Development Of A Rapid Detection Method For The Acetaldehyde In Beer Based On Fluorescent Probe

Acetaldehyde is an important flavor compound in alcoholic beverages.The content of acetaldehyde has a direct impact on the flavor and aging of beer.When the concentration of acetaldehyde is high,it will produce a pungent and irritating smell,bringing bad grassy flavor to beer and shortening the fresh-keeping period of beer.When the concentration of acetaldehyde is low,beer will have a fruity flavor.Gas chromatography is a commonly used method for the detection of acetaldehyde in beer,but there are still problems such as long detection time,low sensitivity,and high detection cost.Efficient and accurate detection of acetaldehyde in beer is being a focus of the industry currently.Fluorescent probe has the advantages of high sensitivity,high selectivity,low interference of detection system and simple operation,and is expected to become a new tool for the detection of acetaldehyde.This study established a detection method for acetaldehyde in beer based on a benzoxadiazole fluorescent probe（FPN1）.The main research results of this paper are as follows.Firstly,because benzoxadiazole fluorophore has the characteristics of high sensitivity,high fluorescence quantum yield and emission wavelength in the visible light range,this study screened a fluorescence probe with hydrazine as the reaction group based on the benzoxadiazole fluorophore.A one-step synthesis method of FPN1 was established（500 mg NBD-Cl was added to 50 m L of 5%hydrazine hydrate for 6h,and after nitrogen purging,it was sealed and left for 1h）,with a yield of 91.20%.The simple synthesis method could reduce the detection cost effectively.The maximum excitation wavelength of FPN1 is 485 nm,and the maximum emission wavelength is 553 nm.Theoretical calculations verified that the functionality of FPN1 depends on the principle of photo induced electron transfer（PET）.Secondly,this study proposed background removal method（BRM）as the preprocessing method for beer samples.BRM can eliminate the interference of ketone acids and acetals in beer samples,which is of great significance for practical applications.Meanwhile,this study determined the optimal reaction conditions for FPN1:The optimum p H of the response of FPN1 to acetaldehyde is p H=2.1;The best solvent is acetonitrile;The optimum temperature is5℃;The optimal reaction time is 20 min;The optimal probe concentration is 300 mg·L^-1.Finally,a detection method for acetaldehyde concentration in beer was established based on FPN1 and BRM（BR-FPN1）.Compared with traditional gas chromatography method,BR-FPN1 method has a wider linear range(0.0053-200 mg·L^-1),higher sensitivity(limit of detection is 0.0016 mg·L^-1),better recovery rate（94.02%-108.12%）,and shorter detection time per unit sample（3 min）for the 24 samples detected in this study.The relative standard deviation of BR-FPN1 method is 0.67%-5.95%,and the Bland Altman results indicate good consistency between BR-FPN1 and gas chromatography method.BR-FPN1 method can also be used to determine the acetaldehyde concentration in Baijiu,Huangjiu and wine.Due to the significant enhancement of fluorescence observed in the probe solution under UV lamp irradiation,this study also explored the test paper method for the detection of acetaldehyde based on FPN1.The limit of detection of the test paper method is 5 mg·L^-1.The fluorescence of the test paper increase gradually with the increase of acetaldehyde concentration.In conclusion,BR-FPN1 method was developed in this study to detect acetaldehyde in beer,which ensures accuracy while avoiding the use of expensive instruments.The method is simple,fast,and low-cost,and has important reference value for the development of online intelligent detection method of acetaldehyde in beer fermentation process.