Changes in hydrolysable and condensed tannins of pomegranate (Punica granatum L., cv. Hicaznar) juices from sacs and whole fruits during production and their relation with antioxidant activity

Abstract

The effects of clarification and pasteurization on hydrolysable tannins (HTs), condensed tannins (CTs) and antioxidant activities of pomegranate juices extracted from whole fruits and sacs were investigated. Tannin contents (53-85%) and antioxidant activities (18%) in juice from whole fruits (JFWF) were found higher than those in juice from sacs (JFS). In both juice samples, clarification led to significant decreases (15-74%) in total polyphenol, HT and CT contents as well as antioxidant activities, whereas pasteurization (1-52%) led to the increases, except for the CT contents. Similar to pasteurization, HT contents also increased (r = 0.956) as the pressure and time increased during pressing. Punicalin, ?-punicalagin, ß-punicalagin and ellagic acid hexoside were the major HTs in pomegranate juices. Among HTs, ellagic acid hexoside was the major HT in JFWF, whereas ß-punicalagin was the major one in JFS. ß-punicalagin was the most susceptible HT to clarification. Strong correlations were found between antioxidant activity values with total polyphenol contents (r = 0.824-0.926), and total HTs contents (r = 0.775-0.994) and CT contents (r = 0.592-0.956). Antioxidant activity of JFWF resulted mainly from HTs (r = 0.994), while that of JFS resulted mainly from CTs (r = 0.956). © 2014 Elsevier Ltd.