Project Number: 6645-41420-005-00
Project Type: Appropriated

Start Date: Dec 02, 2005
End Date: Dec 01, 2010

Objective:
The overall objective of this research is to develop methods to prevent the growth of pathogenic and spoilage microorganisms in minimally preserved, brined, and fresh-cut foods and optimizing safety, quality, and sensory attributes specifically through: 1) development of fundamental knowledge of the biochemistry of bacterial adaptation to acidified environments; 2) determination, through analysis of gene/protein expression profiles, the responses to intrinsic and extrinsic stressors and, in particular, the effect of oxygen imposed on pathogenic bacteria during production, processing, and storage of acid and acidified foods; 3) development of data and its use for the development of mechanistic models for growth, survival and inactivation of pathogens.

Approach:
The effect of common food acids and acid preservatives will be evaluated for their relative ability to enhance killing of acid-tolerant food pathogens, particularly Escherichia coli O157:H7, in the absence of oxygen and independent of pH. Work will be carried out at biosafety level 2 (BSL-2) due to the organisms under investigation. Selected acid/pathogen strain combinations will be analyzed using genetic and biochemical analyses to determine the mechanisms by which acids are responsible for killing E. coli and other pathogens. This information will be utilized to identify common metabolic targets for the killing effects of acids and acid preservatives, as well metabolic targets unique to particular acids. Since we have found that oxygen increases the killing rates of acid-tolerant pathogens at low pH, similar investigations will be done to determine the genetic and metabolic responses of acid-tolerant pathogens to acids in the presence of molecular oxygen and oxygen radicals. These results will be used to determine the mechanisms by which oxygen species enhance killing of pathogens in acid and acidified foods. Data from genetic and metabolic experiments will be used to develop mechanistic mathematical models and validate the models that are developed in order to test hypotheses developed from genetic and metabolic investigations of acid-killing and acid resistance of food pathogens.