Evaluation of the microbiological quality and safety of Maine wild blueberries

The North American blueberry industry produces nearly 350 million pounds of blueberries in 1999, including both wild and cultivated berries. Wild blueberries account for approximately half of this total (48%). Maine is the largest producer of wild blueberries in the world, producing on average 75 million pounds annually, however the 2000 harvest was a record 110 million pounds. The wild blueberry harvest usually occurs in late July through early September. In 1999 this harvest represented 19% of the blueberry production in all of North American, and 99% of the Wild blueberries produced in the United States.; Nearly 99% of the wild blueberry crop in Maine is frozen due to the short harvest period. This freezing is done to allow for further processing into many blueberry containing products, as well as packaged frozen blueberries. This thesis examined this segment of the blueberry processing industry. Individual quick freezing (IQF) is a rapid freezing process often employed to freeze particulate foods like blueberries, corn, peas, and scallops. The wide spread use of this process has lead to an interest and need for baseline data on the microbiological quality of blueberries, and the impact of preparation and processing of blueberries for the IQF process. The development of such a database was begun with the research presented in this thesis. This research has shown that certain processing steps could be detrimental to the microbiological quality of the finished product, and other processes have little or no effect. Evaluations of the potential for safety concerns arising during processing were also of interest to the industry. Research assessing the impact of current processing methods on the reduction of organophosphorous pesticide residues was conducted as part of this thesis.; The author also addressed some of the microbiological safety concerns of the industry by investigating the prevalence of Listeria spp. in field samples of wild blueberries. These samples were collected and evaluated during the 1999 and 2000 harvest seasons in an effort to determine the potential for problems in the industry from such potential pathogens. A rapid commercially available assay requiring a semi-skilled technician was evaluated as a potential method for industry to monitor for the presence of Listeria spp. in wild blueberries. This assay was found to be acceptable, the low incidence of Listeria found in field samples does not rule out the potential for problems to occur. It is recommended for industry to fill the need for such monitoring. Further research into the potential for pathogens such as Listeria to survive and replicate in wild blueberries should be conducted, and may aid industry in making decisions regarding the importance of such monitoring.