Frozen mutton refers to mutton from live sheep that has been slaughtered and processed, passed health inspection for fresh sale, and frozen in accordance with freezing conditions.
Thawed frozen mutton of first-grade freshness has bright, shiny muscle color, and white fat. The surface is slightly dry or has a dried membrane, moist but not sticky. The muscle structure is firm to the touch, with strong fiber toughness, and has the normal aroma of mutton. After boiling, the meat broth is clear and transparent, with fat congealed on the surface, possessing the inherent aroma and umami of fresh mutton broth.
Thawed frozen mutton of second-grade freshness has slightly darker meat color, with the meat and fat lacking luster, though the cut surface is shiny. The fat is slightly yellowish. The surface is dry or slightly sticky, and the cut surface is moist and sticky. The muscle tissue is loose, but the muscle fibers still have some toughness; it may have a slight ammonia or sour smell when sniffed. After boiling, the meat broth is slightly turbid, with fat appearing as small droplets on the surface, and the aroma and umami are poorer.