Extraction Kinetics of Phenolics from Carob (Ceratonia siliqua L.) Kibbles Using Environmentally Benign Solvents

A series of non-toxic and environmentally benign solvent systems, composed of water/ethanol, acidified with either acetic or citric acid, were tested for their efficiency in extracting polyphenols from dried carob kibbles. The best solvent system (30 % ethanol) was then used in a kinetic study, attempted by deploying non-linear regression. The leaching of polyphenols was found to obey 2nd-order kinetics, while the correlation of the total polyphenol yield at saturation with temperature obeyed a 3-parameter exponential growth model. The highest yield of total polyphenols at saturation was 53.76 mg gallic acid equivalents per gram of dry weight, achieved at 60 °C. The analysis of this extract using liquid chromatography–diode array–mass spectroscopy led to the tentative identification of gallic acid, myricetin 3-O-rhamnoside, quercetin 3-O-rhamnoside and quercetin p-hydroxy benzoyl 3-O-rhamnoside. The detection of the last compound in carob extracts is reported for the first time.