Determination of In-Shell Peanut Oil and Fatty Acid Composition Using Near-Infrared Reflectance Spectroscopy

NIR reflectance spectroscopy was used to analyze the total oil and fatty acid concentration of Virginia and Valencia types of in-shell peanuts rapidly and nondestructively. NIR absorbance spectra were collected in the wavelength range from 400 to 2,500 nm using a NIR instrument. Average total oil concentrations of all samples were determined by a standard Soxtec extraction method. Fatty acids were converted to the corresponding methyl esters and measured using gas chromatography. Partial least squares analysis was performed on the calibration set, and models were developed for predicting total oil and fatty acids. The best model was selected based on coefficient of determination (R (2)), standard error of prediction, and residual percent deviation (RPD) values. Virginia-type in-shell peanuts had RPD values of > 5.0 for both absorbance and reflectance models, indicating that the method could be used for quality control and analysis. Valencia peanuts had an RPD value of 3.01, which indicates that the model is good for initial screening purposes. For both types of peanuts, fatty acid prediction gave RPD values of < 5 for all the models, indicating they could be used for initial screening purposes.