Research On The Modification And Mass Transfer Of Antibacterial Composite Protein Film By Static Ultra-High Pressure

Protein is an important component of all cells and tissues of a biological individual.We can see it everywhere in life with a wide variety and high plasticity.As people pay more attention to healthy food today,it has become a research hotspot to prepare excellent food packaging films by adding other active substances or modifying them.In this paper,on the basis of preliminary experiment,we choose whey separation protein and sodium casein as film forming substrate,adding glycerol as plasticizer and adding different active antibacterial substances:potassium sorbate,lactoferrin and lauryl arginine to study the packaging and bacteriostatic performance of the active antibacterial protein films.Study the effect of static ultra-high pressure on the modification of composite protein antibacterial films and the mass transfer of potassium sorbate.（1）Whey Isolate Protein（WPI）,sodium caseinate（NaCas）and glycerol（GLY）were used as film-forming substrate,and study packaging performance and bacteriostatic of active antibacterial composite films with potassium sorbate（PS）,lactoferrin（LF）,and Lauric arginate ethyl ester（LAE）.The ratio was 1%,2%and 5%.The effects of the antibacterial active substances on the mechanical properties,color,particle size distribution and air permeability of the film were tested and analyzed by scanning electron microscope,laser particle size meter,water vapor transmittance,tension test machine and colorimeter.It was proved that PS and LF can be well fused with protein solution,and the particle size distribution of solution is small,and protein film is transparent.With the addition of PS and LF protein films,the tensile strength of the films increased and the elongation at break decreased.Compared with the blank group,the tensile properties of the antibacterial films with 5%PS were the best,and the tensile strength reached to 3.451 MPa and increased by 140%.The experimental results showed that the vapor permeability and oxygen permeability of the protein films withPS and LF antibacterial agents decreased.The protein film added to laul-arginine ethyl ester increases the permeability and permeability of protein due to its insolubility in water.The inhibitory effect of PS,LF and LAE on Staphylococcus aureus and Escherichia coli was proved by the bacteriostatic test.The inhibitory action of LAE on the two bacteria was stronger than that of the Escherichia coli,and the diameter of the bacteriostatic circle was 18.3 mm.（2）Study the effect of static ultrahigh pressure treatment on composite protein antibacterial films.Gradient of ultrahigh pressure:200 MPa,300MPa and 400 MPa;gradient of hold time:5 min,10 min,20 min and 30 min.The experimental results showed that static ultrahigh pressure treatment has different effects on the mechanical properties,optical properties,moisture permeability and oxygen permeability of antibacterial composite protein films.The microstructure of the treated protein film was analyzed by electron microscope.It was found that the ultrahigh pressure modification can make the fracture surface of the protein film delicate,without pores or small pores,and the surface of the film is smooth,uniform and beautiful.The C-H,C≡C,C≡N and C≡C-C≡C groups of the protein films treated with different ultrahigh pressure and time produce different stretching vibration.It shows that the ultrahigh pressure can cause different degrees of dissociation and polymerization of protein.After ultrahigh pressure treatment,the mechanical properties of antibacterial films were enhanced,but the diaphaneity decreased.Ultrahigh pressure treatment can reduce the oxygen permeability and vapor permeability of protein films,and the effect is obvious.The best group of air permeability improvement is B₂,and the oxygen permeability is 4433.97cm³/m²?24h?0.1MPa.However,due to the hydrophilic property of the protein itself,ultrahigh pressure don’t effect on the water solubility of the protein film.2 parameters concerned in the experiment are selected:water vapor transmission rate（WVP）and oxygen permeation（OP）for extreme difference analysis,in which B₁A₃C₂ group（hold time is 10min,pressure is 400 MPa,temperature is 25℃）WVP=1437.7405 g/m²?24h,OP=12462.67 cm3/m²?24h?0.1MPa.（3）Study the mass transfer behavior of potassium sorbate from different static ultrahigh pressure treatments films to food simulants.The groups include:the ratio of different potassium sorbate:1%,2%,2.5%,5%,ultrahigh pressure treatment pressure:200 MPa,300 MPa,400 MPa,different experimental temperatures:5,25,40℃.Based on the Fick diffusion law,a migration model of potassium sorbate to simulated liquid is established through hypothesis.The addition ratio of protein film and experimental temperature are important factors affecting the diffusion and migration of potassiumsorbate.The diffusion coefficient of potassium sorbate increased with the increase of potassium sorbate initial dosage and test temperature,and the diffusion coefficient of potassium sorbate reached 19.420×10^-13when the ultrahigh pressure treatment pressure was 300 MPa and the treatment time of 10 min was 40.The diffusion rate increases and the time to reach equilibrium point decreases.Compared with the static ultrahigh pressure treatment,the release rate of potassium sorbate slowed down obviously after static UHP treatment.The diffusion rate of potassium sorbate decreased and the diffusion coefficient decreased with increasing pressure of ultrahigh pressure treatment.The migration and diffusion of potassium sorbate can be studied by the law of Fick for the protein film of the early experiment and without ultrahigh pressure treatment,because the n value of the diffusion index is less than 0.5.But the protein film after ultrahigh pressure treatment has changed the characteristics of protein because of ultrahigh pressure damage to the internal structure of protein and the formation of new disulfide bond,and this characteristic varies with the time and pressure of ultrahigh pressure treatment.It is necessary to determine the ultrahigh pressure with the Fick law and the experimental data.After the performance,the slow release effect of film against bacteria substance was achieved.