Abstract
Apple and apple-based products are highly appreciated thanks to their antioxidant and nutritional properties. The worldwide availability of apple has facilitated the formulation of apple-based products both at the domestic, as well as at industrial levels. Examples of the most delicious apple-based dishes include apple strudel, apple fritters, apple puree for babies, steamed apple dumplings, apple cinnamon, and many more. However, the processing of apples to prepare dishes could cause some changes that can affect their quality such as degradation of antioxidant functions (antioxidant capacity, activity and potential) and loss of nutritional value. Therefore, it is particularly important to assess the antioxidant functions of them. Several antioxidant assays have developed over time. The most suitable antioxidant assay to estimate antioxidant capacity of biological samples is the Oxygen Radical Absorbance Capacity (ORAC) assay. Despite its popularity, the assay provides only limited information with results often lacking chemical meaning. This work aimed at extending the utility of the assay by implementing a kinetic approach, which can be used to express how fast antioxidants can inhibit the reaction. By fitting the transient changes of fluorescein, the ORAC kinetic model was able to provide inhibition rate constants (antioxidant activity), antioxidant potential and stoichiometry values (antioxidant capacity). This research improved the capability of the ORAC assay offering a more accurate interpretation of the results to screen the radical scavenging activity of antioxidants in apples and complex biological samples.