Detection of Sludge Contamination in Crude Palm Oil Using Dielectric Spectroscopy

Abstract. Degradation and deterioration of crude palm oil (CPO) is a major concern in the palm oil industry because it could affect the quality of palm oil products. The development of rapid and non-destructive measuring techniques is needed to enhance the efficiency of palm oil quality monitoring. This study used dielectric spectroscopy to detect possible sludge contamination in CPO. Dielectric properties of CPO were measured at different temperatures and sludge contamination levels using a liquid dielectric test fixture that was connected to an impedance analyzer with frequencies ranging from 3 to 30 MHz. The variations in dielectric properties were analyzed using ANOVA and Duncan’s multiple range test. Principal component regression (PCR) and partial least squares (PLS) analysis were used for model development to predict sludge contamination. The results showed that there was a significant difference in dielectric constant as the temperature increased from 28°C to 55°C (p < 0.0001). The dielectric constant also increased from 3.01 to 63.53 with increasing contamination levels. Generally, there were significant differences between the dielectric constants of pure and contaminated CPO (p < 0.0001). The PCR and PLS calibration models showed good prediction ability of sludge contamination at different temperature levels. The classification of sludge contamination yielded very strong correlation, with r² values ranging from 0.91 to 0.98. The best result was obtained at 28°C with the lowest value of standard error cross-validation (SECV) of 1.04%. The results showed that dielectric spectroscopy has strong potential for CPO quality monitoring.