Determining the precise maximum concentration of invert sugar in a gummy formulation before it becomes overly hygroscopic is not a fixed number; it depends on several interrelated factors, including the complete sugar profile, water activity (aw), processing conditions, and the specific texture goals. Industry experience and standard practices still offer clear guidelines.
General Threshold Guidelines
In most gummy formulations, invert sugar is a supporting sweetener rather than the main one. At 10-15% of the total sweetener weight it keeps sucrose from crystallizing with little hygroscopic risk; beyond that, moisture pickup becomes a growing concern. The practical thresholds are:
- Below 15% invert sugar: Generally low hygroscopic risk; gummies remain stable with minimal stickiness under normal humidity.
- 15% - 25% invert sugar: Moderate hygroscopic behavior. Gummies may become tacky in humid storage or if the water activity exceeds 0.55.
- Above 25% invert sugar: High hygroscopic risk. Stickiness often becomes unacceptable, especially when the total moisture in the gummy exceeds 18%. At these levels, the gummy can absorb ambient moisture, leading to a soft, sticky surface and clumping in packaging.
When Stickiness Becomes Unacceptable
Stickiness is unacceptable when it leads to:
- Packaging failure: Gummies adhere to packaging or each other, causing product damage or unsaleable units.
- Consumer rejection: The surface feels tacky to the touch, or the gummy leaves residue.
- Increased microbial risk: Water activity above about 0.65, whether from a wet formula or absorbed humidity, lets xerophilic molds grow on the surface. Bacteria need water activity above about 0.85, so in a gummy the practical risk is mold.
To stay within acceptable limits, manufacturers should monitor water activity closely. For invert sugar at 25% and above, keeping aw below 0.55 is critical. If stickiness is observed, reducing invert sugar or balancing it with less hygroscopic sugars such as sucrose or isomalt is recommended. KorNutra’s standard gummy formulations avoid exceeding 25% invert sugar to ensure stability without compromising chewability.
Packaging and dry processing when the formula keeps its invert sugar
If the formulation needs invert sugar for graining control or texture, the other two levers are the package and the processing room. A barrier film with a low moisture vapor transmission rate limits how much ambient humidity reaches the gummy at all. That is what lets higher-invert formulas survive humid distribution. The same logic applies after cooking. Cool and seal the gummies in a room held at low relative humidity instead of leaving warm, high-water-activity pieces in humid air before packing. Moisture moves down the water activity gradient between the gummy surface and the air around it, and both the film and the room slow that movement.
Practical Tip
As a screening check, run accelerated stability at 40°C/75% RH for two weeks. If the gummy develops visible wetness or tackiness during this period, the invert sugar level is too high for that specific formulation. Adjust downward by 5% and retest.