Comparative Study of Subcritical Water and Microwave-Assisted Extraction Techniques Impact on the Phenolic Compounds and 5-Hydroxymethylfurfural Content in Pomegranate Peel.

Two environmentally friendly innovative extraction techniques - subcritical water (SWE) and microwave-assisted extraction (MAE) were applied for the extraction of phenolics from pomegranate peel. The impact of process conditions (SWE: temperature 100-220 °C, extraction time 5-30 min; MAE: solvent water and 50% ethanol, irradiation power 470 and 800 W) on the quality of extracts in terms of the content of total phenolics, total flavonoids, major phenolic constituents (gallic acid, ellagic acid, punicalin, punicalagin), as well as 5-hydroxymethylfurfural(HMF) amount was investigated. For SWE, temperature of 130 °C and 20 min extraction time were found optimal for obtaining high content of bioactive compounds and minimizing the yield of HMF. During MAE, phenolic compounds were effectively extracted by using lower microwave power and 50% ethanol. Comparing two techniques, MAE is more efficient than SWE for the extraction of phenolics from pomegranate peel while obtaining a HMF-free extracts.