Throughout the freezing process the total weight loss is of major concern and can be classified as follows:
• mechanical losses during transport to and from the freezing system and/or in the freezer,
• dehydration losses during freezing, and
• rejects due to damage or breakage during transport to and from the freezer as well as in the freezer.
Mechanical losses appear especially during bulk freezing of unpacked fruits and vegetables on the racks in tunnel freezers and may reach 5% for practical freezing applications. The use of in-line freezing and modernized technologies has reduced the loss rate to almost zero.
Dehydration losses occur mainly during freezing and storage of food products. The amount of the weight lost is influenced by various factors such as the product itself, physical operations (e.g. handling, slaughtering), harvesting technique, cooling, freezing, storage, and distribution. Dehydration during freezing may account for up to 5% weight loss in a badly designed freezing system. But there is a minimum amount of dehydration that can not be avoided if the product is exposed to air or any gas during the heat extraction. For this reason, packaging of frozen foods is of great importance.