Combined Use of Ultrasound and Vanillin to Improve Quality Parameters and Safety of Strawberry Juice Enriched with Prebiotic Fibers

Abstract

In this work, a previously optimized preservation treatment (vanillin = 1.25 mg/mL; ultrasound = 7.5 min, 40 kHz, 180 W) was applied to strawberry juice enriched with inulin and oligofructose. The evolution of microbial, nutritional, and sensory parameters of treated juices was studied. It was confirmed that the inclusion of inulin and oligofructose had no negative implication regarding the quality of fresh juice. Furthermore, the prebiotic addition maintained sensory attributes of the product. The applied preservation treatment improved almost every quality attribute during storage, reducing microbial development, especially lactic acid bacteria and yeast and mold growth, which rapidly grew in untreated juices. Nutritional quality was also improved by the treatment as total polyphenol and total flavonoid content were increased and ascorbic acid content losses were reduced during storage, indicating higher antioxidant capacity. Overall, the evaluated sensory attributes of treated juices were deemed acceptable (>2.5). The addition of vanillin imparted pleasant flavor notes to the juice, compatible with the fruit product. Also, the performance of the treated juice was evaluated against postharvest contaminations with pathogens of interest in the food industry and of health concern (Escherichia coli O157:H7 and Listeria monocytogenes, evaluated through the surrogate Listeria innocua). The optimized treatment was able to reduce the counts of these microorganisms during storage reaching undetectable values after 7 days of storage. Thus, the combination of vanillin and ultrasound could be a feasible alternative to ensure safety and improve quality parameters of strawberry juice enriched with prebiotic fibers.