An innovative grape juice enriched in polyphenols by microwave-assisted extraction

Abstract

The grape juice by-product obtained from grape traditional press was extracted by Microwave Hydrodiffusion and Gravity (MHG); a green extraction technique preliminarily optimized at 1 W/g. The MHG extract (MHGE) was analyzed by HPLC for identification and quantification of anthocyanins and other phenolic compounds. Then, MHGE was added to the natural juice (NJ) to produce an innovative grape juice (IJ). These three juices were evaluated for their total polyphenol content (TPC), total anthocyanin content (TAC) in addition to their sensorial characteristics. MHGE showed the highest values of TPC (21.41±0.04 mg GAE/g DW), TAC (4.49±0.01 μg MVGE/g DW). Moreover, IJ (grape juice enriched with MHGE) was richer in TPC (6.70±0.0 1mg GAE/g DW) and TAC (3.96±0.01 μg MVGE/g DW) than NJ (2.90±0.02 mg GAE/g DW and 3.63±0.06 μg MVGE/g DW, respectively).

Keywords: Anthocyanins; By-product; Enriched juice; Grape; Microwave hydro-diffusion and gravity; Total phenol content.