| Carvacrol is a natural antibacterial and antioxidant,but its high volatility,easy decomposition,and poor water solubility limit its application in food systems.The use of Pickering emulsion encapsulation technology is an effective way to solve these problems.Gelatin is a natural biopolymer with good film-forming properties,biocompatibility,and wide availability at low cost,making it a suitable edible matrix for preparing active food packaging films with antibacterial and antioxidant properties.Based on this,this study first constructed a carvacrol Pickering emulsion(CPE)using zein/casein(Z/CS)composite particles as stabilizers,optimized the best preparation conditions of CPE through response surface methodology,and explored the stability mechanism of Z/CS composite particles and CPE.Then,CPE was mixed with gelatin to prepare an active composite film,and the effect of CPE addition on the structure and properties of the gelatin film was studied to optimize the optimal addition amount.Finally,the prepared gelatin active composite film was applied to beef preservation,and its actual packaging preservation effect was evaluated.The main research results are as follows:(1)The best preparation conditions of CPE were optimized and determined by singlefactor and response surface experiments,combined with principal component and membership analysis comprehensive scoring method.When the mass ratio of zein/casein was 1:1,the total protein concentration was 20 mg/mL,and the oil phase ratio was 45%,the comprehensive score of CPE was the highest at 0.884,with a packaging rate of 92.72%,a particle size of 3.12 μm,a particle size distribution of 1.227,and a Zeta potential of-34.97 mV,indicating high packaging rate,uniformity,and stability.(2)Based on the previous work,the self-assembly of Z/CS nanoparticles at the oilwater interface was investigated,and the stability of CPE under different pH,temperature,and ionic strength conditions was studied.Scanning electron microscopy and particle size analysis showed that compared to Zein nanoparticles,Z/CS composite particles had smaller particle size(107.7 nm)and better particle dispersion(PDI=0.274).Zeta potential values and infrared spectroscopy results indicated the potential electrostatic and hydrogen bonding interactions between Zein and Casein nanoparticles,which attracted each other.Fluorescence spectroscopy(FS)results showed that Casein successfully improved the wetting properties of the Zein nanoparticle surface through hydrophobic interactions,resulting in a three-phase contact angle of 90.5°.In addition,the stability of CPE emulsion showed no significant changes in encapsulation efficiency and particle size Zeta potential values under pH(6-10),temperature(≤60℃),and ionic strength(0-250 mM)ranges,indicating good stability.This demonstrated that the stability of the emulsion would not significantly affect the preparation of the gelatin film,ensuring the feasibility of the scheme for the sustained release of carvacrol in the gelatin film.(3)CPE with different mass fractions were added to the active film to explore its influence on the structure and properties of the film.The results of Fourier infrared spectroscopy and scanning electron microscopy showed that there was hydrogen bond interaction between CPE and gelatin matrix,and the surface and cross section of gelatin film became smoother and more compact,indicating that CPE and gelatin had good compatibility.With the increase of the mass fraction of CPE,the tensile strength(TS)of the active film decreased somewhat,while the breaking elongation(EAB),water vapor transmittance(WVP)and oxygen permeability(OP)increased gradually,which could provide a certain gas exchange for food packaging.The DPPH free radical scavenging rate of the composite membrane reached the highest 39.04% at 5% addition level,and showed strong antibacterial activity against E.coli and S.aureus,with the diameter of the inhibition zone being 46.60 mm and 37.30 mm,respectively.In the 95% ethanol high-fat food simulation solution,the release of carvacrol in the composite film(CPE)is slower than that in the gelatin film(G-C)containing carvacrol,which has a good application potential in the active food packaging material.(4)Explored the preservation effect of G-PE5(5% w/v)film with the highest comprehensive score in Chilled beef.The results showed that,compared with the control group of uncoated,pure film and plastic wrap,meat deterioration occurred on the 6th day.CPE coated group has high antibacterial and antioxidant activity and slow release properties,can effectively delay the growth and metabolism of microorganisms in beef and lipid decomposition caused by automatic oxidation and deterioration,has the best preservation effect,slow down the growth of pH,total volatile base nitrogen(TVB-N),and the rapid change of beef color,the storage time of meat samples was extended to 8 days. |
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