1. To fill knowledge gaps in the regulatory framework for acidified foods, including: a. Development of linear models for thermal processing of acidified foods with pH above 4.1 (pH 4.1-4.6) that meet microbial-destruction targets. b. Determination of the pH, organic acid, and environmental conditions (temperature, dissolved oxygen) that allow spoilage bacilli such as Alicyclobacillus species, Bacillus coagulans, Bacillus licheniformis, and others to grow and potentially raise pH of acidified foods. c. Determine cold fill hold times and temperatures that assure safety for food with a pH value above pH 3.3.
This work will include the use of novel organic acid additives to acidified foods such as fumaric acid, which have recently been shown to be highly effective in killing enteropathogenic E. coli strains in acidified foods. Methods will include determination of the efficacy of combined organic acids on killing E. coli O157:H7 (and other enteropathogenic serotypes), Listeria monocytogenes, and Salmonella strains in acidified foods. Mathematical models of killing kinetics will be developed. Microbiological testing will include fractional factorial experimental design, spiral plating with automated plate reading, and 96 well microtiter plate most probable number techniques. These methods will significantly reduce the supplies and time needed to generate robust and repeatable killing curve data. Inoculated pack studies will include acidified vegetable products such as cucumber pickles (which lack antimicrobial phytochemicals), taking into account bacterial strain and product variation, pre-conditioning cells to acid stress, the sensitivity of acid injured cells to plating media, the effects of ionic strength and dissolved oxygen on acid stress, and other variables that could lead to “fail dangerous” conclusions.