Application of NIR Reflectance Spectroscopy on Determination of Moisture Content of Peanuts: A Non Destructive Analysis Method

Abstract

NIR spectroscopy was used to measure the moisture content of Virginia and Valencia type in-shell peanuts. Peanuts were conditioned to various moisture levels between 7 and 26 % (wet basis) and the moisture content verified using a standard oven method on a sub-sample of each level. The various moisture levels were separated as calibration and validation sets of samples. NIR absorption spectra data from 400 to 2500 nm were collected from peanuts within the calibration and validation sample sets. Measurements were obtained on 30 replicates within each moisture level. Spectral data were mathematically treated to get its derivative function. Partial Least Square (PLS) analysis was performed on the calibration set and models were developed using the raw spectral data and its derivative function data. These models were used to predict the in-shell moisture content of peanuts in the validation sample set. The Standard Error of Calibration (SEC) and R2 of the calibration models were calculated to select the best calibration model. Predicted and reference moisture contents were compared. Relative Percent Deviation (RPD) and Standard Error of Prediction (SEP) were calculated to validate the calibration models