Characterization of commercial Spanish non-citrus juices: Antioxidant and physicochemical aspects

The presence of many different antioxidant species makes fruit juices to be perceived by populations as a very healthy beverage easy to include in the daily diet. These antioxidant actions have been reported in a large number of papers, however the information correlating the antioxidant profile with the physicochemical characteristics derived from the industrial processing of fruit juices is limited. In a previous paper, our research group demonstrated that the antioxidant properties of citrus juices were underestimated when measuring by traditional methods and that our improved methodology, so-called GAR, is a better approach to analyze the global antioxidant response of juices. In this paper, we confirm that statement, establishing that the overall antioxidant capacity of non-citrus juices is 10-times higher with the GAR method (including an in vitro gastrointestinal digestion) that with the other methodologies. In some cases, such as pineapple juice, the antioxidant action was distributed between the soluble and non-soluble fractions almost at 50%. But, surprisingly, in some other (like tomato juice) the non-soluble fraction accounted for the higher antioxidant capacity. This fact definitively underlines the importance of the non-soluble fraction and shows the suitability of the GAR method to consider it. Physicochemical parameters, such as color, fluorescence, 5-hydroxymethylfurfural and furfural contents were correlated with antioxidant characteristics in some samples. Lastly, we unravel a mathematical model to classify non-citrus juices depending on their nature or storage conditions.