Optical path length and wavelength selection using Vis/NIR spectroscopy for olive oil's free acidity determination

Summary Four different optical path lengths, namely 0.5, 1, 5 and 10 mm, were assayed for olive oil's free acidity determination using Vis/NIR spectroscopy. Results illustrated that the use of higher path length during spectra acquisition resulted in more accurate PLS models, especially when us...

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Published inInternational journal of food science & technology Vol. 50; no. 6; pp. 1461 - 1467
Main Author Garcia Martin, Juan Francisco
Format Journal Article
LanguageEnglish
Published Oxford Blackwell Publishing Ltd 01.06.2015
Wiley Subscription Services, Inc
Subjects
Acidity
algorithms
Food science
near-infrared spectroscopy
NIR spectroscopy
Olive oil
optical path length
rapid methods
Spectroscopy
Spectrum analysis
wavelength selection
wavelengths
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Summary:Summary Four different optical path lengths, namely 0.5, 1, 5 and 10 mm, were assayed for olive oil's free acidity determination using Vis/NIR spectroscopy. Results illustrated that the use of higher path length during spectra acquisition resulted in more accurate PLS models, especially when using solely the NIR region. The PLS model obtained with the NIR spectrum using the 10‐mm cuvette was subjected to optimisation by Monte Carlo uninformative variable elimination (MCUVE) and successive projections algorithm (SPA). Both methods drastically reduced the number of spectral variables and markedly improved the performance of the PLS model, especially the SPA‐PLS model, which achieved a SEP (0.051) quite close to SEL (0.048). Interestingly, only twelve of the eighty spectral variables selected by SPA were among the 314 variables provided by MCUVE. All in all, NIRS incorporated to MCUVE‐PLS or SPA‐PLS may be applied as an alternative method for the rapid determination of olive oil's free acidity. Scheme for selecting optical path length and wavelengths in the olive oil's free acidity determination by VisNIR spectroscopy.
Bibliography:Figure S1. Selected wavelengths (squares) by the SPA method. Figure S2. Variation of root mean square error of cross-validation (dashed line) and root mean square error of prediction (continuous line) with the number of selected variables by Monte Carlo uninformative variable elimination for the free aidity of olive oil. Table S1. Criteria for the evaluation of the results. Table S2. Calibration and prediction results of free acidity by partial least squares models with 0.5-mm path-length cuvette. Table S3. Calibration and prediction results of Free acidity by partial least squares models with 2-mm path-length cuvette. Table S4. Calibration and prediction results of free acidity by partial least squares models with 5-mm path-length cuvette. Table S5. Calibration and prediction results of free acidity by partial least squares models with 10-mm path-length cuvette.
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ArticleID:IJFS12790
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ISSN:0950-5423
1365-2621
DOI:10.1111/ijfs.12790