Raw Honey Guide · refractometer → shelf life
What does that moisture reading actually mean?
Slide your refractometer reading. See water activity, the Beutler fermentation-risk zone, and estimated sealed-jar shelf life at room temperature.
Only ferments if the jar contains over ~1 000 yeast CFU / g, which raw unifloral honey almost never does (typical loads are 1–100 / g). Codex-compliant.
What to do: Seal tightly and keep out of humid kitchens. Honey is hygroscopic — an open jar slowly absorbs moisture from the air.
Beutler 1975 yeast threshold: Fermentation risk above ~1 000 CFU / g.
The physics (Beutler 1975, White 1978):
Honey is preserved by low water activity, not sugar, pH, or heat. Osmophilic yeasts (Zygosaccharomyces rouxii and relatives) tolerate high sugar but stall below aw ≈ 0.60 — the microbiological waterline. Every +1% moisture adds roughly 0.02 to aw. Cross 0.60 and the jar is one warm week from fizzing.
Model assumes sealed jar, 20 °C, raw Apis mellifera unifloral honey. Does not apply to thixotropic heather (Calluna vulgaris — EU allows up to 23 %) or stingless-bee honey (Meliponini — MSM 2683:2017 allows 25–35 %); those have different preservation chemistry. Refrigeration (2–7 °C) slows both fermentation and crystallization roughly in tandem.