Microbial safety and consumer risk perception of high pressure processed juices

juice, pathogen, pressurization, resistance, risk perception, consumer

Motivated by the natural properties of beverages and by the “clean label” trend, the adoption of high hydrostatic pressure for juices preservation is growing rapidly, requiring further studies and development of validation protocols to guarantee the safety of pressurized products. The main objective of this thesis was to evaluate the intrinsic factors of the food matrix in the inactivation of pathogenic microorganisms in juices processed by high hydrostatic pressure. The thesis begins with the general introduction followed by the first chapter, which consists of a review manuscript in which we focused on the selection of strains of E. coli, L. monocytogenes and Salmonella spp. to be used in challenge tests for the microbiological validation of pressurized juices and beverages. The influence of the food matrix on the inactivation of pathogenic strains and their substitutes was also evaluated. Then, the preliminary results of the experimental part are presented, in which the procedure of selection and preparation of test cultures applied in a challenge test of juice processed by high hydrostatic pressure (HHP) was performed. In the third chapter, the process conditions (300 to 600 MPa for 1 and 3 min at 5 °C) were evaluated for the inactivation of E. coli, L. monocytogenes and Salmonella spp. and the recovery of these microorganisms during refrigerated storage at 7 °C for 42 days. In addition, the influence of pH (4.0 to 5.5) and soluble solids content (2.9 to 14.9 oBrix) on the microbial resistance of açaí juice processed at 400 MPa for 3 min at 5 °C was evaluated. Finally, in the third chapter, the consumers perception regarding the risks associated with the consumption of fresh and processed fruit juices (pasteurized and refrigerated, cold-pressed, pressurized, and UHT) was evaluated. The results of the first study showed that there is a wide variation in the resistance of E. coli, Salmonella and L. monocytogenes strains to High Hydrostatic Pressure (HHP), even when belonging to the same serotype and isolation origin. In addition, no association was found between the genetic profile strain and resistance to pressure. Clearly, the food matrix influences the microbial viability regardless of the pressure processing, as well as on the resistance of pathogen strains to inactivation by HHP. In the second study, the results showed the HHP at 400 MPa for 3 minutes reduced more than 5 logs of the three pathogenic microorganisms in the açaí juice (pH 4.3 and 2.9 Brix). However, with increasing pH or soluble solids, there was an increase in the strain’s resistance to processing, as well as a positive interaction between these two factors, requiring the use of more aggressive process conditions. Finally, the results of the fourth study indicated that consumers perceive processed juices as having greater potential for health risks. They also indicated that industry, regulatory and inspection authorities are responsible for ensuring juices safety. Furthermore, they rely on scientific publications, on nutritionists, and on physicians to receive information about the health risks associated with juice consumption.