Construction Of Gluten-based Electrospun Film And Its Application In The Field Of Food Detection

Electrospinning is a technology that prepares nanofiber films from polymer solutions through high-voltage electric fields.The prepared nanofiber films have the characteristics of a three-dimensional network structure,high specific surface area,and high porosity,and have been widely studied and applied in the fields of food active packaging,sensor detection,immobilized enzymes,and drug sustained release.Gluten is a by-product from wheat starch processing.Due to its shortcomings such as low solubility,poor processing stability,and high swelling rate,the development and application of gluten materials are traditionally limited.In this study,monoglyceride laurate（GML）was used as a spinning aid to prepare Gluten/GML electrospun nanofiber films by electrospinning.The effect and mechanism of GML on Gluten nanofibers were explored,and the antimicrobial activity of Gluten/GML nanofiber films were evaluated.Gluten/Zein electrospun nanofiber film（GZEF）was prepared by blending electrospinning with Zein,and the effect of glycation crosslinking on the performance of GZEF and its mechanism were investigated.Then,using GZEF as a flexible substrate to construct a 4-ATP@AgNPs@GZEF SERS sensor for nitrite detection by electrospraying method,and its application in food detection was explored.Then,the sensitivity of the GZEF based SERS sensor was improved by means of nanoparticles selecting,loading amount selection,and ZIF-8 modification,and the constructed AANS@ZIF-8@GZEF SERS sensor was used for chlorpyrifos detection.Finally,the AANS@MIPs@GZEF sensor capable of specifically recognizing aflatoxin B₁（AFB₁）was constructed by combining molecular imprinting technology,and its application to the detection of AFB₁ in peanut oil was explored.The main research content of this paper includes the following five parts:（1）Gluten nanofibers with GML loading rate of 0%,4%,8%,12%,and 16%were prepared by electrospinning.The changes of conductivity,viscosity and surface tension of electrospinning solution with different GML additions were evaluated,and their effects on the morphology of gluten nanofibers were explored.The results showed that GML affected the fiber morphology by changing the surface tension and viscosity of the electrospinning solution.When the addition amount was 8%,the most uniform gluten nanofibers with a diameter of 149 nm was obtained.The results of XRD and FTIR revealed that GML was uniformly dispersed in the gluten nanofibers at low concentration,but existed in crystal form at high concentration,and hydrogen bonds were formed between GML and the nanofibers.The obtained gluten nanofibers became stiffer and more brittle with the increase of GML addition.The water stability of the nanofibers also enhanced,and the structure of nanofibers were still retained after the 7-day immersing and shaking experiment,which was attributed to the formation of hydrogen bonds that made the fibers more tightly to limit the deconstruction.In addition,the Gluten/GML nanofibers showed significant inhibitory effects on both E.coli and S.aureus.（2）Hybrid nanofibers with Gluten/Zein ratios of 1:0,3:1,and 1:1 were prepared by electrospinning,and cross-linked by glycation with xylose at 60℃and 40%relative humidity for 24 h.It was found that the average fiber diameter of the hybrid nanofibers decreased from 551.4 to 343.7 nm with the increase of the proportion of zein,and increased to 521.0 nm after glycation.The thermal denaturation temperature of the nanofibers increased from 129.9℃,135.2℃,and 135.8℃to 134.5℃,142.4℃,and 174.2℃,respectively,after glycation.Circular dichromatography results showed that the proportion of ordered structures decreased from 40.32%to 23.56%after glycation.The tensile strength of the crosslinked GZ31 nanofibers increases from 2.2 to 13.3 MPa and the elongation rate increased from 41.7%to 142.2%.These results indicated that the mechanical properties of the nanofibers were improved,which was due to glycation enhanced the entanglement and interaction between polymer molecular chains.In addition,the water vapor transmission rates of the nanofibers decreased from 5.7,4.6,4.7 mm/m² h k Pa to 4.7,3.7,and 4.2 g mm/m² h k Pa,respectively.Furthermore,it was found that the weight loss rate of the hybrid Gluten/Zein nanofibers decreased from 44.5%,34.8%and 42.1%to 34.1%,26.7%and 34.6%,respectively after glycation,indicating that the water stability has been significantly improved.（3）A 4-ATP@AgNPs@GZEF sensor was constructed by loading the Ag NPs with4-ATP on the surface of the Gluten/Zein electrospun nanofiber film（GZEF）through electrospraying method for nitrite SERS detection.The constructed 4-ATP@AgNPs@GZEF sensor was characterized by SEM,EDS,and XRD.It was found that the surface of the electrospun film substrate could load more 4-ATP@AgNPs than the coated film.The results of Raman test showed that the enhancement factor of the electrospun film SERS sensor was 2.6557×10⁸,while that of the casted film SERS sensor was 2.6311×10⁵.The 4-ATP@AgNPs@GZEF sensor has good reproducibility,and good stability within the storage at first 28 days.Moreover,the linear range of the4-ATP@AgNPs@GZEF sensor for the quantitative detection of nitrite was explored in the range of 0.1-1000μmol/L,and the detection limit was 3.5×10^-10 mol/L.In addition,it was also verified that the 4-ATP@AgNPs@GZEF sensor has specific selectivity for the recognition of nitrite ions,and it can still detect sodium nitrite in the compound solution.Finally,the constructed 4-ATP@AgNPs@GZEF sensor was used to detect the sodium nitrite content of five foods,and the influence of different sampling methods on the detection results was compared.It was found that for foods with low moisture content,the SERS test results after direct wiping were significantly different from the standard value.However,the SERS test results after fine extraction were not significantly different from the standard test value.The results of the t test proved that the method of SERS detection after fine extraction can be used for the quantitative detection of sodium nitrite in food.（4）The sensitivity of the GZEF based SERS sensor was improved and used for the pesticide chlorpyrifos detection.Four different nanoparticles were synthesized on the basis of gold and silver materials:Au NPs,Au@AgNPs,Au@Ag NSs and Ag@Au NUs.It was found that Au@Ag NSs had the highest enhancement factor for probe R6G,which was reach to 2.75×10⁹.Therefore,AANS@GZEF sensors were constructed with electrospraying time of 5 min,10 min,15 min,20 min,and 25 min respectively.It was found that the SERS signal enhancement effect of electrospraying time of 20 min was the best.Further,the AANS@ZIF-8@GZEF sensor was prepared by in-situ synthesis and compared with the AANS@GZEF sensor.The results showed that the SERS signal intensity of the AANS@ZIF-8@GZEF sensor peak at 1509cm^-1was 1.58 times than that of the AANS@GZEF sensor.The AANS@ZIF-8@GZEF sensor was used to detect chlorpyrifos,and the concentration-peak intensity relationship for quantitative detection was obtained by fitting.In addition,it was also found that the AANS@ZIF-8@GZEF sensor has a good gas phase detection effect,which is attributed to the enrichment of small gas molecules by the porous structure of ZIF-8.The AANS@ZIF-8@GZEF sensor was used for the collection and detection of chlorpyrifos on apple epidermis,and the overall recovery rate was found to be between 91.18-96.83%,and the relative standard deviation was less than 5%.（5）The specificity of the GZEF-based SERS sensor was explored,and the AANS@MIPs@GZEF sensor for AFB₁ detection was constructed by combining molecular imprinting technology.The functional monomers required for AFB₁ specific recognition of MIPs and their ratios to template molecules were calculated based on DFT,and the AANS@MIPs were synthesized.The AANS@MIPs@GZEF sensor for the specific detection of AFB₁ was constructed by assembling AANS@MIPs on the surface of the GZEF substrate by electrospraying.The calculated AFB₁ quantitative detection range of AANS@MIPs@GZEF sensor is 10^-2-10¹ ng/m L,and the LOD value is 4.1 fg/m L,and it is verified that it has good specific selectivity for AFB₁.Using the AANS@MIPs@GZEF sensor to detect AFB₁ in the spiked peanut oil,the recovery rate was found at the range of 95.1%-112.0%,and the relative standard deviation was at the range of 3.5%-7.9%,indicating that the constructed AANS@MIPs@GZEF sensor has good application potential in the detection of AFB₁ in food system.