Effect Of ⁶⁰Co Gamma-ray Irradiation On Degradation Of Pesticide Residue And Strawberry Quality

With the delicate tissue and characteristics of high water content,the strawberry is highly susceptible to diseases and pests,which will cause widespread pesticide abuse and affect people’s health.Therefore,it is great significance in effectively reducing pesticide residue of strawberry and keeping quality to find a method which can not only degrade pesticide residues in strawberry,but also maintain quality during the storage.Therefore,on the basis of investigating the effects of different irradiation treatments on the 8 fungicides of strawberry,the report analyzed the effect of different irradiation treatments on the quality of strawberry,aiming to provide the theoretical basis and technical reference for application of irradiation technology in strawberry.1.In this research,ultrasonic-assisted extraction（UAE）was applied to extract total phenolic contents（TPC）.On the basis of single-factor tests,optimization of extraction for TPC by response surface methodology（RSM）.The optimal extraction conditions were obtained as:70%of ethanol concentration as extracting agent,44 min of ultrasonic time,48℃of ultrasonic temperature.Under the optimal condition,TPC was（14.162±0.075）mg/g,and the model prediction relative error was 0.11%.2.Eight fungicides were screened from commercial Sichuan beauty strawberry sample,the initial contents of Pyrimethani,Cyprodinil,Dimethomorph and Myclobutanildid were not exceed the maximum residue limits（MRLs）in strawberry according the Chinese standard,while Flupirocin,Pyraclostrobin and Trifloxystrob were not established the MRLs for strawberry.The results showed that the degradation dynamic equations of eight fungicides in strawberry were accorded with the first-order kinetics equation in different irradiation treatments by liquid chromatograph-mass spectrometer（LC-MS）method.The degradation half doses(D₅₀)from large to small of Trifloxystrobin,Boscalid,Fluopyram,Pyraclostrobine,Myclobutanil,Cyprodinil,Pyrimethanil and Dimethomorph-z were3.28,3.16,2.96,2.77,2.47,1.83,1.25 and 0.28 kGy.The degration rates of eight fungicides in strawberry were over 53%by 4.0 kGy dose.3.This study evaluated the effect of ⁶⁰Co-γdynamic irradiation doses（0⁴.0 kGy）on color,aroma components,total soluble sugar content（TSS）,firmness,total phenolic content（TPC）and total antioxidant capacity（TAC）of strawberry during 4℃cold storage.The results showed that the change with the color,TSS,TPC and TAC were less obvious（p>0.05）by irradiation treatments compared with contrast（CK）.2.0 and 3.0 k Gy treatments guaranteed color,TSS,firmness and TPC levels of strawberry during storage.⁶⁰Co-γirradiation treatments below 3.0 kGy presented not significantly effects（p>0.05）in contents of characteristic aroma components including ethyl acetate,anoic acid ethylester and hexanoic acid methylester by headspace solid-phase micro extraction（HS-SPME）and gas chromatography-mass spectrometry（GC-MS）detection.The1,1-Diphebyl-2-picryl hydrazy（DPPH·）scavenging rate after 3.0 kGy irradiated treatment was（82.26±1.04）%,which was 5.26%higher than that of the CK.The2,2’-azino-bis（3-ethylbenzothiazoline-6-sulphonic acid）（ABTS⁺·）scavenging rate after 2.0kGy was（64.83±0.93）%,which was 1.56%higher than the CK.The results showed that⁶⁰Co-γirradiation treatments at 2.0³.0 kGy proper doses can enable to deliver larger amounts of high quality strawberry with extended shelf life.