Konu: Thermal Destruction of Microorganisms

Thermal Destruction of Microorganisms

• Heat is lethal to microorganisms, but each species has its own particular heat tolerance.
• During a thermal destruction process, such as pasteurization, the rate of destruction is logarithmic, as is their rate of growth.
• Thus bacteria subjected to heat are killed at a rate that is porportional to the number of organisms present.
• The process is dependent both on the temperature of exposure and the time required at this temperature to accomplish to desired rate of destruction
• Thermal calculations thus involve the need for knowledge of
• the concentration of microorganisms to be destroyed,
• the acceptable concentration of microorganisms that can remain behind (spoilage organisms, for example, but not pathogens).
• Also the thermal resistance of the target microorganisms (the most heat tolerant ones),
• and the temperature time relationship required for destruction of the target organisms.


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I. Introduction to microbiology

Microbiology is a branch of biological science. Microbiology deals with microscopic sized organisms: microorganisms (m/o’s); bacteria, molds, yeasts, protozoa, algae and viruses.

Name of microbiology: three Greek words, micros (small), bios (life) and logos (science). They mean the study of microscopic life.

It deals with their form, structure, reproduction, physiology, metabolism and classification. It concerned with distribution of m/o’s, their effects on man, plant animals. It also deals with the problems of agriculture, medicine and food industry.

Microorganisms are widely distributed in nature. They cause;
Desirable changes: Food Fermentation
Undesirable changes: Food Spoilage, Production of toxins.
Food borne disease: Pathonic microorganisms, botulism, intoxication, infection.

When a student attains to microbiology course: this student should gain some basic knowledge about microbiology and microorganisms.

Large scale food production: biotechnology industrial microbiology.
Citric acid => Aspergillus niger
Beer => Saccharomyces cerevisia