Pathogen Presence and Agricultural Practices: Microbial Analysis of Wild Blueberry Harvesting and Processing Environments

Wild blueberries, native to Maine, are primarily of two species: Vaccinium angustifolium and Vaccinium myrtilloides. The state hosts 512 farms that manage 47,600 acres of wild blueberry farmland. Unlike cultivated blueberries, wild blueberries grow up to 60 cm tall, making them more prone to soil contact. Harvesting methods are relatively standard across farms, involving either a walk-behind harvester or a hand rake to collect berries, which are then transported in bins to the processing area. The berries are processed through a winnower to remove leaves and sticks, followed by sorting on a conveyor belt to eliminate undesirable berries. Currently, nearly all wild blueberries harvested in Maine are frozen. However, there is a growing interest in expanding the fresh pack industry. The food safety implications of harvesting low bush blueberries are not yet fully understood, which can cause challenges to the industry's growth. The Food Safety Modernization Act (FSMA) introduces new food safety guidelines that farms must adapt to. Understanding the microbial presence during harvesting and processing can improve food safety standards, helping identify critical pathogens and develop more effective mitigation strategies. The main objectives of this study were to: (1) identify if farms adhere to specific FSMA guidelines and to ensure food safety and quality and understanding where improvements must be made, (2) determine the predominant pathogens affecting wild blueberries and investigate the sources of microorganisms in the harvesting and processing environments. In the first part of the study, farmers were surveyed about their food safety practices, based on FSMA requirements. These responses were quantified into a food safety practice indicator. Results indicated significant room for improvement, highlighting the need for more educational content and training for farmers. The second part of the study involved quantifying coliforms, Escherichia coli, yeast, and mold in wild blueberry harvesting and production to assess the safety and quality of the blueberries. Coliforms served as sanitation indicators, while yeast was considered an indicator of spoilage. Identifying the sources of these microorganisms within the harvesting and processing stages helps target cleaning practices, particularly focusing on bins and harvesters. A key finding of the study was the identification of Shiga toxin-producing E. coli (STEC) as the pathogen of interest in wild blueberry harvesting and processing, with 17.65% of harvester samples testing positive for STEC in 2022. This underscores the necessity for improved sanitation and cleaning practices to ensure the safety of wild blueberries. The study’s results highlight the critical need for enhanced food safety education and more rigorous cleaning protocols, especially as the fresh pack blueberry industry grows.