a No microbiology analyses
were performed on products that
were thermally damaged.
Several tropical fruits were tested at the general optimum conditions of 138°C steam for 0.1 seconds using one, two, or three cycles and a vacuum time of 0.1 seconds. The results for kiwis, mangoes, and avocados are listed in Table 21.8. All samples were inoculated with L. innocua for 10 minutes and dried under ambient conditions for 1 hour. The log reduction for kiwis was 4.8; for mangoes, 4.0; and for avocados, 3.1.
Another tropical fruit, banana, was tested. However, the process caused the peel to split and the fruits to darken immediately. Milder conditions (104°C for 0.1 seconds and one cycle) were tried with green bananas, but the samples still were destroyed. No microbiological analyses were performed on products that were thermally damaged.
Other products processed without success were peppers, broccoli, and cauliflower. When subjected to vacuum, the peppers exploded. Upon exposure to steam the delicate florets on broccoli turned a bright green indicative of blanching or heat treatment. Although the flower part of cauliflower was essentially unscathed, the stalk and the remnants of the leaves turned bright green as in blanching.
Other fruits and vegetables were tested at the conditions stated above. The results are listed in Table 21.8. The bacterial reduction (APC) on uninocu-lated carrots was 4.1 logCFU/ml. Treatment of cucumbers, inoculated for 10 minutes with L. innocua and dried at ambient conditions for 1 hour, resulted in 3.8logCFU/ml reduction with three cycles. Peaches were inoculated for 10 minutes with L. innocua and were allowed to dry for 1 hour under ambient conditions. Using two cycles, the reduction for L. innocua was 3.6logCFU/ml with no thermal damage.
In addition to bacteria, some insects such as red scale infest the surface of fruits. Red scale is a major problem on citrus fruits. Currently, methyl bromide is used to eliminate insects such as red scale, but the impending loss of methyl bromide in 2005 requires alternative methods of quarantine treatment for disinfestations of produce imported or exported each year.
The VSV process was used to process lemons infested with red scale . No scale insects survived the process. The process resulted in 100% kill of insects at all stages of development. As a bonus, up to 96% of first molt scales were physically removed, but the process was much less effective in removing other stages from the fruit, especially those that had advanced beyond the second instar. However, the process was completely effective in killing the scales.
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