Isolation of Yersinia enterocolitica ‐resembling Organisms and Alteromonas putrefaciens from Vacuum‐Packed Chilled Beef Cuts

Yersinia enterocolitica ‐resembling organisms were found at levels of 10 7 /g on a high pH (pH ≧ 6·0) vacuum‐packaged beef striploin held for 6 weeks at 0·2°C, but did not exceed 10 5 /g on normal pH (pH < 6·0) striploins held for 10 weeks. Gram negative bacteria that produced H 2 S on peptone iron agar were isolated from high pH vacuum packed striploins. These organisms were identified as Alteromonas putrefaciens . They attained levels of about 10 7 /g in 6 weeks at 0–2°C, at which time greening of the fat surface and ‘drip’had occurred. On meat of normal pH, counts of A. putrefaciens were less than 10 4 /g after 6 weeks and no greening was evident.