Quantitative Fourier transform infrared analysis for anisidine value and aldehydes in thermally stressed oils

Abstract

A Fourier transform infrared (FTIR) transmissionbased spectroscopic method was investigated for the simultaneous monitoring of aldehyde formation and the determination of anisidine value (AV) in thermally stressed oils. Synthetic calibration standards were prepared by adding known amounts of hexanal, t-2-hexenal and t,t-2,4-decadienal to canola oil (these compounds considered representative of aldehydic compounds formed during oxidation) plus random amounts of other compounds representative of oxidation by-products. The standards were analyzed for their chemical AV. With the partial least squares (PLS) technique, an FTIR spectrometer was calibrated to predict both the concentrations of individual aldehyde types and AV, with the individual aldehyde contributions being related to the chemical AV by multiple linear regression to derive "apparent" AV values. The predictive capability of the PLS calibrations was assessed by analyzing canola oils that were thermally stressed at 120, 155, and 200~ The apparent AV, predicted for these samples, matched the chemical AV values within +I .65 AV units. A PLS calibration also was derived by using thermally stressed samples as calibration standards. This approach provided similar predictive accuracy as the use of synthetic calibration standards. As such, quantitative determination of AV by FTIR spectroscopy was shown to be feasible, and the synthetic calibration approach provided additional information on the aldehyde types present in a sample and allowed the use of a simple gravimetric approach for calibrating an FTIR spectrometer. This study provides the basis for the development of a rapid, automated FTIR method for the direct analysis for AV of thermally stressed fats and oils in their neat form without the use of chemical reagents. The implementation of such a method as a quality control tool would eliminate the use and disposal of hazardous solvents and reagents, required by the conventional chemical method, and drastically reduce analysis time (-2 min/sample). Possible applications include monitoring of the oxidative state of frying oils or evaluation of oxidative stability of biodegradable lubricants.JAOCS 73, 787-794 (I 996).

Chemometric Analysis of Croatian Extra Virgin Olive Oils from Central Dalmatia Region

“…17 The medium band at 1711 cm −1 corresponds to the stretching of free fatty acid carbonyl group. 71 The absorption band with very weak intensity at 1654 cm −1 is due to the C=C stretching vibration of cis-olefins. 53,72 In the range 1500−1300 cm −1 , absorbance peaks at 1465 and 1377 cm −1 could be assigned to CH 2 and CH 3 bending vibrations, at 1418 cm −1 to rocking vibrations of CH bonds of cis-disubstituted olefins and at 1397 cm −1 to in plane bending vibrations of CH cis-olefinic groups.…”

Caracterização físico-química de queijo prato por espectroscopia no infravermelho e regressão de mínimos quadrados parciais

“…[5][6][7][8] Além de versátil, permitindo a análise de uma grande diversidade de matrizes de interesse, a técnica apresenta-se precisa, rápida e segura, [8][9][10] o que favorece a sua utilização na implementação de rotinas de trabalho. 11 Levando-se em consideração os objetivos deste trabalho, resulta especialmente interessante destacar o trabalho de Vannini,12 que demonstra a capacidade da espectroscopia no infravermelho para o monitoramento de mudanças físico-químicas na estrutura de proteínas, em conseqüência da atividade proteolítica microbiana desenvolvida durante a maturação de queijos, e o trabalho de Mcqueen et al, 13 que demonstra a viabilidade da caracterização química de queijos, recorrendo-se à espectroscopia no infravermelho.…”

Spectroscopy: Developments in instrumentation and analysis

“…Mid-infrared spectroscopy is also widely used to determine the fat content of high fat products such as butter and margarine or milk products. The dairy industry uses MIR spectrometry in routine analysis and the official control laboratories make the analysis with this kind of instrument (Wilson 1990;van de Voort et al 1992 Dubois et al 1996;Ma et al 1997Ma et al , 2000. Near-infrared spectroscopy is also used to analyse the fatty acid profile of high-fat products Alonso et al 2000).…”