Effect of transportation and storage conditions on the quality of milk and its products

During the production and manufacturing stages, milk is liable to microbial contamination. Unless protective measures are taken to prohibit the microbes growth during the transportation and storage of milk, its properties will, in turn, deteriorate rapidly. This is determined by the contamination volume, handling and storage conditions. Temperature is regarded as one of the most important factors that determine the preservability of milk and its products. Unless unprocessed milk is rapidly cooled, its properties will deteriorate and may not be good for pasteurization. Therefore, a particular care should be taken to maintain the milk cool at a temperature of 4.5ºC during storage and transportation. Several experiments have indicated that the pasteurized milk, produced cleanly, can be preserved for two weeks in a refrigerator at 4-5ºC, before the spoilage symptoms appear on it. When stored at higher temperatures, milk preservations period will decrease. It was found that milk can hold good for consumption for 7-10 days when stored at 10 ºC. Psychotropic bacteria is regarded as responsible for most spoilage cases of the cooled pasteurized milk. Concerning yoghurt, where acidity plays a significant role in the determination of its acceptability to the consumer, this acidity increases when the yoghurt is stored at relatively high temperatures (7-10 ºC ). But, when it is stored at temperature higher than 10 ºC, yeasts will grow and, in turn, impart an unacceptable flavor to the yoghurt. While liquid milk products are more affected by temperature than any other environmental effects such as light, humidity, and air, the light may lead to the oxidization of milk and its products if they were packed in transparent or light-permeated containers. The dried milk is affected by temperatures, air, and humidity. Milk powder might lose its solubility and much of its nutritive value if it is stored at a relatively high temperature (37ºC) and under high humidity that increases its moisture content to exceed 4.7 percent