Study On Removing Pesticide Residues From Tea Leaves By Subcritical Butane Extraction

From ancient to present,tea is one of the most popular healthy drinkable.It includes many kinds of multiamino acids,tea polyphenols,alkaloidals and vitamins.Drinking tea often is good for our health.But with the development of agriculture,the abuse of fertilizers and pesticides has threatened the quality of tea.People need pay more attention on the problem of pesticide residues.So far,many studies focus on the degmdatinon technoledges of pesticide residue.And most of them focus on the degradation of pesticide residues in water and soil.The study of pesticide residue on leaves and products are relatively few.The existing physical,biological and chemical means have various restricted factors.At present,the production technology of removing the pesticide residue from tea leaves still blank.This study conducts a thorough and soistematical study of removing the pesticides residuse by subcritical butane.The study chose the different kinds of tea with pesticide residues as samples and conducted the subcritical butane process systematically.By controlling the conditions such as temperature,pressure,time,cycles and proportion of materials,we selected the best technological conditions for wiping off the pesticides residues.The removal efficiency of subcritical butane for different kinds of pesticides residue on different types of tea was tested,meanwhile,the experiment carried out,which based on the influences of subcritical butane on polyphenol oxidase,theanine,caffeinum and the aroma substance of tea.1.In this study,the subcritical butane extraction technology was used for removing the pesticide residues,diafenthiuron,bifenthrin,abamectin and acetamiprid from fresh tea leaves.The different extraction temperature,time,cycles and proportion of materials have various effect on the removal efficiency.The effect of temperature on four kinds of pesticide residue removal efficiency reached extremely significant level and the extraction time and extraction time reached significant level.And the removal rate was as high as 92.28%.The relative enzymatic activity of PPO was determined to be 15.9~68.9%.The surface of the scanning electron microscopy(SEM)were observed before and after treatment of fresh tea leaves,suggesting no obvious changes of microstructures.2.In the trial of subcritical butane treatment residue in dry tea,we optimized the extraction conditions using single factors and Box-Benhnken(BBD)of response surface methodology.The remove rate of the pesticide residues such as diafenthiuron,bifenthirn,abamectin and acetamiprid can be deterimined when the single factor experiment used.With the Design-Expert.V8.0.6.1 for analysis,the optimum condition of subcritical butane process selected.It found that the maximum value of caffeinum is 2.36% and the minimum is 0.43%.Theanine content changes in the value of 1.04~3.48%,while the variation of different kinds of catechinic acids within1.9~13.1%.And in black tea,the variable qualities are within 0.28~3.77%.And the variation of thearine in black tea is within 0.71~4.65%.And it had different effects on different catechinic acids and the variation is within 1.7~16.7%.There is no bid change on shape of leaves,color and taste of tea liquor before or after the treatment.It proved that the subcritical butane can remove the pesticide rescidue more efficiency and there is no pestcide rescidue in solvent.3.In this study,the subcritical butane extraction technology were used for removing the pesticide residues from the commerica fresh tea leaves.There are about over 20 kinds of commercia tea have the problem of pesticide residues.After treatment by subcritical butane the kinds of pesticide residues have reduced significantly.And most of them can not be detected or the level has below the limits after treatment.It found that the shape and color of dry tea after treatment by sensory analysis.The characteristics of tea liquor had almost no significant changes,includes color,taste,shape and even the special product like Baihao.4.The analysis experiments were carried out on aroma component of uncrushed tea leaves and crushed tea leaves which treated by subcritical butane with GC/MS.After comparision,the treatment of removing residues had no big influences on aroma meterials of tea leaves.The removal rate is much higher than uncrushed tea.Through the researches of pesticide residues removal treatment on different types of tea samples by subcritical butane,we gradually realized the basic rules of the subcritical technology which applied in removing pesticide residues in tea.It was aimed at providing the technical support for popularizing the subcritical technology in agricultural industrialized application.