Determination of water activity change due to crystallization in honeys from Argentina

As most honeys are supersaturated solutions of glucose, this sugar may crystallize spontaneously at room temperature in the form of glucose monohydrate. Crystallization of honey lowers the glucose concentration in the liquid phase and thus increases the water activity (aw) which sometimes can allow naturally occurring yeasts cells to multiply, causing fermentation of the honey. It is the purpose of present work to measure the water activity of 49 samples of crystallized honeys from Argentina, as well as the shift in water activity (Δaw) when the samples were re-dissolved upon heating. It was found that Δaw for most samples studied was in the range 0.03–0.04 aw. Studies with sugar model systems resembling honey confirmed that the observed change in water activity quantitatively corresponded to that caused by glucose crystallization.