Enzymatic action
Many foodstuffs, such as fruit, vegetables, meat and fish, contain enzymes, which have a catalytic action and break down nutrients. Like microorganisms, enzymes are also dependent to a considerable extent on the temperature and water content of the goods.
The optimum temperature for enzymatic activity is 45°C. Lower temperatures slow down activity; however, activity is possible at far lower minus temperatures than is the case with microorganisms. Most enzymes are not inactivated until a temperature as low as -20 to -30°C is reached. Frozen goods therefore have only a limited storage life: if stored for many months, enzymatic processes may cause undesired changes and finally lead to spoilage.
Enzymatic activity is also associated with water: enzymes only become active when they are in the form of swollen proteins. Table 5 shows the activity of enzymes and microorganisms as a function of temperature.

°C Enzymes which affect flavor and structure Microorganisms which cause mold growth Microorganisms which cause food
20 high level of activity rapid development rapid development
0 slow development
- 5 slow development inactive
- 10 inactive
- 15
- 20 low level of activity
- 25
- 30
- 35

Table 5: Activity of enzymes and microorganisms as a function of temperature; taken from Alders [2]  

Contact  |  Site Map  |  Glossary  |  Bibliography  |  Legal Notice  |  Paper version