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ARS Home » Southeast Area » Raleigh, North Carolina » Food Science Research » Research » Research Project #430619

Research Project: Intervention Strategies for Controlling Human Pathogens Associated with Fermented and Acidified Vegetables

Location: Food Science Research

2018 Annual Report


4. Accomplishments
1. Establishment of standards for challenge studies for processing cold-filled acidified food products. To file a scheduled process for acidified foods producers must cite or carry out a scientific study to determine if the product meets federal food safety standards. ARS researchers at Raleigh, North Carolina had a leading role in the development of a protocol (and a webinar) detailing the appropriate scientific methods for challenge studies for the assurance of safety of cold filled acidified foods that do not receive a heat process. The webinar was developed and presented in collaboration with scientists from the University of Georgia, Athens, Georgia and the University of Wisconsin, Madison, Wisconsin. The webinar was hosted by the ‘Beverage and Acid/Acidified Foods Professional Development Group’ of the International Association for Food Protection. Over 200 people registered as attendees. This webinar is now freely available on the IAFP website. The protocol details the scientific considerations needed to conduct such a study, including the methods for growing cells, conducting an acid challenge, and analyzing the data. Many factors can influence the survival of bacterial pathogens in acid and acidified foods, and researchers may not be aware of some of them. We reviewed these factors, primarily based on previous publications from the ARS, Raleigh, North Carolina laboratory, and described how to appropriately control them. The webinar will be useful to researchers, industry stakeholders, and aid FDA to help assure that challenge studies are done with consideration of details that can assure safety.

2. Determining the presence of nitrate and nitrite in fermented and acidified vegetables. The influence of nitrate and nitrite in foods on human health has been controversial, with literature citing both positive and negative health effects. ARS researchers at Raleigh, North Carolina, measured the concentration of these compounds in a wide variety of acidified vegetables (made by adding vinegar or other acids to fresh fruits and vegetables), as well as some fermented foods currently available in the U.S. market. This was done in collaboration with a researcher from Jiangnan University, Wuxi, China, who was a visiting scientist at the Raleigh, North Carolina location. The naturally present antioxidants in foods were also of interest in the study of nitrite and nitrate levels in foods due to interactions between these compounds, so antioxidant levels were also measured. We found that nitrite was relatively rare in acidified vegetables, but was present in some of the fermented foods tested. Nitrate, on the other hand, was found to be present at varying levels in many acidified products. These results provide new information for evaluating nitrate and nitrite content in pickled fruit and vegetable products, and may be used to help assess the potential health consequences of these compounds in US consumer diets.


Review Publications
Ding, Z., Johanningsmeier, S.D., Price, R.E., Reynolds, R., Truong, V., Conley Payton, S.B., Breidt, F. 2018. Evaluation of nitrate and nitrite contents in pickled fruit and vegetable products. Food Control. 90:304-311. https://doi.org/10.1016/j.foodcont.2018.03.005.

Kay, K., Breidt, F., Fratamico, P.M., Baranzoni, G., Kim, G., Grunden, A., Oh, D. 2017. Escherichia coli O157:H7 acid sensitivity correlates with flocculation phenotype during nutrient limitation. Frontiers in Microbiology. 8:1404. https://doi.org/10.3389/fmicb.2017.01404.