FOOD. Science. Technology. Quality

Food. SCIENCE. Technology. Quality

Food. Science. TECHNOLOGY. Quality

Food. Science. Technology. QUALITY




Changes in the natural antioxidant content in and antioxidant capacity of concentrated apple juice occurring during the manufacturing process


The objective of the study was to determine changes in the content of some selected antioxidants and in the levels of antioxidant capacity (AC) occurring during individual phases of a process of manufacturing the concentrated apple juice. Crushed apples of two cultivars Szampion and Idared, were first enzymed using a pectolytic preparation, and, next pressed. The centrifuged juice obtained was pasteurized, once more enzymed using a pectolytic preparation, and filtered, micro-filtered, and concentrated using an evaporator. After each individual phase of the technological process, the following parameters were determined: the level of antioxidant capacity using ABTS•+ and DPPH radicals; the total content of phenolics, the total content of some selected phenolic compounds using a HPLC technique, and the total content of l-ascorbic acid. The initial AC levels in the Szampion and Idared apple cultivars were similar, and amounted to about 5.5 and 2.5 μmols of Trolox in 1 g f.w.; the AC levels were determined using ABTS•+ and DPPH radicals, respectively. The total phenolics contents in apples of the two cultivars were also similar, and amounted to 2.4 mg/g f.w. The L-ascorbic acid content of 2 mg/kg was found only in fresh Szampion apples. It was noted that immediately after the apples had been crushed, their AC levels became highly reduced, especially in the Idared apples, in which the AC level was by 70% decreased. Furthermore, the AC levels were reduced during the phase of: apple pulp pressing, juice filtrating, and juice concentrating, whereas the treatment phases of enziming the apple pulp and juice, juice centrifuging, pasteurizing and microfiltering did not affect the AC levels nor caused any increase therein. The main phenolic compound in fresh Idared apples was chlorogenic acid, and, as for the Szampion apples, procyanidin C1. These two compounds also predominated during all the process phases, as did they in the final product. Clear juice concentrates obtained from the Szampion and Idared varieties contained approximately 80% and 20%, respectively, of the initial AC level as found in the fruit used to manufacture the juice concentrate.


apples, concentrated juice, antioxidant capacity, phenolic compounds