Characterization of actinidin from Chinese kiwifruit cultivars and its applications in meat tenderization and production of angiotensin I-converting enzyme (ACE) inhibitory peptides

- The actinidin from cultivar Xuxiang showed high protease and milk-clotting activity.
- The actinidin showed favorable tenderization effect on both pork and rabbit muscle.
- The actinidin could be a promising protease for production of ACE-inhibitory peptides.

Protease activity, milk-clotting activity and protein pattern were compared among seven Chinese kiwifruit cultivars. The actinidin from cultivar Xuxiang exhibited highest protease activity and milk-clotting activity. The purified actinidin from cultivar Xuxiang was a cysteine protease with an optimal pH and temperature of 3.5 and 40 °C, respectively. Improved tenderness was observed with pork and rabbit muscle after actinidin treatment. The shear force was reduced by more than half with pork and rabbit muscle using the purified actinidin at a dosage of 0.5 mg/100 g muscle. Furthermore, angiotensin I-converting enzyme (ACE) inhibitory peptides were produced from five plant-derived proteins using actinidin. The yield of peptides varied from 7.2% to 14.2%, and the ACE inhibitory rates ranged from 71.1% to 88.3%. The results indicate that actinidin could be used as a promising protease for meat tenderization and ACE inhibitory peptides production.