Phenomena of matter transfer in food composed by different phases are unavoidable until reaching system balance. This is especially true in confectionery products where a soft filling, containing a liquid fraction of triglycerides or moisture, is in contact with a solid chocolate coating. During storage, the liquid begins to migrate through the solid layer, causing undesired changes in the appearance and structure of the product. In a recent survey, a group of international researchers (Svanberg et al., 2012), has developed a new method of measuring these changes, that is based on the use of a universal testing machine (Instron). In particular, this method has been tested using samples with chocolate coatings and fat or water-based fillings. The samples were submitted to tensile strength and Young’s modulus during a period of 60 days storage at 20° C (55% relative humidity). The results show that the migration of humidity during product storage causes a significant decrease in tensile strength. In particular, it was noted that the samples’ fragility increases progressively since their first days of storage. The migration of fat instead, causes an initial lubrication of the system and its consequent increase in elasticity. In general, the results show that Young’s modulus is less sensitive to both moisture and fat migration phenomena, than tensile strength. In conclusion, the authors affirm that the tool used in the survey provides a detailed analysis of migration phenomena according to the recipe of the product. Finally, the parameters provided by such analysis can be used to develop predictive mathematical models of other undesired events such as those involved in the break of chocolate pralines.
L. Svanberg et al., Journal of Texture Studies, 43, 2012, 106-114