EVALUATION OF COMMERCIAL NONTHERMAL PROCESSING TECHNOLOGIES USED TO INACTIVATE FOODBORNE PATHOGENS IN FRUIT JUICES AND BEVERAGES
Nonthermal processing technologies have attracted an increasing interest in the food industry for processing foods to ensure food safety in food products and retention of fresh-like qualities. Two important technologies that have been explored for treating fruit juices are the use of chemical inhibitors, such as dimethyl dicarbonate (DMDC), and high-pressure processing (HPP). The efficacy of these technologies against foodborne pathogen inactivation under specific experimental parameters and conditions have been studied. Two concentrations of DMDC (172 and 200 ppm) were evaluated for Salmonella enterica and spoilage microbiota inactivation in orange juice. It was found that at both concentrations, a greater than 5-log reduction of Salmonella could be achieved at 4C after 24 hr. In addition, the effects of high pressure on pathogen inactivation on juices have been investigated, with the focus placed on water processing temperature and product composition, focusing on pH and water activity values. All HPP experiments were conducted at 550 MPa for 1 minute and the juice inoculated with E. coli O157:H7, Salmonella enterica, and Listeria monocytogenes. In the study concerning water processing temperatures, experiments were performed at both ambient (20C) and refrigeration (5C) temperatures. Results showed that across three juices, inactivation for all pathogens was generally higher at 20C. Further studies were carried out to understand the effects of pH in product composition. HPP treated juices were evaluated at initial pH, and at pH values of 4.0, 4.5 and 5.0. The data showed despite acidic conditions (pH <4.6), a 5-log reduction could not be achieved for all pathogens in some juices at pH <4.5. As a counterpart to the study, the effect of water activity on pathogen inactivation was also assessed under acidic and neutral conditions. Two solutes (sodium chloride and fructose) were used to adjust the water activity in a narrow range (0.95 - 0.99). It was found that significantly higher inactivation occurred in solutions at pH 4.5, with NaCl solutions requiring aw 0.96 while fructose solutions requiring aw 0.98 for a 5-log reduction of all pathogens. As a newer technology, HPP has yet to be optimized and streamlined, and estimated costs associated with high pressure treatment have been evaluated and reported.
Worobo, Randy W.
Padilla-Zakour, Olga I; Schmit, Todd M.
Food Science and Technology
Ph. D., Food Science and Technology
Doctor of Philosophy
dissertation or thesis