Application of steam explosion pretreatment for accelerating the phenolics extraction from pomegranate peel: Mechanism and modeling

Steam explosion (SE) pretreatment was applied to modify the physicochemical characterization of pomegranate peel, and the mechanism and kinetics of phenolic compounds extraction was investigated. The SE pretreatment conditions included pressure (0.5, 1.5, and 2.0 Mpa) and time (60, 120, and 180 s). Compared to untreated samples, the SE pretreatment at 1.5 and 2.0 Mpa pressure strengths significantly altered the appearance color, damaged the fiber structure, altered the composition of the cell wall, increased phenolic compounds extraction, and improved the phenolics release and antioxidant activity of pomegranate peel. Based on Fick's second law, the rise of SE strength resulted in the increase of kinetic constants and diffusion coefficients of phenolics, which increased from 1.55 × 10−3 to 3.55 × 10−3 min−1 and 1.97 × 10−9 to 10.35 × 10−9 m2/min, respectively. The activation energy of the extraction of the phenolic for 60, 120, and 180 s pretreatment groups were 11.64, 11.71, and 27.60 kJ/mol, respectively.