Experimental Study On Microwave Extraction Of Limonene And Pectin From Citrus Peel

Citrus is a fruit with huge global production.A large amount of citrus peel residue is produced,which causes environmental pollution and ecological damage.How to deal with it scientifically and efficiently is a major problem facing the citrus processing industry.At the same time,citrus peel is rich in active substances,such as limonene and pectin,which have important economic value.Therefore,extracting high-value-added products from citrus peel to make waste resources into resources has become a research hotspot.Microwave extraction has the advantages of high yield,rapid and uniform heating,low solvent consumption,energy saving and environmental protection.It has been used in the extraction of some natural ingredients in recent years,showing great potential for application.In this paper,the method of microwave extraction of limonene and pectin in citrus peel is proposed,and the microwave extraction process,product composition and yield characteristics are systematically studied.First,the process of microwave extraction of limonene and the distribution characteristics of the product were studied,which revealed the change trend of the product with time and power during the microwave extraction of limonene.It was found that the gas generation rate was consistent with the temperature change trend,The gas production rate increased sharply within 2.5-8 minutes,and the gas yield was the highest at about 8 minutes.At this time,the temperature also reached the highest temperature of 350?.The limonene yield in the liquid product showed a trend of increasing first and then decreasing.The reaction time increased by 3.7%from 7.5 to 10 minutes,After that,the yield of limonene decreased,the proportion of oxygenated compounds increased,and the yield of liquid products changed fastest between 450 and 720W at an increase of 183.96%.Consistent with the increasing trend of liquid products,the volatile content of solid products varied most from 450W to 720W,decreasing by 7.33%.Three limonene production paths were obtained to predict the production mechanism of limonene,namely the thermal isomerization of ?-pinene to limonene,the co-cyclization of a-pinene to obtain limonene,and the thermal conversion of 3-carene to limonene.For the accurate quantification of multiple substances,the effective carbon number method is used to correct the output of each substance,which has important reference value for the quantitative analysis of substances in complex component systems.The law of production of limonene under the action of microwave was investigated,and different factors,such as microwave power,microwave time,type and flow rate of carrier gas,raw material pretreatment methods were studied,the highest yield of limonene was 3.1%under these factors.Compared with the traditional steam distillation extraction method,there is a significant difference in terms of precipitation method and energy action method of limonene.In addition,the effect of temperature on the yield of limonene during the extraction process was studied,and the optimal temperature range was 250?300?.The production of limonene is roughly divided into three stages.When it is lower than 177?,a small amount of limonene is carried out with the evaporation of water.After the temperature reaches the boiling point of limonene(177?),the main occurrence of limonene volatilization is the main production stage of limonene.As the temperature continues to increase,the isomerization reaction of limonene with various substances is likely to occur,and the yield decreases.The output rule of pectin,another substance with high content in citrus peel,was studied,and the effects of different extraction processes,microwave conditions,solvent systems,etc.on the yield of pectin were investigated,and the highest yield of pectin was obtained,the highest yield was 10.93%.The comparison between microwave extraction and conventional extraction was carried out,and the optimal extraction temperature was determined to be 90?.In order to maximize the utilization of orange peel resources,the joint extraction characteristics of limonene and pectin were explored,and it was found that the joint extraction of the two cannot be considered at the same time,but it has certain practical value for reducing overall energy consumption and improving raw material utilization.