When you combine the rapid setting of gellan gum with the slow-drying properties of starch molding, you can create a gummy with a firm shell and a soft core, all in a single deposition step. This produces a layered texture without a secondary coating or extra processing stages.
The process works in three parts:
- Rapid gelation of gellan gum: Gellan gum sets quickly on cooling and in the presence of cations such as calcium. In a single deposition step, the outer layer of the gummy forms a firm, stable shell as soon as it contacts the mold. The rapid set prevents the core and shell from mixing, keeping a clear boundary between them.
- Slow-drying of starch molding: Starch-based molds, like those used in traditional gummy production, draw moisture out gradually over the stoving period. Because the surface gives up water first, the interior of the deposited gummy stays hydrated and soft longer. This gradual moisture movement keeps the core pliable and tender even as the outer gellan gel firms up.
- Single-step deposition: Instead of forming the shell first and then injecting a soft center, as two-step methods do, this technique deposits the entire gummy in one pass. The outer portion, rich in gellan gum, sets fast, while the inner portion, formulated with added humectants such as glycerin, stays soft as the starch mold dries the surface.
Key benefits of this approach
- Texture contrast: Consumers experience a firm bite that gives way to a soft, melt-in-the-mouth center.
- Simpler production: Removing the extra coating or injection step cuts processing time and equipment needs.
- Consistent quality: Because the shell forms rapidly, there is minimal risk of the core blending with the shell, leading to a uniform product batch after batch.
Formulation considerations
To get this texture in a single deposition step, balance the gellan level in the deposit with ingredients that delay setting in the core. In a one-pass deposit the mix starts uniform, but the starch mold pulls water from the surface first, which concentrates the gellan and any calcium there. That surface layer gels first into the shell, while the core stays hydrated behind it and sets softer, helped by humectants such as glycerin. The starch mold itself also plays a role. Selecting a mold with the right moisture absorbency controls how fast the surface dries relative to the core.
What to control so the shell and core stay distinct
A one-pass deposit holds a clean shell-to-core boundary only when the surface gels before the interior. Three process variables decide that. Molding starch moisture comes first: starch above roughly 9% moisture absorbs less, so a wet mold dries the surface too slowly and the shell stays thin. Deposit temperature and calcium level matter next, because low-acyl gellan sets on cooling and in the presence of calcium. The stoving profile finishes the work: a steep early drying gradient can form a skin on the surface before the core releases moisture, so the start of stoving runs gentler. You tune the three together rather than in isolation.
KorNutra specializes in custom gummy formulations. For a dual-texture product like this one, our formulators set the gellan level, the humectant package, and the starch mold profile so the shell firms while the core stays soft in a single deposition step.