Microbiology Methods for ERP Review 3-2020

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GENE-UP SLM Matrix Extension

June 19, 2017

agar, Xylose, Lysine Desoxycholate (XLD) and a non ‐ selective agar, Tryptic Soy Agar (TSA) to determine 1 percent reduction. The degree of injury was estimated as 2

3 where n select = number of colonies on selective agar and n non ‐ select = number of colonies on non ‐ selective 4 agar. For matrices using a non ‐ stressed culture, the diluted culture was used to inoculate the matrices. All 5 perishable food matrices were held for 48 ‐ 72 h post inoculation at 2 ‐ 8°C to allow for equilibration of the 6 organism within the matrix. The bulk samples of dry and shelf ‐ stable products were inoculated and held at 7 room temperature (24 ± 2°C) for a minimum of 2 weeks. See Table 2 for individual product specifications. 8 9 To prepare the 375 g test portions, a bulk lot of product was inoculated to a final concentration of 0.2 ‐ 2 10 cfu/25 g test portion. Test portions (25 g) were removed for the reference method analysis and an 11 additional 25 g test portion was removed from the bulk lot and mixed with 350 g of uncontaminated matrix 12 resulting in a 375 g test portion that was used for the GENE ‐ UP Salmonella method. For chicken carcasses, 13 excess fluid was drained from the carcass and transferred from the carcass to a sterile Stomacher™ 3500 14 bag. Four hundred mL of BPW was poured into the cavity of the carcass contained in the bag. The bird was 15 rinsed inside and out with a rocking motion for one minute (ca. 35 RPM). The sample rinse fluid was 16 transferred to a sterile container.

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