Explorative spectrometric evaluations of frying oil deterioration

Abstract

The potential of spectroscopy as a reliable and fast method for determining the deterioration of frying oils was investigated. Daily oil samples were collected from a commercial Chinese spring roll plant. The plant was operated one shift, 5 d a week, then cleaned and restarted with fresh oil every 4 wk. Each oil sample was analyzed by 11 chemical/physical methods and fluorescence, near infrared/visible (NIR/VIS), Fourier transform infrared (FT-IR) and FT-Raman spectroscopic procedures. The results were evaluated and compared by principal-component analysis and partial least squares regression. Most chemical/physical and all spectroscopic methods detected the deterioration during the first half of the frying cycle. Thereafter, an equilibrium occurred between deterioration processes and replenishment with new oil. At equilibrium, the correlation between frying time and the various methods was nonlinear. FT-IR with the attenuated total reflectance sampling technique was the most direct and accurate method of monitoring gross changes in the frying oil. Fluorescence was the technique that provided the best models for anisidine value, oligomers, iodine value, and vitamin E. NIR/VIS spectroscopy proved to be a good general-purpose technique. The study demonstrated that spectroscopic sensors have the potential to replace titration and chromatographic procedures, and can be used in combination with chemometric data analysis to optimize deep-frying operations.

Analysis of Olive Oils by Fluorescence Spectroscopy: Methods and Applications

“…Fluorophores in olive oils are compounds that can participate in oxidation, thus fluorescence spectroscopy can serve as a tool for better understanding of oil oxidation. The fluorescence was compared to other spectroscopic techniques (NIR/VIS, FT-IR and FTRaman) and chemical and physical methods in determining the deterioration of frying oils, collected from a commercial Chinese spring roll plant, (Engelsen, 1997). Fluorescence has been measured by using five selected excitation wavelengths varying from 395 to 530 nm.…”

Vibrational Spectroscopy of Food and Food Products

“…In another study in which an industrial frying operation was monitored by a variety of techniques, including FT-IR, NIR, and Raman spectroscopy, FT-IR spectroscopy proved to be the most direct and accurate method of monitoring gross changes in the frying oil over time. 28 A quantitative FT-IR method for monitoring the oxidative state of frying oils, based on the determination of anisidine value (AV), a measure of aldehydes that are major secondary oxidation products in polyunsaturated oils, has also been reported. 29 FT-IR methods have also been developed to serve as alternatives to the peroxide value (PV) test, which is widely employed by the fats and oils industry to assess the oxidative status and stability of refined oils.…”

“…The feasibility of employing NIR spectroscopy to evaluate the extent of oxidation of oils and the quality of used frying oils has also been examined. 28,124,125 …”

Determination of Food Quality by Using Spectroscopic Methods

“…All refined oils showed only one intense peak at 445 nm, which is due to fatty acid oxidation products formed as a result of the large percentage of polyunsaturated fatty acids present in these oils. Fluorescence is regarded as the technique that provided the best models for anisidine and iodine values, oligomers and vitamin E content in deteriorated oil after repeated frying cycles [24].…”

“…The reaction between unsaturated lipids and atmospheric oxygen under ambient conditions, termed lipid autooxidation, is a leading cause of deterioration of fats and oils, as well as of any lipid-containing food, as it gives rise to the off-flavors and unpalatable odors associated with oxidative rancidity. FT-IR spectroscopy proved to be the most direct and accurate method of monitoring gross changes in the frying oil over time [24,42]. A quantitative FTIR method was used for monitoring the oxidative state of frying oils, based on the determination of anisidine value (AV), a measure of aldehydes that are major secondary oxidation products in polyunsaturated oils, has also been reported [43].…”