Determination of melting properties of white chocolate by rheological method

Crystallization mechanism of cocoa butter should be fully understood and known for the necessary the production of chocolate in good quality. Changes in the polymorphic composition of cocoa butter significantly affect the stability of crystals and their conversion into other forms. Determination of the crystal type contained in solid phase chocolates is made partially by using DSC, however, no clear results can be obtained. In this study, it is aimed to determine the crystal types of white chocolates by using rheometer based methods considering melting temperature differences. White chocolates from three different brands used in this study were obtained from local markets. Samples, melted at different temperatures (37°C, 50°C) and brought back to solid phase under different storage conditions (25°C, 4°C, -18°C), were subjected to oscillatory rheological analysis by temperature sweep test. It is aimed to find the white chocolate melting temperature by determining the onset where the gap started to drop with the effect of the normal force in the rheometer. Software of the rheometer was used to find the values accepted as the point where the white chocolate started to melt. This point was determined by the intersection of the slopes. Until now, it has not been possible to determine what type of crystals chocolate has in solid form by any rheological method. As a result, it was found that all the samples taken from the market melted around 32°C and thus, the main structure that provided the samples to withstand the compression force came from form V crystals. However, it was observed that the samples, which were melted at 50°C, melted around 28ºC and thus contained form IV crystals. It was determined that the samples, which were melted at 37°C, melted around 24°C and had a form III crystal. It has been observed that the chocolate started to melt earlier than desired and thus the melting quality decreased. Thus, the effect of melting and solidification of chocolate on the possible cocoa butter crystal variety was observed. At the same time, the fatty acid composition in the white chocolate samples was examined by gas chromatography, and it was examined whether the possible differences in the crystal variety were due to the fatty acid composition. It was observed that palmitic acid, stearic acid and oleic acid were dominant in white chocolate samples and there was no statistically significant difference between the fatty acid compositions of the samples (P> 0.05).