title: Effect of zinc sulphate on gelling properties of phosphorylated protein isolate from yellow stripe trevally.
abstract: Impacts of zinc sulphate (ZnSO4) (0-140 μmol/kg) on gel properties of yellow stripe trevally surimi added with sodium tripolyphosphate (STPP) (0.25% and 0.5%, w/w) and protein isolate phosphorylated with STPP at 0.25% and 0.5% (w/w) were studied. Gels from surimi added with 60 μmol ZnSO4/kg in the absence and presence of 0.5% STPP had the increases in breaking force and deformation by 20.9% and 33.3%, and 11.6% and 18.6%, respectively, compared with the control surimi gel (without additives). Gel of protein isolate phosphorylated with 0.5% STPP containing 100 μmol ZnSO4/kg had the increases in breaking force and deformation by 14.87% and 5.6%, respectively, compared with the gel from non-phosphorylated protein isolate at the same ZnSO4 level, suggesting that the phosphorylated protein isolate was more crosslinked by Zn(2+). The addition of ZnSO4 at the suitable level lowered the expressible moisture content, but increased whiteness of surimi or protein isolate gels (P<0.05). Non-covalent bonds, more likely salt bridge and ionic interactions, played a major role in cross-linking of proteins in both surimi and protein isolate added with ZnSO4, regardless of phosphates incorporated. Microstructure study revealed that a gel having highly interconnected and denser network with smaller voids was formed when protein isolate phosphorylated with 0.5% STPP was added with ZnSO4 at a level of 100 μmol/kg. Thus, gel with improved properties could be obtained from protein isolate from yellow stripe trevally phosphorylated with STPP in conjunction with addition of ZnSO4 at an appropriate level.
authors.affiliation: Department of Food Technology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
authors.forename: Yasir Ali
authors.initials: YA
authors.lastname: Arfat
authors.forename: Soottawat
authors.initials: S
authors.lastname: Benjakul
mesh_terms: D000818:Animals; D005396:Fish Products / Q000032:analysis*; D029941:Fish Proteins / Q000737:chemistry*; D005511:Food Handling; D005782:Gels / Q000737:chemistry; D010473:Perciformes; D010766:Phosphorylation; D011122:Polyphosphates / Q000737:chemistry; D019287:Zinc Sulfate / Q000737:chemistry*
chemical_list: D029941:Fish Proteins; D005782:Gels; D011122:Polyphosphates; D019287:Zinc Sulfate; C005692:triphosphoric acid
keywords: Divalent cation; Gelation; Phosphorylation; Protein isolate; Salt bridge