Determination of Fruit Oil Content and Fatty Acid Composition in Symplocos Paniculata Using Near Infrared Reflectance Spectroscopy

Symplocos paniculata is an important shrub or small tree with high fruit oil content. It can be used as potential feedstocks for biodiesel and cooking oil production. The feasibility of using near-infrared reflectance spectroscopy (NIRS) for rapid and nondestructive determination of the fruit oil content and fatty acid composition of S. paniculata was investigated. Fruits were collected from 124 trees at different geographic locations in Hunan province, China. All fruits were air-dried and then scanned using NIRS. The fruit oil content and fatty acid composition were also analyzed using chemical method including petroleum ether extraction and gas chromatography. The raw spectra were pretreated using four chemometrics such as first and second derivative (FDE and SDE), standard normal variate transformation (SNV), Savitzky-Golay smoothing (SG), and multiplicative scatter correction (MSC). Of the spectrum pretreatments, the FDE+SG were the best method for oil content, palmitic acid, and oleic acid, whereas the best model for stearic, linoleic, and linolenic acid were SDE+SNV, SDE+MSC, and FDE, respectively. Such pretreated spectra were used for developing NIRS calibration models via partial least squares (PLS) regression. Cross and external validation was conducted to test the reliability and accuracy of the calibration equations. The coefficients of determination (R²) in external validation were 0.96, 0.90, 0.71, 0.91, 0.91, and 0.73 for oil content, palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid, respectively, whereas the residual prediction deviations (RPD) were 3.7, 2.9, 2.8, 3.4, 3.3, and 2.6, respectively. These results indicated that NIRS successfully determined the oil content and fatty acid composition and the developed NIRS models have great potential for rapid and nondestructive determination of the fruit oil content and fatty acid composition in S. paniculata