ABSTRACT
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603
II. Frozen Foods: Why it is Difficult to Predict Shelf-Life . . . . . . . . . . . . . . . . . . . . . . . 604
A. Unfrozen Water and Glass Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
B. Deterioration Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605
III. Shelf-Life Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608
A. Time Temperature Tolerance (TTT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608
B. Practical Storage Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608
C. High-Quality Life (HQL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608
D. Accelerated Measurement and the Q10 Approach . . . . . . . . . . . . . . . . . . . . . . 610
IV. Methods Used for Specific Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611
V. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612
It is difficult to produce a common method for the prediction of the shelf-life of frozen foods. Fresh
or chilled foods normally have a single dominant deterioration mechanism (e.g., microbial spoi-
lage). So, it is relatively easy to model the temperature changes in the product and to superimpose
microbial growth and decay models on these temperatures, the integration of which over time will
result in a good approximation of when the microbial load will exceed a safe limit and so define the
safe shelf-life [1]. Lest one thinks that the foregoing sentence solves the problem for fresh and
chilled products, let me quickly add that a deficiency in kinetic data on microbial growth and
decay for spoilage organisms at the temperatures involved and their interactions with food compo-
sition make this a far from easy task.
