Gummy hardness over time is a common challenge in the supplement industry, caused mainly by moisture loss and starch retrogradation. As a gummy sits, water molecules migrate to the surface and evaporate, creating a drier, harder matrix. If the gummy contains starch or certain hydrocolloids, the starch molecules can recrystallize, a process called retrogradation, which stiffens the texture. Temperature fluctuations and low-humidity storage accelerate these changes. To build a gummy that stays soft for two years, you need to control moisture retention, inhibit crystallization, and protect against environmental factors.
Key Formula Adjustments
- Moisture Stabilizers: Use humectants like glycerin or sorbitol, which bind water tightly and slow evaporation, keeping the gummy chewy. Sorbitol can make up 15-20% of a sugar-free formula; glycerin is used at lower levels, since too much humectant makes a gummy sticky.
- Prevent Retrogradation: Replace or reduce high-amylose starches with modified starches or maltodextrin. A blend of pectin and a low-amylose starch (e.g., waxy maize) reduces hardening over time.
- Optimize Gelling Agents: Pectin-based gummies are less prone to hardening than gelatin-based ones. Go with a high-methoxy pectin with a rapid-set formulation for a stable, resilient gel network. High-methoxy pectin only sets in a low-pH, high-solids environment, so sugar-reduced and sugar-free formulas need a low-methoxyl pectin or a different gelling system.
- Add Plasticizers: Ingredients like vegetable oil or medium-chain triglycerides (MCTs) at 0.5-2% help improve flexibility and reduce brittleness without affecting stability.
Processing and Packaging Controls
Deposition and Drying
Control the drying process carefully. Deposit gummies at a consistent temperature (e.g., 80-90°C) and cool them in a low-humidity environment to prevent surface moisture loss. Avoid over-drying in starch molds. Lower final moisture makes the candy harder and more brittle, so hold residual moisture at the top of the range your formula allows.
Packaging as a Barrier
Use high-barrier packaging films. Aluminum foil laminates hold water vapor transmission below 0.1 g/m²/day, because an intact foil layer is nearly impermeable to moisture. Metallized PET is a step down: its vapor-deposited aluminum is thinner and carries pinholes, so it doesn't reliably reach that rate. Include a desiccant pack (e.g., silica gel) to absorb any moisture in the headspace. Seal packages under nitrogen to minimize oxidation and moisture migration.
Accelerated Stability Testing
To validate your design, run stability studies at 40°C and 75% relative humidity for six months, the standard ICH accelerated condition. Test hardness weekly using a texture analyzer (e.g., TA.XTplus). If hardness increases by more than 10%, adjust humectant or gelling agent levels. For a two-year shelf life, aim for less than 15% change in hardness after the equivalent accelerated period.
Track Water Activity Alongside Moisture
Moisture content and water activity aren't the same number. Moisture content tells you how much water a gummy holds; water activity (aw) tells you how much of that water is available to migrate, recrystallize, or support microbial growth. Two formulas can carry the same moisture and different aw, because humectants like sorbitol and glycerin bind water and lower its availability. That's why humectants protect texture twice: they hold water in and make the water that remains less mobile. Record aw at every pull point in your stability study, alongside hardness. A gummy whose moisture reading looks flat can still be drifting internally, and aw will show it before the texture analyzer does. Setting an aw specification for the formula and holding to it is the cleanest way to keep texture stable across two years.
At KorNutra, we stick to these principles. Combining careful ingredient selection, precise processing controls, and reliable packaging makes it possible to ship a gummy that stays soft and chewy through a two-year shelf life. If you are developing a product with those requirements, our team can help tailor the formulation to reach that stability without compromising other quality parameters.