Inspection Of Beer By Electronic Tongue

There are deficiencies when beer is examined and appraised by traditional methods, such as timeconsuming, appraising only certain ingredients which cannot represent the overall quality, cannot realizethe real-time examination, and so on. It is found that, the electronic tongue system, which is used inrapid liquid and taste analysis, can give qualitative and quantitative measurements within few minutes,easy to use, no sample preparation, objectivity compared to sensory panel, and no risk of panelcontamination or bad taste effect on the panel. It is a new and revolutionary smart technique in the fieldof rapid liquid and taste analysis. However, the research in the application of electronic tongue in theappraisal of beers is less studied. In this thesis, quality of different beers is studied, with the help ofelectronic tongue. Chemical index such as pH, alcohol concentration, concentration of CO₂, VDK inbeer are detected. Optimization of Experiment parameters, discrimination of different brands of beers,study of aging characteristics of beer in short period, factors (product line and time) that affect thequality of beer are studied. The correlation between the inner characteristic and response of sensors hasbeen analyzed, and prediction models of beer-pH have been established. It provides a new method ofnondestructive evaluation of food industry for further research.1. Optimization of Experiment parametersThe electronic tongue has different response to different cleaning solutions. The effect of deionizedwater, the Xihu beer and 2%(v/v) of alcohol are studied, the sequence of cleaning solution and dataprocess are studied. Results areâ‘ Xihu beers are better than the other two, However, the quality of Xihubeer changes quickly after its opening, which does not satisfy the quest of cleaning solution. 3%(v/v) ofalcohol is chosen as cleaning solution, as its alcohol concentration is more closer to that of beers, and itscleaning effect are superior than the others.â‘¡The best cleaning order is after one examination, thesensors of the electronic tongue are merged in the cleaning solution directly, than the next sample isexamined.â‘¢As the electronic signals at 120s are more stable, and helpful in the discrimination ofresults,, response signals at 120s are chose for data analysis in the analysis parts of this thesis.2. Discrimination result of different brand beer by Electronic tongueDiscrimination of different brands of beers are studied, findingâ‘ Different brands of beer are welldiscriminated by electronic tongue. Moreover, high relevance (R²=0.909)between the electronic tonguesignal and sample pH is found. The electronic tongue can be used in identification and discrimination ofdifferent kinds of beer, and predict the pH of the samples.â‘¡Eight kinds of beers produced in onefactory can easily identify and discriminate one kind from the others only by the radar plot, averagevalue and the standard deviation of the sensor signals. In the PCA and DFA plots, eight kinds of beersare separated in different parts of the plot, with a high discrimination index. The electronic tongue can differentiate the identical brewery production, even the same brand kind of beer which are produced indifferent time, or different line at the same time. In the results of DFA analysis, the sensor signals areconsistent with production date of beers, and the freshness of beer changes along with the tendency ofthe arrow in the map. What's more, the DFA model can discriminate the unknown sample correctly.â‘¢Beers produced at four different time of a month can be discriminate both in PCA and DFA analysis.Moreover, the production date are consistent with the reduce along with PCI and DFI.3. Study of aging characteristics of beer in short period by electronic tongueThe aging characteristics of beer in short period are studied by electronic tongue, the results areâ‘ Different aging degrees of beer are discriminated by the DFA analysis, and the aging process isconsistent with the increase of DF1.â‘¡The PLS calibration model established by the sensor signal isfeasible in forecasting the pH of aging beer.â‘¢The sudden change of beer quality occurs in the first fourhours after its opening.The quality of beer drops gradually in short period (8 hours) after opened.4. Effect of product line and time on beer qualityThe effect of product line and time on beer quality are studied in this part. The results areâ‘ Ninekinds of beer samples produced by three lines can be differentiated in the PCA analysis results. Samplesof different line lies in different regions of the plot, different time of one line also lies in different regionwith partially overlaps. Obviously, there exist certain relations between the electronic tongue signal andthe production line & time, and the electronic tongue results can reflect the affects of these factors onthe quality of beers in the certain degree.â‘¡Beers produced by one line at different month can be wellidentified by PCA and DFA analysis; there are certain relations between the sensor signals and the affectof production time on the quality of beer.â‘¢Beers produced by different line at same time can be wellidentified by PCA and DFA analysis; there are certain relations between the sensor signals and the affectof production line on the quality of beer.