Construction Of Intelligent Controlled-Release Active Packaging Composite Film For Alpinia Galanga Oil And Its Application In Food Preservation

Alpinia Galanga（L.）Willd（A.galanga）is a perennial plant of the genus Alpinia in the ginger family.Fresh A.galanga has a high moisture content,which makes it difficult to store and often requires reduced moisture when used as a spice and herbal medicine.Drying is important to extend its storage life and to utilize it as a whole resource.The pungent flavor of A.galanga is mainly derived from the essential oil content,which is one of the main indicators to evaluate its quality and is also the focus of its development and utilization.A.galanga essential oil is the main source of its pungency,but there are many limitations to its direct application as an active ingredient（poor water solubility,environmental sensitivity,uncontrolled release,adverse sensory effects,etc.）.Incorporating essential oils into encapsulation systems can not only overcome the limitations,but also improve the application properties of essential oils.Among them,Pickering has good application advantages for improving the stability of essential oils due to its high stability,low toxicity,and biocompatibility.In addition,liposomes as essential oil carriers can improve their penetration and biocompatibility,and have slow release and targeting properties.However,as research on encapsulation technology continues to advance,people are no longer satisfied with simple slow release,but want to achieve precise regulation of the release of active substances in essential oils by sensing changes in signals,thus achieving on-demand release.Light response and pH response applied to trigger the liposome system to achieve controlled essential oil release became possible.And the combination of smart release essential oil liposomes with composite membranes to improve membrane structure and give membrane functionality,and applied to the preservation of food,provides a theoretical basis and practical application ideas for the new controlled release of A.galanga essential oil.The research work and main conclusions of this paper were shown as follows:（1）This study evaluated drying characteristics,structure,essential oil chemical composition and biological activity of A.galanga by hot air drying（HAD）,vacuum drying（VD）,and freeze-drying（FD）.The results showed that HAD had the shortest drying time while FD could better maintain the microstructure.In addition,E-nose,HS-GC-IMS and HS-SPME-GC-MS could effectively distinguish the essential oil chemical composition of the four samples because different drying methods induced the changes in the profile and content of the compounds.HS-SPME-GC-MS detected 43 compounds,of which alcohols,alkenes,and esters were the main substances in fresh and dry samples.In comparison,HS-SPME-GC-IMS detected 80 compounds,including alcohols,aldehydes,ketones,esters,and alkenes.The FD samples showed outstanding advantages by evaluating antioxidant properties and antibacterial activities.Therefore,FD was more suitable for A.galanga drying as it maintains appearance and biological activity.（2）This study focused on analysis of glycosylation and modulation of chitosan mass-modified soybean isolate protein in stabilizing Pickering emulsion of A.galanga essential oil.The results showed that the soy protein isolate’s morphology changed from spherical to irregular after glycosylation.Glycosylation reduced the particle size and hydrophobicity of soybean isolate protein,and improved the Zeta potential,centrifugal stability.Covalent interactions occurred during the glycosylation of soybean isolate protein and changed its molecular conformation.Covalent interaction occurred during the glycosylation of soy protein isolate（SPI-Dex）,and its molecular conformation was changed.The structure and properties of SPI-Dex were further improved by modified chitosan.With the increase of chitosan addition,the assembly rate and anti-gravity stability of composite particles increased and then decreased,and the particle size and hydrophobicity decreased and then increased.The chitosan modification led to the fluorescence burst of SPI-Dex and their binding to each other led to changes in the secondary structure of the protein.The presence of chitosan significantly reduced the particle size of the emulsion,and a large number of composite particles were adsorbed on the oil-water interface to form a dense protective layer,thus improving the centrifugal and storage stability of Pickering emulsion.The rheological properties indicate that the modification of chitosan reinforces the gel network structure inside the SPI-Dex Pickering emulsion.（3）This study prepared A.galanga essential oil liposomes（EO-Lip）.A light-responsive liposome（EO-Plip）was designed for the controlled release of A.galanga oil based on the light-responsive properties of Pheophorbide-a.The dependence of Pheophorbide-a on illumination time was proved by UV spectroscopy.Characterization techniques such as UV spectroscopy,TEM and FT-IR demonstrated that the essential oils were successfully encapsulated in liposomes.Moreover,the particle size of EO-PLip was166.30 nm and the encapsulation efficiency was 30.83%.EO-Lip and EO-Plip have high sustained-release effects on essential oil and showed light-responsive release characteristics under infrared stimulation.The prepared liposomes had good storage stability at 4°C.EO-PLip exhibited light-responsive release properties and has excellent light-responsive antioxidant and antibacterial properties.（4）This study prepared A.galanga essential oil liposomes（EO-Lip）and pH-sensitive liposomes（EO-pHLip）capable of sensing pH signal changes byγ-polyglutamic acid modification were designed.The spectroscopic properties ofγ-polyglutamic acid were characterized by UV spectrophotometry and verified thatγ-polyglutamic acid possesses pH-loud behavior.The characterization techniques such as UV spectroscopy,TEM and FT-IR spectroscopy showed that A.galanga essential oil was successfully encapsulated in liposomes.The particle size of EO-pHLip was 246.50 nm and the encapsulation rate was 29.24%.Both EO-Lip and EO-pHLip showed good retardation of essential oils and good stability when stored at 4°C.Moreover,EO-pHLip exhibited pH-responsive release properties under different pH conditions and had excellent pH-responsive antioxidant and antibacterial properties（5）Stable and slow-release biodegradable active packaging materials were prepared.The results showed that the the film surface was flatter,but the roughness values were lower than those of pure PVA films.With the increase of acetylated pullulan polysaccharide substitution,the light transmission,tensile strength and L*of PVA/essential oil Pickering emulsion composite films gradually decreased,and the amorphous structure,a*,△E and degradation characteristics gradually increased.The substitution of polysaccharide significantly reduced the water vapor transmission and water absorption of the composite film when the substitution of acetylated pullulan polysaccharide was less than 75%.In addition,with the addition of essential oil Pickering emulsion,the light transmission,L*,a*,b*,water absorption,water vapor transmission and tensile strength of the PVA₇₅P₂₅ composite film decreased,and△E and elongation at break increased.In addition,the prepared composite films exhibited good sustained-release ability of essential oil,antioxidant function and antibacterial properties.In addition,PVA₇₅P₂₅-4SPC could extend the shelf life of chilled pork up to 12 d.（6）Light-stimulated responsive-release biodegradable active packaging materials were prepared.The composite films did not show phase separation,but their roughness values increased compared to the pure PVA films.With the increase of esterified starch substitution,the crystalline structure,light transmission,L*,crystallization temperature parameters,tensile strength and elongation at break of PVA-1 Lip films gradually decreased,and a*,b*,△E,melting parameters and degradation characteristics gradually increased.In addition,with the addition of essential oil liposomes,the light transmittance,water absorption and water vapor transmission of P₇₅S₂₅ composite film were reduced,and its△E and elongation at break were increased.And the lowest L*,T_c,T_m,△H_m and tensile strength as well as the highest a*and△E were observed in P₇₅S₂₅-1 Lip.In addition,the prepared composite film showed good sustained-release ability,anti-oxidation ability and bacteriostasis of essential oil,and had excellent photo-responsive anti-oxidation and bacteriostasis properties.Moreover,P₇₅S₂₅-2Lip could prolong the shelf life of chilled pork to 13 d.（7）pH-responsive releasable biodegradable active packaging materials were prepared.The surface of the composite film was smooth and flat,but the roughness value increased compared to the pure PVA film.With the increase of esterified konjac glucomannan substitution,the crystalline structure,tensile strength and elongation of PVA-1 PLip composite films gradually decreased,and b*and degradation properties gradually increased,and showed the highest T_c and L*,and the lowest water absorption and water vapor passage rate in P₇₅K₂₅-1 PLip.In addition,with the addition of essential oil liposomes,the crystalline properties,light transmission,L*,b*,water absorption,and water vapor transmission of P₇₅K₂₅ composite films were decreased,and their?E and elongation at break were increased.In addition,the composite membranes exhibited good essential oil slow release and pH responsive release ability.Moreover,P₇₅K₂₅-3 PLip exhibited good preservative preservation ability and delayed citrus quality deterioration.