Fundamental Food Microbiology, Third Edition - Fuad Fathir

516 FUNDAMENTAL FOOD MICROBIOLOGY
I. INTRODUCTION
Many of the conventional food preservation methods used at present and discussed
here have several disadvantages. High-heat treatment given to foods for safety and
long shelf life results in loss of heat-sensitive nutrients (e.g., thiamine, riboflavin,
folic acid, and vitamin C); denatures proteins and causes changes in texture, color,
and flavor; and induces formation of new compounds through covalent bondings
(e.g., lysinoalanine). Low-heat processing, such as pasteurization, minimizes the
disadvantages of high-heat processing of foods, but the foods have limited shelf life
even at refrigerated storage. Drying and freezing also reduce nutritional and acceptance
qualities of food, especially when stored for a long time. Irradiated foods have
not been well accepted by consumers. Many of the chemical preservatives used are
of nonfood origin and have limited efficiency.
Since the 1980s, health-conscious consumers, especially in the developed countries,
have been concerned about the possible adverse effects that “harshly produced”
and “harshly preserved” foods might have on their health and on the health of future
generations. There is a concern that the cumulative effects and interactions of
different types of food preservatives on the human body during one's lifetime are
not properly understood. The revelation about the harmful effects of some of the
additives that were once allowed to be incorporated in foods has shattered consumer
confidence. The philosophy of the consumers has changed from “How long will I
live?” to “How well will I live?” which, in turn, has shifted the desire of these
consumers to nutritious, natural, and minimally processed foods that have not been
subjected to harsh processing or harsh preservation techniques. Because of changes
in the socioeconomic patterns and lifestyles, many consumers are also interested in
foods that have a long shelf life and take very little time to prepare. 1
The suitability of several thermal and nonthermal processing and preservation
methods are being studied to produce such foods. The principal advantages, disadvantages,
and the current status of some of these methods are briefly described here.
Major emphasis is given to their antimicrobial properties. 2,3
II. SUMMARY OF PROCESSING METHODS
Some of the novel technologies currently being studied to process foods to control
microorganisms as well as to produce new types of foods and their current status
in the application of food are briefly described. This includes processing under
thermal and nonthermal conditions. For further information, a recent review may be
consulted. 3
A. Microwave and Radio-Frequency Processing 3
The methods involve exposing a food to electromagnetic waves at microwave and
radio frequencies. Generally, microwaves at 915 MHz and 2450 MHz and radio
frequencies at 13.6, 27.1, and 40.7 MHz are used in food applications, but very little
study has been conducted with radio frequency. Both techniques generate internal