AUTHOR’S NOTE: The author acknowledges Tânia Mendes, Marina Oliveira, Tiago Fernandes, and António Vicente for the support and endless discussions about the subjects presented in the article and to Adriana Machado for the assistance in preparing the article.
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History of Glazing
The first U.S. patent describing a process to artificially freeze and preserve fish was published in 1861. In his patent, Enoch Piper claims the invention of a new and improved method of preserving fish that includes a 24-hour freezing process and suggests glazing the fish, by a dip in cold water, forming a coat of about 1/8 inch in thickness. After being glazed, the frozen fish is transferred to an insulated chamber and cooled with a freezing mixture within vertical metallic tubes to keep the fish frozen until used.
In 1902, D. W. Davis patented a process of freezing in a rectangular pan covered with a lid and packed in an ice-and-salt mixture for freezing. In his patent, Davis describes that before placing in cold storage, the frozen cakes are to be immersed and held submerged for several minutes in a body of water, which absolutely must be at a temperature of 32 degrees Fahrenheit.
Later, in 1926, the Appendix VIII to the report of the U. S. Commissioner of Fisheries mentions that fish must be frozen in metal pans and then warmed slightly by spraying or immersing in cold water to loosen them. The report states that glazing tanks are commonly made from wooden or concrete, provided with a movable wooden platform suspended by ropes to a windlass by which it was moved up and down the tank.
Today, the glazing of frozen fish has undergone significant technological improvements, especially in terms of the equipment used (and the materials of which they are made). However, regarding the type and function of the glazing solution used, the industry is still currently stuck in the 19th century.—N.S.