Different heat and treatments are given to raw milk in order to remove pathogenic organisms, increase the shelf life, help subsequent processing, e.g. warming before separation and homogenization or as an essential treatment before cheese making, yoghurt manufacture and production of evaporated and dried milk products. Ultra-high temperature (UHT) process is a method of milk preservation where it should reduce both the bacterial and enzymes content of the product to a commercially acceptable level that will ensure consumer safety and extending shelf life of milk. However, during this heat treatment as well as storage, number of changes undergo in chemical, physical and microbiological characteristics of the product. These changes may render the product unacceptable because of the development of off-flavor and color or gelation. This book aims to cover the changes in UHT milk occurring during storage.