Effect of ultrasound combined with papain treatment on the tenderness of equatorial squid (Dosidicus gigas): in terms of myofibrillar protein modification.

Ultrasonic combined papain treatment was effective in tenderizing equatorial squid. When the ultrasonic power was 200 W combined with papain treatment, the shear force decreased by 23.35 %, and the tenderness of squid was the highest. Structural analysis of myofibrillar proteins showed that the myofibrillar proteins treated with ultrasound combined with papain treatment was decomposed to the highest extent at an ultrasound power of 200 W, when the particle size was the smallest and the α-helix content was reduced. Ultrasonic power of 300 W combined with papain treatment can also improve the tenderness of squid, but this treatment increases the degree of water loss in squid, makes the myofibrils more tightly packed, and increases hardness. Papain activity reduced by 400 W ultrasonic power treatment, which was not conducive to the tenderness of the squid. These findings may provide new insights into the tenderization of meat products.