Improving Quality Parameters of Functional Strawberry Juices: Optimization of Prebiotic Fiber Enrichment and Geraniol Treatment

Abstract

Enrichment of strawberry juices with prebiotic fiber (inulin and oligofructose) and their preservation treatment (with ultrasound and geraniol) were optimized by response surface methodology with a Box-Behnken design in order to simultaneously maximize microbiological, nutritional, and sensory quality of juices after 2 weeks of refrigerated storage. The optimal conditions were inulin/oligofructose proportion of 5:3, 0.225 μL/mL of geraniol and ultrasound time equal to 0, with a desirability value of 0.77. After that, strawberry juices were treated at optimal conditions to investigate changes on microbiological (native microflora), nutritional (including ascorbic acid content and antioxidant capacity indicators), sensory quality and safety (simulating an eventual postharvest contamination with Escherichia coli O157:H7 and Listeria innocua) during storage. Finally, a study evaluating the performance of the optimized treatment on stability of prebiotics added to strawberry juices was carried out. The optimized treatment was highly effective to reduce native microflora counts, as well as, to inhibit those inoculated pathogens in juices. Treatment at optimal conditions did not induce any negative effect neither on antioxidant capacity indicators nor on ascorbic acid content of juices. Furthermore, the optimized treatment ensured the stability of inulin and oligofructose added to juices during storage. The simultaneous optimization allowed lower concentrations of geraniol, reducing the impact on sensory quality. Therefore, the enrichment and treatment of strawberry optimized and proposed in this work could be a feasible alternative to thermal pasteurization to ensure the microbiological quality and safety in juices, as well as, to improve nutritional and sensory quality.