Evaluating food safety challenges of blueberry harvesting

Blueberry growers/packers have gone to a great expense in recent years to adhere to FDA guidelines by implementing Good Agricultural and Management Practices to ensure berry safety. However, berries are grown in the field, and are prone to contamination by microorganisms. Our recent work found that berry lugs can carry a relatively high level of microorganisms. If not properly cleaned and sanitized, the lugs can transfer the microorganisms on them from one load of fruits to another. Thus, the hygiene condition of berry lugs and other harvest containers and equipment is very important to microbial safety of harvested blueberries. In this project, we will find out how berry growers clean and sanitize their harvest containers and mechanical harvesters in an anonymous practice survey. We will subsequently determine whether some of these cleaning and sanitation practices can indeed improve the hygiene status of harvest containers and mechanical harvesters in several anonymous in-field validation studies. The knowledge gained from the project will help berry growers/packers improve their cleaning and sanitation practices, subsequently the microbial safety of harvested blueberries.

As a “super food” with many health benefits, fresh blueberry, like any other fresh fruits and vegetables, can be a potential vehicle of transmitting gastrointestinal diseases and pose a risk to public health. Industry cleaning and sanitation practice directly impacts the hygiene status of harvest containers and equipment, subsequently the microbial safety of harvested blueberries. This proposed project addresses the No. 2 research priority in the Center for Produce Safety’s 2020 Request for Proposal - Harvest: a). Cleaning and sanitation of harvest equipment; b). Cleaning and sanitation of harvest bins/containers. The ultimately goal of the research is to overcome critical food safety challenges of blueberry harvesting by identifying and validating key promising industry practices in cleaning and sanitization of harvest containers and equipment. We hypothesize that 1). Blueberry growers/packers have adopted different practices to clean and sanitize picking buckets, flats/crates, lugs, and mechanical harvesters; 2). These practices do not have equal efficacies in decontaminating harvest equipment and containers, 3). Blueberry growers/packers are currently inadequately informed about the best industry practice in decontaminating harvest containers and mechanical harvesters, and 4) Blueberry growers/packers are open minded about adopting better and more effective cleaning and sanitation practices that are currently being used by some of their peers. The proposed research will first collect information about the cleaning and sanitation practices currently used by blueberry growers/packers through combination of an anonymous electronic and in-person survey in different states of the U.S. According to results of the survey, promising cleaning and sanitation practices will be identified through a collaboratory effort between the project team and an advisory board comprising of selected berry growers/packers, members of best practice committee of blueberry association/council, and experts who used to work in the blueberry industry and currently still have a close contact with berry growers/packers as their consultants. Identified cleaning and sanitation practices will be validated in blueberry production fields and/or packing facilities for their effectiveness in decontaminating mechanical harvesters and harvest containers, and those with desired efficacies in improving the hygiene status of harvest containers and equipment will be promoted for broad adoption. In the laboratory setting, the identified cleaning and sanitation practices will be evaluated for their effectiveness in removing microbial buildups and biofilm mass accumulated on the materials that are used to manufacture mechanical harvesters and harvest containers. This would be undertaken because microorganisms from blueberry and its production environment will likely attach to, and accumulate as biofilms over time on, the surface of harvest equipment and containers, if they are not cleaned and sanitized properly and routinely during the harvest season. Information generated by the proposed research would be useful to blueberry, and perhaps other fresh produce, growers/packers to improve their cleaning and sanitation practices and produce safer products for consumers. Strong consumer confidence on safe food products will likely further boost industry revenues.

1. Collect information about cleaning and sanitation practices for harvest containers and mechanical harvesters among blueberry growers/packers through an anonymous survey in several U.S. states. 

2. Validate the efficacies of selected key cleaning and sanitation practices in decontaminating harvest containers and mechanical harvesters in the fields and/or packing facilities. 

3. Evaluate, in a laboratory setting, whether identified key industry cleaning/sanitizing practices can effectively remove microbial buildups and biofilm mass on materials used to manufacture harvest containers and mechanical harvesters. 

4. Transfer the knowledge gained from the project to berry growers/packers and promote best industry practices for broad adoption.

The study collected information on growers’ practices in cleaning and sanitizing blueberry harvest containers and machine harvesters. Results of the validation survey suggest that the current cleaning and sanitation practices are largely working, but there is space for further improvement. A multilingual education program based on the results of this study would help improve the food safety knowledge of personnel working in the blueberry field and packing facilities. Growers are transitioning to the use of modified machine harvesters for harvesting fresh market blueberries due to labor and production constrains. Machine harvester manufacturers are using soft elastic polymer sheets to cover hard surfaces such as catch plates on the machine to reduce physical damage to harvested fruits. These polymer sheets are hydrophobic and likely encourage a higher level of microbial buildup on machine surfaces. This should be a potential food safety issue for the blueberry harvesting.