Study On Transglutaminase-Induced Crosslinking On Gelation Of Myofibrillar/Soy Protein Isolate Mixtures

Three main parts were involved in this paper : (1) effect of transglutanimase-induced cross-linking on gelation of myofibrillar / soy protein isolate mixtures at different temperatures; (2) effect of transglutanimase-induced cross-linking on interactions of myofibrillar / soy protein isolate mixtures for various times; (3) Study of hardness and water holding capacity of heat-induced gelation of myofibrillar / soy protein isolate mixtures induced by transglutanimase.chapter I Effect of transglutanimase-induced cross-linking on gelation of myofibrillar / soy protein isolate mixtures at different temperatures : It was studied by SDS-PAGE technique and Differential Scanning Calorimetry that the gelation reaction of mixed myofibrillar (MPI) and soy protein isolates (SPI) catalyzed by transglutaminase (TG) at the different temperatures. A substantial amount of cross-linking of SPI With TG treatments in demonized water occurred at≥50℃. Essentially all the SPI constituents, except the basic subunits (B) of glycinin, were linked covalently forming a streak of polymers most of which were too large to enter the separating gel. All MPI components, except actin, were cross-linked by TG at 60℃-90℃, but the products (gel) were most likely of an ordered structure because theyexhibited a high elasticity. For heated MPI/SPI mixtures, TG treatment converted myosin heavy chain and actin into lower molecular-weight polypeptides; a reduced intensity in the electrophoretic bands of soy proteins (7S and 11S except the basic subunits) was observed in all treatments, suggesting cross-linking with MPI. The enzyme treatment greatly enhanced (P<0.05) the thermal denaturation temperatures of β -conglycinin and glycinin in MPI/SPI mixtures, but insignificantly increased the thermal transition temperatures of myosin when compared with untreated samples (P>0.05 ) .The three proteins all exist at 40 and50℃; The peakl disappeared at about 60 ℃ suggesting that myosin denatured; At 70 and 80 ℃ ,both peakl and peak2 vanished, suggesting that myosin and β-conglycinin absolutely denatured; The three peaks all died away when heated at 90 ℃,suggesting that all proteins absolutely denatured.Chapter II Effect of transglutanimase-induced cross-linking on interactions of myofibrillar / soy protein isolate mixtures for various times: Transglutaminase (TG)-catalyzed interaction of mixed myofibrillar (MPI)/ soy protein isolates (SPI) were invested at varying ionic strengths by electrophoresis, Differential Scanning Calorimetry(DSC) and Dynamic rheological properties. The intensity of the 310KD band from the acidic(As) as well as the α' subunits increased with incubation time and by 240min an appreciable amount of cross-linking products was produced that did not enter the gel. For MPI/SPI mixtures. TG treatment converted myosin heavy chain and actin into lower molecular-weight polypeptides, which gradually diminished as the ionic strength increased up to 0.6. The addition of KC1 gradually diminished the protein changes: the smearing became less noticeable, and the occurrence of neo-polypeptides below the main muscle proteins became less pronounced. A reduced intensity in the electrophoretic bands of soy proteins (7S and US except the basic subunits) was observed in all treatments, suggesting cross-linking with MPI. The enzyme treatment significantly increased (P<0.05) the thermal transition (denaturation) temperatures of MPI/SPI mixtures, and the endothermic peak temperatures increased with the aggregation times. In addition, TG treatment greatly enhanced (P<0.05) the elasticity of the MPI/SPI mixed protein gels when compared with untreated samples, independent of incubation time.chapter III study of hardness and water holding capacity of heat-induced gelation of myofibrillar / soy protein isolate mixtures induced by transglutanimase: Effect of myosin concentration ratio, pH, ionic strength, heating temperature, TG on heat-induced gelation properties (hardness and water-holding capacity) was studied. The results showed that the addition of SPI decreased si...