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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Produce Safety and Microbiology Research » Research » Publications at this Location » Publication #327005

Research Project: Biology and Control of Human Pathogens on Fresh Produce

Location: Produce Safety and Microbiology Research

Title: Inactivation of Toxoplasma gondii on blueberries using low dose irradiation without affecting quality

Author
item Lacombe, Alison
item Beard, Anna - University Of Maine
item Hwang, Cheng-an - Andy
item Hill, Delores - Former ARS Employee
item Fan, Xuetong
item Huang, Lihan
item Yoo, Byong
item Niemira, Brendan
item Gurtler, Joshua
item Wu, Vivian

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2016
Publication Date: 10/4/2016
Citation: Lacombe, A.C., Beard, A., Hwang, C., Hill, D., Fan, X., Huang, L., Yoo, B.K., Niemira, B.A., Gurtler, J., Wu, V.C. 2016. Inactivation of Toxoplasma gondii on blueberries using low dose irradiation without affecting quality. Food Control. 73(2017):981-985.

Interpretive Summary: The U.S. Food and Drug Administration (FDA) has recently identified fresh fruits and vegetables as commodities with a high potential risk of Toxoplasma gondii contamination. Toxoplasma gondii is a common protozoan parasite, whose environmentally-resistant stage, the oocyst, can contaminate irrigation water and fresh edible produce. Current washing steps in produce processing may not be effective for eliminating T. gondii from at-risk varieties of produce. The objective of this study was to evaluate low-dose irradiation as a means to inactivate T. gondii oocysts on blueberries. Results indicated that irradiation treatments at doses as low as 0.2 kGy effectively inactivate T. gondii oocysts on blueberries surfaces with minimal impact on texture, color, or anthocyanin content of treated berries. Since this study examined surface contamination of T. gondii on blueberries, the inactivation of the oocysts was not affected by the chemical properties in the product. Therefore, the effective irradiation doses may also be applicable to other berries or produce for decontaminating T. gondii.

Technical Abstract: Toxoplasma gondii is a common protozoan parasite, whose environmentally-resistant stage, the oocyst, can contaminate irrigation water and fresh edible produce. Current washing steps in produce processing may not be effective for eliminating T. gondii from at-risk varieties of produce. The objective of this study was to evaluate low-dose irradiation as a means to inactivate T. gondii oocysts on blueberries. Blueberries (10 g) inoculated with T. gondii (5 log oocysts/g) were exposed to an absorbed dose of 0 (control), 0.2, 0.4 or 0.6 kGy gamma radiation at 4°C. After treatment, oocysts were recovered from berries by washing, and excysted sporozoites were enumerated using a plaque assay. Vero cells were maintained as monolayers in a 6-well microplate, exposed to sporozoites recovered from berries, and incubated for 7 days to determine plaque-forming units (PFU). Immediately after treatment, blueberries without inoculated T. gondii were analyzed for compression firmness, surface color, and total anthocyanins. The results from this experiment demonstrate that the viability of T. gondii oocysts was significantly reduced after an irradiation treatment of 0.2 kGy. All treatments produced reductions of 4 log PFU/g beyond the detection limit of 1 log PFU/g. Quality analysis showed that there was no significant change in compression firmness, anthocyanins, or color in berries after the irradiation treatment. Results of this study indicated that low-dose irradiation is a potential intervention measure for controlling T. gondii contamination on blueberries without affecting product quality.