Optimization of extraction process and chemical characterization of pomegranate peel extract

Abstract

The purpose of this study is to optimize the extraction process of tannins from pomegranate peel (Punica granatum L.) using conventional maceration technique. The variables studied were the temperature in the range of [30–80 $$^{\circ }$$ C], pH of [2–8], solid–liquid ratio [1/2–1/50 g/mL] and particle size ranges from [0.1–0.2] to [4–5.3] mm. The effect of solvent was also studied. Three solvents have been tested: water, ethanol, and acetone. Tannins extraction from fresh pomegranate peel (PGP) was studied for the first time to our knowledge. The comparison of extracted yield from fresh and dried PGP has been made. UV–Vis spectral studies of the extract have been carried out. Fourier transform infrared spectroscopy (FTIR) was used to identify the dominant chemical groups of PGP and PGP extract. Thermogravimetric analysis (TG) was used to study the stability of PGP and of the extracted tannins. Results showed a variation in absorbance maxima with respect to pH, temperature, and solvent nature used during extraction. Optimum conditions were found to be 62 min, 60 $$^{\circ }$$ C, 1/8 g/mL, and 6 for extraction time, temperature, solid–liquid ratio, and pH, respectively. Water provided better extraction results than ethanol and acetone. The maximum extract yield obtained from fresh pomegranate peel at the optimum conditions was found to be 50% which is higher than the yield obtained from dried PGP.