Why Honey Does Not Spoil

Jars of honey recovered from tombs thousands of years old have been found unspoiled. [A] The reason is not a preservative added by the bees but the composition of the substance itself. [B] Honey is a solution so concentrated that water makes up less than a fifth of it. [C] A bacterium landing on the surface loses water to its surroundings faster than it can take water in, and it dries out. [D]

Concentration is not the whole story. The bees add an enzyme that converts a small part of the sugar into hydrogen peroxide, and the acidity of honey is closer to that of vinegar than to that of water. Each of these on its own would deter some organisms; together they leave almost nothing able to grow.

The protection depends on the honey staying dry, which is why the lid matters more than the jar. Honey takes up water from damp air, and a surface layer that has absorbed enough moisture will ferment like any other sugar solution. The ancient jars survived because they were sealed and because the tombs around them were dry. A jar left open in a humid kitchen demonstrates the same point in a few months.