Microbial Inactivation in a Non-commercial Juice of Mango and Papaya Submitted to Pulsed Electric Fields in Presence of a Stevia rebaudiana Bertoni Extract

Abstract

Unpasteurized fruit juices are perishable products whose microbiological spoilage supposes great economic losses for the food industry. Besides, they can support the survival and growth of human pathogens. Actually, different juices have been involved in major foodborne illnesses outbreaks. Therefore, they should be submitted to treatments that prevent their microbiological spoilage and ensure their microbiological safety. In response to consumer demand for minimally processed foods, without synthetic additives, significant efforts are leading to the development of novel non-thermal technologies, such as the application pulsed electric fields (PEF), to extend juices’ shelf life avoiding thermal processing. The combination of those technologies with preservatives from vegetal, animal and microbial origin could be a convenient strategy to obtain high-quality foods, from farm to fork. Considering Stevia rebaudiana Bertoni (Stevia)antibacterial and antifungal properties, PEF antimicrobial potential in a juice containing Stevia was assessed. With this aim, the effect of PEF and Stevia on the microbial load of non-sterile and sterile samples inoculated with Listeria monocytogenes was determined. In view of the results obtained, PEF processing reduced the microbial load of the juice under study. Based on cell counts performed before and after different PEF treatments, in presence of different concentrations ofStevia, it was observed that the higher the electric field and the treatment time, the higher the inactivation. Stevia addition reduced PEF effectiveness against yeast, molds and mesophiles, but increased its effectiveness against L. monocytogenes. Anyway, the joint application of PEF and Stevia not fulfilled with the microbiological criteria required for this kind of products. Further studies are needed to evaluate Stevia effects during post-processing storage. In addition, the study of other strategies should not be neglected for juices’ preservation exploiting the antimicrobial potential of PEF.