Comparison of Antioxidant Content in Apple Cultivars Using Methanol Extracts and Simulated Gastro-Intestinal Digest Extracts

There is a great interest in improving human health through improving functional quality of fruits and vegetables. An outcome of this trend is the push to include functional contents as selection criteria for breeding new cultivars. The evidence to justify this direction for breeding in apples is based on limited information, mostly comparing relatively old cultivars of apples and assuming that phenolic content of methanol extracts should represent the health potential of a particular cultivar. This work was undertaken to evaluate new and established dessert cultivars of apples for phenolic and antioxidant contents (i.e. peroxyl radical scavenging capacity; PRSC). The evaluation was performed on methanol extracts as well as on in vitro simulated gastro-intestinal digest extracts. The results of the work show that only approximately 30% of the total phenolics measured in methanol extracts was soluble in the digest extracts.  Clearly not all phenolics in an apple are bioaccessible. The newly released cultivar ‘Nicola’ had consistently the highest phenolics content. When evaluating PRSC, it was found that contents in the digest for a cultivar were either similar to or higher than in the methanol extract. Air storage duration and year had some effect on overall PRSC but significant differences among cultivars were not found. Therefore antioxidant capacity in the apples was not clearly associated with total phenolic contents in the apple cultivars tested. These results suggest that while it may be possible to identify apples with higher phenolic contents this does not necessarily translate to increased antioxidant content (i.e. PRSC). It is likely that only a small subset of phenolics and other constituents, such as ascorbic acid, may be determinants of antioxidant content (PRSC) in apples.