Process validation and efficacy of antimicrobial systems used in foods; understanding the bacterial stress response

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Although Canada is recognized to have a fairly safe food supply, the Public Health Agency of Canada estimates that four million people (one in eight Canadians) get sick every year due to domestically acquired food-borne illnesses. Meat is the most commonly incriminated food with a financial burden of $500 million a year and another $200 million for spoilage. Consumer demand for easily prepared, minimally processed foods with fewer additives, challenges food scientists to find innovative ways to maintain the safety and the quality of our food supply. The efficacy of antimicrobial systems is traditionally evaluated by cell enumeration on solid growth medium during challenge studies. However, viable organisms that are too stressed or injured do not grow immediately to form distinct colonies on solid media. Viable but non-culturable organisms may recover during storage to later resume growth in foods. Hence, the efficacy of an antimicrobial treatment can be overestimated if solely based on cell counts. To develop effective and practical means of microbial control, we must understand their microbial physiological response at the molecular level. So, using cell log number reduction, recovery time and efficacy in permissive and industrial storage conditions, the decline of cellular ability to response to antimicrobial stresses, and the level and type of residual metabolic activity upon severe treatment as threshold limits, we will optimize the severity of antimicrobial systems to secure safe foods/meats without compromising product quality. Using this approach, we have demonstrated that duck liver pate can be sterilised at an F° of 1 instead of 3, resulting in a final product that now meets the high standard of international markets. Also, by following the decline of bacterial stress markers, such as DnaK and GroEL, we determined the conditions under which antimicrobial systems start to be effective. In this grant, we will investigate the efficacy of cooking and milder heat treatments applied at different rates to control spoilage and pathogenic organisms. Our search for new alternatives to control microbial spoilage and pathogens has led us to study the efficacy of natural antimicrobials from various sources (e.g., essential oils of plant origins, nisin, peptides from crab hydrolysate) in meat products. Their efficacy in meat systems will be investigated as well. In Quebec alone, 15,000 tonnes of onion per year are rejected and found unfit for human consumption for various reasons. Effective use of polyphenols extracted from by-products of plant production in food or feed aligns with a global vision for sustainable agriculture and economic efficiency. To use these novel antimicrobials to their full potential in a complex food matrix such as meat, we must determine their efficacy and understand the physiological stress they elicit, as proposed in this grant application.