noun which may take the genitive case particle 'no'
fresh-frozen; quickly frozen
Primarily used for fish or seafood that is frozen very soon after being caught, preserving freshness. Often appears as a label or in food descriptions.
この刺身は活じめなので、解凍しても鮮度が良い。
This sashimi is fresh-frozen, so it stays fresh even after thawing.
活じめの魚は、漁港からすぐに冷凍される。
Fresh-frozen fish is frozen right away at the fishing port.
急速冷凍 is quick freezing as a process; 活じめ emphasizes the state of being frozen while still 'alive' (fresh).
Compound of 活 (いき, 'alive, fresh') and じめ (from 締める, 'to tighten, to kill'), referring to the practice of killing and immediately freezing fish to preserve freshness.