Microbiology

Microbiology Study Guide

Coliform and Fungal Determinations Coliform bacteria generally do not spread any fatal diseases, but these gram-negative intestinal rods indicate the presence of fecal contamination, which makes it unfit for the purpose of consumption. One of the most common coliform bacteria that are found in food items, or even water, is Escherichia Coli. The violet red bile agar is used as the medium for detecting the presence of this bacterium. The count of the bacteria can be detected using the standard plate count method. The presence of fungi in food items can be detected using the medium Sabouraud Dextrose Agar, as it encourages the germination of fungi, forming the visible screen of filaments over the food, known as mycelia. The mycelia can be counted to learn the magnitude of contamination in the food. The Phosphatase Test When compared to the plate count test, the phosphatase test provides faster results when one has to determine the contamination in milk and related products. Milk is pasteurized and the enzyme phosphatase is not able to keep up with the process of pasteurization. The result of the test is determined after testing themilk for the presence or absence of this enzyme. If phosphatase is present after testing the milk, it can be interpreted that the pasteurization process has not been done properly and the milk is contaminated. 6.3 Industrial Microbiology Fermentations The alcohol industry is one of themost popular industries tomake use of microbes for the preparation of liquor. The most important microbial determinant of the alcoholic industry is the use of yeast for the fermentation of carbohydrates. For instance, wine is prepared by aging fruits. While preparing wine, grapes are crushed and stemmed using yeast to produce the substance known as must. This must is treated with sulfur dioxide so that the yeast and other microbes are killed. Finally, the treated must is fermented under controlled conditions with the help of the species Saccharomyces . It should be noted that the skin and seeds of grapes form part of the ingredients of wine and are not removed, since their function is to add color and flavor to wine. The fermentation process lasts for many days, which leads to the production of alcoholic percentage of about 15 percent in wine. An aging process follows in which the wine is placed in barrels to develop its full flavor, aroma, and bouquet. The wine extracts chemicals from the wood. Then it is filtered, pasteurized, and bottled for markets unless secondary fermentations are intended. For example, sparkling wines are inoculated with sugar and permitted to continue to ferment. The carbon dioxide produced accounts for the bubbles in a sparkling wine, such as champagne. For the production of beer a type of grain, usually barley grain, is used. It is mashed, soaked, and filtered to produce liquid called wort. The wort is inoculated with Saccharomyces and permitted to ferment. The final alcoholic content of the beer is approximately 7-8%. The beer is pasteurized or

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