Study On Detection Method Of Pathogen In Korla Pear Based On Surface-Enhanced Raman Spectroscopy

Korla pear is an important part of Xinjiang’s characteristic forest fruit industry,and it is the main industry for Xinjiang to earn foreign exchange.However,the pears are susceptible to infection by pathogenic bacteria during storage after harvesting,Penicillium expansum and Alternaria alternata are the main pathogenic bacteria causing decay,resulting in a decrease in fruit quality and an increase in rot rate.Therefore,the detection method of the pathogen of Korla pear has great application value for the rational use of pear and the added value of the product.Surface-enhanced Raman spectroscopy（SERS）has the characteristics of simplicity,rapidity and high sensitivity,and has been widely used in the field of agricultural product safety testing.This thesis takes Korla pear as the research object and qualitatively analyzes the Penicillium expansum and Alternaria alternata of pear by SERS spectroscopy.The main research contents of this paper are as follows:1.Using PDA as a medium to activate and extract the pathogens of Penicillium and Alternaria alternata,until a single colony is cultured,and the cultured colonies are formulated into a certain concentration of spore suspension,and the trisodium citrate reduction method is used.Gold sols and silver sols were prepared,and their properties were characterized by UV spectroscopy.The sols with uniform distribution were obtained,and the enhancement effect was tested.The gold and silver sols were enhanced to enhance the pathogen of Korla pear.2.Using gold sol and silver sol as the reinforcing substrate,comparing the ordinary Raman spectroscopy and SERS spectra of the aqueous solution of Penicillium and Alternaria alternata disease,the common aqueous solution of the pathogen of Penicillium and Alternaria alternata disease is obtained.Raman itself does not produce a signal.When the gold sol is used as the reinforcing substrate,the reinforcing effect is weak.When the silver sol is used as the reinforcing substrate,Raman signals appeared in both pathogens.Raman peaks appeared at 551 cm^-1,702 cm^-1,1016 cm^-1,1151 cm^-1,1484 cm^-1 and 1590 cm^-1 in the aqueous solution of Penicillium spp,and Alternaria alternata disease was Raman peaks appeared at 624 cm^-1,693 cm^-1,780 cm^-1,936 cm^-1,1210 cm^-1,1237 cm^-1,1315 cm^-1,1386 cm^-1,1466 cm^-1,1597 cm^-1 and 1701 cm^-1.These peaks can be used as a basis for determining the presence of molecules of the aqueous solution of Pathogens of Penicillium and and Alternaria alternata disease.3.The common Raman and SERS spectra of the two diseases were collected,and the Raman spectral signals of the diseased fruit were analyzed.the pear fruits infected with the pathogens of Penicillium and Alternaria alternata disease could not be detected Raman signal,when the gold sol is used as the reinforcing substrate,the Raman signal of the two diseases is weak,and when the silver sol is used as the reinforcing substrate,the Raman peak appears in both diseases and the Raman peak of the aqueous solution Basically similar,the Raman peak of 586ccm^-1,700cm^-1,934cm^-1,1315cm^-1 and1572cm^-1 was most obvious in the fruit of the Penicillium disease,and 586cm^-1 is the bending vibration of C-O-C,700cm^-1 is Strong=C-H out-of-plane bending vibration,934cm^-1 is C-C stretching vibration,1315cm^-1 is C-N stretching vibration,1572cm^-1 is C=C stretching vibration;Alternaria alternata disease fruit is 785cm^-1,1009cm^-1,1392cm^-1,1468cm^-1,Raman peak appeared in place,of which 758cm^-1 is the out-of-plane bending vibration of O-H,1009cm^-1 is C-C stretching vibration,1392cm^-1 is the stretching vibration of C-N,and 1468cm^-1 is the in-plane bending vibration of C-H.The Raman peak of the Penicillium disease and the Alternaria alternata disease fruit does not coincide,and can be used as the basis for the Raman distinction between the two diseases.4.The colour difference of pear fruits infected with pathogenic bacteria at different time was analyzed.With the prolongation of infection time,the L value of color difference showed a downward trend,while a and b showed an upward trend.The results showed that the fruit color of fragrant pear gradually changed from green to yellow,faded and darkened from green,and the change speed of pathogenic pear was faster than that of healthy pear.