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

10.2 KINETICS OF FOOD DETERIORATION
10.2.1. Reaction modeling principles
Applying fundamental chemical kinetic principles the rate of food quality change may in
general be expressed as a function of composition and environmental factors (Saguy and
Karel, 1980):
dQ
dt = F (C i, E j ) (1)
where C i , are composition factors, such as concentration of reactive compounds, inorganic
catalysts, enzymes, reaction inhibitors, pH, water activity, as well as microbial populations
and E j environmental factors, such as temperature, relative humidity, total pressure and
partial pressure of different gases, light and mechanical stresses. What the food kineticist
is thus faced with, is a physicochemical system of high complexity involving numerous
physical and chemical variables and coefficients which in most cases are imposible or
impractical to quantitatively define. Even if the system could be explicitly expressed in
terms of measurable parameters, an analytical solution is usually nonexistent and exact
numerical solutions are too complicated and laborious to be useful as working tools.
The established methodology consists of first identifying the chemical and
biological reactions that influence the quality and the safety of the food. Then, through a
careful study of the food components and the process, the reactions judged to have the
most critical impact on the deterioration rate, are deternined (Labuza, 1985). Excluding the
effect of the environmental factors, E j , by assuming them constant, at the most propable
level or judging it negligible within their expected variation, a simplified reaction scheme
that expresses the effect of the concentration of the reactants, is developed. The ultimate
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