A gummy stops feeling like a gummy once its gel network loses enough water that the texture moves from chewy and elastic to tough, then brittle and glassy. That threshold is the critical moisture content. Gummies come off the line at 10-20% moisture by weight. As a piece dries below about 10%, it leaves the chewy range and the hydrocolloid network stiffens toward a glassy state, ending up as a brittle, glassy gel. That state is distinct from a hard candy, which is a boiled sugar glass finished near 1-3% moisture and cooled below its glass transition temperature.
The critical moisture content depends on the type and concentration of the hydrocolloid and on the sugar system around it. The main gelling agents shift that boundary in different ways:
- Gelatin: Gelatin's protein network is long and elastic, so gelatin gummies keep stretching as water leaves and turn brittle only after drying well past the normal range.
- Pectin (especially high-methoxyl pectin): Pectin gels set shorter and more rigid than gelatin, which gives a quick bite but little plastic give. Pectin makes a gummy more brittle and less chewy, so a pectin piece that dries out turns crumbly, then glassy, faster than a gelatin piece.
- Modified starches and blends: Starch granules such as tapioca or cornstarch hold water and add compressibility. Blending them with gelatin holds chew a little longer at the dry end, pushing the brittle point down.
- Agar and kappa carrageenan: These set into firm, brittle gels, so they turn chalky or hard at higher moisture than a gelatin or pectin piece. Iota carrageenan is the exception, forming softer, more elastic gels.
Moisture content versus water activity
Water activity (aw) predicts shelf texture more reliably than moisture percentage alone. Moisture content measures total water; aw measures the water that is free to move, and that free water drives hardening, softening, and migration. Two gummies at the same moisture content can behave differently if their sugar profiles differ. Dissolved sugars and humectants bind water and lower aw. For gummies, formulators typically hold aw between about 0.5 and 0.75, a window that favors a soft texture and a longer shelf life. When aw differs between a gummy and its surroundings, or between layers inside a single piece, water migrates until both sides reach equilibrium. That migration dries out a finished gummy over time, or pulls moisture in and makes the surface sticky. In practice, formulators set the moisture target and the aw window together, as one measurement pair.
At KorNutra, we formulate to hold gummies inside the chewy zone, on the drier and more shelf-stable end of the typical 10-20% range. The hydrocolloid sets how the gel network behaves as water leaves, and the sugar system matters as much: glucose syrup and polyol humectants hold water and shift the dry-out point. We match the gelling agent to the humectant system so a finished piece stays put through storage and temperature swings, and the "too dry" point stays well below where the product will ever land. No single moisture number applies to every gummy; the hydrocolloid and the sweetener system together define the boundary.