Optimization and flavor analysis of enzymatic hydrolysis for sea cucumber blanching liquid protein

To improve the undesirable odors such as fishy and smoky smell, and enhance the added value of sea cucumber (Apostichopus japonicus) blanching liquid, we optimized the enzymatic hydrolysis conditions through single-factor and orthogonal experiments, and systematically analyzed the flavor changes by using electronic tongue, high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and headspace solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The results show that trypsin exhibited the best hydrolysis effect, with the optimal conditions of 50°C, pH 7.0, 5 h, and 5% enzyme dosage. Under these conditions, the hydrolysate achieved sensory scores and degree of hydrolysis of (8.50±0.27) and (19.77±0.37)%, respectively. Flavor analysis reveals that: 1) Electronic tongue detection showed enhanced umami, sweetness, saltiness, and richness, but reduced bitterness, astringency, and sourness; 2) HPLC-MS/MS identified arginine (130.4‰) and glutamic acid (106.7‰) as the main flavor-active amino acids, with significant increases in sweet-tasting amino acids such as serine and threonine; 3) SPME-GC-MS detected 33 volatile compounds, where increased benzothiazole (0→3.79%) contributed meaty, vegetable, and nutty aromas, while decreased 1-octen-3-ol (1.52%→0), p-cresol, amines, and ketones (37.46%→24.64%) effectively reduced off-flavors such as fishy and smoky odors.