Freezing is one of the most important long-term preservation techniques for foods, and offers a means to suppress microbial growth and to preserve taste and nutritional value superior to any other method. However, during freezing, cold storage and thawing, changes in physical and chemical structures due to the formation of ice crystals, recrystallization or various chemical reactions can affect the quality of foods. The causes, types and degree of quality loss vary depending on the food items, and scientific reports on the mechanisms responsible for the quality loss as well as the technical solutions of pretreatment, freezing, storage and thawing technology have accumulated. Also, various analytical and observational technologies of ice crystal and tissue structure in foods have contributed to the development of effective freezing, storage and thawing technologies. The purpose of the present paper was to review the current state of studies on freezing and thawing technologies, and on evaluation technologies of physical and chemical properties of frozen foods, and to present future issues of the technologies concerned with frozen foods to enable their further development.
