Physical-Chemical Principles in Freezing

Abstract

Water is the most abundant substance on earth and is essential to life. In almost all living cells, water molecules account for 60–90% of the mass of a cell. Water is a major component of most foods and biological specimens and affects food quality and shelf-life stability [1]. Freezing is regarded as one of the best methods for long-term food preservation as chemical reactions and microbial growth are reduced at low temperatures. During freezing, water is converted to ice. The formation of ice removes water from food systems lowering water activity. In this chapter, water and ice structures, ice formation (nucleation and crystal growth), state diagrams, vitrification, freezing mechanisms in plant and animal tissues, and the physical and chemical effects of freezing in different food systems will be discussed.