Study On Detection Method Of Food Volatiles Design Based On Infrared Absorption Spectroscopy

In the process of food processing,storage to spoilage,due to the change of its physical and chemical properties and microbial reproduction,a variety of volatiles related to the freshness of food can be produced,and the quality and freshness of food can be detected by volatiles.Early detection methods for food volatiles were usually based on gas chromatography-mass spectrometry(GC-MS)or electrochemical sensors such as electronic noses.However,the complex sample pretreatment required by GC-MS and the severe cross-sensitivity of the electronic nose method limit its practical application in the food field.Therefore,in view of the problems of the above methods,in order to meet the needs of the rapidly developing food industry,based on infrared absorption spectroscopy,this paper uses long optical path FTIR to quickly detect the food quality through the detection of food volatile matter.However,long-path FTIR also requires the collection of gas and cannot be used for in-situ detection.Aiming at this shortcoming,this paper also developed two food quality in-situ detection methods based on fiber-optic evanescent wave(FOEW)and gas absorption spectroscopy in scattering medium(GASMAS)for different application scenarios.The main research contents are as follows:1.A feasibility study was carried out on the rapid detection of milk quality by using long wavelength Fourier Transform infrared spectrometer(FTIR).Based on the team’s previous research results,this study took milk as the research object and used long optical path FTIR to detect the gas volatilized during milk deterioration,and detected specific markers such as ethanol,which showed good consistency with the detection results of conventional proton transfer reaction mass spectrometer(PTR-MS).In addition,principal component analysis(PCA)were used to reduce the dimension of the data,and partial least squares discriminant analysis(PLS-DA)algorithm was used to model the spectral data of fresh and spoiled milk.The model successfully classified fresh and spoiled milk,and the classification accuracy reached 100%.The experimental results show that long optical path FTIR can quickly and effectively detect food quality by food volatiles,but its detection process requiring gas extraction still needs to be improved and optimized.2.Based on FOEW technology,the method of in situ detection of food quality without gas collection was studied.In the experiment,silver halide fiber was coupled into the optical path of FTIR,and a set of FOEW gas detection system was built by using spiral optical fiber probe.The feasibility and repeatability of the method was verified by using ethanol solution.In this experiment,milk was taken as the research object,and the milk headspace volatile gas was directly detected without gas collection.The specific markers such as ethanol were effectively detected and showed good consistency with the detection results of long optical path FTIR.After that,PLS-DA algorithm was used to model the data of fresh and spoiled milk,and a part of unlabeled samples were used to verify the classification accuracy reached100%.The experimental results show that FOEW can effectively detect food volatiles without gas collection,expanding the application of infrared absorption spectroscopy in food volatiles detection.3.Based on GASMAS technology,the method of detecting fruit quality and storage time in sealed packaging box without opening the package was studied.A complete and compact oxygen detection system was constructed by using a 760nm distributed feedback(DFB)laser and a photomultiplier tube(PMT),and wavelength modulation and demodulation technology was introduced to improve the sensitivity of the system.An oxygen concentration calculation algorithm without gas calibration is developed in Python language.The experiment used foam chamber to verify the feasibility of detecting oxygen concentration in the chamber without opening the lid.The oxygen content in sealed fruit boxes was continuously monitored for grapes and strawberries,and the spoilage of the fruit boxes was assessed without damaging the fruit packaging.At the same time,the prediction model of oxygen concentration and storage time of grape and strawberry was established.The R~2 of prediction set was 0.9220 and 0.9543,and the root mean square error(RMSE)was 0.4426 and 0.3079 days,respectively.The experimental results show that GASMAS can detect the gas concentration in the box without opening the package,so as to completely detect the food quality in a real sense.To sum up,this paper has carried out a method study for detecting volatile substances in food without collecting gas or opening packaging.The application scenarios of volatile substance detection in food were expanded and the flexibility of detection was improved.It provides a new reference for the application of absorption spectrum to detect volatile compounds in food.