Phenolic compounds extraction from Iranian pomegranate (Punica granatum) industrial waste applicable to pilot plant scale

Industrial pomegranate waste (IPW) derived from the commercial processing of about 0.35 MMT fresh pomegranate is commonly disposed of at the Iranian landfills at a high cost and risk to environment. This paper describes a successful utilization of process condition optimization and modeling of the solvent extraction of phenolic compounds from IPW with preserved high antiradical and/or antioxidant activity. They are value added products with potential commercial application in food industries and preventive medicine due to their well-known beneficial health effects. Process conditions to maximize the total phenolic content (TPC), hydrolysable tannins (HT), total flavonoids (TF), radical scavenging activity (assessed as DPPH%) and ferric reducing antioxidant power (FRAP), were considered as optimal extraction conditions. HT as major constituents of TPC (about 50%) were also characterized and quantified by LC/MASS analysis. The optimum operating conditions were an ethanol concentration of 60%, a solvent to dry waste ratio of 30 mL/g, the temperature of 46 degrees C and the time of 6 h, which were also successfully implemented in a pilot plant scale. The FRAP and the DPPH results correlated to the TPC and the HT, and were influenced mostly by the solvent to dry waste ratio, followed by the ethanol composition. Other objectives considered in the present study included reductions in the process steps and operating costs, the use of an environmental friendly extraction solvent and its recovery, and the minimization of waste.