Determination of iodine value and acid value of red fruit oil by infrared spectroscopy and multivariate calibration

A rapid method for the quantitative determination of iodine value (IV) and acid value (AV) of red fruit oil (RFO) using FTIR spectroscopy and multivariate calibration of partial least square (PLS) is described. A calibration standard was developed using a series of RFO subjected to thermal treatment at without heating (ambient temperature); 100°C, 150°C, 180°C, 200°C and 300°C, respectively. Based on optimization processes, the FTIR spectra of RFO samples were measured in the frequency region of 1080 - 1114 cm^-1 for IV determination, and at frequency region of 1731 - 1762 cm^-1 for AV determination. PLS calibration model was developed for the prediction of IV and AV in RFO samples. The relationship between actual values of IV and AV as determined using AOCS method and FTIR predicted value as determined with PLS calibration model show a close relationship with coefficient of determination (R2) of 0.998 for IV and 0.998 for AV. The values of standard error of calibration were 0.70% for IV determination and 0.49% for AV using FTIR spectroscopy. This study concludes that ATR- FTIR spectra can be used to determine the IV and AV values of RFO. The developed method is simple, rapid with a total analysis time per sample of less than 2 min, and environmentally friendly.