Quality Analysis of Peanut Oils and Peanut Diacylglycerol Edible Oils After Frying Using Raman Spectroscopy Combined with Oil Microscopy Method.

Abstract

The thermal stability and quality of fats change during oil-frying, directly impacting food safety and nutritional value; however, traditional analysis methods are time-consuming and complex. This study aimed to develop a rapid monitoring protocol using a portable Raman spectrometer for peanut oils and peanut diacylglycerol (DAG) edible oils after frying zero to five times at 150°C. Raman spectral data and the acid and peroxide values were determined for 48 oil test samples. Raman spectral data were analyzed using the characteristic band intensity ratio method and oil microscopy method. The peroxide values of peanut oil correlated with I729/I1076, I1076/I1300, and I1268/I1655 (I: Raman spectral intensity; subscript: wave number corresponding to Raman shift), whereas the acid and peroxide values of peanut DAG edible oil correlated with I863/I1655, I1076/I1300, and I1268/I1655. Oil microscopy method analysis revealed that the fried peanut DAG oil had higher trans-fatty acid and acid values (AV) and lower unsaturated fatty AVs than regular peanut oil. Furthermore, oil microscopy method revealed changes in the functional groups of the oils and fats, further elucidating the quality changes that occur in oils and fats after frying. Raman spectroscopy combined with oil microscopy method can be used to rapidly monitor the quality of frying oil after frying. Peanut DAG oil is more oxidatively stable after frying than peanut oil; a characteristic band intensity ratio method can be used to classify frying oils; the peroxide value of peanut oil is related to I729/I1076, I1076/I1300, and I1268/I1655; the acid and peroxide values of peanut DAG edible oil are related to I863/I1655, I1076/I1300, and I1268/I1655; oil microscopy method revealed oil functional group changes and could improve frying quality analysis.