The Effect of Produce Type, Season, and Postharvest Handling on Microbial Quality of Fresh Produce Collected Near the U.S.-Mexico Border Open Access
Adam, Elizabeth (2012)
Abstract
Food quality has important implications to human health, and
fresh produce is becoming
increasingly recognized as a vehicle for pathogen transmission to
humans. Since produce
is often eaten raw and pathogens may persist after washing, it is
essential to identify
potential routes of contamination in the production environment in
order to establish
preventative measures. The study goals were to evaluate the effects
of produce type,
season, and packing shed step on produce microbial concentrations
and to assess how
statistical treatment of samples below the microbial assay's limit
of detection would
affect results. Produce samples were collected from farms and
packing sheds near the
U.S.-Mexico border (n=727) and processed by enumerative methods for
E. coli,
Enterococcus, total aerobic bacteria (APC), and total coliforms.
Linear regression and
maximum likelihood estimation for left-censored data (Tobit
regression) were compared.
Cantaloupe, mustard greens, cabbage, fall and spring sampling, and
most packing steps
were significantly and positively correlated with microbial
concentrations on produce.
Both regression methods produced estimates of similar direction and
significance, but
beta estimates from the Linear models were underestimated and the
standard deviations
were too small. In summary, produce type, season, and packing shed
step were
significantly associated with microbial concentrations on produce.
Additionally, the Tobit
regression produced more accurate results compared to the Linear
regression. This
investigation highlights several potential routes of produce
contamination in the
production environment and demonstrates the need to account for
left-censored data in
the analysis of microbial datasets.
Table of Contents
Table of Contents
INTRODUCTION.......................1
METHODS..............................7
RESULTS..............................11
DISCUSSION.........................16
REFERENCES.........................24
TABLES................................30
FIGURES...............................33
APPENDIX A: IRB CLEARANCE....35
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