Effect of cold-pressed and normal centrifugal juicing on quality attributes of fresh juices: do cold-pressed juices harbor a superior nutritional quality and antioxidant capacity?

Cold-pressed juices are claimed to contain higher levels of antioxidants and bioactive compounds compared to normally centrifuged ones. Herein, we evaluated the antioxidant capacity and the bioactive compound contents of some freshly prepared fruit juices, extracted by a cold-pressed juicer and compared them to those prepared by a normal centrifugal juicer. We observed no significant differences between cold-pressed and normal centrifugal juices in terms of the contents of bioactive compounds (ascorbic acid, total phenolic, and total carotenoid) and antioxidant capacity (ferric ion reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity). Storage at room temperature (∼28 °C) adversely affected the ascorbic acid, total phenolics, total carotenoids, FRAP and DPPH values of the cold-pressed juices within 48 h. However, under simulated home-refrigerated storage conditions, the antioxidant capacity, contents of bioactive compounds and physicochemical properties of the cold-pressed juices remained unchanged till day 5 post-storage. However, at day 6, most of the parameters exhibited a decreasing trend and reached their lowest values at day 7. Principal component analysis confirmed significant changes in the quality of juices at day 7 of storage related to the first two principal components (ascorbic acid and FRAP). Our results strongly question the claim regarding the superior quality of cold-pressed juices. Moreover, our findings provided compelling evidence regarding the possible adverse effects of long storage under home-refrigerated conditions on the quality of cold-pressed juices.