Study On Extraction Of Perilla Essential Oil,Preparation And Properties Of Corresponding Anticorrosive Compounds

With the increasing emphasis on food safety and health,it has become a hot topic in recent years to extract natural products from plants and apply them to food.As one of the first batch of the ministry of health issued by medicine and food plants in China,perilla is rich in essential oils,and applicable to add in food as a kind of renewable resources,but less research about its practical value was reported.This topic was carried on the extraction technology of essential oil,components analysis,biological activities and prepareration of its anticorrosive composite material,This study provides the theoretical basis and technical support for the development of natural antioxidants and preservative.The main results were as follows:?1?Perilla essential oils?PEO?were extracted by three methods,ultrasonic assisted organic solvents?UASE?,steam distillation?SD?and supercritical CO₂ extraction?SFE-CO₂?and qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry?GC-MS?technique.There were differences in the composition of PEO from different extraction methods.A total of 31 components were detected by UASE,and the detection rate was84.88%.A total of 23 components were detected by SD,and the detection rate was 87.92%.A total of 23 components were detected by SFE-CO₂,and the detection rate was 92.85%.Given the safety and maneuverability of the experiment,SD was optimized by single factor test and orthogonal test to abtain optimum technological conditions of extracting perilla oil:solid-liquid ratio of 1:15,soaking time of 4 h,extracting time of 4 h,PEO extraction rate reached0.89%.DPPH,ABTS and FRAP methods were used to evaluate the antioxidant properties of different growing periods of PEO.The results showed that PEO in different growth period had certain antioxidant properties.In the seedling stage and bud stage,the antioxidant capacity of the selected cultivars was stronger,and the need of plant growth and reproduction was taken into consideration,bud stage was preliminarily considered as the optimal harvest time of the perilla leaf.?2?The content,composition,antioxidation and bacteriostatic properties of different varieties of PEO were preliminarily discussed.The results showed that there were significant differences in the content of different varieties of PEO,among which,YX was the most abundant,0.834%,and the lowest of YN varieties was 0.092%.A total of 55 compounds,accounting for 85.73%-98.08%of the essential oils,were identified by GC-MS.Different varieties of PEO had qualitative and quantitative differences in components,among them,2-hexanoylfuran?2.36-29.15%?,thyme?28.88-32.14%?,eugenol?0.26%-19.34%?,2,5-dimethyl-2-?1-methylethyl?-cyclohexanone?18.76%-64.05%?,Apiol?0.37%-18.05%?,1-methyl-2-methyl-2-methyl benzene?1.55%-23.79%?,2-allylbase-1,4-dimethoxy-3-toluene?21.45%?were the major components of different varieties of PEO.The antioxidative and antibacterial properties of different varieties of oil were significantly different,among which,YX and ZB-1 were the most biologically active,and could be used as the main source of perilla essential oil.?3?By studying the bacteriostatic mechanism of PEO,the results showed that PEO could enhance permeability or lose the integrity of the bacterial cell membrane.The increasing of the conductivity,the soluble protein and the reducing sugar contents of the bacteria were decreased.The activity of SOD,CAT and POD could be effectively inhibited during a certain time,so as to weaken the protective defense mechanism,affect energy metabolism and aggravate cell damage.SDS-PAGE indicated that the PEO could achieve the bacteriostatic effect by affecting the synthesis of bacterial proteins.The scanning electron microscopy showed that the E.coli cell wall and membrane were defected and had protrusive structure or hole.It was concluded that PEO worked by destroying the integrity of E.coli cell wall or cell membrane to inhibit proliferating normally of bacteria,so as to achieve the effect of bacteriostatic sterilization.?4?The microencapsulation of PEO was an effective way to reduce the volatilization rate of essential oil.This study researched the preparation methods of PEO microcapsule by orifice-coagulation bath,and their characters were tested by scanning electron microscope?SEM?,Infrared spectroscopy?FTIR?,and thermos-gravimetric analysis?TG/DTG?.The results showed that the better conditions was,homogeneous speed of 9830 rpm,homogeneous time of 5.10 min,essential oil concentration of 2.20%?v/v?.The average particle size of microcapsule was 94?m,and the encapsulation efficiency?EE?and loading efficiency?LC?were 57.75%and 37.99%respectively.EO-alginate microcapsules could effectively delay the volatilisation of EO.There was not chemical reaction between perilla essential oil and sodium alginate,it was just only physical action.Strawberry preservation studies showed EO-loaded microcapsules could significantly inhibit strawberry decay,maintain the quality of strawberries,and prolong the shelf life.PEO-loaded microcapsules therefore have potential for use as an antimicrobial and preservative agent in the food industries.?5?It was another important way to reduce the volatilization rate of PEO and to regulate the slow-release behavior of essential oil by using emulsion blending method.In this study,perilla essential oil composite film was prepared,chitosan and sodium alginate as the carrier,the composite film modified by adding PPEO.The characters were tested by SEM,FTIR,XRD and TG/DTG.The results showed that the better conditions was,chitosan concentration of 1.99%,sodium alginate concentration of 1.98%,the proportion of sodium alginate solution in the blend solution of 50%,glycerol concentration of 0.67%.Addition of PEO to the above composite film couid significantly decrease the water vapor permeability,swelling degree and light transmittance.With the PEO concentration of 0.6%,the mechanical properties,barrier properties and sensory properties of the membrane reached the best.In addition,PEO can significantly improve the bacteriostatic properties of the composite film.PEO effectively filled the mesh of skeleton structure of chitosan and sodium alginate,the composite film was smooth,dense,and its mechanical properties was stable.Strawberry preservation studies showed compared with PE,perilla essential oil preservative film could effectively delay the strawberry rot,reduce the loss of nutrients,extend the shelf life of strawberry for 2 days.In this study,the preservative film of PEO was effective in the preservation and anti-corrosion of strawberry,and it was expected to be used in place of PE preservative film.