Effects Of Hsian-tsao Gum Upon Functional Properties Of Edible Protein-based Films And Their Mechanism

Edible protein films have low mechanical strength and water resistance, poor heat sealing, weak antioxidant and antibacterial properties, which might restrict their practical applications. For forming protein film or coating which has the excellent properties, the protein need modification by different methods. Polysaccharide blending is an effective method for modification of films.This study prepared the blend films based on hsian-tsao gum(HG) which has antibacterial, antioxidant, and procoagulant effect and three kind of proteins(CAS, SPI, GE). In the present work, the main purpose was to analyze the effects of HG on the functional properties of protein films such as rheological properties, physical-mechanical properties, antibacterial and antioxidant activities. Additionally, for understanding the interaction mechanism between HG and protein, author analyzed the effects of HG on changes of chemical bond and molecular conformation of protein films. These findings have provided fundamental theoretical basis for development of HG/protein films and their application in active package. The results are listed below:1.Rheological properties of forming-film solutions were investigated. The results indicated that viscosity and viscoelasticity of protein forming-film solution was significantly changed by blending HG. Network structure of FFS significantly changed due to the interaction between HG and protein.The research of static rheology found that all the film-forming solution displayed shear-thinning behaviors.They were all non-Newtonian fluid. HG obviously effected the apparent viscosity of protein forming-film solutions. Apparent viscosity of CAS forming-film solutions were increased with blending HG. Apparent viscosity of SPI and GE forming-film solutions decreased first and then increased.The research of dynamical rheology found that viscoelastic behavior of CAS forming-film solution more like a liquid. And, when the casein blend with moderate HG, viscoelastic behavior of CAS forming-film solutions more like solid. When the SPI and GE blend with few HG, viscoelasticity of SPI and GE forming-film solutions decreased. When the SPI and GE blend with a few HG, viscoelasticity of SPI and GE forming-film solutions increased.2. It’s found that addition of moderate HG in protein films could improve mechanical properties, wet resistance, color,and thermodynamics of protein films by measuring tensile strength(TS), elongation at break(EAB), water vapor permeability(WVP), moisture content(MC) and total soluble matter(TSM), light transmission properties, glass transition temperature(Tg), contact angle and so on.3.Antioxidant and antibacterial experiments showed that blending HG could improve antioxidant and antibacterial properties of protein films. The antioxidant and antibacterial activities of the blend films were attributed to the polysaccharide, phenols, flavonoid and terpene compound in HG and some Maillard reaction products(MRPs).4.The characteristics of blend films by nuclear magnetic resonance(NMR), X-ray diffractometry, FTIR spectrum, amino acid analysis and chemical bond measurement were performed to analyze the interaction mechanism. The results are listed below:(1)It has been found that there was a strong interaction between HG and protein by analyzing the changes of amino acid and FTIR spectrum of films, including covalent cross-linking of Maillard reaction, the intermolecular hydrogen bond, et al. Therefore, HG and protein have good compatibility. HG had a great effect on the change of conformation of protein in films. Blending moderate HG in protein films resulted from increase of order structure and decrease of disorder structure. Blending excess HG resulted in increase of disorder structure. The random coil structure of films deteriorated the structure of films. This result further verifies the blending HG in protein film can change micro network structure and macro properties. So as to improve the mechanical and the barrier properties of the films. This is in according with result of mechanical properties analysis.(2)The results of measurement of chemical bond indicated that blending HG led to significantly changes of specificity crosslinking, ionic bond, hydrogen bond, hydrophobic interaction force and disulfide bond in films. These changes might explain the changes of mechanical strength of films.(3)X-ray diffraction analysis showed that the structure of film become more amorphous when blending few HG in protein films. It was beneficial to increase the uniformity and density of films. When blending excess HG, there were a mount of Maillard reaction products. Excessive concentration, crystallization of these products increased the crystallinity of films and destroied the structure of the films.(4) It anylyzed the relationship between change of water state and formation of blend films by NMR measurement. It was found that there were three different states of water:bound water, immobilized water and free water. Blending HG significantly effected on the capacity of which film bound the water. This was closely correlated with changes of structure of HG, covalent crosslinking between HG and protein, hydrogen bond.5.This study investigated the effect of protein films and HG/protein blend films on quality of chilled pork. The changes in TVB-N, TBARs values, color, toughness, firmness and microbes were measured for all the samples. These results indicated the protein films blended with hsian-tsao gum were used for packaging the chilled pork, which could effectively control the increase in TVB-N, TBARs values, total number of microbe colonies of the pork, and the decrease in toughness and firmness of the pork. The quality of pork packaged by HG/protein blend films was better than other two groups. Blend films could effectively extend shelf life of chilled pork.Above all, HG played a important role on modification of function of protein films. And blending moderate HG can improve or increase functional properties of protein films. Additionally, this paper studied the mechanism of the HG modified protein films at the molecular level. These results provided theory basis for development of different functional properties of protein films or coatings. And this theory provided a reference for the other polysaccharides modified properties of protein films.