The maximum shear rate a gummy syrup can take before its gel structure breaks down is what keeps texture and quality consistent. The answer depends on the specific formulation, but in our experience at KorNutra, the critical shear rate typically falls between 100 and 300 s⁻¹ for standard depositing operations. This is a general guideline; the exact threshold varies with gelatin bloom strength, solids content, and the presence of starches or pectins.
When the shear rate exceeds this range, the gel structure begins to degrade. The damage shows up as poor texture in several ways:
- Loss of Chewiness: The gummy becomes softer or more brittle than intended.
- Graininess or Grittiness: Sugar crystals or other ingredients may form unevenly, creating a sandy mouthfeel.
- Stickiness: The gel may become overly tacky, sticking to the mold or packaging.
- Syneresis: The syrup may weep liquid (water or oil) after setting, leading to an unappealing surface.
The mass leaves the nozzle hot, before the gel network has formed. The network sets as the deposit cools in the mold. Shear does the most damage when the syrup is cool enough that structure is already building, and pectin systems show it first. Pectin sets at a higher temperature than gelatin, and its network is shear-sensitive, so the same depositing step that a hot gelatin mass tolerates can tear a pectin gel that is already setting.
To pinpoint the exact maximum for your production, we recommend a two-step approach. First, run a rheological analysis of your specific gummy syrup to identify its yield stress and flow behavior. Second, check your depositing equipment; high-speed piston depositors or positive displacement pumps can generate shear rates over 500 s⁻¹, which may be too aggressive for delicate gels. If you do not have rheology data on hand, estimate the shear your nozzle generates from flow rate and nozzle diameter. Wall shear in a round nozzle scales with flow rate divided by the radius cubed. Shrink the nozzle and shear climbs. At KorNutra, we fine-tune depositing parameters like nozzle size, flow rate, and temperature to keep shear rates below 200 s⁻¹, which keeps the gel structure stable and the texture right.