Explain about the Fermentation - methods of food processing?

In contrast to other preservation methods, multiplication of microorganisms and their metabolic activities are encouraged. In this, microorganisms break down complex organic compounds into simpler substances either in aerobic or anaerobic conditions. The chemicals excreted by the microorganisms cause the preservative effect of fermentation. The principal chemicals involved are the acids (especially, lactic acid) and alcohol. These inhibit the growth of common pathogenic organisms in foods. Examples of food preserved by fermentation are yogurt, cheese, beer, wine and other alcoholic beverages.