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 degrees 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.