| In this paper, composite films based on alginate, agar and gellan were developed, whichwas to improve the water solubility of composite film with agar and gellan, and to meet therequirements of instant inner packaging films. Meanwhile, three antioxidants (Vc, teapolyphenol and VE) were added into the matrix to develop antioxidant films and then thestorage stability and the applications of the developed films were investigated.The optimal film forming formula was determined by investigating the effects of alginatecontent, the ratio of agar to gellan, glycerol content and blending concentration on theproperties of the developed films including water solubility, water vapor transmission ratio，tensile strength and elongation at break. The results indicated that the films composed ofsodium alginate10%(the proportion of dry matter), the ratio of agar to gellan5:5, glycerolcontent0.3%(w/v), blending concentration1%(w/v) exhibited optimal properties withsoluble time58s, tensile strength41MPa and elongation at break17%. Meanwhile,transparency, infrared spectrum, scanning electron microscopy and X-ray diffraction wereused to analyze the compatibility among the three polysaccharides. The results showed thatstrong interactions and good compatibility existed among them and the prepared films weresmooth and transparent with a light transmittance of85%.Active antioxidant films were prepared by the incorporation of Vc, VE and teapolyphenol into an sodium alginate-agar-gellan composite matrix. The test of water solubility,barrier properties and mechanical properties of the developed films showed that the additionof Vc and tea polyphenol had slight effect on the water solubility of the films but modifiedtheir barrier properties at low relative humidity (RH33%). However, VE decreased the watersolubility of the developed films significantly and did not improve their barrier properties.The presence of the three antioxidants resulted in a considerable decrease in tensile strength.The results of transparency, infrared spectrum and scanning electron microscopy indicated that Vc and tea polyphenol showed good compactibility with the matrix and the developedfilms exhibited smooth and transparent appearance. Whereas the films containing VE werecoarse and opaque with only30%light transmittance, properly due to the presence of VEparticle dispersed in the matrix.DPPH radical scavenging activity and protective ability against peanut oil oxidation ofactive antioxidant films were investigated as well as the release of antioxidants in95%thanol.The results domonstrated that the developed films exhibited certain DPPH radical scavengingactivity by adding antioxidants and the films containing Vc displayed the higher scavengingrate of90%. In addition, the antioxidant films could delay oxidation of peanut oil and thefilms containing tea polyphenol had optimal protection against oxidation of peanut oil. VEand tea polyphenol released rapidly in95%thanol in two hours and then the release speedslowed down greatly. Moreover, the release of Vc in95%thanol was little.Sodium alginate-agar-gellan films with and without antioxidants were stored at relativehumidity33%and53%for two months to study the storage stability of the developed films.Moreover, the prepeared films were applied to package the seasoning, vegetable and oil ofinatant noodle. The results showed that the barrier properties and tensile strength of the filmswith and without antioxidants were improved, and the water solubility decreased, which wasattributed to the rearrangement of the polysaccharide moleculars. The appearance of thefilms without antioxidants and with VE and tea polyphenol changed little during two monthsstorage, but the films added Vc turned slightly yellow as a result of Vc degradation. TheDPPH radical scavenging activity of the films added VE and tea polyphenol decreasedslightly, yet the activity of the films added Vc decreased considerably, which happened morequickly at53%relative humidity. In addition, sodium alginate-agar-gellan edible film couldinhibit moisture absorption of seasoning and vegetable during short storage. The films withantioxidants could protect against oil oxidation and the films incorporated Vc were theoptimal protectors. |
PDF Full Text Request