Physicochemical properties on the bone of hairtail (Trichiurus lepturus) under various treatments of cooking pressure and vinegar

Abstract

Hairtail flesh is delicious but its side fin bones are difficult to remove and detect while eating. This study aimed to evaluate the effects of pressure, vinegar concentration, and heating time on the physicochemical properties of hairtail backbones, dorsal and anal fin bones, and flesh to develop fish fillets with edible bones. The fishbone hardness decreased significantly after heating under 40-70 kPa at 20-60 min heating times at 0.9 % rice vinegar, where a higher pressure and longer heating time resulted in a lower backbone hardness. Heating at 70 kPa with various rice vinegar concentrations (0.225-0.9 %) achieved similar softening effects. Fishbone structures revealed that vinegar treatment caused fragmentation with numerous protruding fragments and holes. Higher vinegar concentration led to lower pH values and higher acidity in the fish flesh. Sensory evaluation of the acidity intensity in hairtail with fishbones followed the same trend. The vertebral bone hardness showed no significant difference (p < 0.05) when the pressure exceeded 60 kPa or vinegar concentration exceeded 0.45 % with 60 min of heating. The combination of 60 min heating, pressure (70 kPa), and vinegar solutions (0.225 % and 0.45 %) could soften the hairtail fishbones (hardness <10 N), and they were edible without an unfavorable taste and aroma without safety concerns.