Natural antimicrobials combined with ultrasound treatments to enhance quality parameters and safety of unpasteurized strawberry juice

Abstract

The search for novel non-thermal preservation technologies is continuously growing, as traditional thermal processing may have undesirable effects on sensory and nutritional properties of fruit juices. Therefore, the aims of this study were to find the ultrasound, pomegranate extract and geraniol levels that simultaneously optimize different quality parameters of strawberry juice after 14 days of refrigerated storage (5°C) and evaluate the performance of the optimal combination of these treatmentsto control a contamination with Escherichia coli O157:H7. Response surface methodology was applied for optimization study where geraniol was applied at 0, 0.15 and 0.30 μL/mL; pomegranate extract, at 0, 180 and 360 μg/mL; and ultrasound treatments were performed at 40 kHz during 0, 15, and 30 min. The optimum combination resulted in 0.15 μL/mL of geraniol, 360 μg/mL of pomegranate extract and 30 min of ultrasound. This treatment was able to significantly reduce microbial counts, with a low impact on sensory attributes, while improving the antioxidant capacity of the product compared tountreated juice samples. Also, it allows reducing the contamination with E. coli to undetectable values. Thus, the optimized treatment resulted adequate for extending the shelf-life as well as increasing the safety of strawberry juice.