Microbiology

Microbiology Study Guide

Dairy Foods It is impossible to run the dairy industry without microorganisms. Fermentation is one of the principal activities used in this industry, and different milk products are generated from milk after fermenting it with microorganisms. For instance, the species of streptococcus, lactobacillus, and leuconostoc are used to produce substances like diacetyl and acetaldehyde. These substances add flavor to buttermilk, which is produced by using lactic acid in low fat milk. Further, for the preparation of yogurt from milk, species like streptococcus thermophilus and lactobacillus bulgaricus are added to warm milk and kept at a warm temperature to facilitate the growth of these bacteria. Similarly, the same experiment is used for preparation of sour cream from cream instead of milk. Microorganisms also help to produce cheese and cheese products with the help of the protein content of milk, known as casein. The protein curd is helpful inmaking cottage cheese while the leftover liquid, termed whey, can further be utilized to prepare other cheese foods. Treated with different microorganisms, cheese can be ripened to produce other forms of cheese. For instance, fungi Penicillium Camemberti is used to produce soft cheeses like Camembert cheese. In contrast, hard cheeses are produced when bacteria and fungi are used for the purpose of ripening, and much of the water is extracted from cheese. Propipnibacterium is used to generate gas holes in cheese and form Swiss cheese. Penicillium Roqueforti is used to produce veins in cheese and facilitates the preparation of Bleu cheese. Other Fermented Foods The process of fermentation is also used to produce other products, such as pickles. The species of Leuconostoc and Lactobacillus are allowed to grow in shredded cabbage in order to produce sauerkraut. Further, the fermentation of cucumber with these microorganisms helps to prepare pickles. Bread Microbes are also used to prepare bread and related products. The dough for bread is prepared with the reaction among yeast, flour, salt, and water. The widely used species of yeast for preparing bread is Saccharomyces Cerevisiae . This microbe is added so that the carbohydrates in the mixture of dough is fermented and facilitates the production of carbon dioxide. The result of this reaction is the formation of the soft texture of bread by adding fluffiness to it. If yeast is not added to the mixture, the bread formed is known as unleavened bread. Moreover, the bacteria generating lactic acid are used to prepare sour bread. Food Spoilage by Microorganisms Until now, we have studied how microorganisms are added explicitly to produce different products used by people in their daily lives. However, microbes are not always useful. When food items are exposed to unwanted microbes, the food may become contaminated and spoiled. This phase is an unwanted condition, as it departs the food from its normal taste. The change in food depends on three major components: food composition, microorganisms present in food, and chemical reactions due to

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