Effect Of PH On Gel Properties Of Fish Gelatin-Pectin System

Fish gelatin is the best substitute for mammalian gelatin due to its abundant raw materials,diverse functions and safety of food.However,the application of fish gelatin in the field of medicine and food was limited because its worse melting point,emulsification and poorly rheological stability properties.Based on non-covalent bond interaction of fish gelatin-polysaccharide can significantly improving the fish gelatin gel,viscosity,inter-facial characteristics and giving the fish gelatin a good processing properties and quality.In this thesis,fish gelatin and high methoxyl citrus pectin were used as raw materials and were constructed fish gelatin-pectin composite systems based on different pH values.The mechanism of the influence of different pH values on the gel formation of fish gelatin-pectin composite system was revealed,which provided a theoretical basis for the directional improvement of fish gelatin gel properties and the development of high-quality composite colloids.The following conclusions were drawn:1.Construction of fish gelatin-pectin composite system:At pH 5,the turbidity and the particle size became the largest,and the absolute value of the ?-potential was the smallest,the system had strong hydrophobic interaction and electrostatic attraction.At pH 7 or 9,the absolute value of ?-potential increased,the hydrogen bonding and electrostatic repulsion effect became strong.2.The influence of pH on the gel properties of fish gelatin-pectin composite system.the result showed:At pH 5,the composite system was under strong electrostatic attraction,and formed the super-macromolecule aggregates.The gel network is unstable.At pH 7 and 9,the composite system dominated by hydrogen bonding and electrostatic repulsion,respectively,had high gel strength,rheological properties and stability.3.The influence of pH on the micro-structure and molecular structure of fish gelatin-pectin composite system:At pH 5,the micro-structure of composite system showed large aggregates,irregular internal structure.At pH 7,the uniform micro-structure of the composite system was much more.The system was dominated by hydrogen bonding,the triple helix content was high level,the internal structure was highly uniform,and the gel characteristics were good.At pH 9,the fluorescence intensity and triple helix content of the composite system were high level,and the internal structure was highly uniform.The system was dominated by electrostatic repulsion interactions.The gel properties and stability of the fish gelatin-pectin composite colloid enhanced.4.The dynamic changes of molecular behavior of fish gelatin-pectin composite colloid during the gelling-melting process:At pH 5,the thermal denaturation temperature of the fish gelatin-pectin composite system was the smallest.The macromolecule pectin hindered the formation of the triple-helix structure,forming many random curl structures,the gel rate was high.At pH 7 and 9,hydrogen bonding and electrostatic repulsion were the dominant forces respectively.The heat denaturation temperature was large,the gel formation rate was low,the triple helix content was high,and the stability was strong.The low pH value had a high gel formation rate,but the gel network structure had poor stability;during the process of increasing pH,the gel network structure formation rate was hindered and the structure was more stable.