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Introduction
Temprecord can calculate and display Refrigeration Index values. The Refrigeration Index is calculated from the start sample to the end sample, or over the whole sample record if these have not been set. See Refrigeration Index Graph View for details.
The following text is based on a document supplied by Meat Livestock Australia. It describes how to apply the RI values calculated by Temprecord.
Lag phase
A lag phase may occur when a bacterium moves from one environment to another, especially if it has to adjust to a new environment. The hot boning work described above demonstrated a good correlation when 5 generations of lag were introduced to the equation. 5 generations of growth (1.5 log10) can be subtracted from the calculated refrigeration index in situations where a lag may occur.
The question ‘the starting temperature is hot’ determines whether a lag is applied. If the meat is hot or warm, then it is assumed that E. coli has recently been introduced to the meat surface and a 5 generation lag is allowed. If the meat is cold, then it is assumed that E. coli may already be present on the meat, has adjusted to the environment and is ready to grow as soon as the temperature rises.
The lag phase can be programmed from the RI options.
Temperature
Temperature is the only parameter that can be entered by the user. Temprecord uses the temperature samples from the Start Sample and calculates the RI value cumulatively from then on until the end sample is reached. If the temperature record cools to below 7C the RI value at this point is recorded also.
The Predictive Model
The predictive model used in this calculator was developed by Dr Tom Ross and colleagues at the University of Tasmania. The model has been published (Ref. 1 below).
An evaluation of the model against data in the literature has also been published (Ref. 2 below).
The use of these models in hot boning applications and validation data has been described in an MLA publication that accompanies the Hot Boning Index Calculator CD ROM (Ref 3 below).
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Remember that you must have the Statistics option 'Show Refrigeration Index Statistics' checked in order for Temprecord to display RI statistics |
References/Further reading
1.Ross, T., Ratkowsky, D. A., Mellefont, L. A. and T.A. McMeekin, T. A. (2003)
Modelling the effects of temperature, water activity, pH and lactic acid
concentration on the growth rate of Escherichia coli. Int.J.Food Microbiol. 82: 33-44.
2.Mellefont, L.A., McMeekin, T.A. and Ross, T. (2003) Performance evaluation of a model describing the effects of temperature, water activity, pH and lactic acid concentration on the growth of Escherichia coli. Int.J.Food Microbiol. 82: 45-58.
3.Meat & Livestock Australia (2004) Validation of the chilling of hot boned manufacturing meat and primals. PRMS.020
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