Märgaktiviteten

Märgaktiviteten, often translated as "moisture activity" in English, is a critical concept in food science and preservation. It refers to the amount of unbound water available in a food product for microbial growth and chemical reactions. It is not the same as total water content, but rather the fraction of water that is not tightly bound to food molecules and is therefore accessible for biological and chemical processes.

The measurement of märgaktiviteten is typically represented on a scale from 0 to 1. A value of 1 indicates pure water, while a value of 0 represents a completely dry substance. Most microorganisms, including bacteria, yeasts, and molds, require a certain level of märgaktiviteten to survive and multiply. For instance, bacteria generally need a märgaktiviteten of at least 0.85 to grow, while yeasts and molds can proliferate at lower levels, some down to 0.60 or even less.

Controlling märgaktiviteten is a primary strategy for extending the shelf life of food products and preventing spoilage. By reducing the märgaktiviteten through methods like drying, adding solutes (such as salt or sugar), or using humectants, the growth of microorganisms is inhibited. This principle is fundamental in the production of dried fruits, cured meats, jams, and many other preserved foods. Understanding and managing märgaktiviteten is essential for ensuring food safety and quality.