Immersion vacuum cooling of cooked beef - Safety and process considerations regarding beef joint size.

Cooked beef samples (1, 2, and 3kg; 4.7, 5.6, and 6.2cm average radius, respectively) were cooled from ∼72 to 4°C core temperature using either air blast (AB), immersion vacuum (IVC) or vacuum (VC) cooling. IVC cooled larger samples within 4h and took less than 2.5h between 72 and 10°C. IVC cooling times were on average shorter than AB and longer than VC for all sizes. Differences increased with size. IVC and AB cooling losses were comparable (P>0.05) while lower on average (P<0.05) than VC losses for same size samples. Additionally, samples between 1.0 and 4.3kg (4.2-8.7cm average radius) were cooled by either IVC or VC. Cooling times were between 2.8 and 5.5h for IVC and between 1.1 and 3.2h for VC. There was a significant effect (P<0.01) of sample size on IVC cooling times. Cooling profiles of larger samples were tested using USDA cooling growth model for Clostridium perfringens in beef broth. According to the model, none of the analyzed profiles would support significant growth of the bacteria.