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theses

Recently, an increasing number of outbreaks related to produce consumption have been reported. Tomatoes are considered as one of the main produce consumed in the United States; approximately 14 million tons of tomatoes are produced every year. However, the microbial safety of raw tomatoes has been questioned following many outbreaks associated with eating tomatoes contaminated with human pathogens. The CDC reports that eating raw tomatoes caused at least 12 Salmonella multistate outbreaks from 1990-2009, and resulted in over 2,000 illnesses. Therefore, developing a novel and alternative method to improve the microbial safety and quality of raw tomatoes is necessary. In the U.S., post-harvest tomatoes are often washed in chlorinated water (50-150 ppm) to remove debris, soil and prevent cross-contamination, with an additional effect of lowering the microbial load on the tomatoes. However, previous studies showed that tomatoes washed with chlorinated water (320 ppm) failed to completely inactivate Salmonella. Chitosan is a non-toxic, bio-degradable and antimicrobial compound, which has been reported for its efficacy of extending the shelf-life and reducing the microbial decay of fresh produce. The objective of this study is to investigate the efficacy of chitosan-based coating against surface attached Salmonella and natural microbiota on fresh tomatoes. All tomatoes were inoculated with Salmonella. After drying, tomatoes were washed in 100 ppm chlorinated water for 90 s. Tomatoes were then dipped in either 0.2% or 1.0% chitosan solution for 90 s. Controls were only dipped in tap water. Change in population of Salmonella and total aerobic microbes (Aerobic Plate Count, APC) were evaluated at pre-determined times. Results showed that the population of Salmonella and total aerobic microbes with the treatment of 1.0% chitosan solution following 100 ppm chlorinated wash step provided immediate inactivation on day 0, compared to control. On day 1 and day 5 post-treatment, the population of Salmonella and total aerobic microbes on tomatoes both increased during the five days of storage, except on tomatoes treated with 1.0% chitosan solution following 100 ppm chlorine wash step. Future research should consider evaluating up to 4.0% chitosan solutions for controlling microbial growth and extending the shelf-life of tomatoes.

ETD_6241

M.S.

Includes bibliographical references

by Yi-Chun Lai

doi:10.7282/T3SX6G2H

ETD graduate

The author owns the copyright to this work.