it is a basic globulin composed of 129 amino acids. It is ubiquitous in birds, mammals, and even some bacteriophages, and it is one of the best-studied proteases to date.

As a non-toxic and harmless protein, lysozyme has many uses and can be used as a preservative in the food industry. Its main function is to hydrolyze the bacterial cell wall, and in the cell, it destroys the pathogenic bacteria after phagocytosis. The enzyme can decompose Bacillus subtilis and Micrococcus radioduran in Gram-positive bacteria. It also has a certain degree of lytic effect on Gram-negative bacteria such as Escherichia coli, Proteus vulgaris and Vibrio parahaemolyticus, and its most effective concentration is 0.05%. Used in conjunction with phytic acid, polyphosphate, glycine, etc., can improve its antiseptic effect.

Lysozyme has the following advantages as a preservative:

(1) Lysozyme is a very stable protein with strong heat resistance. Egg white lysozyme is type C, the most thermostable enzyme known;

(2) Lysozyme will not be inactivated due to the treatment of organic solvents, and when transferred to an aqueous solution, the activity of lysozyme can be fully restored;

(3) Lysozyme can be frozen or dried, and its activity is stable;

(4) Lysozyme is suitable for pH5.3~6.4, and can be used for antisepsis of low-acid food;

(5) The production cost of lysozyme is low;

(6) Lysozyme has a wide antibacterial spectrum, not only limited to G+ bacteria, but also has inhibitory effect on some G- bacteria;

(7) Lysozyme is highly safe as a preservative. Lysozyme is a natural protein. In 1992, the Food Additives Association of FAO/WTO has determined that lysozyme is safe to use in food.

1. Application in aquatic products

Lysozyme has a strong decomposition effect on Bacillus subtilis and Micrococcus radiodurans in G+, and also has a certain degree of dissolution on G- such as E coli, common proteus and Vibrio parahaemolyticus. Its optimal concentration is 0.05%, and it can be used in conjunction with phytic acid, polyphosphate, glycine, etc. to improve its antiseptic effect and prolong the shelf life of aquatic products and cooked meat products.

In the unpackaged fish cake, the ground fish meat (containing 3% salt) was steamed for 30 minutes, added 0.05% lysozyme, packed in a sterilized plate, and heated at 90°C for 15 minutes, the number of bacteria did not increase significantly. % gelatin and 0.05% lysozyme solution for 10 seconds and then preserved, also showed almost the same preservative effect. This is due to the lysozyme breaking down the bacteria on the surface of the fish.

Fresh aquatic products such as live sea urchins, fish eggs, shrimps, and peeled clams can be kept fresh for longer after being treated with lysozyme. For example, immerse the sea urchin in a mixture containing glycine (0.1M), lysozyme (0.05%) and salt (3%) for 5 minutes, remove the water, store it in a cold storage at 5°C, and eat it directly after 9 days , no festering, no change in color. However, in the above mixture, when glycine is removed, it cannot be eaten after 8 days; when glycine and lysozyme are removed, it cannot be eaten after 4 days.

2. Application in pastry

Cream cakes are one of the most rapidly spoiling foods in cream-filled desserts. The spoilage bacteria isolated from this kind of creamy food are inoculated into gravy agar medium for cultivation, and then lysozyme is added, which can also decompose some spoilage bacteria.

Mix the aqueous solution of lysozyme in the cream cake, and cultivate it at 30°C and 37°C for two days, and it is found that it has a slight effect. In addition, when fresh powder was used to make food balls, lysozyme was found to be very effective when mixed with water containing lysozyme and adjusted to a pH of 5.5. But in ice cream, even with the addition of lysozyme, the number of bacteria was reduced. This phenomenon may be due to the different types of contaminating bacteria.

3. Application in wine

For example, lysozyme is used in the preservation of sake (Japanese sake). Sake contains 15-17% ethanol, 3-4% extract and other organic acids. Due to the antiseptic effect of ethanol, most microorganisms cannot survive in sake, and only Pyrocolonium (lactic acid bacteria) can grow. Add egg white lysozyme to sake, and then inoculate Pyrocolonium, which is easily contaminated by sake, and found that egg white lysozyme can significantly inhibit the growth of Pyrocolon bacteria.

15mg/L lysozyme has roughly the same effect as 250mg/L salicylic acid. Lysozyme inhibits the growth of Pyrofallenia, undoubtedly due to bacteriolysis. However, its bacteriolytic effect is different from the bactericidal effect of salicylic acid. The effect of lysozyme decreased when the inoculum size of Pyrofallenia increased. But pyrobacterial contamination does not occur in modern brewing.

Therefore, in practical application, adding lysozyme can achieve the purpose of sufficient preservation. After sake fermentation, in order to achieve the purpose of sterilization, it is usually heated at 50~60°C for several minutes to tens of minutes. Egg white lysozyme is a relatively heat-resistant enzyme, which will not be inactivated under the above heating conditions.

4. Application in dairy products

In Europe, it is mainly used for human emulsification of cow milk. One of the main differences between human milk and cow milk is the content of lysozyme. The activity of lysozyme in human milk is 6 times that of cow milk. Add lysozyme to In cow's milk and its products, it can emulsify the cow's milk and improve the immune function of the body of the cow's milk, so that it is more suitable for babies to eat. Adding lysozyme to milk will also have the ability to sterilize and enhance the growth of bifidobacteria.

Adding 0.05~1mg of lysozyme to each ton of milk and incubating at 37°C for 3 hours can make the content of bifidobacteria in cow milk almost the same as that in human milk, thus ensuring the good reproduction of bifidobacteria in the intestinal tract of infants. During the fermentation process of cheese, butyric acid and gas are often produced by the action of butyric acid bacteria, which is easy to cause cheese expansion. Adding a certain amount of lysozyme in cheese production can prevent casein fermentation caused by microbial contamination and ensure the quality of cheese. Therefore, the effects of adding lysozyme to dairy products such as cheese have been extensively studied.

5. Application of health food

Lysozyme is a high-basic protein with certain health care effects, anti-infection and enhanced antibiotic efficacy; blood coagulation and hemostasis, tissue regeneration and wound healing. Lysozyme can directly or indirectly promote the proliferation of intestinal bifidobacteria in infants, promote the formation of curdled milk casein in infants’ stomach and intestines, and facilitate digestion and absorption of infants. Especially for premature infants, it can prevent weight loss, prevent digestive organ diseases, Increase body weight and other functions, therefore, lysozyme is an ideal additive for infants, food for the elderly, infant formula milk powder, beverages, milk for the elderly, and beverages.

Japan's Morie Company uses egg white lysozyme to preserve dairy products eaten by infants, and finds that lysozyme can prevent enteritis and allergies, so it is added to infant food, especially infant dairy products, and lysozyme is added to infants and the elderly In the food, it can increase the intestinal bifidobacteria, indicating that lysozyme has a balancing effect on the intestinal flora of infants and the elderly. Fresh milk contains only 13mg/100mL of lysozyme, and human milk contains 40mg/100mL of lysozyme. Adding a certain amount of lysozyme to fresh milk can not only play an antiseptic role, but also have a strengthening effect and increase the baby's health.

Yotabio is a Chinese company that specializes in providing clean shelf life technology services and natural shelf life extension solutions for food. We use natural raw materials and biotechnology to produce various high-quality ingredients to keep the appearance, color, aroma, taste and nutritional quality of food more stable during the shelf life.

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