| Due to the influence of using non-degradable material in human activities on the deterioration of the living environment, edible film formed by biological macromolecules, such as with protein, polysaccharide(PS), lipid and so on, becomes one of the most important method of replacement. As the single protein film had the disadvantages of poor mechanical and barrier properties, polysaccharide was usually added to prepare SPI/PS co-blending film, in order to improve film properties. Nevertheless, due to the mutually exclusive and mutually attractive interactions between protein and polysaccharide, direct co-blending system was unstable, furthermore, resulting in the incompatibility between protein- rich phase and polysaccharide-rich phase. The SPI/PS co-blending film formed under such conditions had bad filming property, un-ideal mechanical property and barrier property. Thus it’s very important to study the method to improve the filming property and gel property of SPI/PS co-blending film system by improving the compatibility between different components.Soy isolate protein(SPI) was co-blended with 5 different kinds of polysaccharides(alginate(ALG), propylene glycol alginate(PGA), pectin(PEC), carrageenan(CAR) and inulin(INU)) with co-drying process, and co-blended powder of SPI/PS was firstly prepared under a wide range of concentrations(SPI:PS=5:1, or 10:1, or 20:1, or 30:1). Secondly, SPI/PS co-blending film was prepared by water solution of co-blended powder formed. Finally, the change of compatibility by viscosity method and microstructure characterization method based on μ criterion and Huggins interaction parameter Δ[η] was comprehensively evaluated. It was revealed that SPI/PS co-dried blending system had better compatibility than directly addition, especially when SPI: PS=10:1 and SPI:PS=20:1, indicating that the addition of polysaccharides by co-drying could increase the surfactants between SPI and polysaccharides, decrease the interfacial tension between different phases and increase the adhesion, thus improve the interactions between protein and polysaccharides, and improve the compatibility. From microstructure, stronger crosslink between SPI and polysaccharides was observed in SPI/PS co-dried blending system, and a certain network of protein and polysaccharides was formed, coinciding with the compatibility testing results.As different interactions of two different kinds of polysaccharides, surface-active polysaccharides and non-surface active polysaccharides, on SPI/PS co-blending system, we studied the influences of the changes in phase compatibility of co-blending SPI film by using surface-active polysaccharides(ALG, PGA) and non-surface active polysaccharides(PEC, CAR, INU), on the changes in water vapor permeability(WVP), tensile strength(TS), elongation at break(E%) and oxygen permeability(OP), observed the influences of co-dried blending and directly addition blending method on film properties, studied the influence of single lipid and complex lipid(lauric(LA) and oleic acid(OA)) on film properties, especially the influence on film overall performance. It was revealed that WVP of SPI/ALG-CO(20:1) and SPI/PGA-CO(20:1) decreased 28.2% and 26.1% separately, compared with SPI/ALG(20:1) and SPI/PGA(20:1), while the OP of SPI/ALG-CO(20:1) and SPI/PGA-CO(20:1) decreased17.0% and 21.5%. Compared with singly addition of LA or OA, addition of blended LA and OA with same proportion could significantly decrease WVP and OP(P<0.05), the mechanical properties of which is between the singly addition of two lipids. Same conclusions could be gotten from two different kinds blending methods, directly addition and co-dried blending.Considering that filming process of co-blending film was the transition process of co-blending system from liquid system to solid system, the changes in compatibility could bring in the changes in thermodynamics and gel properties of co-blending system. Using thermodynamic characterization techniques, confocal laser scanning microscope, cryo-transmission electron microscope, we comprehensively evaluated the correlation between compatibility degree, the phase state and thermodynamic property of co-blending SPI/ALG film, observed the correlation between the changes in compatibility and gel dynamic property of co-blending SPI/ALG film, studied the influence of different distribution ratio of different components on compatibility, glass transition temperature(Tg), and gel property. It was revealed that for non-phase separation system(SPI/ALG(30:1), SPI/ALG-CO(30:1), SPI/ALG-CO(20:1), SPI/ALG-CO(10:1)), Tg was well fitting with the calculation results of Couchman-Karasz quotation, while for phase separation system(SPI/ALG(20:1) and SPI/ALG(10:1)), Tg was mainly determined by the morphology and phase separation degree of co-blending system. Initial state of SPI/ALG(20:1) and SPI/ALG(10:1) after homogeneous, and the state of SPI/ALG(20:1) after homogeneous and deposit for 30 min had good uniformity, the properties of which were determined by the phase characteristic, thus single Tg value was determined by film morphology and compositions. Properties of phase separation of SPI/ALG(10:1) co-blending system after homogeneous and deposit for 30 min were determined by both two phases, thus three Tg values were determined. SPI/ALG(20:1) and SPI/ALG(10:1) co-blending system after centrifugal could form two completely separated phases and a little interphase, thus two Tg values were determined. For SPI/ALG(30:1) and SPI/ALG(30:1) co-blending system, the addition of too less ALG will not significantly modify SPI, Tg of which was indicated to be similar as single SPI solution. For SPI/ALG(10:1) co-blending system, the directly addition of high proportion polysaccharide resulted in phase separation, the properties of which were indicated to be similar as polysaccharide itself, thus cannot modify SPI solution. With the addition of proper proportion of polysaccharide, The gelation temperature(Tgel) and the storage modulus(G’) were between single SPI solution and single polysaccharide solution, which could combine the advantages of both components, thus improving the physic properties of film solution, improving barrier and mechanical properties of final formed film. With co-dried treatment, SPI/ALG-CO(20:1) system and SPI/ALG-CO(10:1) system could form Core-Shell structure, in which SPI was the “Core”, while ALG was the “Shell”, therefore at the same time of improving compatibility, improving the interface properties and the surface activity of each component. Using physical instrument to observe the dynamic gelation process of SPI/PS co-blending system and texture analysis about the formed gel system, changes in consistency, firmness, viscosity index and cohesiveness was characterized. Furthermore, by using normalization methods, revealed changes in overall performance of gel textural properties. Compared with directly addition of polysaccharide, co-dried blending process could improve compatibility of co-blending film solution, could form gel network, and significantly increase gel textural properties and overall performance.By using nanomaterial montmorillonite(MMT) and volatile antimicrobial agent thymol(THY), SPI/ALG/MMT/THY-CO nanocomposite films were prepared with co-drying process based on compatibilization effect. Film barrier property and mechanical property were compared and studied. The influence of the addition of MMT in co-blending film system on THY release result and the influence of THY in co-blending MMT film on antibacterial effect of E. coli and S. aureus in Chinese sausage were observed. It was revealed that film thickness and optical property were determined by contents of THY and MMT. Better thermal stability was found with co-blending film containing MMT. Release rate of THY in co-blending film was influenced by the preservation temperature, preservation time and MMT concentration, and the addition of MMT could significantly prolong the release of THY in co-blending film. Furthermore, the prolong effectiveness was more significant when the MMT concentration was increased. SPI/ALG/THY film and SPI/ALG/THY-CO film on surface of Chinese sausage had significant antibacterial effect, which could effectively inhibit the growth of E. coli and S. aureus in Chinese sausage. Due to the faster release of THY in SPI/ALG/THY film, from preservation results of 20 days, SPI/ALG/THY film was shown to have the best antibacterial effect. From preservation results of 30 days or even longer, SPI/ALG/THY-CO film with significant sustained-release function had better antibacterial effect on E. coli and S. aureus in Chinese sausage, shelf life of which could be prolonged. From food application aspect, by adjusting MMT concentration in antibacterial co-blending film and adjusting environment temperature, the release of volatile antimicrobials in co-blending film could be controlled, thus increasing the application value of food package material containing volatile antimicrobials. |
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