| A quick dissolvable and edible film was prepared successfully, pullulan and gelatin as main materials and glycerol as plasticizer. The composition of pullulan-gelatin film was optimized by single factor tests and response surface methodology. The optimal conditions were pullulan of2.00%, gelatin of5.00%, and glycerol of1.40%. Under the optimal composition, the tensile strength of film is97.21±10.39MPa, elongation at break is13.48±1.29%, water-vapor permeability is109.08±11.23g/m2·day, oxygen permeability is0.15±0.03mL/m2·day, light transmittance is90.37±0.53%, soluble time is20±3s, and oil permeability is not detected.The thermal stability of composite film is slightly lower than gelatin film by the TG and DSC analysis, and there are not chemical reaction occurred when pullulan and gelatin mixed. PG2has the best compatibility by the light transmittance, SEM and AFM analysis. The hydrogen bonds strengthened and semi-crystalline region formed when pullulan and gelatin mixed by FT-IR, XRD and rheological analysis. Maybe just of these, the tensile strength of composite film was reinforced and oxygen permeability of that was reduced.The sealing technique of pullulan-gelatin film was optimized by single factor tests and orthogonal test. The optimal conditions were sealing temperature of140℃, sealing time of1s, and sealing pressure of0.4MPa. Under the optimal technology, the sealing strength of film is2.6N/15mm.The effects of ambient temperature and relative humidity on mechanical properties, barrier properties, color and water solubility of pullulan-gelatin film was evaluated, meanwhile compared the properties of pullulan, gelatin and composite film. The results indicated that the mechanical properties of pullulan, gelatin and composite film were improved by higher ambient temperature (40℃), and there was not significant effect on barrier properties and water solubility, but the color of composite film turned yellow. The relative humidity of80%lowered the tensile strength, water resistance and water solubility of pullulan, gelatin and composite film, improved its flexibility, and showed no significant effect on their oxygen resistance, oil resistance and transparency. In addition, the flexibility and water resistance of composite film were between that of pullulan and gelatin film, water solubility of that was weaker than pullulan and gelatin film, but tensile strength and oxygen resistance were higher than pullulan and gelatin film in the same ambient temperature and relative humidity. The combination properties of composite film are better than that of pullulan and gelatin film.Optimal pullulan-gelatin film was stored under40℃and13%relative humidity for half a year. The results indicated that the tensile strength and water resistance of pullulan-gelatin film were improved, the elongation at break and water solubility decreased and the color of film turned yellow, and there were not significant effects on the oxygen permeability, oil permeability and transparency during storage.Pullulan-gelatin film was applied on the oily bag of instant noodles for half a year, based on optimal composition and sealing technique of pullulan-gelatin film, detecting the acid value and peroxide value of soybean oil. The results indicated that acid value and peroxide value packaged with pullulan-gelatin film are within the standard of soybean oil. Comprehensive consideration, the pullulan-gelatin film was able to use instead of the oily bag of the brand. |
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