Effect of Boiling and Juicing on the Content of Polyphenols, Invitro Bioaccessibility and Antioxidant Activity of Commonly Consumed Vegetables and Fruits

Abstract

This study was aimed to investigate the effect of boiling and juicing on selected vegetables and fruits such as carrot, beetroot, tomato, mint leaves, pomegranate and apple. Total and individual polyphenols were evaluated by Folin-Ciocalteu and RP-HPLC. Antioxidant capacities of the selected foods were measured by DPPH, FRAP, ABTS and ORAC assays. In vitro bioaccessibility of total and individual polyphenols were analyzed by mimicking human gastro intestinal system. Results of this study revealed that pomegranate was found to be higher in total polyphenols (55.90±1.02) and the lesser content was observed in boiled mint leaves (3.16±1.12). Also carrot pure juice (37.35%) was observed higher total polyphenols bioaccessibility and lesser content was observed in tomato puree juice (13.71%). The predominant polyphenols present in the selected foods are simple polyphenols such as chlorogenic, caffeic, ferulic and gallic acids, glycosides of flavones and flavonols such as apigenin, luteolin, quercetin and catechins such as epigallocatechin, epicatechin and their individual polyphenol bioaccessibility were also analyzed. Among the selected foods pomegranate juice contained highest AOA, moderate AOA was observed in juices of beetroot, apple, tomato and lesser activity was observed in carrot juice compared to the raw and boiled foods. From these findings, it was observed that the food matrix, method of cooking, polyphenol content (total and individual) and bioaccessibility are the key determining factors of net antioxidant capacity of the selected fruits and vegetables.