Validation of the chilling of hot boned manufacturing meat and primals

Summary

​Chilling requirements for hot boned meat in Australia have been established based on predictive microbiology precepts.
Hot boning is regulated via AQIS Notice 2001/20 using a Hot Boning Index - HBI - to describe predicted growth of E. coli.
Company chilling regimes are assessed against the following criteria at the site of microbiological concern - the slowest cooling point:average HBI of no more than 1.580 per cent of the HBIs must be no more than 2.0upper target HBI of no more than 2.5
A predictive microbiology model has been developed with parameters of pH 6.5, water activity 0.993 and lactate 51.7 mM (Ross et al. 2003).
The model has been evaluated and found to predict growth more accurately than existing predictive models (Mellefont et al. 2003).
Validation of the model has been carried out by inoculating hot boned meat in cartons with faeces or E. coli cultures with acceptable correlation between observed and predicted growth - R2=0.89.
Validation of the model has been carried out by inoculating lean or fatty surfaces of primals with faeces or E. coli cultures with a reasonable correlation between observed and predicted growth (R2=0.56). It is expected that the use of different model parameters to account for fatty or lean surfaces would improve the correlation and lead to a more realistic estimate of the HBI.
Simulated boxed product modelling suggests that the average HBI for a whole box of product would be almost 1 less than the HBI at the slowest cooling point. Similarly, the average HBI for the whole mass of a slow-cooling rump, not just the surface, was determined to be almost 1 less than the HBI at the slowest cooling point.
Microbiological and chilling data from in-plant monitoring demonstrate that the HBI is achievable and that the microbiological quality of the chilled product is excellent.
In the next revision of the Export Meat Orders, the term HBI will become subsumed within the term "Refigeration Index" which will be used to regulate chilling of meat throughout the Australian industry. The criteria used to assess whether a meat processor is conforming with the Refrigeration Index are identical with those now used for the HBI.