Effects Of Gellan Gum On The Gelling Properties And Gel-forming Mechanism Of Silver Carp Surimi

Silver carp（Hypophthalmichthys molitrix）muscle is very tender,enriched with water and strong earthy/musty taste as well as containing too much intramuscular small bones.It is hard to suwari and easy to modori.In China,silver carp,one of the major fresh-water fish species,abundant and cheap,is a good material to develop and process surimi-based products.Gellan gum is a novel gelling agent and its excellent performance will be widely used in food industries.In this paper,the changes of the nutrients contained in silver carp mince and surimi,the effects of gellan gum on the mechanism of gel formation and the modori and three kinds of salts on the properties of surimi gel were inverstigated.The effects of gellan gum on the modori of surimi gel during the heating process at 65 ℃ were studied.With the prolonging of heating time,the gel strength,water holding capacity and whiteness of the modori surimi were improved.The contents of hydrophobic interaction,disulfide bonds and non-disulfide bonds increased significantly.So the gellan gum can inhibit the emergence of surimi gel deterioration phenomenon.Effects of gellan gum and three kinds of salts on gel properties of surimi gel from silver carp were studied.The results showed that effects of three kinds of salts on gel strength,whiteness and WHC of low-salt surimi gel were different.The effects of three kinds of salts on gel strength,whiteness and WHC were KCl >NaCI > CaCl₂,CaCl₂> KCI> NaCl and KCl > NaCl> CaCl₂,respectively.When the gellan gum was added into these three kinds of low-salt surimi,the gel strength of calcium chloride low-salt surimi increased significantly（p<0.05）,and the water holding capacity of potassium chloride low-salt surimi gel was the most significant（p<0.05）,but the changes of whiteness were not obvious.The results of chemical forces showed that more hydrophobic interactions and disulfide bonds were contained in the three kinds of low-salt surimi gels.The protein solubility of surimi gel after the combination of gellan gum with CaCl₂ was the lowest,and the addition of gellan gum was significantly higher than that of the other three groups.The protein solubility analyses indicated that myosin heavy chains（MHC）of surimi gels could not form more non-disulfide covalent bonds by adding gellan gum singly without salt.The microstructures of the surimi gels added with gellan gum and NaCl or KCl could improve the gel properties of silver carp surimi gel,as well as its dense,uniform and meticulous structures,and better gel qualities.The surimi gels added with gellan gum and CaCl₂ showed loose structures and poor qualities.Response surface methodology was adopted to obtain the optimum formula,and the result indicated that the gellangum with three kinds of salts optimum formulas were:（1）gellan gum 0.75%,sodium chloride 1.00%,calcium chloride 0.60%;（2）gellan gum 0.75%,sodium chloride 1.00%,potassium chloride 1.00%.Compared with the formula（1）and the formula（2）,the gel strength of the formula（1）was higher,the water holding capacity was lower,the whiteness was not changed significantly,and the gel solubility also became lower.Through the use of scanning electron microscope（SEM）observation,the surimi gels added with formula（1）,gellan gum,NaCl and CaCl₂,were more dense,the holes outside or inside the surimis were relatively smaller,but less smooth than the surimi gels added with formula（2）.