Effects of continuos dense-phase CO2 system on antioxidant capacity and volatile compounds of apple juice

The effects of different operating conditions applied to a continuous dense-phase carbon dioxide (DPCD) system on antioxidant capacity and volatile compounds of apple juice were compared with current heat pasteurisation method. Only the microbial tests required by Italian Regulation to assure microbiological safety to ‘fruit juices and vegetables’ were performed, and DPCD-treated (15 MPa, 35 C, 15 min; 25 MPa, 35 C, 15 min), heat-pasteurised (75 C, 15 s) and untreated apple juice samples were considered. The DPCD processing carried out at 15 MPa resulted as effective as 25 MPa in reducing microbial cells. Trolox equivalent of DPCD treated at 25 MPa (0.41 mm) resulted significantly (P < 0.05) lower than DPCD treated at 15 MPa (0.48 mm). Head space analysis of volatile compounds indicated the lowest decrease in apple aroma compounds (59% esters and 59% aldehydes) in DPCD treated at 15 MPa.