Chocolate is very popular with consumers throughout Europe – milk chocolate in particular is considered the most popular type due to its fresh milk taste. The added milk powder determines the taste of the end product.
The sensory characteristics of the milk powder are determined, for example, by its geographical origin, type of drying and fat content, and are later further influenced by temperature, time and humidity during conching. Thus, it is a challenge to choose a suitable milk powder to achieve the desired sensory quality in the final product. Another aspect of the manufacturing process is the problem that the finished chocolate mass often solidifies during inter-
mediate liquid storage in the tank.
The Chocolate Technology WG at the German Fraunhofer IVV has recognized the need for research. The publicly funded project aims to provide information on the targeted use of the raw material milk powder in the chocolate industry and on the processing and storage conditions in the production of milk chocolate. To this end, the research group physically characterized eight different sprayed skimmed milk, sprayed whole milk and rolled whole milk powders in work package 1. The proportion of amorphous lactose was determined using a sorption test system, the proportions of free and bound fat were determined using DSC measurements, and the water content was determined using Karl Fischer titration. As a fourth physical property, the particle structure of the milk powders was evaluated under the scanning electron microscope.
In work package 2, the milk powders were evaluated from a human sensory point of view and examined for aroma substances that could have an influence on the sensory properties of the chocolates using gas chromatography-olfactometry. Various lactones, vanillin and short-chain fatty acids such as acetic and butyric acid were identified.
Based on the results, four milk powders with different physical and sensory properties were selected for further trials. In work package 3, the influence of different conching conditions on the sensory properties and storage is investigated. The following varying parameters were chosen for the experimental design: conching times (4 h, 6 h and 8 h), temperature (50 °C, 60 °C and 70 °C), ventilation (open/closed), direction of rotation (left/right) and speeds (600 rpm, 900 rpm and 1,200 rpm).
In combination with the four milk powders, this would result in over 200 test combinations. With the help of a statistical test design, this number could be reduced to 47 representative tests. The conching trials with sprayed skimmed milk powder have already been completed, and sheets and rolled material have been produced for physical (water content, amorphous lactose, free fat), chemical and sensory tests. The conching trials with the selected roller milk powder are underway, and investigations into the stability of the chocolates under different storage conditions are also taking place. The final results and their publication are expected at the end of 2022.
