Acidification Process Technology to Control Thermophilic Spoilage in Canned Mushrooms

Alternative processes involving the use of citric acid and/or EDTA in mushroom canning operations were evaluated and compared to a standard commercial process as means to control thermophilic spoilage. An average of 68% thermophilic spoilage was observed with the standard control process. Spoilage was reduced to an average of 23.9% by the addition of citric acid to the can brine, and to 16.8% when 500 ppm EDTA was also added to the can brine. However, the best results, 2.4% average spoilage, were observed when mushrooms were vacuum hydrated in a buffered citric acid solution (0.05M, pH 3.5) and EDTA was added to the can brine at 200 ppm equilibrium concentration. This treatment was as the Acid-Vacuum Hydration-Chelation (A-VH-C) Process. Bacteriological evaluation indicated that the A-VH-C Process caused no significant reduction in product spore load counts (after blanching) compared to the control, but did reduce spore load counts after thermal processing. However, cans from all treatments contained viable spores. Outgrowth studies conducted with spores that survived thermal processing and inoculated into Beef Extract Tryptone Iron (BETI) both indicated that spores from cans processed with the A-VH-C Process had the longest generation time. Similar experiments where the BETI broth was treated to simulate the conditions in the cans indicated that the addition of EDTA to the medium had the greatest effect on reducing outgrowth rate of surviving spores.