Water Activity
A measure of free moisture that predicts microbial and mold risk - critical for gummies.
Water activity measures the free, available moisture in a product on a 0-1 scale - not total water, but the portion microbes can actually use. It's the single best predictor of mold and microbial risk in moist formats.
Most commercial gummies target 0.50-0.60; above 0.65 you need preservatives for any real shelf life, and above 0.85 even bacteria can grow. It's a cheap, fast test ($30-$80) that every gummy and liquid brand should run.
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