Antioxidants and enzimatic inactivation of optimized blackberry juice by thermoultrasonication compared with pasteurized juice

Abstract

Blackberry juice is a beverage with bioactive compounds which present antioxidant capacity, among them phenolic compounds like anthocyanins, nevertheless during the termal processing there are a loss of this compounds, therefore in this study the objective was to investigate the polifenol oxidase and pectin metylesterase activity, antioxidant capacity and the anthocyanins content of the thermoultrasonicated blackberry juice and was compared with the pasteurized juice (90 °C/ 15 s). The response surface methodology was employed to obtain the optimum conditions of thermoultrasonication and significant differences between mean values (thermoultrasonicated, pasteurized and control) were determined by Tukey pairwise comparison test at a significance level of p<0.05. Thermoultrasonication treatment, compared with pasteurization, showed higher reduction of polyphenol oxidase (>98 %) and pectin metylesterase (63.7 %) activity, higher antioxidant activity as well as anthocyanin content (13,964.96 μmol ET/L and 922.55 mg Cy-3-Gl respectively). The response surface methodology allows obtain the optimum conditions of thermoultrasonication for blackberry juice. This technology is better than conventional in terms of enzymatic inactivation and improvement of the antioxidant properties of blackberry juice.