Impact of zinc salts on heat-induced aggregation of natural actomyosin from yellow stripe trevally

Abstract

Impact of zinc sulphate (ZnSO(4)) and zinc chloride (ZnCl(2)) on heat-induced aggregation of natural actomyosin (NAM) extracted from yellow stripe trevally (Selaroides leptolepis) was investigated. In the presence of ZnSO(4) or ZnCl(2), the transition temperature (T(max)) of myosin shifted from 47.83 ± 0.30°C to 46.05 ± 0.36 and 46.49 ± 0.49°C, with the coincidental decreases in ΔH from 1.07 ± 0.03 J/g to 0.63 ± 0.02 and 0.67 ± 0.04 J/g, respectively (P<0.05). Additionally, Ca(2+)-ATPase activity of NAM decreased with increasing the concentrations of ZnSO(4) or ZnCl(2) during heating up to 40°C. During heating from 20 to 75°C, higher turbidity, surface hydrophobicity and disulphide bond formation were obtained in NAM added with ZnSO(4) or ZnCl(2) at temperatures ranging from 40 to 75°C, compared with the control. Nevertheless, a higher aggregation was found in NAM added with ZnSO(4,) compared with ZnCl(2.) Zeta potential (ζ) analysis suggested that the surface of NAM added with ZnSO(4) became less negatively charged, compared with that of ZnCl(2) counterpart. Transmission electron microscopy showed that the structure of NAM was highly interconnected, finer and denser when zinc salts, especially ZnSO(4) were incorporated. Therefore, ZnSO(4) could be used to induce aggregation of fish muscle proteins, thereby improving gelling property of fish mince or surimi.