Combined effect of squid ink tyrosinase and tannic acid on heat induced aggregation of natural actomyosin from sardine

Abstract

The mixture of squid ink tyrosinase (SIT) at 300 and 500 U/g protein and tannic acid (TA) at 0.5 and 1% (based on protein) increased the turbidity and surface hydrophobicity of natural actomyosin (NAM) from sardine (Sardinella albella) in a dose dependent manner. Total sulphydryl group content decreased in the NAM solutions with coincidental increase in disulphide bond content, when added with SIT/TA mixture. Ca2+-ATPase activity was also lower in NAM solutions added with SIT/TA mixture. Higher aggregation of protein filaments was noticeable in NAM added with SIT at 500 U/g protein and 1% TA, which also had the highest storage modulus (G′) and largest particle size. Negative charge of NAM was decreased when SIT/TA mixture was incorporated. Therefore the mixture of SIT and TA, particularly at higher level, could be used as the novel protein cross-linker in fish mince and surimi.