Preparation, Proerties And Application Of Low Acyl Gellan Gum-gelatin Edible Films

Food packaging is one of the most important parts in packaging industry.Due to the environmental pollution and potential food safety problems caused by traditional synthetic packaging materials,it is a trend to prepare packaging materials with biodegradable film-forming polymers.In this paper,an edible composite film was prepared by using low acyl gellan gum(LA)and gelatin(GN).The rheological properties of LA/GN mixed solutions were investigated.Moreover,the effects of total polymer concentration,LA/GN weight ratio,plasticizer and cross-linker on the physicochemical properties,mechanical properties,thermal properties and microstructure of LA/GN edible composite film were measured.In addition,the application of LA/GN edible composite film on fresh cut pineapple preservation was carried out.The effects of total polymer concentration,LA/GN weight ratio,temperature,plasticizer and cross-linker on the rheological behavior of LA/GN mixed solution were investigated.The results of steady rheological tests showed that the apparent viscosity of the mixed solution increased with increasing the LA/GN weight ratio,total polymer concentration,cations and plasticizer concentration.The apparent viscosity of the LA/GN mixed solution can be significantly reduced by a small amount of gelatin addition.The flow curves of LA/GN mixed solution can be divided into two regions,the shear thinning region at low shear rate and Newton flow region at high shear rate.In shear thinning region,the apparent viscosity and shear rate can be expressed in a power law equation.The addition of TGase has little effect on the rheological behavior of the mixed solution.It is found through the dynamic measurements that the LA/GN mixed solution undergoes the sol-gel transition upon cooling.The dynamic modulus of LA/GN mixed solution increased with the increasing of LA/GN weight ratio,total polymer concentration,cation concentration and plasticizer concentration.The addition of TGase had little effect on dynamic viscoelastic properties of the LA/GN mixed solution.The gelation temperature increased with the increasing of the total polymer concentration,LA/GN weight ratio and cation concentration.While the TGase concentration has almost no effect on the gelation temperature of LA/GN mixed solution.The LA/GN edible composite films were prepared by solution casting and their microstructure,thermal properties and macroscopic(optical,water content,mechanical,water and oxygen barrier)properties were characterized.The effects of total polymer concentration,LA/GN weight ratio,plasticizer and cross-linker were investigated.The results showed that the total polymer concentration had more significant effects on macroscopic properties of LA/GN composite edible film.With the increasing of total polymer concentration,the thickness,opacity index,water solubility and the tensile strength of LA/GN mixed films increased,while the moisture content,water vapor permeability,oxygen permeability and tensile elongation decreased.With the decreasing of the LA/GN weight ratio,the opacity,tensile elongation,water solubility and oxygen permeation rate of the film increased,while the moisture content and tensile strength decreased.The higher the concentration of plasticizer,the higher the water vapor permeability.With the increase of plasticizer concentration,the oxygen permeability and water solubility decreased firstly and then increased,In contrast,the tensile strength increased to the maximum and then decreased with the increasing of plasticizer concentration.The water vapor permeability,oxygen permeability,tensile strength and elongation of glycerol plasticized edible films were higher than those of glycol plasticized edible films.The addition of cross-linker and cations can improve the compactness of the edible film and the amount of cation and cross-linker has an optimum value.At this value,the water solubility,water vapor permeability and oxygen permeability of the LA/GN mixed edible composite film has the minimum value while the tensile strength has the maximum value.The melting temperature of the LA/GN composite film was increased after the addition of gelatin,plasticizer and cross-linker.The applications of LA/GN composite films in fresh-cut pineapple preservation were carried out.The effects of composite films treatment on the quality of storage fresh-cut pineapple were investigated.The results showed that LA/GN composite films were able to inhibit browning,maintain high soluble content and inhibiting the growth of microorganisms.The LA/GN composite films played a good preservation effect for fresh-cut pineapple packing.