Production of high-functional fruits snacks by combination of mild technologies

Vacuum impregnation (VI) represents a promising mild non-thermal technology for development of functional foods of these recent years. In this study, vacuum impregnation combined with drying was used to incorporate prebiotic fructooligosaccharides (FOS) from Yacon juice into different fruits: apple slices and entire strawberries to produce snacks and ready-to-eat fruits with improved prebiotic functionality. The present work was performed in the framework of MILDSUSFRUIT European project. Methods: Apple slices and entire strawberries were subjected to VI with Yacon juice (10 minutes; 200 mbar). After impregnation, fresh strawberries were stored at 4 °C while apple slices, were dried at 70 oC for 8 hours in convection oven. On these products microbiological shelf-life, technological parameters (aw, texture) and prebiotic properties (FOS, polyphenolic compounds and antioxidant activity) were investigated. The ability of VI fruits to promote the vitality or the growth of selected probiotic strains from Lactobacillus (L. rhamnosus GG and C112) and Bifidobacterium ((B. breve 20091and B. longum 20088) genus was evaluated in simulated intestinal fluid (SIF: 0.1% w/v pancreatin, 0.15% w/v Oxgall bile salt, 100 mM phosphate saline buffer pH 8) for 24h. Results: Introducing Yacon juice into tissue of the apple fruit and strawberries, resulted in increased content of FOS, polyphenolic compounds and antioxidant activity. Low water activity in the obtained dried apple slices improved the microbiological safety up to 50 days of storage. Ready-to-eat strawberries showed 5 times more FOS compared to the untreated samples. Moreover, a positive effect of impregnation on the antioxidant stability of the fruit after drying was noted. Ready-to-eat strawberries and dried apple slices sustained the vitality of selected probiotics strains or reduced their death kinetics in SIF during 24h especially of the Bifidobacterium species considered. Conclusion: VI of fruits with functional compounds could be considered as a valid method to produce high nutritional value ready-to-eat products. The combination of vacuum impregnation and drying is a suitable way for the production of snacks with improved nutritional and functional properties.