18D-15 |
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O. RODRIGUEZ1, N. Ekpanyaskun1, M. E. Castell-Perez1, R. G. Moreira1, and A. Castillo2. (1) Dept. of Biological & Agricultural Engineering, Texas A&M Univ., College Station, TX 77843-2117, (2) Dept. of Animal Science, Texas A&M Univ., 314 Kleberg Ctr., College Station, TX 77843-2471 Appropriate irradiation treatment planning must yet be developed to ensure safety while minimizing product quality losses. Microbial surrogates are an alternative to validation studies when the use of pathogens could compromise the integrity of the processing environment. Our purpose was to identify surrogates for use in irradiation processing of foods using model food systems. Unflavored gelatin (10% w/v) was mixed with distilled water, heated until dissolved, cooled to 45° C, adjusted to pH 7.0 and boiled. This gelatin was aseptically transferred to Petri dishes (0.01m height) and cooled in a flat surface at 4°C overnight. Three core samples were separated with a sterile sharp corer and inoculated with three pathogenic and five non-pathogenic strains. The cores were irradiated (0.2 - 1.0kGy) using a 2MeV Van der Graaff linear accelerator at ambient conditions. After irradiation, 1ml of homogenized melted gelatin was serially diluted and plated on TSA for plate count of surviving populations. D10 values were obtained from the negative inverse slope of the log of viable population (CFU/ml) versus dose (kGy). Escherichia coli K-12 MG1655 (D10=0.88kGy) showed similar resistance to irradiation as Listeria monocytogenes ATCC 51414 (D10=1.09 kGy) while the tested strains of Listeria innocua (NRRL B33003 and B-33314) were more sensitive to irradiation than L. monocytogenes (D10=0.66, 0.72 kGy, respectively). The highest resistance to irradiation was observed for Enterobacter aerogenes B199A (D10=1.92 kGy) and the least for Salmonella LT2 (D10=0.12 kGy). Our results indicate that E. coli K-12 MG1655 may be a suitable surrogate for L. monocytogenes and could be a good indicator of decontamination of S. Poona (D10=0.38 kGy) and E. coli O157:H7 (D10=0.36 kGy). Further studies should explain these relatively large D10 values. These results demonstrate that determination of the resistance of specific organisms is a useful tool for process design without the risk of potential contamination.
Session 18D, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |