Lysozyme

Butyric acid fermentation, the late-blowing defect in cheese is caused by the outgrowth of clostridia spores. Late-blowing can create considerable loss of product, especially in the production of semi- hard and hard cheeses like for example Gouda, Edam, Emmental, Maasdam, Greyere and Parmesan. With the use of Lysozyme, the production and ripening of cheese may be carried out without concern for butyric acid fermentation. This has led to widespread use of lysozyme in cheese production.

Contamination of cheese milk with spores of clostridia, especially Clostridium tyrobutyricum, originates mainly from the use of silage in the feeding of dairy cattle. Spores of the bacteria are ingested by cows from contaminated silage and subsequently arise in the dung. Contamination of milk with even very small quantities of the dung (for example from the utter) leads to the presence of Clostridium tyrobutyricum in milk.

Spores of Clostridium tyrobutyricum have been found to survive the normal heat treatment of milk during the production of cheese and later propagate to cause late blowing. During the ripening of salt brined, semi- and hard cheeses Clostridia ferments lactate into butyric acid and large quantities of gas (CO₂ and H₂). The formation of gas produces undesirable effects in texture (cracks and irregular eyes) and the acids cause unacceptable tastes and smells.

Working mechanism of Lysozyme

The use of lysozyme in cheese will prevent the growth of Cl. tyrobutyricum as lysozyme is able to lyse the cell walls of the vegetative form of Cl. tyrobutyricum through the enzymatic cleavage of the bacterial cell wall. Lysozyme binds to the casein prior to clotting of the milk, remains active in the curd throughout the ripening process and can disrupt the vegetative cell walls once the spores germinate.

The salt absorbed by the cheese during brining inhibits the germination of the spores. However,

this salt absorption is a slow process and does not offer sufficient protection against butyric acid fermentation during the brining as well as during the early stages of ripening. Adding lysozyme prevents the butyric acid fermentation.

Factors influencing growth of butyric acid formation

The critical number of spores to bring out butyric acid fermentation varies with the type of cheese shape and size, pH value, ripening time and temperature and cheese structure including normal eye formation. Recent studies have shown that if the number of spores exceeds 500 spores/litre a high risk of cheese defects may occur.

Characteristics of Lysozyme

Lysozyme is an anti-microbial enzyme which is extracted from fresh chicken egg white. Lysozyme has preservative properties and is particularly effective against gram positive bacteria and bacterial spores. Lysozyme is a clear, colourless solution, available in a 22 % strength (w/v) and suitable for foodstuffs.

Benefits of Lysozyme

• Very efficient to prevent late blowing;
• Good alternative preservation if nitrate is not allowed due to national regulations;
• Suitable for all types of cheese;
• Improvement of organoleptic characteristics of the cheese;
• Easy implementation without specific equipment and large capital expenditures;
• Where bactofugation is applied, lysozyme can be added in low levels to safeguard against post-contamination through out the entire cheese making process;
• When valorisation of whey is required, whey from lysozyme-produced cheese is more suitable than whey from nitrate-produced cheese.

Lysozyme can be used either alone or in combination with mechanical treatment like bactofugation. When applying lysozyme please pay attention to following guidelines for optimal cheese preservation:

• Choose the optimal dosage depending on the spore load of butyric acid bacteria in the cheese milk (see figure 1.).
• Add lysozyme after all heat treatments and as early as possible before addition of rennet and cultures.

Figure 1. Advised dosage of lysozyme in relation to the spore load

Strength and packaging

Lysozyme is available in liquid form with a solid content of 22 %.

The liquid lysozyme is available in:

• 20 litre jerry cans

Storage and shelf life

Lysozyme can be stored for 9 months, provided it is stored in its closed packaging, in a cool and dark place, at a temperature between 0 and 6 °C. When stored at 20 °C a shelf life of 6 months can be guaranteed.

Quality and safety

Lysozyme (extracted from egg white) can be safely used in cheese production and is approved as a preservative (E1105) in the EU directive on food additives. Legislation on lysozyme differs from country to country. Always consult national legislation. The product must always be used in accordance with prevailing rules and regulations.

Technical assistance

CSK’s technical sales staff members have years of experience in the application of preservatives in cheese production. For further information, please contact CSK.