Preparation And Properties Of Collagen Fiber-starch Composite Films Incorporated With Polyphenol

Many biochemical reactions causing deterioration of its original physical,chemical and sensory properties could occur when the food is in the period of processing,transportation and storage.The changes of these properties could result in the loss of the nutritional value of the food commodity,and even affect its quality and safety.Food packaging materials with excellent properties plays an important role on food protecting.While plastic is widely used in food packaging,but it can cause environmental pollution after being discarded since it is non-degradable and non-recyclable.Starch is derived from natural materials and possesses excellent film-forming capacity and degradability,which makes it possible to being a good source of biodegradable film materials.However,due to the poor moisture resistance and lower tensile of the starch film,its application in food packaging is limited.Hence,modifying the starch films to improve its mechnical performance is intersting.In this paper,starch was used as the film-forming matrix,and the fish skin collagen fibers were used as the filler to prepare the collagen fiber-starch composite film.Furthermore,the polyphenols with crosslinking and antioxidant capacity,like tannic acid,caffeic acid,oxidized tannic acid and oxidized caffeic acid,were used to modify the composite film.The mechanical properties,antioxidant activity andrelease properties of the composite films were investigated and discussed.The main research contents and results are listed as follows:1.The different type of collagen fibers(CF3,CF6,CF9 and CF12)were prepared by pretreatment of the fish skin with acetic acid for 3 h,6 h,9 h and 12 h.The effect of the type of collagen fibers and its adding amount on the properties of starch films were investigated.The results showed that the flexibility and water vapor permeability of the composite films is higher than the starch film.Compared with the starch film,the films adding a moderate amount of CF3 and CF6 collagen fibers showed stronger tensile strength,while adding different amount of the CF9 and CF12 made the films tensile strength poorer.Taking the tensile strength as a consideration,the collagen fiber-starch composite film with 10% of CF6 were used for the next study.2.In order to optimize the performance of the composite films,the modification of collagen fiber-starch composite films by using tannic acid and caffeic acid,oxidized tannic acid and oxidized caffeic acid was studied.And the effect of the selected polyphenols on film performance was investigated.The results showed that the mechnical properties of the composite films were improved by adding tannic acid,caffeic acid,oxidized tannic acid and oxidized caffeic acid.The tensile strength of the composite films increased,the elongation at break and the solubility decreased.The moisture resistance and light blocking performance of thecomposite films are significantly enhanced,but the transparency was reduced.Tannic acid has better crosslinking performance than caffeic acid,and oxidized polyphenol is super than non-oxidized polyphenols.3.The results of structural characterization of films showed :although the hydrogen bond is formed between the collagen fibers and the starch granules,the thermal stability of the composite film is decreased.which can be attributed to the behavior of collagen fibers on destroying the interaction between starch granules,thus making films more flexible.While the degree of crosslinking of the collagen fibers were enhanced when adding all types of polyphenols respectively into the composite films,due to the intensifying of the hydrogen bond interaction between collagen fibers and polyphenols.The structure of composite films became more compact,and the rigidity and thermal stability of the films increased.4.Using the reducing power and ABTS free radical scavenging rate as the index,the antioxidant capacity of the collagen fiber-starch composite films modified by tannic acid,caffeic acid,oxidized tannic acid and oxidized caffeic acid was investigated.Then using the DPPH free radical scavenging rate as the index,the release properties of composite films in five kinds of food simulation systems under room temperature were investigated.The results showed that the addition of tannic acid,caffeic acid,oxidized tannic acid and oxidized caffeic acidcould improve the antioxidant properties of the composite films.The anti-oxidation property of the composite films improved by increasing the amount of polyphenols.And the films with tannic acid and caffeic acid performed better antioxidant capacity than that with oxidized tannic acid and oxidized caffeic acid.The release amount was higher when the composite films was in pure water,20% and 50% ethanol solution than that in 75% and 95% ethanol solutions.The polyphenols is hard to release in the 75% and 95% ethanol solutions.Meanwhile,Polyphenols in films released fast in pure water and 20% ethanol solution,but its released slow in 50% ethanol.