the handbook of food engineering practice crc press chapter 10 ...

Figure 8.
Characteristic fluctuating temperature distributions used to
verify validity of kinetic models. a o is the amplitude of the sine,
square and spike wave functions.
Alternatively the effect of variable temperature distribution can be expressed
through an equivalent time (t eq ), defined as the time at a reference temperature (is) resulting
in the same quality change (i.e. same value of quality function) as the variable temperature.
The practicality of t eq is that if the chosen T ref is the suggested keeping temperature e.g.
4°C for chilled products, it will directly give the remaining shelf life at that temperature.
Note that if the mean temperature is chosen as the reference temperature, T ref =T m , then
t eq /t=Γ.
Further a short mention of the Equivalent point method is relevant. This
approach has been used for evaluation and modelling of thermal processes (Nunes and
Swartzel, 1990) and the response of Time Temperature Indicators (TTI) (Fu and Labuza,
1993). The same methodology would apply for quality loss during the shelf life of foods.
Using the expression of the quality function
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