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Why must fish pass quickly through the temperature range where ice crystals form most easily?
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fish processing
Fish on a conveyor belt entering a processing plant, Newfoundland, Canada.
Fish must pass quickly through the temperature range of −2 to −7 °C (28 to 20 °F) because this is the zone of maximum ice crystal formation within the cells of the flesh.1
Rapid freezing ensures that ice crystals remain small, which minimizes damage to the cellular structure. Conversely, if the freezing process is slow, large ice crystals form and rupture the cell membranes. When the fish is later thawed, these ruptured cells release water and essential flavor compounds—a process known as drip—resulting in a product that is dry and lacks flavor. To maintain quality and minimize this drip loss, it is recommended that fish pass through this critical temperature zone in less than one hour.1