Sample preparation methods for the determination of the antioxidative capacity of apple juices

Abstract

The elevated ecological awareness nowadays led to a higher consumption of apples juices. Apples juices are rich in dietary fiber, pectin, potassium, and vitamins A and C as well as in different classes of phenolic compounds, which can protect the human body against oxidative stress by scavenging oxygen free radicals. During production and storage some bioactive compounds might decompose resulting in a reduced antioxidative capacity. Common methods for the determination of the antioxidative capacity of other food stuff are based on the extraction of the compounds under study using acetone, which is senseless in aqueous juices. But acetone might have an influence on the compounds responsible for the antioxidative capacity. Thus, self made apple juice samples were analyzed without organic solvent as well as mixed with acetone to see differences caused by the solvent. The results obtained with both procedures were compared using a paired t-test in order to see statistically significant differences in the results. No statistically significant differences were found between the testing with and without acetone. Thus the time of analysis, the amount of solvents needed, and the required labor force can be reduced without loosing analytical quality. Total content of phenolic compounds ranged from 400 to 650 mg gallic acid equivalent /L (Folin-Ciocalteu method) and antioxidative capacity from 1.0 to 1.6 mmol Trolox ®/L (ABTS assay).