Advances in freezing technology and distribution systems have led to an increase in the amount of highquality frozen seafood on the market. As demand for frozen fish and shellfish has grown, so has the vocabulary to describe these products. Here’s a sampling of the frozen lexicon. 

FAS (Frozen At Sea). FAS products may be frozen whole for later thawing and reprocessing on a factory ship or at a plant ashore, or they can be landed, filleted and frozen aboard the same vessel. Groundfish like pollock and cod are often filleted and frozen at sea. FAS products offer a quality advantage because they are frozen quickly after harvest.

IQF (Individually Quick-Frozen). Pieces of finfish or shellfish fast-frozen as single units, then glazed, bagged and boxed. The “quick” in IQF can refer to cryogenic methods that employ liquid nitrogen or carbon dioxide, or to blast freezing. It simply means the product was frozen in a matter of minutes or hours, not days. Products marked IQF that have been frozen in a storage freezer are incorrectly labeled, as they have been frozen too slowly and thus do not qualify as IQF. 

Products frequently sold in IQF form include small, dressed whole fish like whiting, herring or smelt; peeled or shell-on shrimp, crab clusters and legs; whole fish like salmon, which are normally blast frozen, glazed and individually bagged; and scallops for retail sale.

Refreshed. Seafood that has been frozen, often in blocks, then thawed (or “slacked out”) for resale. If handled properly, the quality of this product is high, though it should be labeled “refreshed” or “previously frozen” to avoid confusion or deception. Fillets labeled “fresh” that appear dry may have been previously frozen. 

Twice-frozen (also known as double-frozen). Fish or shellfish that has been frozen at sea, then thawed for reprocessing ashore and frozen a second time after processing. Microwave heating may be used to partially thaw a frozen shrimp or fish block, permitting separation of individual units still in a frozen state. Fish or shrimp blocks are often “tempered” in this manner, heated until their temperature is just below freezing, at which point portions are chipped off, then battered, breaded and immediately refrozen. 

Refrozen, or “double-frozen,” products like these should offer only minimal quality loss if handled properly.

Glazed. IQF products that have been sprayed with cold water or dipped into icy water, which freezes instantly into a protective film that eliminates air pockets and reduces the likelihood of freezer burn or rancidity. Glaze should be uniform and completely cover the product. Cracks in the glaze (not simply hairline fractures) or “holidays” where the glaze is missing entirely may indicate improper glazing and the necessity to re-glaze. Re-glazing is customary and necessary during prolonged storage when the original glaze has diminished. 

Beware, however, of excessive glazing and improper weight claims based on glazed weights.