Written by Paige Beuhler and Ines Hanrahan, Washington Tree Fruit Research Commission, March 2025
For 2025, the Washington Tree Fruit Research Commission approved $292,480 to help fund four (4) new Apple Horticulture and Postharvest projects.
2025 New Apple Horticulture and Postharvest Project Details
Phase 2: Biocontrol Strains from WA Native Plants for Postharvest Use
Organization(s): Washington State University, University of Washington, Washington Tree Fruit Research Commission
Principal Investigator(s): Zhu, M.; Doty, S.; Mendoza, M.
Total Funding Amount for All Years: $211,428
Length: 3 Years
Postharvest losses remain a significant economic challenge in the apple industry, with fungal infections accounting for up to 50% of total annual fruit production losses. Repacking due to decay in packed boxes is becoming an increasingly pressing issue, likely driven by stricter quality tolerances on the customer receiving end. This process is not only labor-intensive but also incurs significant financial burdens on growers and packers. Biocontrol agents (BCAs) are naturally occurring microorganisms like bacteria and yeasts that can suppress pathogens responsible for postharvest decay. They leave no toxic residues and are less prone to developing resistance, making them an excellent eco-friendly alternative to conventional chemical fungicides for postharvest decay control and suitable for organic practices. However, not all commercially available BCAs are suitable or maintain viability on apples during extended commercial cold storage. Preliminary findings suggest that certain commercial BCA strains gradually decline in population during prolonged cold storage periods. This study aims to assess the stability and effectiveness of the most promising isolates for controlling decay in apples during postharvest handling. The overall goal is to identify BCA strains that can be formulated for commercial use, providing sustainable and effective solutions for apple growers in Washington and beyond.
Objectives:
1) Test the stability of newly identified BCAs under various postharvest storage conditions.
2) Analyze the effectiveness of the promising and stable BCAs in suppressing fruit pathogens on apples.
3) Develop an effective BCA cocktail for synergistic action against fruit pathogens on apples artificially infected by the major decay pathogens in commercial cold storage without wounding.
Evaluation of Environmental Monitoring Best Practices for Brush Beds
Organization(s): Washington State University
Principal Investigator(s): Murphy, C.; Galinato, S.
Total Funding Amount for All Years: $129,016
Length: 2 Years
Previous foodborne outbreaks and recalls of fresh produce have been linked to cross-contamination with L. monocytogenes within packing facilities. Notably, two of the deadliest produce-related outbreaks, the 2011 cantaloupe listeriosis outbreak, and the 2014 caramel apple listeriosis outbreak, were traced back to contamination on food contact surfaces of packing equipment. While past and ongoing research has focused on improving cleaning and sanitation practices for brushes, there is also a critical need to understand environmental monitoring program (EMP) options and best practices to ensure these cleaning procedures are truly effective. An EMP is used to detect and manage contamination risks, mainly microbial, in food production environments. The goal of an EMP is to monitor surfaces to identify potential sources of contamination and/or verify the effectiveness of cleaning and sanitization programs. The results of EMP testing help facilities pinpoint high-risk areas, or “hot spots,” where contamination is more likely, enabling them to implement corrective actions such as enhanced cleaning, sanitation, or procedural changes. Despite the clear benefits of EMPs for food safety, there is currently no universal standard or consistent best practices for their implementation in the apple industry, and many facilities may lack an EMP altogether, leaving significant gaps in food safety practices. Thus, the team of researchers will conduct a series of research projects aimed at data, education, and actionable insight for the apple industry that can be used to inform decisions around EMPs, improving food safety and operational efficiency. Results from these studies will yield valuable insights into the effectiveness and practicality of swab rapid tests, helping to enhance environmental monitoring programs and provide actionable guidance to commercial apple packinghouses.
Objectives:
1) Conduct laboratory experiments on clean and fouled (e.g., debris, wax, background microflora) brush rollers, polishing brushes, and bristle rollers to validate the sensitivity (true positive) and specificity (true negatives) of swab methods (e.g., sponge swabs) processed using standard FDA methods and rapid tests for detecting different levels of Listeria spp. and L. monocytogenes on brush bed surfaces.
2) Implement the methods from Objective 1 in commercial apple packinghouses to evaluate their effectiveness in real-world conditions.
3) Perform a cost-benefit analysis for each method, considering equipment, consumables, in-house labor, third-party costs, and testing sensitivity.
4) Develop educational materials, including videos and fact sheets on environmental monitoring program best practices (e.g., how to collect environmental samples and the pros and cons of incorporating rapid tests).
Bin Sanitation for Postharvest Decay Control in the Apple Industry
Organization(s): Washington State University, Washington Tree Fruit Research Commission
Principal Investigator(s): Zhu, M.; Mendoza, M.
Total Funding Amount for All Years: $260,410
Length: 3 Years
Effective sanitation of harvest and storage bins is an important but under-investigated step in mitigating the risk of postharvest decay pathogens and ensuring the safety and quality of apple production. The apple industry has shown increasing interest in hot water sanitation; however, optimal treatment parameters, duration, and potential benefits within this specific application need to be determined. The overall goal of this project is to systematically evaluate the efficacy of commonly used sanitizer treatments for bin sanitation against decay pathogens and to further assess the effectiveness of hot water dipping under industry-relevant conditions in reducing decay pathogens harborage. The project will deliver optimized bin sanitation strategies that reduce decay pathogens and improve fruit quality and safety. It will also offer insights into the cleanability of different bin types and the efficiency of washing systems, aiding informed decisions on bin and washing system selection to enhance economic sustainability. This research will empower the industry to adopt improved, science-based bin sanitation practices.
Objectives:
1) Survey of bin sanitation practices and decay pathogen loads at various stages of bin handling in the Washington apple industry.
2) Evaluate the efficacy of commonly used sanitizers against decay pathogens on wooden and plastic bins under varying conditions.
3) Assess hot water treatment for reducing decay pathogens on wooden and plastic bins under varying conditions.
Food-Grade Antimicrobial Coatings for Storage Bins to Prevent Decay
Organization(s): Oregon State University, Washington State University
Principal Investigator(s): Ma, L.; Wang, Q.; Murphy, C.
Total Funding Amount for All Years: $232,388
Length: 3 Years
This project addresses critical concerns for the Washington apple industry regarding cross-contamination of decay organisms between apple bins and apples (and vice versa). Apples in orchards may be contaminated with decay organisms from various sources, such as agricultural water, insects and equipment. These contaminants can then transfer to the bins, leading to cross-contamination of additional apples stored in the same bin. As contaminated apples move through the packing line, they can spread decay organisms, potentially contaminating a larger volume of apples. Therefore, preventing cross-contamination in apple bins is critical for reducing initial contamination levels before postharvest processing and storage, ultimately helping to minimize apple losses. Finding better solutions to reduce the cross-contamination of decay organisms is a priority. Currently, apple bins are cleaned and sanitized, most commonly with chemical sanitizers like chlorine, but this approach has its limitations. To address these challenges, novel bin coatings will be developed in this project. Bin coatings will encapsulate FDA-approved sanitizers like chlorine or GRAS-grade plant-based antimicrobials into pre-treated yeast cells to ensure long-lasting effectiveness. The baking yeasts will be inactivated, with their intracellular content removed, leaving yeast shells intact to serve as natural encapsulation materials for antimicrobial agents. Previous studies have demonstrated enhanced antimicrobial efficacy by encapsulating chlorine in yeast cells to inactivate foodborne bacteria such as Listeria innocua in the leafy produce industry. However, its application against decay organisms, such as fungi species P. expansum, and its use on apple bins remain to be explored and the team of researchers will do so while working on this project.
Objectives:
1) Evaluate the antimicrobial efficacy of bio-encapsulated FDA-approved agents against Penicillium expansum (blue mold).
2) Develop antimicrobial coatings using the bio-encapsulated agents on wooden and plastic coupons that simulate apple bin materials to inactive blue mold.
3) Assess the efficacy of antimicrobial coatings in reducing cross-contamination of blue mold and natural microflora (e.g., total coliforms, yeasts, and molds) in apple bins in orchards, as well as their cost and impact on apple quality.
Contact:
Paige Beuhler, Administrative Officer
paigeb@treefruitresearch.com
(509) 665 – 8271 ext. 2
Ines Hanrahan, Executive Director
hanrahan@treefruitresearch.com
(509) 669 – 0267
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