Thermosonication impact on blueberry juice quality preservation

Background: The FIVE A DAY rule promotes fruit juice consumption for its flavor and nutritional benefits, aiming to fulfill daily nutrient requirements. However, thermal processing challenges food products' nutritional quality, prompting a rise in non-thermal methods within the beverage market to promote healthier choices. This study explores the application of ultrasound, an emerging, cost-effective, energy-efficient, and ecofriendly technology. Methods: Blueberries, recognized as superfruits for their high content of health-promoting compounds, were chosen for their phenolic and anthocyanin amounts. Ultrasound was applied at 60% and 100% amplitude, combined with heat treatments at 55 °C and 45 °C. L. innocua, a non-pathogenic surrogate for L. monocytogenes, served as a safety indicator. Total phenolics, anthocyanins, and rheological properties of the juices were evaluated. Results: Significant antimicrobial effects were observed, achieving a 5-log reduction after 1 min at US100 55 and US60 55. US100 45 and US60 45 achieved 4.9 and 5.0 log reductions after 25 min. Controls (55 HT and 45 HT) showed a 6- and a 5-log decrease after 10 and 60 min, respectively. At 45 °C, ultrasounds retained higher levels of total phenolics and anthocyanins, with US100 45 showing the highest phenolic retention at 82%. Although anthocyanins decreased across all treatments, US100 45 retained the most at 69%. Rheological parameters did not show significant differences, and the non-Newtonian shear-thinning behavior of blueberry juice remained unchanged after thermosonication. Conclusions: The research highlights the potential of thermosonication, particularly at 45 °C, in preserving blueberries' phenolics and anthocyanins. Moreover, ultrasound amplitude levels did not significantly influence microbial inactivation, suggesting it maintains the juice’s fundamental flow behavior. This finding evidences ultrasound's effectiveness in enhancing blueberry juices' safety and nutrition without compromising their rheological properties.