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

Impact of zinc sulphate (ZnSO4) and zinc chloride (ZnCl2) on heat-induced aggregation of natural actomyosin (NAM) extracted from yellow stripe trevally (Selaroides leptolepis) was investigated. In the presence of ZnSO4 or ZnCl2, the transition temperature (T-max) of myosin shifted from 47.83 +/- 0.30 degrees C to 46.05 +/- 0.36 and 46.49 +/- 0.49 degrees C, with the coincidental decreases in Delta H from 1.07 +/- 0.03 J/g to 0.63 +/- 0.02 and 0.67 +/- 0.04 J/g, respectively (P < 0.05). Additionally, Ca2+-ATPase activity of NAM decreased with increasing the concentrations of ZnSO4 or ZnCl2 during heating up to 40 degrees C. During heating from 20 to 75 degrees C, higher turbidity, surface hydrophobicity and disulphide bond formation were obtained in NAM added with ZnSO4 or ZnCl2 at temperatures ranging from 40 to 75 degrees C, compared with the control. Nevertheless, a higher aggregation was found in NAM added with ZnSO4, compared with ZnCl2. Zeta potential (zeta) analysis suggested that the surface of NAM added with ZnSO4 became less negatively charged, compared with that of ZnCl2 counterpart. Transmission electron microscopy showed that the structure of NAM was highly interconnected, finer and denser when zinc salts, especially ZnSO4 were incorporated. Therefore, ZnSO4 could be used to induce aggregation of fish muscle proteins, thereby improving gelling property of fish mince or surimi. (C) 2012 Elsevier Ltd. All rights reserved.