Three different kinds of produce (uninoculated) were processed to assess thermal damage and bacterial reduction. The commodities were chosen to represent aerial fruits (grapefruits), fruits growing on the ground (cantaloupes), and vegetables that grow in the ground (carrots). Table 21.6 summarizes the results. There was no visual thermal damage, and the bacterial population reductions were 3.4 to >5logs, but these process conditions were not optimized. The optimum conditions give maximum bacteria reduction with minimal or no thermal damage to the product. Therefore, a series of optimization experiments were conducted to determine the best processing conditions . Beets were substituted for the in-ground crop because the shape of the treatment chamber was more amenable to spherical foods and tended to chop off the ends of carrots. (A VSV processor for carrots or other cylindrical crops would require a differently shaped treatment chamber.) Papayas were added to the list of products tested. Table 21.7 lists the optimum process condition and bacterial reduction for cantaloupes, grapefruits, papayas, and beets. Because of the high natural bacteria count on beets, they were not inoculated; cantaloupes, grapefruits, and papayas were inoculated with Listeria innocua.
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