CPS – Research Project Funding 2022 – Bulb Onions


Assessing the potential for production practices to impact dry bulb onion safety

In 2020, the dry bulb onion industry faced their first significant outbreak of foodborne illness when red onions grown in California were epidemiologically linked to >1,000 cases of salmonellosis. Since then, industry and food safety experts have been scratching their heads to figure out how this could have happened. After review of outbreak data and consultation with various stakeholders, we have identified a small number of practices with the potential to contribute to a large-scale contamination event, through water or agricultural input contamination. We have designed field trials to determine the risks of using contaminated water source or other agricultural input when 1) applying crop protection sprays (pesticides and/or clay) and 2) during irrigation (overhead vs. drip). Our primary goal is to collect evidence demonstrating risks of these practices and to communicate our findings to relevant stakeholders to reduce the potential for outbreak like this from recurring in the future. We will share our findings via a broad outreach strategy that communicates with industry throughout the two-year study. Outreach activities culminate with the development and delivery of a workshop and best practices guide that enables growers to better understand risks and implement changes to minimize the likelihood of crop contamination.


Strategic approaches to mitigate Salmonella contamination of bulb onions

The proposal aims to address the recent multi-state Salmonella outbreak associated with red onion, resulting in nationwide recalls of onions and associated products. The outbreak highlights the pathogen’s ability to persist and survive on bulb onions during production, handling, or storage, causing significant concern to the onion produce industry. Although Salmonella’s persistence on other farm produce is documented, there is a general lack of knowledge on Salmonella’s behavior on bulb onions. We propose developing an onion-specific risk reduction plan by investigating Salmonella’s survival and growth on onion bulbs using different genetic backgrounds, nutritional compositions influenced by agronomic practices, seasons, and managed stress environments. Additionally, to understand the potential to serve as a transient host for transmission, we will investigate the effects of genetic, nutritional, and physiochemical characters on Salmonella survival and growth. This project will provide the industry with tools (1) to identify factors in the onion production and supply chain that may allow a Salmonella to persist, (2) identify varieties and agronomic practices that would minimize or eliminate its persistence, and (3) to help the produce industry in developing guidelines to manage risks of Salmonella in onions effectively.

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