The juice HACCP rule required a 5 log reduction (100,000-fold decrease) in the pertinent pathogen, but did not specify the means by which the reduction was to be achieved. This approach facilitates development and implementation of treatment alternatives to thermal pasteurization. Many of these alternative treatments are discussed elsewhere in this book. Since most are still under development, the primary means of juice pathogen reduction remains thermal pasteurization.
Thermal pasteurization is a well-studied method of pathogen reduction. D- and z-values for various pathogens are available in the literature [78-81]. To apply thermal pasteurization to juice, processors must first determine the pertinent pathogen for their product. In most cases the pertinent pathogen will be either E. coli O157:H7, salmonella, or C. parvum. Physicochemical factors influencing thermal death time in juice include pH, viscosity, particulates, and Brix. Since actual time and temperature parameters may vary depending on heating menstrua and the equipment used, each processor should verify their systems once a process has been validated.
An alternative intervention treatment that is currently in use for apple cider processing is ultraviolet (UV) light irradiation. UV light irradiation was shown to destroy pathogens in apple cider [82-86]. The efficacy of UV light treatment on any liquid is strongly and negatively affected by turbidity and the sizes of any particles present [87-91]. For this reason, using UV treatment requires turbulent flow to expose all portions of the juice to the light treatment . It is important to note that the majority of studies examining the efficacy of UV light irradiation in apple cider have been undertaken using systems that do not achieve turbulent flow. Although limited efficacy with nonturbulent flow devices has been demonstrated, these units would not conform to current FDA regulations, which require turbulent flow. In the application of any processing technology, juice processors have the responsibility of ensuring that all appropriate government regulations are met.
Juice manufacturers also have the option of combining treatments to achieve the 5 log pathogen reduction standard. Comes and Beelman demonstrated 5 log reductions in populations of E. coli O157:H7 in apple cider using a combination of fumaric acid, sodium benzoate, and a 25° C holding time prior to refrigeration . In an earlier study, Uljas and Ingham achieved 5 log reduction through a combination of freeze-thaw cycles and preservatives . Ingham and Schoeller went on to test the acceptability to consumers of a multistep intervention method capable of a 5 log reduction . In this study, despite treatment similar to their first study, some juices did not show the expected 5 log reduction. The cause of the failure to achieve a 5 log reduction in these juices was unknown, indicating more research was necessary before this system could be commercially applied. In addition, consumers typically rated the multistep-treated juice lower than untreated juice.
Citrus processors may utilize surface treatments to achieve the required 5 log reduction in the pathogen that is most resistant to the intervention treatment applied. Interventions applied to the surface of citrus fruit must be applied after the fruit has been cleaned and culled. Interventions aimed at the surface of citrus fruits are often similar in type to that applied to the extracted juice. One of the most effective interventions remains thermal treatment. Pao et al. demonstrated greater than 5 log reductions in pathogen levels when oranges were submerged at 80°C for 1 or 2 minutes .
When surface interventions, such as a thermal treatment, are used in the production of citrus juice, additional microbiological process verification is mandated by 21 CFR 120.25. These requirements specify the number and volume of juice samples that must be tested for generic E. coli. Testing must be performed according to established standard methods . A "moving window'' scheme is used for the testing protocol. If two of seven samples tested are positive for E. coli, then the intervention measures in place are considered inadequate and corrective measure must be taken.
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