Microbiology

Microbiology Study Guide

the metabolism activity in the food item. This unwanted and contaminated state of food can be diagnosed using vision, touch, smell, and taste. This contamination can be natural as well as artificial. In cases where the microbes attach themselves to food products during the developing phases of food, they create natural contamination. For instance, fruits are attacked by yeasts and ferment the carbohydrate content present in fruits, contaminating it. In contrast, artificial contamination occurs during the handling and processing stages of food items. For instance, due to improper handling, transportation, and storage, food items can be affected and contaminated by fecal bacteria. Types of Spoilage Spoilage in food products is caused due to physical, chemical, and biological factors. Rancidity is the type of spoilage that results from the growth of microbes in sweet butter. These microbes are fungi and bacteria, like the species of gram-negative bacterial rod of Pseudomonas, which produce acids and glycerol by breaking down fats in butter that finally lead to a rancid smell and taste in butter. Meat is another example in which the species of Proteolytic bacteria leads to the formation of chemical products like putrescine and cadaverine by breaking down the protein content inmeat. This is because the bacteria interfere and facilitate improper utilization of the amino acids in the protein content of meat. The sour taste inmilk is another popular example of food spoilage. If milk is kept at room temperature for a long time, the milk will become sour. This is because bacteria survive the pasteurization process and produce different acids using the carbohydrate lactose present in milk. Some of the food acids that affect food products and contribute to spoilage are lactic acid, butyric acid, and acetic acid. Sources of Microorganisms There are many sources of microorganisms, but the major ones include soil, air, sewage, and animal and plant waste. Food items that grow on the ground are at potential risk for spoilage due to these microorganisms. Other food items, like meat, get contaminated due to the bacteria present in the internal organs, skin, and feet of animals and birds. Further, when used after chopping for the purposes of preparing hamburgers, the bacteria at the outer covering of meat easily travels in the inner pockets, thus spoiling it. Another food category that is highly prone to contamination is canned food items if they are not sterilized properly. In the case of canned foods, the species of Chostridium leads to production of gas and swells up the can. The species of bacillus is responsible for sour spoilage of canned foods, without any production of gas in it; it is popularly known as flat sour spoilage. The genre of species lactobacillus breaks carbohydrates in food, which spoils the food by producing significant acid. It should be noted that it is imperative to learn about the types of spoilage occurring in food items. In order to know this, it is vital to know the nature of food, processing and handling methods of food,

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