Why Does Honey Never Spoil?

Honey is a remarkable preservative with multiple antimicrobial defences. Its water content is typically below 18%, and its sugar concentration above 80% creates such high osmotic pressure that microorganisms are dehydrated and killed. Its pH of 3.2-4.5 (acidic) inhibits most bacterial growth. Additionally, the enzyme glucose oxidase (introduced by bees) slowly produces hydrogen peroxide, a natural disinfectant. Honey also contains trace amounts of defensin-1, a bee-derived antimicrobial peptide. Archaeologists have found 3,000-year-old honey in Egyptian tombs that was still edible. The only condition under which honey can ferment is if its moisture content rises above about 20% — which is why proper sealed storage matters. Manuka honey from New Zealand has additional antimicrobial compounds (methylglyoxal) making it especially potent.