When a gummy manufacturer shifts from producing individual shapes to a continuous sheet that is later cut, the formulation and process controls must be rebalanced to ensure the sheet remains uniform, workable, and structurally sound. The key differences revolve around managing viscosity, set time, and cooling to prevent defects like tearing, sticking, or inconsistent thickness.
Viscosity Constraints
For a continuous sheet, viscosity must be low enough to flow evenly across the depositor or belt but not so low that it runs off the edges or produces a thin, fragile sheet. Unlike individual molds, where a slightly thicker gel can be forced into cavities, a sheet requires a consistent, self-leveling consistency. The target viscosity is typically higher than for injection-molded shapes because the sheet must hold its shape after deposition without sagging. A viscosity in the range of 8,000-12,000 cP (at deposition temperature) is common for sheet production, whereas individual shapes might allow for 6,000-10,000 cP. The formulation must also avoid air entrapment, as bubbles in a sheet will produce holes after cutting.
Set Time Constraints
Set time for a continuous sheet is more critical than for individual shapes because the entire sheet must set uniformly before cutting. If the gel sets too quickly on the edges but not in the center, cutting will cause uneven edges or sticking. Conversely, if it sets too slowly, the sheet may deform under its own weight. The ideal set time for a sheet is usually 20-40% longer than for individual shapes of the same thickness to allow moisture to evenly distribute. This often requires a slower-acting gelling system-using a combination of pectin and gelatin, for example, or adjusting the pH buffer to delay the gelation of pectin. The manufacturer must also ensure the set time is consistent across the entire production run, as batch-to-batch variations become more apparent in a large sheet.
Cooling Constraints
Cooling is perhaps the most distinct challenge for a continuous sheet. While individual shapes can be cooled rapidly in a tunnel, a sheet must be cooled uniformly from the inside out to prevent warping, surface cracking, or center collapse. The cooling rate must be slower and more controlled-typically using a multi-zone cooling tunnel with graduated temperatures (starting at 10-15°C and decreasing to 5-8°C) rather than a single cold blast. The sheet thickness also affects cooling: for a sheet intended to be cut later, the thickness is usually 8-12 mm, compared to 5-8 mm for individual shapes. This extra thickness demands longer cooling times (30-50% longer) to ensure the center reaches the required firmness. Additionally, the cooling belt or tray must be non-stick and perfectly level to avoid creating thickness variations that lead to jagged cuts.
Summary of Key Differences
- Viscosity: Higher (8,000-12,000 cP) for sheet to prevent spreading and ensure uniform thickness.
- Set time: 20-40% longer to allow even gelation across the entire sheet.
- Cooling: Slower, multi-zone process to avoid thermal stresses, with thicker sheets requiring more dwell time.
- Post-processing: Cutting requires the sheet to be fully set but still slightly tacky-if over-dried, it will shatter; if under-set, blades will drag.
By adjusting these parameters, a manufacturer can produce a uniform, defect-free continuous sheet that cuts cleanly into any desired shape-whether squares, rectangles, or custom shapes-without the limitations of individual molds.