Skip to main content
ARS Home » Southeast Area » Raleigh, North Carolina » Food Science and Market Quality and Handling Research Unit » Research » Publications at this Location » Publication #349868

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

Location: Food Science and Market Quality and Handling Research Unit

Title: Recommendations for designing and conducting cold-fill hold challenge studies for acidified food products

item Breidt, Frederick
item ANDRESS, ELIZABETH - University Of Georgia
item INGHAM, BARBARA - University Of Wisconsin

Submitted to: Food Protection Trends
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2018
Publication Date: 9/1/2018
Citation: Breidt, F., Andress, E., Ingham, B. 2018. Recommendations for designing and conducting cold-fill hold challenge studies for acidified food products. Food Protection Trends. 38(5):322-328.

Interpretive Summary: 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. A challenge study must show that appropriate scientific methods were used for assurance of safety. This report details the scientific considerations that are 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. Using examples from the scientific literature, we review these factors, and describe how to appropriately control them. This report will be useful to researchers, and will help assure that challenge studies are done with consideration of details that can assure safety.

Technical Abstract: A scheduled process for an acidified food must be validated with existing data or a product-specific challenge study. We outline recommendations for designing, conducting and interpreting cold-fill-hold challenge studies for acidified foods and discuss information that should be included in reporting challenge study results to the U.S. Food and Drug Administration. Cold-fill challenge studies for acidified foods, designed and evaluated by expert food microbiologists, must take into account variability in ingredients, packaging, preservatives, and native microbiota. The studies should clearly document a 5-log pathogen reduction over four or more sampling times from at least two independent replicate trials, with pH measured at each sampling point. Inoculation is generally done in bulk and should account for no more than 1% of the product volume. The inoculum is most often a cocktail of at least three strains grown statically in broth containing 1% glucose to induce acid resistance. The pH challenged becomes the maximum pH for the scheduled process; the temperature becomes the lower limit for the hold time. Data analysis should consider the expected non-linearity of survival curves. These recommendations will help ensure that design, implementation, and interpretation of challenge studies for cold-fill-hold acidified foods meet scientific standards and adequately support product safety.