The tension between fast setting and slow drying is real, but the two halves of it sit on different equipment. The cooling tunnel handles the fast-setting side: a rapid, even gel set that locks the shape so pieces can be demolded and the line can keep moving. The slow-drying side happens after demolding, in a drying or conditioning room held at roughly 20-30°C and 25-40% relative humidity for several hours to a day, so the pieces reach their target moisture and final chew. At KorNutra, we approach the tunnel side with multiple temperature zones that can be independently adjusted, letting the product set quickly in the first zone to solidify its shape and enable higher line speeds, then finish the set more gently in the later zones.
Key factors in this optimization include:
- Temperature profiling: A cold first zone sets the exterior quickly, and the zones that follow finish the set; dropping the temperature all at once cracks or distorts the pieces.
- Airflow control: Adjusting both velocity and direction. Higher airflow pulls heat out faster and accelerates the surface set; lower, more laminar flow later keeps the surface from drying to a shell before the center releases moisture.
- Belt speed and tunnel length: KorNutra designs tunnels with variable-speed belts and enough length to cover the required residence time, typically 20 to 60 minutes, so the line speed doesn't outpace the set the gel needs before demolding.
- Product-specific parameters: We calibrate each tunnel to the formulation. The gelling system, binders, moisture content, and fat levels all set how quickly a piece can firm up without compromising quality.
Dew point and condensation control
If the air inside the tunnel, or the surface of the pieces, falls below the dew point of the surrounding air, moisture condenses onto the product. On a sugar-based gummy, that wet film makes the surface sticky, so pieces clump in the mold or pick up a dull, grainy film. Tunnel design manages this by controlling the absolute humidity of the air along with its temperature, and by staging the temperature drop so the surface never crosses the dew point. The same physics produces sugar bloom in chocolate; in gummies it shows up as stickiness and clumping, and the fix is the same: dehumidify the tunnel air and keep the exit zone above the dew point.
The goal is a set fast enough to hold line speed without sacrificing mouthfeel or stability. At KorNutra, we test these parameters in our pilot tunnels and fine-tune the balance for each client's product line.