Text

theses

The occurrence of Salmonella on whole, fresh tomatoes presents a risk to human health. The development of a quantitative microbial risk assessment will aid in identifying steps in tomato processing and handling that may either lead to contamination or amplify existing contamination. The findings from Chapter II suggest that growers should harvest dry tomatoes to reduce the risk of contamination since Salmonella transfer to tomatoes from soil or mulch is greater when moisture is present. Generally transfer to tomatoes was greater from new or used plastic mulch than from soil. This finding may have profound implications for growers since some believe plastic mulch reduces risk rather than increases it. The results in Chapter III highlight that Salmonella survival on tomatoes and plastic mulch is strain dependent, though the direct cause cannot be contributed just to the relative humidity (RH) of the environment or colony morphologies (rdar - rough dry and red) and subsequent biofilm production on tomatoes and plastic mulch. Chapter IV shows that NJ packinghouses implemented very different sanitary procedures that resulted in a wide range of bacterial reductions. Significant (p<0.05) reductions in total plate and coliform counts for any one of five packinghouses typically occurred in half of all visits (2 or 3 visits out of 5). These results suggest that standardization of sanitizing procedures could aid in achieving a more consistent bacterial reductions. The main finding in Chapter V was that minimal Salmonella growth (<0.5 log CFU) was predicted on bagged salad during transport from the store to the home. Growth prediction for Salmonella on whole tomatoes was not possible (see Chapter VI results below). Growth on whole tomatoes or bagged lettuce is more likely during transport from the packinghouse to retail, or at retail due to expected times and temperatures. The models in Chapter VI demonstrate how currently available data on Salmonella transfer to and survival on tomatoes can be used in a full farm to fork model. The survival model demonstrates how unpredictable Salmonella survival on tomatoes can be. Further research should lead to a better understanding and potential solution on how to control Salmonella on tomatoes.

ETD_7913

Ph.D.

Includes bibliographical references

by Jennifer Todd

doi:10.7282/T3TB19TV

ETD doctoral

The author owns the copyright to this work.