Application Of Raman Spectroscopy Analysis Technology In Monitoring The Quality Of Chinese Rice Wine

Chinese rice wine is a traditional alcoholic beverage in China with a history of more than5000 years and is honored as“the national banquet wine”.In recent years,Chinese rice wine industry is booming,however,the detection technology for Chinese rice wine is comparatively backward.Most of the current detection technologies are often time-consuming,labor intensive and require complicated operation procedures.Therefore,there has been a growing need in developing detection methods which are not only accurate,but also rapid and inexpensive for Chinese rice wine industry.In this study,the application of Raman spectroscopy analysis technology in monitoring the quality of Chinese rice wine was systematically studied and corresponding novel detetcion methods for critical fermentation parameters,quality indexes,ethyl carbamate,histamine and Salmonella Typhimurium were established.Our research could not only provide new detection methods for Chinese rice wine industry,but also play important roles in reducing costs,guranting the quality of Chinese rice wine and promoting the standardization and scientization of Chinese rice wine industry.Raman spectroscopy,Fourier transform near infrared spectroscopy?FT-NIR?and Fourier transform infrared spectroscopy?FTIR?were applied to monitor the fermentation process of Chinese rice wine.The peak intensities of 451 cm^-1,520 cm^-1,1124 cm^-1 and 879 cm^-1 for Raman spectra,5590 cm^-1 and 4338 cm^-1 for FT-NIR spectra and 1090 cm^-1,1042 cm^-1 and2995 cm^-1 for FTIR spectra changed along with the changes of fermentation time,indicating that there were characterized information closely associated with the fermentation process for all of these three kinds of spectra.The results of discriminant partial least squares analysis?DPLS?based on three different spectra demonstrated that among the three kind of spectroscopy,FT-NIR was the worst one while the classification results based on FTIR and Raman were similar.Multivariate regression models based on Raman,FT-NIR and FTIR were eatabilshed for three critimal fermentation parameters,i.e.,ethanol,total sugar and total acid.The analysis results from models based on Raman spectra were superior to that based on other two kinds of spectra.The R² values of partial least squares?PLS?models based on Raman spectra were 0.95 for ethanol,0.94 for total sugar and 0.93 for total acid,respectively,suggesting that the method was suitable for Chinese rice wine fermentation monitoring.Raman spectroscopy was combined with chemometrics to rapidly determine the common qulity indexes and antioxidant capacity indexes of Chinese rice wine.Clear separation of Chinese rice wine samples from different brands and geographical origins were observed,revealing the excellent classification ability of Raman spectroscopy.For ethanol,pH and total phenol,PLS models were suitable;however,for most of quality indexes,spectra variables selection process was necessary,satisfactory results were obtained for total sugar,total acid,ABTS and FRAP from the models based on the variables selected by synergy interval partial least-square?SiPLS?.However,even with the assiatance of variables selection process,the results were still not good enough for detecting DPPH?R² was still lower than 0.90?.Taking the advantages of both FTIR and Raman spectroscopy,data fusion technology was used to select the characterized spetcra information and megerd them to establish new models.Among these new models,due to the complexity of Chinese rice wine,the performance of nonlinear model was better than linear model.Finally,SiSVMC model was chosen for DPPH detection,and R² was as high as 0.93,much higher than those without using the data fusion strategy.In addition,high correlation between total phoneol content and antioxidant capacity was obtained.Furthermore,it was found that the most important phenol components in Chinese rice wine were syringic acid,?+?-catechin and protocatechuic acid.A“two-step”method for fast and sensitive detection of ethyl carbamate?EC?in Chinese rice wine based on the integration of molecularly imprinted polymers and surface-enhanced Raman spectroscopy?MIPs–SERS?was developed.MIPs was synthesized by polymerization of EC?template?,MAA?functional monomer?,AIBN?initiator?and EGDMA?cross-linking agent?on the surface of silica gel particles.TEM showed that the size of MIPs synthesized was uniform?²00 nm?,while TGA results suggested that MIPs were resistant to relative high temperature and had good thermal stabilities.Adsorption tests validated the existence of specific binding sites to EC in MIPs.The MIPs for EC after ten concecutive reuses still remained 87.2%of the initial adsorption capacity,suggesting that MIPs employed in this experiment had good stability and reusability for EC adsorption.The synthesized MIPs was used as sorbents in solid-phase extraction?SPE?and the amount of MIPs in SPE-cartridge,flow rate,washing solvent and eluent solvent were optimized.Under optimal condition,the method was applied to detect EC contents in real Chinese rice wine samples,the recovery was between 87%and 102%,R² and RPD was higher than 0.90 and 3.0,respectively,suggresting that the established method can be used for fast and efficient detection of EC in Chinese rice wine.Upconversion nanoparticles?UCNPs?was synthesized uing the pyrolysis method and then they were modified with PAA.UCNPs@MIPs-AgNPs was synthesized by coating a layer of MIPs doped with silver nanoparticles?AgNPs?on the surface of PAA modified upconversion particles?UCNPs?.TEM,XRD and FTIR results revealed that UCNPs@MIPs-AgNPs synthesized in this study were uniform and well-dispensed while the static,dynamic and selectivity adsorption experiments demonstrated the excellent specific selectivity of UCNPs@MIPs-AgNPs.The novel material?UCNPs@MIPs–AgNPs?simultaneously possessed a positive SERS response and negative fluorescence response.The correlation of coefficients for fitting curves based on SERS mode and fluorescence mode were all higher than 0.98,suggesting good fitting performances.The recovery of this method was also very good,ranging from 93.30%to 108.30%.In addition,no significant difference?p>0.05?in the results were observed from the proposed analysis and those obtained with HPLC-UV,indicating that the proposed method had great potential for histamine detection in Chinese rice wine samples.With the involvement of“magnetic focus”strategy,SERS based LFICA was used to detect Salmonella Typhimurium in Chinese rice wine.Fe3O4@Au was systematically characterized by TEM,VSM,zeta potential,XRD,TGA,UV-Vis and FTIR,the results suggested that Fe3O4@Au core–shell nanostructures synthesized in this study were uniform with good magnetic response property and thermal stability.After optimization,the optimal LFICA conditions were as follows:nitrocellulose membrane:90-CNPH-N-SS40;the amount of antibody immobilized on the surface of nitrocellulose membrane:0.3?g;the volume of the signal probe:0.5?L.Enzyme amplification based LFICA and SERS based LFICA with and without using magnetic focus strategy were used to detect different concentrations of Salmonella Typhimurium,the results suggested that SERS based LFICA was more suitable than enzyme amplification based LFICA in the detection of Salmonella Typhimurium in Chinese rice wine,in addition,the magnetic focus strategy could greatly decrase the limit of detection.A good linear relationship was found between the signals and Salmonella Typhimurium concentrations in the range of 25-5000 CFU/mL with the regression equation of y=5722.71-7556.88 and R² of 0.992,the LOD and LOQ of this method were calculated to be15 CFU/mL and 25 CFU/mL,respectively.The recovery ranged from 96.00%to 103.33%,indicating that the proposed detection procedure was accurate and reliable to be used in the detection of Salmonella Typhimurium in Chinese rice wine.