Study Of The Rheological Properties And Gel-forming Mechanism Of Myofibrillar Protein And Fat Substitute Mixed Gels

Chicken meat contains high protein, low cholesterol, low fat. it is rich innutrition, so chicken meat is the alternative preferred raw materials of meat processingenterprises for production of various kinds of meat such as pork meat. The diseasescaused by too much fat intaken have aroused great attention. The fat substitute wasused to develop more low-fat meat products which were conductive to human health.The properties of myofibrillar protein and fat substitute mixed gel determined thequality of low-fat meat products, it had a certain guiding significance to researchgel-forming mechanism and develop new meat products. There were four parts in thispaper:（1） the study of static rheological properties of myofibrillar（MP） and fatsustitute（FS） mixed solution;（2） the study of dynamic rheological properties ofmyofibrillar-fat substitute（MP-FS） mixed samples;（3） the study of gel-formingmechanism of MP gel;（4） the study of MP-FS mixtured gel-forming mechanism.Chapter two: The effects of concenration、pH、ionic strength on MP, MP-FSsolution to static rheological properties were studied by rheometer. The resultsshowed that flow behavior index n values’ range of MP and MP-FS were respectivelybetween0.162-0.463,0.219-0.609, they were both pseudoplastic fluids. The shearstress of MP solution increased with the increasing of protein concentration, the shearstress of MP、MP-FS solution had the maximum at4℃, and it was elevated when thepH increased from5.0to6.5, while it were in decreased within the range of pH6.5to7.5increasing, the values of shear stress increased within the increasing of ionicstrength. The concentration of MP increased from10mg/mL to30mg/mL, the K valuewas raised from1.446to27.123, n values was reduced from0.358to0.162. The Kvalue of20mg/mL MP increased from7.577to15.037and then reduced to13.564;the K value increased from5.119to8.099within pH increasing from6.0to7.5; Kvalues of MP solution increased gradually within the increasing of ionic strength.When the mass concentration ratio of MP-FS was20:10, the K value had themaximum value8.053, n value had the minimum value0.219; MP-FS solution hadthe maximum k value9.046, the smallest n value0.245at4℃; K values of MP-FSsolution decreased from10.284to4.469, n value increased from0.153to0.287whenpH was raised from6.0to7.5; K values of MP-FS solution increased gradually from0.086to8.669within the increasing of ionic strength.Chapter three: The effects of mass concenration ratio of MP and FS、pH、ionic strength on the dynamic rheological properties of MP-FS mixed samples wereinvestigated by rheometer. The mass concentration ratio of MP-FS at20:10increasedthe G’ and G’’ of mixed samples, but when it was20:20, G’ and G’’ decreased, thesuitble FS addition was half of the mass concentration of MP; pH affected therheological properties of MP-FS mixed samples, the G’ and G’’ was smallest at pH5.0,increased at pH5.5, biggest at pH6.0, and the G’ and G’’ decreased within pH from6.0to7.0increasing; G’ and G’’ of MP-FS mixed sampls was lowest in the ionicstrength of0.2, it became larger and larger within the ionic strength increasing, andreached the maximum at ionic strength of0.6. The factors influencing the rheologicalproperties of MP-FS mixed gels at65℃were investigated byresponse surfaceBox-Behnken test. The result indicated that effects of mass concentration ratio of MPand FS（A）, ionic strength（C） on G’ were super significant, the effects of pH（B） on G’were significant. The regression equation was G’＝125.60－6.46A－23.59B＋6.10C＋6.08AB－2.55AC－2.75BC－21.39A²＋3.36B²－10.21C². The G’ had themaximum value, when mass concentration ratio of MP and FS was20:10, pH6.0,ionic strength0.6.Chapter four: The DSC showed that the denaturation temperature of myosinand actin in MP were58.99℃、69.80℃. The CD showed that in the heating rangefrom30to80℃of MP, the α-helix content decreased significantly from95.77%to45.05%and β-sheet content increased significantly from0.20%to12.65%. The G’showed that the initiation gelling temperature was42℃. The texture propertiesshowed that the initiation gelling temperature was40℃, MP gel’s hardness increasedgradually within heating temperature increasing, and it reached a maximum values of51.4g at75℃. Heating temperature and MP molecule’s α-helix, β-sheet, G’, hardnesshad significantly correlated, there was no correlation between β-sheet and hardness,T₂₂. The heat-induced gel-formating mechanism of MP: the MP molecule expanded,aggregated continuously in the heating process, began to gel at about40-42℃, MPmolecule’s secondary structure and properties had significantly changes（denaturation）at60℃, and then within temperature raising, the strength, hardness, G’ of gelationincreased constitutely, and it had the strengest gelation at75℃.Chapter five: The denaturation temperature of myosin and actin in MPrespectively became advance and delayed after FS was added. MP-FS in the heatingrange from30to80℃, the α-helix content decreased significantly from96.89%to39.70%and β-sheet content increased significantly from0.10%to14.93%. The G’ of MP-FS was higher than MP in the heating process. The hardness of MP-FS gelationincreased significantly as heating. The10mg/mL FS could not form gelation undersingle condition, MP played a major role in the gel-forming of MP-FS; the hardnessof MP-FS gelation was higher than MP gelation during setting, FS gelled duringcooling process. Heating temperature and MP-FS molecule’s α-helix, β-sheet, G’,hardness had significantly correlated, there was no correlation between α-helix,β-sheet and springiness, T₂₂. The heat-induced gel-formating mechanism of MP-FS:heating caused MP which was in MP-FS expandedness, aggregation, gelling; FSgelled at cooling process. The addition of FS promoted MP molecule secondarystructure’s expandness and aggregation, eventually it induced the hardness, G’ toincrease, but FS did not change MP molecule’s gelling initation temperature and theoptimum gel-forming temperature.