Strategies to influence temperature stability of dark chocolate in tropical regions

Chocolate is a complex matrix, for which the preparation involves several physical and chemical processes, requiring a diverse set of technological operations to obtain the desirable quality and sensory characteristics. Fat bloom formation and melting point are challenging to control in the chocolate industry, especially in tropical regions. Tempering, is the process where chocolate obtains the appropriate polymorphic form in cocoa butter (form V) which influences important physical and functional characteristics; it also is associated with avoiding fat bloom formation and, consuming significant time and energy, thus, conventional processing of chocolate has its disadvantages. The independent addition and fractionation of various lipids and ultrasonication technology have been explored to avoid bloom formation and increase melting point. However, the combination of these technologies has not been reported. The use of palm oil in the chocolate industry has gained attention for its ability to imitate the cocoa butter Triacylglycerol (TAG), its β-carotene content (500-1500 ppm), and its low cost when compared to cocoa butter. Thus, it is viewed as a good cocoa butter replacer. High Intensity Ultrasound (HIU) application to dark chocolate formulation has been demonstrated to influence crystallization by promoting primary and secondary nucleation through the mechanisms of cavitation and acoustic streaming, creating the right polymorphic (form V). The overall goal of this project was to develop optimal conditions for producing high quality chocolate in developing countries within tropical regions such as Honduras. The central hypothesis was that the combination of fractionated lipids (palm oil and cocoa butter) and ultrasonication will produce high-quality chocolate, reduce fat bloom formation and increase melting point. This thesis work was divided into two phases. In Phase 1, the objective was to evaluate the addition of palm stearin (5%) in the chocolate formulation as a partial replacement for cocoa butter. Dark chocolate was formulated with and without 5% palm stearin, conched, and either tempered or sonicated. In phase 2, the objective was to compare chocolate that was made with palm stearin (5%) and cocoa butter stearin with chocolate that was made with only cocoa butter stearin. Dark chocolate was formulated with fractionated lipids (stearin fraction), conched, and either tempered or sonicated. In both phases, cycling experiments were conducted. Various parameters were investigated, including whiteness index (WI), physical dimensions, X-ray Diffraction (XRD), textural attributes, and melting point. Treatment differences were determined using a two-way analysis of variance (2-way ANOVA) and mean differences were calculated using the Tukey’s honest significant different (HSD). Data were analyzed using the Statistical Software RStudio (RStudio, Boston, MA). In Phase 1, temperature cycling resulted in decreased visual and textural quality. Tempered samples with 5% palm stearin presented less WI at 34°C cycle 3 as compared to tempered controls, indicating that chocolate with 5% palm stearin can resist some degrees of temperature changes. Tempered samples without palm stearin presented lower hardness than sonicated samples before cycling. Cycling at 34°C exposed greater hardness in tempered chocolate w/o palm stearin than in sonicated samples w/o palm stearin. Samples with 5% palm stearin, tempered or sonicated had less physical changes after cycling at 37°C for 3 cycles. Polymorphic form 5 was obtained with a melting point range of 32 to 35°C. In Phase 2, temperature cycling resulted in decreased visual and textural quality. Sonication and fractionation of lipid were able to significantly reduce bloom formation after 3 cycles at 34°C, indicating that chocolate with cocoa butter stearin and 5% palm stearin can resist some temperature fluctuations. Sonication applications, w/o palm stearin after cycling experiment, did not present significant changes in hardness value, indicating that sonication with fractionated fats can maintain the same value of hardness after cycling experiment. Chocolate with fractionated lipid did not spread dimensionally after cycling, while control samples spread dramatically. Polymorphic form 5, the optimal form in chocolate, was obtained with ultrasound and fractionation technologies with a melting point range of 31 to 34°C. This research demonstrates the potential application of fractionation with ultrasonication technology for producing quality chocolate. Optimization of this combination of ultrasonication and fractionation may have great implications for the chocolate industry in tropical regions