Microbiology

Microbiology Study Guide

©2018 of 132 and time elapsed between processing and consumption. Keeping track of these measures helps not only to reduce the spoilage of food, but aids in preserving the food for a longer time. Food Preservation The role of food preservation methods is to eliminate the presence of microorganisms from food items and to stop their growth and metabolism activity in the food. One of the best ways to preserve food is to check on contamination during the preparation of food items. This can be done by sterilizing the utensils and equipment used for food preparation, sanitizing the food items and equipment, and wrapping them carefully in sealed containers so that the moisture, and microorganisms, can be kept out. For liquid products, contamination can be avoided by way of filtration and sedimentation activities. Moreover, washing and trimming also helps to keep away the microorganisms. For instance, fruits and vegetables should be properly washed before using, and proper trimming of meat and other poultry products is essential to safeguard them from contamination. Heat Heating is a widely used method for preserving food, as it kills many microorganisms from food items. However, the quantum of microbes found in food, often known as the microbial load, is a vital factor that determines the success of the method. The nature of microbes is another important consideration. For instance, heating is highly successful for combating vegetative bacilli, while the bacterial spores are tough to kill using this method. One way that supports the killing of microbes using heat is the addition of acidity in the food contents. Some popular heating methods used for preserving food are pasteurization, hot filling, and steam treatment under pressure. In the process of pasteurization, food items are treated at a temperature of 62° C for a duration of 30 minutes, which can be reduced to 15 to 17 seconds if the temperature is increased to 72°C. Hot filling is generally used for liquid food items and is done when the liquid foods are boiled before they are stored in jars and containers. Finally, canned products are steamed under high pressures before they are packaged for the purpose of consumption. A number of steps need to be followed before preserving foods in cans. The soil of the food items must be removed by washing them thoroughly. Then the enzymes must be deactivated by blanching the washed products with hot water. This helps to remove the diseased portions, and finally with the help of filling machines, the cans are filled. Next, sterilization machines, like retort, are used to preserve the sealed cans for a predetermined time period and at a designated temperature. Before these methods are applied on different food products, the food items and the nature of microbes must be examined to learn the time it should take to kill the microbes. This helps to determine heat resistance in terms of thermal death time, that is, the time taken by microorganisms to die under specified temperature and conditions. Achieve Page 98