EVALUATION OF THE TOTAL ANTIOXIDANT ACTIVITY AS A MARKER OF THE DETERIORATION OF APPLE JUICE OIL STORAGE

The total antioxidant-activity (TAA) has been evaluated as a marker of the deterioration of apple juice during storage. Unfortified juice, juice fortified with vitamin C, and an apple ''drink'' (6% juice), to which vitamin C (300 ppm) is added during manufacture, were evaluated. Vitamin C activity represented a minor fraction of the TAA (ca. 1%) of ''longlife'' apple juice, with chlorogenic acid and phloretin glycosides as the major identifiable antioxidants (ca. 32% and 11% of the TAA, respectively). Antioxidant activity ascribable to these substances was stable under the storage conditions examined, whereas ascorbic acid added into the juice was unstable; in fortified whole apple juice the TAA value correlated significantly with the decline in the ascorbic acid concentration, while in the apple drink there was a direct relationship between TAA and ascorbate.