Before the advent of infrared moisture analyzers, gummy drying was an art as much as a science. Operators relied on a combination of tactile observation, visual cues, and hands-on experience that constituted the "tacit knowledge" of the craft, which is now largely lost to automation. The target was a narrow window: too wet, and gummies stick together, grow mold, and soften in the package; too dry, and they turn hard and lose their chew. This know-how was never written down but was passed from veteran to apprentice on the production floor.
Key Tacit Knowledge of Pre-IR Moisture Control
1. The “Stick Test” and Tactile Feedback
The most common method was the stick test. An operator would gently press a gloved finger into the surface of a gummy. The response told them everything:
- Too wet: The gummy would feel tacky or leave a residue on the glove. The surface would be soft and easily deformed, often sticking to the tray.
- Just right: The gummy would spring back slightly when pressed, with a smooth, slightly firm surface that did not adhere to the finger. This was the "sweet spot" of final moisture content.
- Too dry: The gummy would feel hard, brittle, or rubbery, and the surface might look slightly cracked or chalky.
This test required a practiced, consistent touch. Different gummy recipes (pectin-based vs. gelatin-based) felt different at the same moisture level, so operators developed an intuitive feel for their specific product.
2. Visual Surface Appraisal
Operators became expert at reading the surface of a gummy for clues:
- Shine: A high, uniform gloss indicated adequate moisture content. A dull, matte surface was a sign of over-drying or "case hardening."
- Firmness and Skin: The formation of a thin, dry "skin" on the surface while the interior remained moist was a critical sign of correct drying progress. Operators learned to recognize the precise texture and opacity of that skin.
- Edge checking: Tiny cracks at the corners or edges of gummies were a late-stage warning of over-drying.
Case hardening happened when the outside dried too fast and sealed, leaving the center wet while the surface looked done. A dull skin that still felt soft underneath was the tell.
3. Weight and Feel of a Whole Tray
While not precise, experienced operators could tell moisture content by the weight of a full drying tray in their hands. They developed a kinesthetic memory for how a tray of finished gummies (at the correct final moisture) should feel versus a tray of wetter gummies. They also learned the subtle sound of a properly dried gummy when gently tapped against the tray: a solid, non-sticky thud versus a dull, sticky slap.
4. The “Break Test” and Internal Moisture Gradients
A more invasive check was the break test. An operator would snap a gummy in half to examine the internal structure:
- A clean break with a smooth, non-sticky interior indicated uniform drying.
- A gummy that bent instead of breaking or showed a tacky interior core was still too wet and needed more time in the drying rooms.
- An overly dry gummy often cracked before breaking, revealing a dry, porous center.
Codifying Tactile Checks into Measured Standards
Most of these checks did not have to vanish. The stick test read spring-back and tack; a texture analyzer measures the same properties with a probe that presses into the gummy and records force and recovery. The break test maps to a fracture measurement, and the tray-weight check maps to loss on drying, which is the number an infrared analyzer reports after heating a small sample until the moisture boils off and weighing the difference. Confectionery producers that once relied on sensory testing to judge when sweets were ready during stoving now test hardness as a predictor of elasticity.
What operators once carried in their hands now sits in spec sheets: a target moisture window, a water activity limit often below 0.65 to hold off mold, and a texture profile for each SKU. Interpretation is harder to replace. An analyzer reports one number; the veteran noticed when the number and the feel disagreed. Written standards recover some of that when they record the cues machines miss: surface tack, skin opacity, edge cracking, the sound of a tray. Manufacturers that document those cues, and train new operators to check them beside the analyzer, keep more of the craft than those that switched to numbers alone.
What Is Now Lost?
While automation with infrared analyzers brings consistency and speed, the tacit knowledge of sensory-based moisture assessment is difficult to replicate. Operators who honed these skills could:
- Predict drying times by feeling the humidity in the room and the texture of the first batch of the day.
- Adjust recipes on the fly by noticing subtle shifts in a gummy's texture, alerting them to inconsistent raw materials (e.g., gelatin bloom or citric acid variability).
- Detect problems early: a slight tackiness on a tray might signal a cooling unit malfunction before any alarm went off.
Today, many production managers and experienced operators at KorNutra have retired, taking this sensory expertise with them. Newer staff are trained to trust the analyzer's numbers rather than their fingers. While this reduces inconsistency, it also means a finer sensitivity to process variation is lost: the ability to feel when a batch is "just right" even if the machine says it's 0.2% off target. At KorNutra, we still value the intersection of this historic craft and modern precision, but we acknowledge that the human touch in moisture analysis is now a fading art. The best operators today combine the data from their analyzers with a trained eye and a gentle press of the thumb.