Study On Enzyme-assisted Water Vapor Extraction Of Clove Essential Oil And Its Antioxidant And Nitrite Removal Activities

Cloves（Syzygium aromaticum（L.）Merr.&L.M.Perry）are flowering plants of Amygdalus in the family Myrtaceae.They are hermaphroditic flowers,with male and female sex organs in the same flowers.The cloves are also known as flos caryophylli,eugenia caryophyllata,and lilac.Clove essential oil is mainly extracted from dried flower buds,stems and leaves of cloves,which can be widely used in the grain,oil,animal husbandry and feeding segments,with high utilization value in medical,food,chemical and other Industries.Exploring the extraction method of clove essential oil with simple operation,low cost,short time,and studying the antioxidant activity and nitrite scavenging activity of the clove essential oil are essential to the comprehensive utilization of clove.For this purpose,the extraction conditions were optimized via a single factor test and a response surface methodology,Comparison of the clove raw material microstructures before and after extraction,and the physical and chemical properties,composition,main functional group structure,thermodynamic properties of clove essential oil were detected,to compare the effects of steam distillation extraction method and enzyme-assisted steam distillation extraction method on the composition and properties of the clove essential oil;The antioxidant activity and nitrite scavenging activity of the clove essential oil were studied.The main findings are as follows:（1）By controlling the cellulase addition of 1.1%,enzymolysis time of 75 min,liquid material ratio of 13:1（m L/g）,enzymolysis temperature at 40℃,pH 4,distillation time of165 min,the extraction rate of the clove essential oil was 16.98%,higher than that by the steam distillation extraction（13.67%）.The enzymatic method assisted extraction time of240min and water vapor distillation for 300min reduced the extraction time by 60min.The SEM observation showed that the surface of untreated clove material was smooth and complete,with little damage;After the steam distillation,the surface cell structure of the clove material was significantly damaged,with many pits and small holes,and the microstructure after the enzyme-assisted extraction of clove material was largely damaged,which contributes to the rapid extraction of the essential oil.There was no significant difference in the physical and chemical properties,composition,main functional group structure and thermodynamic properties of the clove essential oil extracted by the above two methods.（2）The IC₅₀values of clove essential oil extracted by the two methods for scavenging DPPH radicals（DPPH radical,DPPH·）were 0.707mg/m L and 0.715mg/m L,0.572mg/m L and 0.596mg/m L for hydroxyl radical（hydroxyl radical,·OH）,and 0.724mg/m L and0.679mg/m L for superoxide anion radical（Superoxide anion radical,O²-·）,showing basically similar scavenging ability.In addition,clove essential oil extracted by the two methods had ferri ion reducing capacity.At 0.2-1 mg/m L concentration of clove essential oil,the reducing capacity was similar,which was positively correlated with the concentration of clove essential oil.Additionally,the clove essential oil extracted by the two methods had similar antioxidant activity and cellulase under the enzyme-assisted extraction had no effect on the antioxidant activity of clove essential oil.（3）The clove essential oil extracted by the two methods could partially remove NaNO₂.At a concentration of 40μg/m L,the clearance reached 45.28%and 47.23%.When the concentration of test solution was 10-50μg/m L,the clove essential oil’s removal rate of NaNO₂was similar,which was positively correlated to its concentration.The results indicated that cellulase under the enzyme-assisted extraction had no effect on nitrite removal activity of clove essential oil.The comparison of the above two methods for extracting clove essential oil showed th at the enzyme-assisted extraction takes less time than steam distillation but produces a high er extraction yield.therefore,it can be concluded that the process of enzyme-assisted extra ction of the clove essential oil is feasible.