Lysozyme

Lysozyme is a naturally occurring antimicrobial enzyme found in hen egg white, human tears, saliva, and milk. It functions by cleaving the peptidoglycan layer of bacterial cell walls, particularly those of Gram-positive bacteria. As a food additive it is used primarily in hard and semi-hard cheese making to prevent late-blowing defects caused by Clostridium tyrobutyricum — an anaerobic bacterium that produces CO₂ and butyric acid during cheese ripening, causing unwanted texture defects and off-flavours. Lysozyme provides this anti-Clostridium activity as a natural alternative to the chemical preservative nitrate (E251/E252) in traditional cheese varieties.

JECFA evaluated lysozyme in 1992 and classified the ADI as "not specified," reflecting its status as a naturally occurring protein in human breast milk and other foods that is completely digested to amino acids during normal gastrointestinal processing. Its long history of safe consumption in foods containing egg white supports this benign assessment. No accumulation or novel toxic metabolite arises from dietary lysozyme.

Lysozyme is approved in the EU as E1105 for specific cheese applications and in other markets for cheese and wine production. The key consumer consideration is allergen origin: lysozyme is derived from hen egg white and is therefore an egg-derived food additive. Consumers with egg allergy may react to lysozyme-containing cheeses, and EU regulations require allergen labelling for egg-containing food additives. This means that cheeses treated with lysozyme must declare "egg" in their ingredient list or allergen information. Consumers with egg allergy should check cheese labels carefully, particularly for hard Italian varieties such as Grana Padano and some Goudas where lysozyme use is traditional.