Preparation And Application Of Antibacterial Starch/Gelatin Film

With the development of the times and social progress,traditional food processing and preservation methods,such as the use of chemical preservatives,high temperature sterilization,frozen storage and other technologies have been greatly impacted and challenged.On the one hand,antibacterial packaging as a new food packaging direction,through the slow release of antibacterial substances to maintain food quality.On the other hand,the pollution of water,air and soil caused by traditional petroleum-based food packaging materials is increasingly serious.Therefore,the development of edible fully degradable antibacterial food packaging materials has become a response to the construction of environmentally friendly society.At present,most of the researches on antibacterial packaging materials at home and abroad adopt the solution casting method.This method tends to retain the activity of antibacterial agents.However,it is difficult to produce film on a large scale due to its discontinuous mode,high energy consumption and low efficiency.In addition,relevant studies at home and abroad will add antibacterial agents to traditional petroleum based plastics,using melt extrusion film,these films will also cause environmental pollution.And this topic through the screening of antimicrobial agent,load,and its potential applications in the edible food packaging materials after carried on the thorough study,problems such as selection ofε-poly lysine hydrochloride（ε-PL）as antibacterial agent,directly added to starch/gelatin film matrix composite,using high conveying screw low-temperature blow molding production process（≤120℃）,and finally prepared edible antibacterial film.The effects of antibacterial agents on the physicochemical properties of the film were investigated by means of melt rheology,FTIR spectroscopy,scanning electron microscopy and X-ray diffraction,and the antibacterial activity of the film was determined by bacteriostatic zone method.The influence of processing temperature on the properties of the film was further clarified,and the packaging test of fresh bread was completed.The main results are as follows:（1）The addition amount ofε-polylysine hydrochloride has a significant effect on the properties of the composite membrane.Rheological analysis and characterization results show that theε-PL as starch/gelatin system of compatibilizers,ε-PL to improve the liquidity of continuous phase,the mixture of|η*|good at processing,also make it more smooth surface section.ATR-FTIR and X-RD analysis showed that the addition ofε-Pl promoted the plasticization and ordered crystal transformation of starch molecules,which reduced the crystallinity.The mechanical test results confirm that the membrane has better flexibility.In addition,the S/G-4 films with the highestε-PL content showed the highest static hydrophobic Angle（WCA）（93.57°）and the lowest water vapor transmittance（WVP）(2.47×10^-10 G·m·m^-2·S^-1·PA^-1),which indicated that the surface network was smooth with the addition ofε-pl.The orientation of hydrophilic groups changed,and the membrane obtained higher water barrier ability.The increase of swelling（SD）and solubility（WS）indicates that the film is more sensitive to water environment.It can be inferred from the bacteriostatic results of plate that the antibacterial activity increased significantly with the increase ofε-PL supplemental level.（2）Different blow molding temperature has a significant effect on the structure and properties of antibacterial films.Rheological behavior analysis showed that as the temperature increases,the S/G blend|η*|value increases,which improve the stability of thin film bubble blowing process.The results of electron microscopy confirmed that starch was gelatinized and starch grains expanded at high temperature,which enhanced the stability of continuous phase space network.In addition,with the increase of blow molding temperature,the mechanical properties are improved as a whole.When the temperature increases from 110℃to 140℃,the elongation at break increases by 54%.XRD analysis and water resistance test results show that the crystallization zone of starch is destroyed strongly with the increase of processing temperature,and the water vapor diffusion and permeability of the film are greater.The results of bacteriostatic zone test showed that the higher blowing temperature resulted in stronger hydrogen bonding force between the exposed hydroxyl group and the amino group introduced byε-PL,which had a negative effect onε-PL release.（3）The packaging test proved that starch/gelatin antibacterial film can play its antibacterial role in the food packaging environment,which has application significance.PE and S/G double film packaging can significantly reduce the water loss and weight loss of fresh bread,delay its aging,and maintain a certain texture characteristics.