Ultrasound assisted anthocyanin extraction from sumac and investigation of thermal degradation kinetics of the anthocyanins

Abstract

In this study, an ultrasonic extraction method was used to extract anthocyanins from sumac. In order to maximize the yield of anthocyanins from the extraction, a three-factor Taguchi method with ethanol concentration (25, 50, 75%), sonication time (15, 30, 45 min), and solvent: solute ratio (10:1, 20:1, 30:1) was used. Under optimum extraction conditions, maximum anthocyanin yield (632.024 mg C3G/kg) was obtained by performing 15 min sonication of the mixture prepared with 75% ethanol at 10:1 solvent: solute ratio. The solvent: solute ratio was the parameter that most affected the extraction process. However, as a result of ANOVA analysis, the effect of the ethanol concentration variable on the extraction process was found to be significant (p <0.05). In this study, the thermal degradation kinetics of sumac anthocyanins obtained under optimum extraction conditions as a result of 70, 80, and 90 °C heat treatment were also determined. The results showed that the thermal degradation process fit the first-order reaction kinetics. The kinetic rate constant (k) of thermal degradation of sumac anthocyanins varied between 1.69x10^-3-5.44x10^-3 min^-1 and the half-life (t_1/2) varied between 29.46-9.15 hrs. The activation energy (Ea) of thermal degradation of sumac anthocyanins was calculated as 60.28 kJ/mol. Taguchi method was successfully applied in the extraction of anthocyanins from sumac. There is an urgency to improve the stability of the extracted sumac anthocyanins by considering the food production conditions.