CAN HIGH-INTENSITY ULTRASOUND PROCESSING PRESERVE THE FUNCTIONALITY OF DAIRY PRODUCT? A STUDY ON THE ANTIOXIDANT ACTIVITY AND TOTAL PHENOLIC COMPOUNDS CONTENT OF SKIMMED YOGURT ADDED WITH BLUEBERRY (Vaccinium myrtillus)

Emerging technologies are favorable for enhancing dairy derivatives added with fruit pulp, improving their physicochemical, sensory, and functional characteristics. In this sense, this study aimed to compare yogurts added with processed blueberry pulp using the emerging High-Intensity Ultrasound (HIU) technology, evaluating antioxidant activity, total phenolic content, and pH. Yogurt samples were prepared and then added with blueberry pulp processed by HIU at power levels of 160W (T1), 320W (T2), 480W (T3), 640W (T4), and by pasteurization (TP) at 85ºC, all for 3 minutes. A control sample (TC) was not subjected to any treatment. Antioxidant activity was evaluated by the percentage (%) of DPPH free radical reduction, total phenolic compounds (TPC) content by reaction with Folin-Ciocalteu reagent, and pH using a pH meter. T2 showed the highest antioxidant activity (30.09%; p<0.05), not differing from T4 and T3 (28.77%; 28.12%; p<0.05). The highest TPC content was observed in TC, followed by T2 (35.610; 33.493 mg GAE/100g, respectively; p<0.05), with the lowest content in T1 (26.728 mg GAE/100g; p<0.05). Regarding pH, T1 had the highest value (4.52), not differing from T2, T4, and T3 (4.51; 4.51; 4.49, respectively; p>0.05). The lowest pH value was observed in TC (4.46), which did not differ from TP (4.49; p>0.05). Effects related to the formation of free radicals during the application of the technology may be associated with the reduction of phenolic compound content compared to the untreated sample and the increase in pH. In addition, other bioactive compounds may have been preserved, contributing to a better antioxidant activity than the pasteurized sample. Thus, applying medium-high power levels in HIU may be an alternative for treating blueberry pulp, favoring antioxidant activity and maintaining phenolic compounds similar to conventional treatment.