ABSTRACT
I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
II. The Structure of Water and Ice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
A. Hydrogen Bonds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
B. Hexagonal Ice (Ice Ih) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
C. Properties of Water and Ice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
III. The Freezing Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
A. Homogeneous and Heterogeneous Nucleation . . . . . . . . . . . . . . . . . . . . . . . . . . 9
B. Crystal Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
C. Freezing Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Phase and State Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2. Freezing Point Depression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
D. Freezing under Thermal Gradients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Freezing Rate Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2. Nucleation and Ice Crystal Growth in Water and Aqueous Solutions . . . 15
IV. Vitrification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
V. Mechanisms of Ice Formation in Cells and Tissues . . . . . . . . . . . . . . . . . . . . . . . . . . 18
A. Intracellular and Extracellular Ice Crystals in Frozen Cells and Tissues . . . . . 18
B. Freezing Injury in Living Cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
VI. Physical and Chemical Changes During Freezing and Frozen Storage in Plant and
Animal Tissues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
A. Structure Characteristics of Plant and Muscle Tissues . . . . . . . . . . . . . . . . . . . 20
B. Modifications Produced by Freezing and Frozen Storage . . . . . . . . . . . . . . . . . 21
C. Physical Modifications Induced by Freezing . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Changes in Cell Volume, Water Dislocation during Freezing, and
Mechanical Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2. Freeze-Cracking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3. Moisture Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4. Freezer Burn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5. Recrystallization of Ice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
a. Surface Isomass Recrystallization . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
b. Migratory Recrystallization or Grain Growth . . . . . . . . . . . . . . . . . . 23
c. Accretive Recrystallization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
d. Pressure-Induced Recrystallization . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
e. Irruptive Recrystallization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
D. Chemical Changes Produced by Freezing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1. Concentration of Nonaqueous Constituents During Freezing . . . . . . . . . . 25
2. Effect of Freezing on Chemical Reactions . . . . . . . . . . . . . . . . . . . . . . . . 26
a. Enzyme Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
b. Protein Denaturation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
c. Lipid Oxidation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
VII. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Water is the most abundant substance on the Earth, and the major component of most foods and
biological specimens Water is essential for life. In almost all living cells water is the most abundant
molecule accounting for 60-90% of the mass of the cell. Water is also a very important component
in foods, affecting quality attributes and shelf life stability [1]. Freezing is regarded as one of the
best methods for long-term food preservation. During freezing, water is converted to ice, thus
chemical reactions and microbial growth are reduced at low temperatures; this apart,, the formation
of ice removes water from food systems, lowering the 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 will
be discussed.
