Lysozyme is a natural antimicrobial enzyme, also known as N-acetylmuramidase, that breaks down the cell walls of bacteria, particularly Gram-positive strains. While it is a key part of the innate immune system in humans and animals, it is also found in a variety of dietary sources and is utilized extensively in the food industry as a preservative. Identifying which foods contain lysozyme can be valuable for both nutritional and food science perspectives.
High-Concentration Natural Food Sources of Lysozyme
Eggs
Avian egg whites, especially from chickens, are the richest natural source of lysozyme used for commercial purposes. In hen egg white, lysozyme makes up 3–4% of the total protein content, where it serves to protect the developing embryo from bacterial contamination. The eggs of other birds, such as ducks and geese, also contain notable quantities of the enzyme.
Milk and Dairy
Lysozyme is a component of mammalian milk, though levels can vary dramatically by species. Donkey milk stands out for its significantly higher lysozyme concentrations compared to human or cow milk. Cow milk, while containing lysozyme, has much lower levels. Purified lysozyme from hen eggs is also added to hard and semi-hard cheeses to prevent spoilage.
Fruits and Vegetables
Some produce contains detectable levels of lysozyme, though generally at much lower concentrations than eggs or milk. Examples include cauliflower, papaya, and cabbage. Other produce like rutabaga, kohlrabi, radishes, turnips, parsnips, and broccoli may also contain lesser amounts.
Lysozyme in Processed Foods
Lysozyme is frequently added to processed foods as a preservative. It's used in ready-to-eat meats and seafood to inhibit bacteria like Listeria monocytogenes and in wines and beers to prevent spoilage from lactic acid bacteria. It is also used to preserve tofu products.
Comparison of Lysozyme Sources
| Feature | Hen Egg White Lysozyme | Donkey Milk Lysozyme | Plant Lysozymes (e.g., Papaya) |
|---|---|---|---|
| Natural Abundance | Very high (3-4% of egg white protein) | High (especially compared to cow's milk) | Very low to negligible |
| Commercial Availability | High; primary industrial source | Low; niche market, high production cost | Limited; not a major commercial source |
| Allergenicity Risk | Higher, due to egg protein source | Lower, due to high similarity to human lysozyme | Generally low, but depends on the source |
| Preservative Use | Widespread in dairy, meat, wine, and more | Used primarily for human milk replacement | Minimal or none in modern food production |
| Heating Stability | Fairly stable, but activity can be reduced by high heat | High levels of activity retained even after pasteurization | Can vary depending on the plant species |
| Primary Role in Nature | Protects the developing embryo in the egg | Protects the infant's gut from infection | Potential role in plant defense mechanisms |
Factors Affecting Lysozyme Content and Activity
Factors like heat treatment, source origin, and the presence of other compounds can affect lysozyme levels and activity in foods.
Health Implications of Dietary Lysozyme
Ingesting lysozyme through food may contribute to immune function and gut health, supported by observations of its role in human milk. Find out more about the broader applications of lysozyme in food preservation and health on ScienceDirect.
Conclusion
Foods containing lysozyme include eggs, especially hen egg white, donkey milk, and certain fruits and vegetables like papaya and cauliflower. Hen egg white is the main commercial source for food preservation in dairy, meat, and beverages. Donkey milk offers a naturally rich, lower allergen alternative. This powerful antimicrobial enzyme plays a role in both natural diets and modern food science.
