One of the most controversial subjects in food freezing is the effect of the rate of freezing on the food quality. Many firmly believe or actively promote the idea that quick freezing is essential for a high-quality product. Quick freezing is defined as obtaining the most desirable texture and frozen conditions of the food products and retaining the natural color, turgidity, and acceptable appearance as rapidly as is compatible with reasonable economic operations. The advantages of quick freezing are:
• minimizing destruction of intact cells by favoring the formation of smaller ice crystals,
• shortening the freezing period (solidification),
• arresting the growth of spoilage microorganisms by rapid temperature reduction, and
• retaining quality through greatly slowed enzyme action.
It is significant to point out that time and temperature affect frozen food storage. The higher the temperature, the shorter the safe period for food storage in a freezer cabinet. However, there is considerable confusion and disagreement about the maximum time for storing properly processed food products at any given temperature in the subfreezing range. Some of the variability is undoubtedly caused by different starting materials; such factors as variety, maturity, speed, and handling, insofar as they affect the physical and chemical composition of the food, may contribute to a difference in response to freezing storage. Based on microbiological reactions, the temperature of the food product must be —18°C at least after deep freezing, but for enzymatic reactions it must be at —24°C or lower.