Assessment of sanitation techniques for tree fruit storage bins.

Tree fruit are the leading agricultural commodity in the Pacific Northwest.To assure that this critical industry continues to grow, their products must remain safe.To protect the supply of tree fruit, it is important to assess and understand the risks of microbial contamination and efforts to control them in the production chain.Knowledge gaps exist regarding the ability of current bin sanitation practices to reduce foodborne pathogen risk. The objective of this study is to evaluate bin sanitation effectiveness for wood and plastic bins. The study will examine potential differences in food safety risks between wood and plastic bins, an important economic consideration.The effect of wood and plastic bin age on sanitation will also be included in the study design.Wood and plastic bins will be assessed for overall microbial levels and indicators of fecal contamination before and after sanitation.Hard-to-clean surfaces, such as feet and damaged surfaces, will be examined as part of the sampling regime.Project impacts include 1) assessment of sanitation practices to reduce microbial food safety risks in tree fruit storage bins, and 2) clarification of the influence of bin material (wood and plastic) and bin age on food safety risks.

To protect the supply of tree fruit from food safety risks, it is important to assess and understand the risks of foodborne pathogen contamination at various points in the production chain.Knowledge gaps exist regarding the ability of current bin sanitation practices to reduce foodborne pathogen risk.The objective of this study is to evaluate current bin sanitation practices for reducing food safety risks in wood and plastic bins.An industry survey will be distributed and analyzed to examine current practices related to bin handling and sanitation.The survey will ensure inclusion of appropriate factors in the experimental design based on industry input and will assist in recruitment of additional project partners that encompass the breadth of industry practices.Overall microbial levels (aerobic plate counts, coliforms, generic E. coli) will be assessed in tree fruit storage bins before and after bin sanitation (wood and plastic, approximately 1,000).Factors that will be included in the experimental design include at least three different bin sanitation methods and bin age; other factors may be included based on survey results.The ability of current industry sanitation practices to control microbial risks associated with wood and plastic bins will be examined.Hard-to-clean surfaces, such as feet and damaged surfaces, will be examined as part of the sampling regime.A comparison of the ability to sanitize wood and plastic bins will be examined along with the influence of bin age on sanitation for wood and plastic bins.Project impacts include 1) assessment of sanitation practices to reduce microbial food safety risks in tree fruit storage bins, and 2) clarification of the influence of bin material (wood and plastic) and bin age on food safety risks.

Evaluate current sanitation practices for reducing overall microbial levels and food safety risks in tree fruit storage bins (wood and plastic).

Examination of industry bin sanitation practices: 

• Data collection focused on establishing a baseline using current practices. 

• Based on observation of bin handling practices, it was determined that the entire bin could be considered a food contact surface since the bins are completely submersed in dump tank water and could contribute to microbial levels and organic load in the dump tank system. 

• Most current bin cleaning and sanitation practices observed did not involve efforts to remove heavily soiled areas prior to treatment, which can overwhelm effective cleaning and sanitation practices. o This observation makes drawing conclusions about the data collected in industry settings challenging, as some effective treatments may have appeared less effective on individual bins that heavily soiled (see Photo set 1). 

• The data from this study indicated that a water pre-rinse followed by cleaning and sanitation would be an effective strategy for reduction of total coliforms on wood and plastic bins. 

• Heat treatment appears to be a promising treatment for wood and plastic bins warrants further investigation. 

• Development of a dry-dump mechanism that does not reduce fruit quality could also be an effective strategy to reduce organic load in dump tank systems and maintain dry surfaces for wood bins. 

• Dump tank systems with chlorine or peroxyacetic acid for the majority of wood and plastic bins did not reduce the number of sites with total coliforms present. 

• Pressure washing with water alone for the majority of wood and plastic bins did not reduce the number of sites with total coliforms present. 

• Challenges with dump tank management, chlorine chemistry and water recycling issues were identified in this study. It is recommended that every facility review and evaluate practices related to dump tank management during packing as well as equipment cleaning and sanitation practices. 

• Information gained through this project identified that tree fruit storage bins interface with the farming and fruit packing environment. It is reasonable that different standards and expectations for cleanliness and sanitation exist between these two environments. A challenge identified is that cleaning and sanitation currently rests with bin ownership at the packinghouse. However, the potential for collection of additional soil levels in the farming environment is anticipated. The presence of heavy soils on bins returning from the orchard could present challenges for sanitation in the packinghouse environment (storage and packing), challenges to dump tank management with chlorine sanitizers and challenges with protection of microorganisms during standard bin sanitation practices at the packinghouse. Adjustments to current cleaning and sanitation practices appear to be warranted. Greater communication and partnership between growers and packers to share responsibility for bin sanitation may also be warranted to address this complex agricultural issue. 

Industry survey: 

• The majority of the industry used wood bins for apples and pears; bin liners are primarily used for varieties that are more easily damaged. Plastic storage containers (bins or totes), when used, are more common for use with cherries and soft fruits, like apricots, peaches and plums. 

• The most common methods of bin cleaning and sanitation were immersion in a chlorinated dump tank system or hydrocooler, pressure washing or visual inspection with treatment of soiled bins. 

Laboratory and commercial examination of sampling methods: 

• For the removal of biofilms from wood and plastic storage bin surfaces, 3M ScotchBrite™ pads were the most consistent sampling method. Prior to sampling, it is necessary to treat the 3M Scotch-Brite™ pads with ethanol to remove antimicrobials that are present in the 3M Scotch-Brite™ pads. 

• Although laboratory studies found that Violet Red Bile Agar (VRBA) with an overlay was the most accurate method compared to VRBA and 3M E. coli/Coliform Petrifilm™; Preliminary studies in industry settings found an increased number of false positives with the Violet Red Bile Agar (VRBA) with an overlay. Therefore, CHROMagar™ ECC was used in the remainder of the industry experiments.