title: Growth potential of Clostridium perfringens from spores in acidified beef, pork, and poultry products during chilling.
abstract: The ability of Clostridium perfringens to germinate and grow in acidified ground beef as well as in 10 commercially prepared acidified beef, pork, and poultry products was assessed. The pH of ground beef was adjusted with organic vinegar to achieve various pH values between 5.0  and 5.6; the pH of the commercial products ranged from 4.74 to 6.35. Products were inoculated with a three-strain cocktail of C. perfringens spores to achieve ca. 2-log (low) or 4-log (high) inoculum levels, vacuum packaged, and cooled exponentially from 54.4 to 7.2°C for 6, 9,  12, 15, 18, or 21 h to simulate abusive cooling; the U.S. Department of Agriculture, Food Safety and Inspection Service (USDA-FSIS) recommends a cooling time of 6.5 h. Total germinated C. perfringens populations were determined after plating on tryptose-sulfite-cycloserine agar and  incubating the plates anaerobically at 37°C for 48 h. In addition, C. perfringens growth from spores was assessed at an isothermal temperature of 44°C. Growth from spores was inhibited in ground beef with a pH of 5.5 or below, even during extended cooling from 54.4 to 7.2°C  in 21 h. In ground beef with a pH of 5.6, the growth was >1 log after 18 h of cooling from 54.4 to 7.2°C. However, 15 h of cooling controlled the growth to <1 log, regardless of the inoculum level. In addition, no growth was observed in any product with a pH ranging from 4.74 to  5.17, both during exponential abusive cooling periods of up to 21 h and during storage for 21 h at 44°C. While <1-log growth of C. perfringens from spores was observed in the pH 5.63 product cooled exponentially from 54.4 to 7.2°C in 15 h or less, the pH 6.35 product supported  growth, even after 6 h of cooling from 54.4 to 7.2°C. These challenge tests demonstrate that adjustment of ground beef to pH of 5.5 or less and of barbeque products to pH of 5.63 or less inhibits C. perfringens spore germination and outgrowth during extended cooling periods from  54.4 to 7.2°C up to 15 h. Therefore, safe cooling periods for products with homogeneous, lower pHs can be substantially longer.
authors: U.S. Department of Agriculture, Agricultural Research Service, Eastern Regional Research Center, 600 East Mermaid Lane, Wyndmoor, Pennsylvania 19038, USA. vijay.juneja@ars.usda.gov
authors: Vijay K
authors: VK
authors: Juneja
authors: David A
authors: DA
authors: Baker
authors: H
authors: H
authors: Thippareddi
authors: O Peter
authors: OP
authors: Snyder
authors: Tim B
authors: TB
authors: Mohr
mesh_terms: D019342:Acetic Acid / Q000494:pharmacology; D000818:Animals; D003016:Clostridium perfringens / Q000502:physiology*; D015169:Colony Count, Microbial; D005506:Food Contamination / Q000032:analysis* / Q000517:prevention & control; D005511:Food Handling / Q000379:methods; D005516:Food Microbiology; D018857:Food Packaging; D005519:Food Preservation / Q000379:methods; D005520:Food Preservatives / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008461:Meat Products / Q000382:microbiology*; D011202:Poultry Products / Q000382:microbiology*; D013171:Spores, Bacterial / Q000254:growth & development*; D013696:Temperature; D014618:Vacuum
chemical_list: D005520:Food Preservatives; D019342:Acetic Acid