In supplement manufacturing, particularly during the depositing step where gummy or soft-chew shapes are formed, the physical properties of the syrup are critically important to achieving clean, consistent shapes. The two primary physical properties that determine success are viscosity and surface tension, but their relative importance depends on the specific stage of deposition.
Viscosity: The Dominant Factor
Viscosity is the most critical physical property for clean shape formation. It governs how the syrup flows into molds and whether it holds its shape before setting. Key aspects include:
- Flow control: A syrup with too low viscosity will run or seep into gaps, causing irregular shapes or flashing (thin edges). Too high viscosity may not fill the mold completely, leading to gaps or air pockets.
- Sheer-thinning behavior: Many supplement syrups exhibit non-Newtonian flow, meaning their viscosity decreases under shear (e.g., during pumping or deposition) and recovers once deposited. This recovery is essential for the syrup to "snap back" into shape without spreading.
- Temperature sensitivity: Viscosity decreases rapidly with temperature. Maintaining a consistent deposition temperature (typically 60-80°C for gelatin-based syrups) ensures repeatable filling and shape retention.
Without proper viscosity control, even the best molds will produce defective shapes.
Surface Tension: The Secondary Critical Property
Surface tension influences how the syrup interacts with the mold surface and itself. While less dominant than viscosity, it’s essential for clean edge definition:
- Wetting behavior: High surface tension causes the syrup to bead up and resist spreading, which can lead to poor mold filling and domed tops. Low surface tension helps the syrup wet the mold evenly, but if too low, it can creep up the sides of the mold cavity, causing "feathered" edges.
- Droplet formation: During drop-wise deposition, surface tension dictates whether the syrup separates cleanly from the nozzle. Too high surface tension may cause stringing (long tails) between the nozzle and the deposited mass, distorting the shape.
- Release properties: After setting, the surface tension of the solidified syrup affects how easily the shape releases from the mold. However, during deposition, it primarily affects the initial shape formation.
Which Is Most Critical?
For the deposition step itself, viscosity is the most critical property because it directly controls bulk flow and shape retention. Without appropriate viscosity, the syrup will not fill the mold correctly or hold its shape before setting. Surface tension becomes critical when dealing with fine details, sharp corners, or non-stick mold surfaces, but it typically plays a supporting role.
In practice, manufacturers adjust both properties through formulation (e.g., using gelling agents, humectants, or emulsifiers) and process parameters (temperature, deposition speed) to achieve the desired balance. A well-optimized system ensures that the syrup flows easily into the mold, holds its shape immediately after deposition, and releases cleanly without flash or defects.