Whether nougat, marzipan or confectionery: a large number of products are refined by coating with chocolate. The delicate coating is not just a component of the product’s taste; it also gives the product an appealing look. With the occurrence of the so-called fat bloom, the appealing look quickly turns into the opposite.

Chocolate has a very high value to us. Accordingly, the consumer has a very high expectation of the quality of a chocolate product. A shiny surface and a distinct cracking sound are critical quality criteria for chocolate. Unfortunately, chocolate enrobed products tend to lose these quality criteria during storage: the chocolate is softening, and in extreme cases, the surface is turning dull and even greyish. These undesired visual changes of the chocolate are mostly known as fat bloom.

This loss of quality in chocolate-coated products usually occurs during storage. The reason for this is fat migration from the filling to the chocolate’s surface. This process occurs even long before storage: the filling fats start to accumulate in the chocolate even during the enrobing process.

The products are poured with a generous amount of melted chocolate in the enrobing lines, which dissolves the fat on the filling’s surface. While the remaining chocolate that flows off the products is collected and returned to the enrobing circuit, the liquefied fat from the fillings surface impurifies the chocolate coating material. Since these liquefied fats start to accumulate over time during the recirculation, the products’ quality is decreasing over the production time and leads to an unevenly distributed quality during production.

The amount of filling fats accumulated during the production depends on various factors. On the one hand, the size and throughput of the enrobing machine have a particular influence. On the other hand, the product itself influences the carryover of filling fats. Products with high fat content and huge surface cause a higher carryover of filling fats into the chocolate than products with a low fat content and small surface. Thus, the estimation of the total accumulation of filling fats is difficult by empirical values.

Continuous sampling at the production line and laboratory analysis of the chocolate samples is a conceivable option, yet, this procedure causes a high effort. Additionally, the result of the laboratory analysis might be delayed for several hours or even days. Consequently, effective process control by the machine operator is not possible.

Infrared spectroscopy offers a fast and simple measurement solution for process control. The infrared spectroscopy, particularly mid-infrared spectroscopy, can measure a sample’s chemical composition non-destructively and without the use of chemicals. Chemical changes in the sample, such as the fat content or foreign fat content in chocolate, can be detected within minutes or even seconds.

The compact design of infrared spectroscopy systems provides distinct advantages concerning its integration into production. The installation into pipelines allows integrating process control into existing production machines, such as enrobing machines. In combination with the optical arrangement of the so-called attenuated total reflection, mid-infrared spectroscopy offers the possibility to analyze pasty substances.

In cooperation with the Fraunhofer Institute for Process Engineering and Packaging (IVV), LiquoSystems company developed solutions for a process control in the enrobing machines. There is available an established in-line measurement system with an analysis module for pipeline installation. Also available is a compact handheld device for real-time manual measurements beside the production line (at-line).

The developed measurement systems can be deployed for determining the accumulation of filling fats in enrobing machines automatically and continuously using mid-infrared spectroscopy. This ensures real-time quality control in evaluating the accumulation of filling fats and the tendency for fat bloom formation during storage.

So, fat bloom formation information evaluation does not have to happen in a time-consuming way during the storage, but during production. The direct feedback of the infrared spectroscopy and continuous quality control within the process allows direct and active production control. An adequate adaption of the processing parameters can result in higher and more consistent product quality, and longer production times are achievable.

Besides measuring the fat content or accumulation of filling fats, further parameters can be acquired by infrared spectroscopy, for example, sugar content, cocoa content, glucose-fructose ratio, and many more. Therefore, the application of infrared spectroscopy is not limited to enrobing machines but rather implementable in various further fields of chocolate production or food production.