Analysis and Solutions to Inaccurate Flavoring and Colorant Metering in Lollipop Production Lines

Analysis and Solutions to Inaccurate Flavoring and Colorant Metering in Lollipop Production Line

In the lollipop production process—which includes sugar boiling, sugar dissolution, vacuum processing, mixing, and molding—flavoring agents, colorants, and acids are heat-sensitive additives. Most are added during the cooling and mixing stage after vacuum boiling is complete. Any deviation in measurement, feeding method, temperature, or mixing uniformity will directly result in inconsistencies in aroma, color, and acidity among different batches, or even within the same batch. The sugar paste reaches very high temperatures; acids

decompose at high temperatures, flavorings are prone to volatilization, and colorants change color when exposed to high heat. These three components must not be added to the boiling kettle in advance; the standard process is to add them after the vacuum boiling is complete and the sugar paste has cooled to the 105–115°C range.

I. Major Failure Symptoms
1. Variations between batches of the same formula: Some are too sour, while others have a weak sour taste; the aroma fluctuates between strong and weak; and the color varies in depth.
2. Variations within the same batch: Differences in flavor and color between the beginning and end of the batch; products poured earlier differ from those poured later.
3. Laboratory test results and ingredient weighing records are correct, but finished product specifications fluctuate.

II. Classification of Main Causes
1. Issues with the Dosing System Itself
1) Fluctuations in liquid levels in storage tanks for acid solutions, colorants, and flavorings; manual scooping or weighing; manual batching is subject to operational errors and residue adhering to container walls, resulting in unstable actual addition amounts per batch. Flavorings with low viscosity are prone to adhering to container walls; organic acids (such as citric acid in aqueous solutions) are prone to crystallization and precipitation, causing sedimentation in piping and reducing the actual feed rate.

2) Metering pump malfunctions (diaphragm pumps/peristaltic pumps)
- Aging pump tubing and worn diaphragms cause flow rate drift; calibration becomes inaccurate just a few hours after operation;
- Air bubbles in the tubing cause the pump to run dry, resulting in actual output below the set value;
- Acid solutions corrode the pump’s seals, leading to leaks; highly volatile flavorings cause negative pressure in the tubing, allowing air to enter.
Many production lines calibrate metering pumps only once before startup and do not verify them during the production process, allowing deviations to accumulate over multiple consecutive batches.

3) Inappropriate Flow Meter Selection
Due to significant variations in the viscosity of flavorings and colorants, standard flow meters amplify errors for low-flow materials; acid crystals adhere to the sensor probe, causing distorted readings.

2. “False Metering Errors” Caused by the Characteristics of the Materials Themselves
1) Colorants: Liquid colorants settle and separate into layers; without agitation in the storage tank, the upper layer is lighter in color while the lower layer is darker, resulting in lighter color in the first batch and darker color in the subsequent batch.
2) Acid solutions: Crystallization occurs in low-temperature pipelines carrying citric acid aqueous solutions; crystals block the pipes, causing the actual concentration of the liquid acid pumped through to decrease.
3) Flavorings: Highly volatile; with open storage tanks and prolonged production, the active ingredients in the flavorings evaporate, resulting in a weaker aroma despite the same addition amount.

3. Ingredient Addition Process and Temperature Factors
1) Excessively high sugar paste temperature during ingredient addition
When added at temperatures >120°C: significant volatilization and loss of flavorings; high-temperature decomposition of organic acids, resulting in reduced acidity; and degradation and fading of some pigments due to high temperatures. For the same amount added, higher temperatures result in lower levels of aroma, acidity, and color in the final product. Inconsistent discharge temperatures after boiling sugar in different batches lead to batch-to-batch variations.

2) Incorrect order of ingredient addition
Adding acids first accelerates sucrose conversion, alters the syrup’s viscosity, and simultaneously destroys some pigments; the correct sequence is generally: pigments → acid solution → flavorings.

3) Insufficient Mixing Time and Inadequate Stirring Efficiency
Due to the high viscosity of the sugar syrup, small volumes of flavorings, pigments, and acid solutions cannot be fully dispersed with brief stirring. Insufficient mixing time leads to localized concentration in the syrup; when poured, products from the front of the batch have a stronger flavor, while those from the end have a weaker flavor. Worn-out mixing paddles or insufficient rotational speed can cause the sugar paste to separate into layers.

4. Batch Changeover and Pipeline Residue Issues
When switching batches, colors, or flavors, residues from the previous batch remain inside the pipelines and static mixers. If not thoroughly rinsed, these residues contaminate the next batch; additionally, if rinse water is not completely drained, it dilutes the pigments, acids, and flavorings for the next batch.

III. Systemic Remediation Plan
(I) Modification of the Metering and Feeding System
1. First, adopt mixing-equipped blending storage tanks
Equip flavoring, colorant, and acid solution storage tanks with low-speed agitators to maintain continuous stirring throughout production, thereby preventing stratification and sedimentation. Insulate the acid solution storage tank and maintain a temperature of 35–45°C to prevent citric acid crystallization from clogging pipes. Ensure flavoring storage tanks are sealed to minimize volatilization.

2. Metering Methods
- For materials added in small quantities, use weight-based batching (loss-in-weight feeders) first, as this offers greater stability than flow pumps and avoids flow inaccuracies caused by air bubbles or crystallization;
- If using peristaltic or diaphragm pumps: Verify the actual output flow rate every 2–3 batches; replace pump tubing and seals regularly; install air-release valves on feed lines to eliminate air bubbles; select acid-resistant 316L materials for acid-contact components to prevent corrosion and leaks.

3. Piping: Keep piping as short as possible. Establish a CIP (Clean-in-Place) procedure for color and flavor changes, and ensure the lines are completely drained before starting the next batch.

(II) Strictly Control Feeding Process Conditions
1. After the vacuum stage of sugar boiling is complete, allow the sugar syrup to cool to 105–115°C before adding flavorings, colorants, and acid; adding ingredients at high temperatures is strictly prohibited. Record the temperature of the sugar syrup upon discharge for each batch. Temperature fluctuations are a hidden culprit behind batch-to-batch inconsistencies in many factories.
2. Recommended addition sequence: Add colorants first and stir to disperse → then add acid solution and stir → add flavorings (add flavorings last to minimize volatilization).
3. Ensure adequate stirring time: After all ingredients have been added, allow sufficient stirring time and confirm that the syrup color is uniform before beginning pouring; inspect the stirring blades for wear.
Do not begin pouring immediately after adding ingredients, as this will result in flavor and color differences between the beginning and end of the same batch.

(3) Production Process Control
1. Manual scooping based on experience is prohibited; all flavor ingredients must be measured quantitatively. Before and after adding ingredients to each batch, verify the weight of the storage tanks, record actual consumption, and compare it with the theoretical consumption. If any deviation is detected, immediately shut down the machine to inspect for leaks or crystallization in the pumps and piping.
2. Acid solutions must be reformulated periodically to confirm concentration; liquid colorants must be stirred thoroughly before each shift; flavoring storage tanks must be sealed to minimize loss due to evaporation.
3. When changing flavors or colors: Pipelines and mixing chambers must be thoroughly rinsed; batch production may only resume after a sample has been tested and confirmed to meet color, acidity, and aroma specifications.
4. Take samples from each production batch: Conduct sensory evaluations (color, aroma, acidity) to quickly identify any abnormalities; do not wait until the entire batch is produced to detect problems.

IV. Rapid Troubleshooting Steps
1. Take samples from three consecutive batches and compare the theoretical addition amount with actual consumption to determine whether the issue lies with inaccurate metering hardware or process variables (temperature, evaporation, mixing).
    - If actual consumption matches the theoretical value but the finished product quality fluctuates → This is most likely due to excessive evaporation from high temperature, insufficient mixing, or material stratification.
    - Significant fluctuations in actual consumption → issues with the metering pump, air bubbles in the piping, or crystallization leakage.
2. Check the actual temperature of the sugar syrup at the moment of addition to confirm whether it has exceeded the temperature limit.
3. Observe the three sections of the finished product from the same batch: significant differences between the beginning and end indicate insufficient stirring; significant differences between batches indicate issues with metering, stratification in the material storage tank, or fluctuations in the sugar syrup discharge temperature.

V. Additional Common Misconceptions
1. “The scale reads correctly, so once the sugar syrup is pumped in, it’s a done deal”: Weighing merely ensures the ingredients are properly mixed; transfer pumps, crystallization in the piping, and air bubbles can significantly reduce the actual amount of sugar syrup delivered.
2. Adding flavoring acid and granulated sugar to the boiling kettle at the same time: High-temperature boiling causes significant loss, making batch consistency completely uncontrollable.
3. Calibrating the metering pump only at startup and failing to verify it throughout production—gradual wear on the pump and tubing causes flow rate drift.