Effects of Different Live-Preservation Methods on Soft-Shell Hardening and Flavor Characteristics of the Mud Crab (Scylla paramamosain)

The soft-shell mud crab (Scylla paramamosain) holds high market value, but rapid post-molting shell hardening limits its commercial viability. This study evaluated the effects of four live-preservation methods—ambient seawater (CK, 25 °C, pH 8.10), low-temperature seawater (LT, 14 °C, pH 8.10), ice-chilled storage (ICE, 2–6 °C), and low-temperature acidified seawater (LTA, 14 °C, pH 7.6)—on shell hardening and hepatopancreatic flavor in mud crabs. ICE and LTA significantly delayed hardening (p < 0.05), maintaining the hard-paper stage at 48 h post-molting, while CK and LT samples hardened considerably. Transcriptomic analysis revealed that both ICE and LTA down-regulated key genes involved in calcium signaling, autophagy, and lysosomal pathways, which may be associated with delayed shell hardening. Flavor profiling showed that ICE enhanced umami by increasing aspartate, inosine monophosphate, and adenosine monophosphate levels, and increased sweetness via elevated alanine and glycine, while reducing bitterness by lowering bitter amino acids. In contrast, LTA reduced umami and bitterness but did not improve sweetness. These findings demonstrate that ice-chilled storage effectively extends the soft-shell phase and better preserves flavor quality, offering a viable strategy for enhancing the preservation and marketability of live soft-shell crabs.