Characterization of the antioxidant activity of a commercial juice (apple, carrot, ginger and goji berries) and comparison with its manufactured equivalent

Abstract

Introduction: Fruit juices have been increasing interest due to their antioxidant properties. These antioxidants could act beneficially in the health maintenance by preventing free radicals formation [1]. However, processing and temperature, can modify its antioxidant properties [2]. It is, therefore, relevant to know their antioxidant properties and compare them with their manufactured equivalents. Materials and methods: Ten independent samples of commercial juice (CJ) and ten samples of equivalent manufactured juice (MJ) were analyzed. DPPH and FRAP methods were performed to evaluate antioxidant activity (AA) and Folin-Ciocalteau test evaluated the total phenol content (TPC). The t-Student test was applied to compare the TPC of the two juices, the two-way ANOVA was used to compare the AA of the two juices for the two tests and the Spearman coefficient to verify the correlation between TPC and AA. Results: Regarding de comparison of the juices for TPC, the results revealed a significant difference between juices. A strong interaction between the two factors, juice and method was found, which influences the AA. The AA results revealed no significant difference between methods for CJ in spite of a difference for MJ (Table 1). The Spearman Correlation Coefficient obtained for the association between TPC and AA for FRAP and DPPH tests revealed a strong correlation (R = 0.883 and R = 0.550, respectively) with statistical significance (p < 0.01), for MJ. Concerning CJ, a weak correlation was found between TPC and AA in both methods (R = 0.467 and R = 0.018, respectively), without statistical significance (p > 0.1). Discussion and conclusions: The present study revealed similar values with literature [3,4] that, for the studied juices, the antioxidant properties of CJ are higher than MJ. The results may be related to the presence of ascorbic acid in CJ, added to act as a preservative [4].