Preparation Of Gelatin/Bacterial Cellulose Composite Membrane Catalyzed By Transglutaminase And Its Application In Strawberry Preservation

Food-degrading film refers to an edible film made of biodegradable materials with certain packaging protection and preservation functions.Their main goal in the food industry is to block oxygen,carbon dioxide,aroma,the migration of oil and water from the environment to food and from food to the environment.The main film-forming materials include polysaccharides,lipids and proteins.Gelatin is produced by controlled hydrolysis of collagen,which is the main fibrin component in bones,skin,tendons and all other connective tissues.Because of its biodegradability,low mass production cost,and excellent film-forming properties,it has become a natural polymer widely used in the food and pharmaceutical industries,and has a long application history of gelatin.Besides,it has been certified as a material generally considered safe(GRS).However,the gelatin's high sensitivity to water and the changes in its physical properties also limit its application as a food packaging material.Transglutaminase(TG)has been widely used in the food industry as an enzyme cross-linking agent,which can effectively improve the defects of protein degradable materials.Bacterial cellulose(BC)due to its strong liquid loading capacity,tensile strength,elastic modulus,hardness,good density,strong water retention ability,and high biocompatibility and good biodegradability has been widely used in many fields such as electronics,biomedicine,food industry and energy storage.Therefore,we used gelatin as a matrix,selected transglutaminase as a cross-linking agent,and added bacterial cellulose to prepare edible degradable materials blended with these three substances.The effect of bacterial cellulose on the hardness,water holding capacity,viscosity,formation process was mainly studied.On this basis,different amounts of bacterial cellulose were added to the gelatin crosslinked by two different concentration of transglutaminase.It is prepared into a thin film,and the mechanical properties,optical properties,barrier properties and other properties of the film were measured,and it is used to pave the blended material for strawberry preservation.After determining the properties of the gel and the film,it will be more conducive to understanding the impact of the coating of the blended material on the strawberry on the quality,physiological and biochemical properties of the strawberry,and the blended material can be better applied food industry.The experimental results include the following three aspects:1.Effect of bacterial cellulose content on gelatin gel propertiesUsing gelatin as a matrix,add transglutaminase as a cross-linking agent,and add 0,2%,4%,6%,8%,and 10%of the treated bacterial cellulose based on the gelatin mass.Mixing,stirring,solidifying and other processes are prepared into gels for use.The hardness,water holding capacity and other indexes of the formed gel were measured,and the rheological properties of the gel are tested.The results showed that the addition of bacterial cellulose can effectively improve the water holding capacity of gelatin;the hardness test results showed that the addition of bacterial cellulose is beneficial to the formation of a harder structure of the gel;through rheological experiments found that adding bacterial cellulose have a greater impact on the elasticity modulus and viscosity modulus,and these are also closely related to the structure of the gel.The temperature scanning results show that bacterial cellulose has a certain improvement effect on the thermal stability of the gelatin gel.2.Effect of bacterial cellulose content on the properties of transglutaminase-crosslinked gelatin filmThe amount of transglutaminase added was determined to be 20U/100mL and 80U/100mL.Under the conditions of two amounts of transglutaminase cross-linking,add bacterial cellulose weighed 0%,2%,4%,6%,8 and 10%of gelatin mass respectively,after mixing,stirring and spreading,the film was dried for 24h in an environment with temperature of 25? and relative humidity of 50%.After the preparation of the blended film is completed,various indexes are analyzed,such as mechanical properties,barrier properties,optical properties,infrared spectrum,crystallinity,thermal stability,and microstructure analysis.The results showed that under 20U/100mL transglutaminase cross-linking,when the bacterial cellulose was added at 4%,the mechanical and barrier properties of the membrane reached to the best level;the infrared spectrum scanning analysis showed that the addition of bacterial cellulose can change the secondary structure of the protein and enhance the stability of the membrane;the microstructure results showed that after adding the enzyme and bacterial cellulose,the microstructure of the membrane becomes rough due to the addition of the enzyme and bacterial cellulose,but these rough structure didn't effect other properties of film as we have studied.3.The blended film's application for strawberry preservationAfter studying the properties of the gels and films made of the blended materials,the ratio of the transglutaminase addition was 20U/100mL and the bacterial cellulose addition was 4%of the gelatin mass.The strawberries were dip-coated of the film-forming solution.After being dried,it was stored for 6 days at 25? and 90%relative humidity.The properties of the strawberry were measured to determine the effect of the film on the quality of the strawberry.The experimental results showed that the coating treatment can effectively reduce the weight loss of the strawberry,and can maintain the appearance and color of the strawberry during the storage period better.The vitamin C in the strawberry is also better maintained after the coating treatment.The effect of the coating treatment group of bacterial cellulose was better than that of the coating treatment group with only the enzyme cross-linking agent added;in addition,the determination of the activity and content of antioxidant enzymes also showed the advantages of the coating treatment.