Study On Preparation And Gel-forming Mechanism Of Peanut Protein Concentrate And Its Application

Preparing peanut oil by direct cold pressing could produce the defatted peanut flour synchronously. Although protein in flour remained nature properties, but the protein content was relatively low (only contented 50-55%), the solubility was limited, the gelatin properties was not good, the formability was very bad when adding to the meat product, extremely easy to disperse. In view of above questions, the present paper toke defatted peanut flour as a raw material, prepared the functional peanut protein concentrate by alcohol extraction and modification technology, studied their gelatin properties and gel-forming mechanism simultaneously, then initially discussed their applications in the meat product, which were for the purpose of laying a foundation for further discussing the relations between the modified protein structure and the functional properties, provided the theory basis for the application of functional peanut protein concentrate in meat product.The effect of different preparation methods on the functional properties of peanut protein concentrate (PPC) was compared, one preparation method- ethyl alcohol extraction method was determined, by which could produce environment-friendly PPC with high protein content and good functional properties. Through single factor experiment and orthogonal circumrotation experiment to optimize the technological parameter, the results were: solid and solvent ratio was 1:9.3, ethyl alcohol concentrate was 67.35%, extraction temperature was 36.85℃. The confirmation experiment result indicated that PPC (protein content>70% on dry basis) could be produced under this parameter.Take self-made PPC as raw material, the gelatin property of PPC was improved by using the heat treatment, high speed agitation processing, ultrasonic processing, microwave processing and adding reducing agent-1 and the reducing agent-2. In the physical modification, the heat treatment, high speed agitation processing and the ultrasonic radiation processing were extremely remarkable to influence in the–SH/SS- content in protein (P<0.01), in which was also the highest by the ultrasonic radiation processing. Under the ultrasonic radiation processing, -SH content reached to 11.44μmol/g, -SS- content reduced to 21.06μmol/g, superficial hydrophobic index was 12.14. In chemistry modification, the reducing agent-1 processing had better effect than that of the reducing agent-2,–SH content achieved 15.25μmol/g, superficial hydrophobic index also achieved highest, was 15.344in protein when treated by reducing agent-1.Through research on the vary of dynamic rheology , texture profile properties and thermotropy temperature in the modification/primitive PPC under different pH and ion intensity condition, the lowest gelatin spot of PPC, ultrasonic processes PPC and the reducing agent-1 processes PPC had been determined as 16%,14-16% and 12% (gpro. /ml) when pH 7.0, respectively. When the solvent was the 0.1mol/LNaCl solution, the lowest gelatin spot of primitive PPC was 14% and 12% under nature pH and pH3.0; the complexity dissolution process of the modified/primitive PPC and the relevance between rheology properties and texture profile properties were shown that the salty ion addition was advantageous to form the strong gelatin in the protein when pH value was 3.0, the salty ion joins did not favor the protein to form the gelatin when pH value was 7.0, but protein thermotropy temperature and absorption enthalpy were remarkably increased along with Na salt ion concentration increased; protein compound module (G*), the stored energy module (G') had extremely positive correlation with protein gelatin hardness, also the G* and G' in rheology properties and cohesiveness in texture profile properties were the mostly representational targets in six targets which could represent the target of sample gelatin, their contribution achieved 90.9023%.Different solvent dissolution of modification/primitive PPC, the secondary structure of modification / primitive PPC by FT-IR, amino acid composition and microstructure observation were used to analysis the vary structure of modification/primitive PPC. The results were that the–SS–, the non-covalent bond, the intermolecular secondary bond and the covalent bond were surmised as the main intermolecular action bond of primitive PPC. Hydrophobia bond along with static interaction in hydrophobia region and the hydrogen bond became the main intermolecular action bond after ultrasonic processing. There still had many intermolecular secondary bond and the non-covalent bond in the protein though the–SS– content was low after reducing agent-1 processing. The protein was still conformed by the macro-molecule protein structure after modified processing, although tight structure became loose, but still was the order structure, not the peptide chain which extended at will. The tertrary structure of a protein was determined by using fluorescence spectrum scanning, fluorescence quenching and ultra-violet spectrograph scanning. The results showed that more Trp were exposed in the protein molecule surface after modified processing. The apparent viscosity changes were determined by using rheometer, the result showed that shear viscosity of protein after the modification under low rate was bigger than that of primitive protein, which also had low dependence on shear rate. The NaCl density had different effects on modified/primitive PPC, from which we can deduce that in the solution, intermolecular mutual action of primitive PPC was other covalent bonds and the secondary bond action besides the electrostatic interaction. Intermolecular mutual action of modified protein was mainly occupied by the electrostatic interaction, also modified protein included high proportion of non-polar region. Bivalence salt ion (Ca2+) acted as"salt bridge", caused the protein-salt-protein to form the macro-molecule aggregate, then the protein was cross-linked which promoted protein to form as gel.The emulsified ability, emulsified oil stability, the ECMP stability of modified/primitive PPC and the effect of different protein addition on ECMP yield, texture profile properties and the sense organ appraises were studied. The results indicated that the emulsified ability of primitive PPC was bad, but the modified PPC had quite the same emulsified ability as that of soybean protein separate. The quality order of corresponding texture profile properties of ECMP with different proteins was in turn: the reducing agent-1 processing PPC≈soybean protein separate > ultrasonic processes PPC>PPC. The effect tendency of different protein addition on ECMP yield, texture profile properties was the same, thus ECMP yield and texture profile properties assumed the drop tendency when the addition increased, the addition of modified/ primitive PPC assumed the remarkable negative correlation with ECMP yield, the gelatin elasticity, the sense organ appraisal and gelatin cohesiveness of product had been positive connected, and various targets of texture profile properties in ECMP with reducing agent-1 processes PPC had the remarkable correlation, moreover there was a remarkable correlation between various targets and the sense organ appraisal.