Fundamental Food Microbiology, Third Edition - Fuad Fathir

470 FUNDAMENTAL FOOD MICROBIOLOGY
break, ribosomal RNA degradation, and activation and inactivation of some enzymes
have also been reported in some studies. In sublethally injured cells, the structural
and functional injuries are reversible. In lethally injured (or dead) cells, the damages
are irreversible (Chapter 9). 4–7
IV. INFLUENCING FACTORS
The effectiveness of low temperature in controlling microbial growth and microbial
enzymatic activity in food depends on many factors. These factors can be arranged
into three groups: those unique to low-temperature, those related to the food environment,
and those inherent in microorganisms. These factors not only help prevent
or reduce the growth of microorganisms but can also greatly influence the extent of
sublethal and lethal injury that microorganisms incur in food preserved at low
temperatures. An understanding of the influence of these factors and interaction
among them is important to design an efficient and predictable method to preserve
a specific food at low temperature.
A. Nature of Process
At temperatures above freezing of free water (£–2�C), different types of bacteria,
molds, and yeasts can grow in a food. But the lag and exponential phases become
longer as the temperature is reduced. In the low range, even a difference in