Potentıal of Raman Spectroscopy To Assess the Adulteratıon of Cocoa Butter

Abstract

Cocoa butter (CB) has unique physicochemical properties and is the main ingredient in chocolate formulations. However, due its low availability and high price, modified fats called cocoa butter alternatives (CBAs) which are labeled as; cocoa butter equivalents (CBEs), cocoa butter replacers (CBRs) and cocoa butter substitutes (CBSs) are commercially available in the market. This situation made CB available for economic adulteration with both CBAs and low priced fats. In addition, according to European Legislations the use of CBEs are limited above 5% of the total fat whereas CBRs and CBSs are forbidden in chocolate formulations. Nevertheless, although the chocolate directive defines chocolate according to the fat it contains, currently a specified method is lacking in legislations for authenticity detection of cocoa butter. Consequently, identification of authentication in cocoa butter has become an essential issue in terms of both commercial and health. The main objective of this study was to evaluate the potential of Raman spectroscopy (RS) coupled with principal component analysis (PCA) in detecting the CBAs adulteration in cocoa butter at low percentages (5% and 15%). In addition, fatty ii acids, sterols, melting and crystallisation characteristics were also examined to strengthen the RS results. Commercial CBEs (n=8), exotic CBEs (n=6), CBRs (n=3) and CBS (n=1) samples as CBAs at the two levels (5% and 15%) total 36 adulterated samples were prepared. All pure fat samples were also subjected to RS analysis. According to fatty acid analyses results, palmitic and stearic acids were discriminative fatty acids and successful at detecting exotic CBEs at 15% level whereas stearic acid content allowed to detect CBR and CBS adulteration at levels of 5% and 15%, respectively. The enthalpy values of both the two melting peaks and crystallisation peak enabled the detection of 5% exotic CBE, CBR and CBS adulteration; whereas crystallisation enthalpy were successful to detect commercial CBE addition at 15%. β-sitosterol amount of CB was significantly reduced with the addition of 5% CBR, CBS and exotic CBE. Both the DSC and sterol results were successful to detect exotic CBEs, CBRs and CBS adulteration in CB at 5% level. Although RS coupled with PCA showed a good classification was obtained for pure CBR, CBS and CBs at regions of 800-1800 cm-1, this method has limited potential to detect CB adulteration with CBEs since fatty acid compositions of pure CBs and CBEs were similar. A better discrimination were revealed by RS coupled with PCA for CB adulterated with CBR and CBS up to 15% addition level at 3050-2800 cm-1 regions. Therefore, more promising results could be expected from RS coupled with statistic if higher levels of CBR and CBS are added to CB. The results of this study showed that Raman spectroscopy could be used as a fast and reliable method for detecting the authenticity of CB.