Acoustically assisted supercritical CO2 extraction of cocoa butter: Effects on kinetics and quality

• Supercritical extraction assisted by power ultrasounds was studied.
• Ultrasounds accelerated the kinetics of the supercritical extraction process.
• Acoustic energy caused a structural disruption of the solid matrix of cocoa beans.
• Extracted cocoa butter suffered no physicochemical modifications after process.

The effect of high power ultrasound (US) application and pressure on the supercritical fluid extraction (SFE) kinetics of cocoa butter and on characteristics of the extracted cocoa butter (fatty acids composition, transition temperatures, polyphenol content and antioxidant activity) has been evaluated. Extraction experiments were carried out at 40 °C and at two pressure levels of 400 bar and 550 bar, without and with US application of 50 ± 5 W, the extraction yield being significantly improved as the pressure increased and the ultrasound was applied. A Weibull model allowed the accurate simulation of the extraction curves, considering a constant shape factor α which was affected only by the US application, whilst the rate constant β was affected by both pressure and US application. In general, for all cocoa butter samples, the transition temperatures observed corresponded to the polymorph α, Tc = 9.9 ± 0.3 °C and Tm = 20.2 ± 0.4 °C. With regard to the fatty acid composition, the stearic (37.8 ± 0.8%), oleic (33.7 ± 0.2%), and palmitic (26.0 ± 0.6%) were the major acids, and none were found to be influenced by either pressure or ultrasound application. Similarly, the total polyphenol content and antioxidant activity were not affected by extraction conditions. The microstructure of cocoa beans after processing was affected by pressure and also by ultrasound application which promoted a breaking of the cell arrangement, facilitating the butter extraction.

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