Lysozymes (EC 3.2.1.17) are antimicrobial enzymes that hydrolyse the 1,4-β-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in bacterial peptidoglycans (and between N-acetyl-D-glucosamine residues in chitodextrins), breaking down the cell walls of many Gram-positive bacteria. Found naturally in milk — particularly human milk — and in egg white, they are important natural antimicrobial preservatives. Cheesemakers add egg-white lysozyme to certain cheeses to kill harmful clostridia and prevent late blowing; winemakers use it to control lactic-acid bacteria, and it serves for the cold sterilisation of certain foods and beverages where heat would damage quality. As an egg-derived additive (E1105) it must be allergen-labelled.