How We Solved the Crystallization Issue of Food Thickeners in the Cooling Process: A Practical Case from a Dairy Operation

Photo: Crystal Kwok / Unsplash

In dairy production, we often encounter the issue of food thickeners such as carrageenan or guar gum beginning to crystallize during rapid cooling of mixtures. This problem manifests as pipe clogging, uneven viscosity, and loss of additive functionality. In one specific case, we found that the cause was not the quality of the raw material itself, but a mismatch between the temperature profile of the cooling line and the solubility of the thickener. The solution involved adjusting the cooling rate, mixing, and adding a compatible solubilizer. This case demonstrates how important it is to adapt technological conditions to the properties of a specific additive—and that even a minor change can prevent production losses.

Problem: Unexpected crystallization of thickeners in the cooling process

In dairy operations, there is often a need to stabilize the texture of products such as yogurts, desserts, or cream sauces. For this purpose, food thickeners like carrageenan, pectin, or modified starches are commonly used. However, in our case, as the mixture was cooled to a temperature below 10 °C, microscopic crystals began to form, disrupting the homogeneous structure of the product and impairing its sensory properties—particularly creaminess and smoothness.

The problem was caused by a combination of several factors: an unsuitable concentration of the thickener, the cooling rate, and interactions with other recipe components, particularly calcium and sodium ions. Crystallization was especially evident in thickeners sensitive to low temperatures, where phase separation occurred. Additionally, operational conditions did not allow for a slower cooling process, further complicating the situation. It was necessary to find a solution that would maintain production efficiency while ensuring the desired product quality.

Analysis: Laboratory Testing and Identification of Key Parameters

The first step involved detailed laboratory testing of samples to identify the exact conditions under which crystallization occurs. Using standard testing methods, we monitored the influence of temperature, pH, ion concentration, and storage time on the stability of thickeners. We found that the critical factor was the cooling rate—when the temperature dropped by more than 5 °C per hour, the risk of crystal formation increased significantly.

We also verified the compatibility of individual thickeners with other formulation components. For example, carrageenan showed higher sensitivity to the presence of calcium, while modified starches were more stable but less effective at lower temperatures. Based on these findings, we proposed several solution variants: adjusting the formulation, changing the type of thickener, or optimizing the cooling process. Each of these options, however, had its advantages and limitations that needed to be considered.

Photo: Crystal Kwok / Unsplash

Solution: Formulation and Process Conditions Optimization

Based on laboratory results, we decided to combine two approaches: adjusting the formulation and slightly slowing down cooling in the critical temperature zone (8–12 °C). In the formulation, we reduced the concentration of carrageenan and supplemented it with a phosphate-based stabilizer, which binds free calcium ions and prevents their negative impact on the thickener's structure. This allowed us to maintain the desired viscosity without the risk of crystallization.

Process adjustments involved installing a controlled cooling system, which enabled a gradual temperature reduction at a precisely defined rate. In the critical zone, we slowed cooling to 3 °C per hour, which was sufficient to stabilize the product's structure. This change did not significantly extend the production cycle but resulted in a marked improvement in quality. The outcome was a homogeneous texture without visible or palpable crystals.

Results and Recommendations for Practice

After implementing the changes, we conducted a series of validation tests that confirmed the product's stability even during long-term storage. Crystallization no longer occurred, and the sensory evaluation of the products was comparable to reference samples. The key insight was that even minor adjustments to the formulation and process conditions can have a significant impact on the quality of the final product without the need for costly technological changes.

For food manufacturers facing similar issues, we recommend the following steps: 1) Identify critical process parameters (temperature, pH, ion concentration) through laboratory tests. 2) Test various types of thickeners and their combinations with regard to stability at low temperatures. 3) Optimize the cooling process to prevent excessively rapid temperature drops. 4) Consider using stabilizers to minimize undesirable interactions between formulation components. This approach helps achieve the desired product quality while maintaining production efficiency.

Photo: Petr / Unsplash

Impact of Temperature Gradients on the Stability of Thickening Systems

Crystallization of thickeners during the cooling process is often associated with uneven cooling of the mixture. In dairy operations, we observed that the most pronounced crystal formation occurred in areas with slower medium flow, where the temperature decreased more gradually than in the core of the flow. This temperature gradient can induce local supersaturation of the solution, leading to nucleation and subsequent crystal growth. For polysaccharide thickeners such as carrageenans or xanthan gum, this phenomenon is particularly sensitive to the cooling rate below 40 °C.

To verify the impact of temperature gradients, we simulated various cooling regimes in the laboratory. During rapid cooling (a decrease of 15 °C per minute), no crystallization occurred, whereas during slow cooling (2 °C per minute), crystals formed within 30 minutes. A key finding was that the critical temperature zone for carrageenans lies between 35–25 °C, where phase separation occurs. This insight led us to adjust the cooling cycle to pass through this zone as quickly as possible.

The Role of pH and Ionic Strength in Preventing Undesirable Crystallization

Another factor that significantly affects the stability of thickeners is the pH of the environment and the presence of ions. In our case, we found that a slightly acidic pH (5.2–5.8) promotes the formation of the gel structure of carrageenans, while values below 5.0 or above 6.5 led to their destabilization and subsequent crystallization. Similarly, the concentration of calcium and potassium ions had to be carefully balanced—an excess of these ions caused precipitation of the thickener.

Laboratory tests showed that the optimal ionic strength for a stable gel lies in the range of 0.05–0.1 mol/l. At lower values, sufficient gelation did not occur, while at higher values, precipitation was a risk. The process adjustment included the addition of a citrate-based buffering system, which maintained the pH within the desired range and simultaneously bound excess ions. This successfully eliminated local supersaturation and reduced the risk of crystallization by more than 80 %.

Practical Recommendations for Monitoring and Maintaining Stable Systems

For the long-term stability of thickening systems in cooling processes, it is essential to implement regular monitoring of key parameters. We recommend measuring the viscosity and transparency of the mixture in real time using inline viscometers and optical sensors. Deviations from the specified values (e.g., a viscosity drop of more than 10 % or turbidity above 5 NTU) may indicate the onset of crystallization and allow for timely correction of process conditions.

Additionally, it is advisable to perform periodic checks of pH and ionic strength, ideally every 4–6 hours of operation. For polysaccharide thickeners, it is critical to monitor the temperature profile of the cooling equipment—especially in areas with slower flow. Operational records should include not only measured values but also data on raw material dosing and mixing times. This information enables rapid identification of the causes of potential issues and process optimization without the need for costly laboratory analyses.

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