High-intensity ultrasound processing of blueberry pulp: a pathway to improve physicochemical quality and bioactive retention in enriched skyr

Concentrated yogurts, such as skyr, are gaining prominence as functional foods, especially when enriched with fruits. However, conventional pulp processing methods, such as pasteurization, may compromise some beneficial properties. In this work, the production of skyr-type yogurt supplemented with blueberry pulp processed by high-intensity ultrasound (HIU) was proposed. The procedure was evaluated at HIU power levels of 160 W, 320 W, 480 W, and 640 W (20 kHz) for 3 min. The dissipated power, acoustic intensity, and acoustic density were calculated for all HIU conditions using the calorimetric method. The obtained products were compared to the products after conventional pasteurization and untreated blueberry pulp in terms of pH, total acidity, color, presence of bioactive compounds, rheology, and profile of volatile compounds. The products obtained by the HIU procedure at power levels of 320 and 480 W presented higher water retention and improved consistency, resulting in higher viscosity and lower syneresis compared to conventional pasteurization. Bioactive compounds, such as phenolics and anthocyanins, were better preserved after conventional pasteurization. However, contrarily to the other ultrasound powers, HIU at 640 W showed better retention of monomeric anthocyanins, suggesting that higher power levels are beneficial for maintaining the bioactivity properties. Electronic nose analysis revealed that HIU treatment and pasteurization generate products with similar volatile compounds profile, but a unique profile was observed while using ultrasonic power levels of 320 and 640 W. Although pasteurization maximizes the extraction of bioactive compounds, HIU treatment enhances the stability of the product and increases the sensorial quality for longer periods, indicating that the processing method can be adapted according to the objective of the product.