The Gel Behavior And Mechanism Of Polysaccharide-fish Gelatin Composite System

Polysaccharides and proteins are natural biopolymers,which are widely used in food,medicine,cosmetics and other industries as thickeners,gelling agents and stabilizers.Fish gelatin is the collagen hydrolysate which has been produced from fish processing wastes.And it is expected to replace mammalian gelatin in many areas.In this paper,we investigated the gelation and interactions of the composites of tilapia skin gelatin and anionic polysaccharides(xanthan gum,sodium alginate and?-carrageenan).The aim of this study is to provide some theories for polysaccharide-gelatin gelation.(1)The effects of polysaccharide type and amount,Bloom value on gel properties of the composite of anionic polysaccharide(xanthan gum,sodium alginate and ?-carrageenan)and tilapia skin gelatin were investigated.Gel strength of tilapia skin gelatin was obvious reduced by xanthan gum and sodium alginate,but significantly enhanced by ?-carrageenan(?30%).On the other hand,the hardness,cohesiveness and gumminess of the tilapia skin gelatin gel was significantly decreased by xanthan gum and sodium alginate,but the springiness was not affect by the above anionic polysaccharide.In contrast,the hardness and gumminess of tilapia skin gelatin gel was markedly promoted by ?-carrageenan(?30%),but the springiness and cohesiveness was lowered.The apparent viscosity of the tilapia skin gelatin solution was increased by both xanthan gum and sodium alginate.The apparent viscosity of the composite solutions decreased with the increasing of shear rate,which showed a typical non-Newtonian fluid.(2)The effects of total concentration,pH,salt ions and sugars on the gel properties of xanthan gum-tilapia skin gelatin(TSG188)composite were studied.The gel strength,hardness,springiness and cohesiveness of xanthan gum-tilapia skin gelatin composite increased with the increasing of total concentration.With the increment of pH,the gel strength,hardness,springiness and cohesiveness increased first and then decreased,reaching the maximum values at pH 9.0.The gel strength of xanthan gum-tilapia skin gelatin composite was also notably reduced by the addition of NaCl and CaCl2,in a negative correlation with the contents of NaCl.The hardness,springiness and cohesiveness of the composites was enhanced by NaCl(?0.1%)at low concentration.While the concentration of NaCl increased(>0.1%),the hardness,springiness and cohesiveness of the composite gels was lowered.However,the addition of sucrose(0.1?2.0%)had no significant effect on the gel strength of xanthan gum-tilapia skin gelatin composite system.(3)The interactions involved and aromatic amino acid residue microenvironment was studied between xanthan gum and tilapia skin gelatin(TSG188).Three phase including soluble complex,insoluble complex and visible large aggregates were found in the composite solutions from xanthan gum-tilapia skin gelatin,which had been affected by pH.Electrostatic force was the main interaction involved between xanthan gum and tilapia skin gelatin,and non-Coulombic force(such as hydrogen bonding and hydrophobic interaction)also played an important role in the composites.The formation of xanthan gum-tilapia skin gelatin composite was enhanced when the gelatin/polysaccharide ratio increased.Besides,pH and salt ions were the main factors affecting the interaction between the two biopolymers,which affecting the complex formation by increasing or screening the charges on the surface of the biopolymers.The ions(Na+ and Ca2+)weakened the interaction between xanthan gum and tilapia skin gelatin.