| With the development of the world's apple juice concentrate industry,the proportion of China's apple juice concentrate is increasing year by year and export trade is becoming biger and biger. However,due to peoples pay attention to the food security increasingly,as well as the "trade protectionism" increased in some developed countries,China's exports of agricultural products is falling into the "green barriers" trouble and the export of China's apple juice concentrate is limited too.According to the statistics from customs and institution of commodity inspection,the main reason of repercussion of Chinese apple juice concentrate exports is that some indicators such as lactic acid,fumaric acid,5-HMF,patulin and pesticide residues exceeded the standard.These occurrences impacted other agricultural exports as well as reputation of China's international exports.Therefore,it is necessary to put quality of the fruit juice into practice immediately.On the basis of study on the indicators exceeded standards of apple juice concentrate systematically,three RP-HPLC methods have been established:1) to determine lactic acid,fumaric acid,5-HMF and patulin simultaneously by RP-HPLC.2) to determine dimethoate,carbendazol, 5-HMF,patulin simultaneously by RP-HPLC.3) to determine 11 different types of pesticides simultaneously by RP-HPLC.The purpose of this study is to ensure China's apple juice concentrate product quality and safety,break through the technological barriers and make China's apple juice concentrate enter the international market smoothly.The study of this paper mainly focus on the following of six aspects and the corresponding conclusions were obtained.1.A new method of sample pretreatmentis has been developed,which can enrich 5-HMF and patulin by liquid-liquid extraction and can dilute lactic acid and fumaric acid properly.It makes a good foundation for the four components of the quantitative detection.The results shows that:lactic acid,fumaric acid,5-HMF and patulin recoveries were 95.65-99.91%,96.53-102.35%, 89.96-101.33%,94.11-98.23%respectively and CV＜5%.The lowest detectable concentration of them are lactic acid 0.179mg·L-1,fumaric acid 3.217μg·L-1,5-HMF5.672μg·L-1 and patulin 8.90μg·L-1 for the method of sample pretreatment in apple juice concentrate respectively.2.A new chromatographic method has been developed that is based on technique of dual pathways to separate and detect four materials including lactic acid(210nm),fumaric acid(210nm), 5-HMF(276nm),patulin(276nm) simultaneously.After studied mobile phase's composition, proportion,flow rate,pH and temperature of chromatographic column,the best chromatographic condition has been established that is the mixture phosphoric acid solution(pH 2.5)-acetonitrile (95:5,v/v) as the mobile phase with a flow rate of 1.00 ml·min-1 at 30℃.Limit of quantitation of them are lactic acid 0.597mg·L-1,fumaric acid 10.723μg·L-1,5-HMF18.907μg·L-1 and patulin 29.667μg·L-1,CV of retention time for 10 vices＜0.5%.3.A new method of sample pretreatment has been developed that could enrich 5-HMF,patulin, dimethoate and carbendazol through the path including acetoacetate extracting—lye purifying—acidizing fluid potentizing.The results show that:dimethoate,carbendazol,5-HMF and patulin recoveries were 89.62-98.35%,89.55-99.91%,95.62-101.33%,85.65-95.72%respectively.4.A new chromatographic method has been developed that is based on technique of dual pathways to separate and detect four componentes(dimethoate,carbendazol,5-HMF,patulin) simultaneously.After studied mobile phase's proportion,the best chromatographic condition has been established that is the mixture methanol-acetonitrile-water(1:1:8,v/v) as the mobile phase with a flow rate of 0.80 ml·min-1 at 30℃.In this condition,dimethoate and carbendazoi will be detected at 210nm while 5-HMF and patulin will be detected at 276nm.The standard curve of four components shows that limit of quantitation are 5-HMF 0.04869mg·L-1,patulin 0.0207mg·L-1,carbendazol 0.5801mg·L-1 and dimethoate 0.0207mg·L-1,CV of retention time for 10 vices＜1%.5.Based on solid phase extraction,a new method(SPE-C18) of sample pretreatment has been developed to enrich 11 kinds of pesticides,by studing the composition,dosis of purifying liquid and dosis of eluent.Test of recoveries shows that recoveries of 11 kinds of pesticides were between 86.27%and 103.66%.6.A new chromatographic method has been developed to separate and detect 11 kinds of pesticides simultaneously.After studied mobile phase's composition,proportion and mode of flow rate,the best chromatographic condition has been established that is the mixture water-acetonitrile (45:55,v/v) as the mobile phase with a changed flow rate at 30℃.Standard curve of 11 kinds of pesticides has been developed.Resultes of lowest detectable limit shows that this method could be fit for detection requirement of pesticide residue.
|
PDF Full Text Request