Nir-Spektroskopie zur qualitativen und quantitativen prozessverfolgung bei alkoholischen gärungen

Abstract

Consulta en la Biblioteca ETSI Industriales (7802)

[EN] As a research tool NIR spectroscopy can be used to evaluate raw materials, yeasts, enzymes, nutritional supplements, and production parameters to optimize conditions for a production plant. As a quality assurance tool it can assist production by monitoring and maintaining control of processes. What makes NIR technology so attractive to the ethanol industry as a quality assurance and research tool is that it can measure organic substances very quickly (5-10 seconds) and consistently without the destruction of a sample. In this work, normal alcoholic fermentations and alcoholic fermentations with a lactic acid infection are carried out and measured with the NIR spectrometer. Spectra data are processed by the use of sophisticated multivariate analysis. PCA plots are made for watching the evolution of the fermentations. It was found that the 98% of the information is in the first principal component and the other one 1% is in the second principal component. It was found too that the lactid acid infection makes an impact on the PC1 data. To build a quantitative calibration model using NIR data, one must have a reference analysis method (HPLC, High Performance Liquid Chromatography) to determine the concentrations of the components of interest in the sample, i.e. ethanol, glucose and lactic acid. With these concentrations and the measurements of the NIR spectrometer one can then develop and validate the quantitative calibration models. These calibration models are used for predicting the concentrations of ethanol, glucose and lactic acid along the fermentation time. At the end of the validation the NIR predicted values are compared with those from the reference method and expressed in a plot of NIR predicted vs. reference values. In this plot there are two important indicators for how good the model is. One is the R2 (squared Pearson Correlation Coefficient) and the other one is the SEP (Standard Error of Prediction). It was found that the errors of prediction for the concentration range of the component are fairly high. The NIR technology is a new chance for measuring in alcoholic fermentations. Therefore, this work should be continued in order to improve the results.