Summary of Awards to Date

Identification of routes and mechanisms for distribution and establishment of Listeria monocytogenes and Listeria spp. in avocado packing environments


Apr. 1, 2022 - Dec. 31, 2024

Amount Awarded



Alejandro Castillo, Ph.D.
Texas A&M University


Rosana Moreira, Ph.D., Sapna Chitlapilly Dass, Ph.D., M. Ofelia Rodriguez-García


This proposal focuses on studying the potential for LM to contaminate fresh avocados during postharvest processing at packing plants that practice dry packing, because of small amounts of residual water that can support growth cross-contamination. We plan to determine the effect of residual water on the processing equipment, after wet cleaning procedures, on the ability of LM to colonize the plant surfaces, particularly those surfaces of equipment and utensils that have direct contact with the product. This goal will be approached by using modern DNA-based methods to accurately determine whether Listeria is found in the environment of avocado packinghouses. In addition, we plan to apply a survey of avocado packers to inquire about their level of confidence they have on wet vs. dry cleaning. With the data generated from this study, we plan to develop a model to predict, based on the data collected, the likelihood of avocado contamination under specific scenarios. All these findings will help develop effective and easy to apply, practices in sanitation that will really reduce the risk of foodborne diseases, with a tremendous societal benefit.

Technical Abstract

This proposal focuses on the study of the potential for Listeria monocytogenes (LM) to contaminate fresh avocados during postharvest processing at packing plants that practice dry packing, which consists of completing the avocado packing without any washes or wet treatment. These practices are interesting, since commonly, the cleaning and sanitizing procedures followed are based on wet cleaning and sanitizing, which may introduce some moisture in the environment, favoring the attachment and potential growth of pathogens such as (LM). The project aims at determining how current sanitation practices affect the ability of LM to colonize the packing plant environments. Information on the impact of environmental factors such as air humidity and temperature at different locations of the avocado packing plant on the ability to maintain an adequate level of sanitation is scarce. This project aims at evaluating the impact of current sanitation practices at dry avocado packing plants on the ability of LM to colonize the packing plant environment and the areas of the plant that potentially facilitate harborage at avocado dry packing plants (ADPP) in Mexico (the largest supplier of avocados to the US).