Fermentation And Food Safety Fermentation

Fermentation is one of the oldest methods of food processing. Bread, beer, wine, and cheese originated long before Christ. Although modern food technology has contributed to the present-day high standard of quality and hygiene of fermented foods, the principles of the age-old processes have hardly changed. In industrialized societies, a variety of fermented foods are very popular with consumers because of their attractive flavor and their nutritional value (Figure 1-1).

In tropical developing regions, fermentation is one of the main options for processing foods. In the absence of facilities for home refrigeration, freezing, or home canning, it serves as an affordable and manageable technique for food preservation. Fermentation can also increase the safety of foods by removing their natural toxic components, or by preventing the growth of disease-causing microbes. It imparts attractive flavor and nutritive value to many products. Fermentation is an attractive technique because it is low cost and low technology and it can be easily carried out at the household level, often in combination with simple methods such as salting, sun drying, or heating (e.g., boiling, steaming, frying).

Contrary to unwanted spoilage or toxin production, fermentation is regarded as a desirable effect of microbial activity in foods. The microbes that may be involved include molds

(mycelial fungi), yeasts (unicellular fungi), and bacteria. Examples of food fermentations and the microbes responsible for the desired changes will be presented in this chapter.

In general, the desirable effect of microbial activity may be caused by its biochemical activity. Microbial enzymes breaking down carbohydrates, lipids, proteins, and other food components can improve food digestion in the human gastrointestinal tract and thus increase nutrient uptake. Several bacteria excrete B vitamins into food. As a result of their growth and metabolism, substances of microbial origin are found in the fermented food, including organic acids, alcohols, aldehydes, esters, and many others. These may have a profound effect on the quality of the fermented product. For instance, lactic and acetic acids produced by lactic acid bacteria (LAB) have an inhibitory effect on spoilage bacteria in sourdough bread and yogurt, and the production of ethanol and carbon dioxide determines the acceptability of bread, beer, and wine (ethanol disappears from bread during the baking process).

In addition to enzymes and metabolites, microbial growth causes increased amounts of microbial cell mass. This may be of nutritional and aromatic interest in yeast extract, for instance. The presence of living microbial cells such as in nonpasteurized yogurt may well have advantageous effects on the intestinal microflora and, indirectly, on human health.

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