Rapid FTIR determination of water, phenolics and antioxidant activity of olive oil

Abstract

A rapid Fourier transformed infrared (FTIR) attenuated total reflectance (ATR) spectroscopic method was applied to the determination of water content (WC), total phenol amount (TP) and antioxidant activity (ABTS .þ ) of virgin olive oils (VOO) and olive oils. Calibration models were constructed using partial least squares regression. Oil samples with WC ranging from 289 to 1402 mg water/kg oil, with TP from 46 to 877 mg gallic acid/kg oil and with ABTS .þ from 0 to 5.7 mmol Trolox/kg oil were considered for chemometric analysis. Better results were obtained when selecting suitable spectral ranges; in particular, from 2260 to 1008 cm À1 for WC, from 3610 to 816 cm À1 for TP and from 3707 to 1105 cm À1 for ABTS .þ . Satisfactory LOD values by the FTIR-chemometric methods were achieved: 9.4 (mg/kg oil) for WC; 12.5 (mg gallic acid/kg oil) for TP, and 0.76 (mmol Trolox/kg oil) for ABTS .þ . The evaluation of the applicability of these analytical approaches was tested by use of validation sample sets (n ¼ 16 for WC, n ¼ 11 for TP and n ¼ 14 for ABTS) with nearly quantitative recovery rates (99-114%). The FTIR-ATR method provided results that were comparable to conventional procedures. Practical applications:The presented method is based on ATR-FTIR in combination with multivariate calibration methodologies and permits a simultaneous evaluation of important quality parameters of VOO (WC, TP and ABTS .þ ). This approach represents an easy and convenient means for monitoring olive oil quality with the advantage of ease of operation, speed, no sample pretreatment and no consumption of solvents. The data obtained with this method are comparable to those obtained using the official reference method. Therefore, the technique is highly plausible as an alternative to the standard procedure for routine analysis or control at-line of production processes.

Measurement of antioxidant activity

“…HPLC-TEAC provides an efficient and rapid method for separation and identification of bioactive compounds from the source material (Gong, Plander, Xu, Simandi, & Gao, 2011;Raudonis, Bumblauskiene, Jakstas, Pukalskas, & Janulis, 2010). Better sensitivity and precision of TEAC assay can be achieved when coupled with other detection techniques, such as amperometric (Chan-Eam, Teerasong, Damwan, Nacapricha, & Chaisuksant, 2011;Milardovic et al, 2007) and FTIR (Cerretani et al, 2010), among others. Many of these modified TEAC assays employ online enzymatic generation of ABTS •+ , especially those using continuous flow systems.…”

Prediction of various chemical parameters of olive oils with Fourier transform infrared spectroscopy

“…4b) and the statistical values (Table 1) are quite promising with a high regression coefficient for calibration of 0.99 and the crossvalidation value (0.74). According to another study from the literature (Mailer, 2004), NIR spectroscopy achieved a marginal success in the determination of the TPC while Cerretani et al (2010) obtained promising results for the prediction of total phenol with FTIR spectroscopy.…”

Improving the determination of moisture in edible oils by FTIR spectroscopy using acetonitrile extraction

“…The determination of moisture is no exception, and a variety of approaches have been taken to determine moisture in edible oils by FTIR spectroscopy, from simplistic to more sophisticated, the latter focusing more on the accurate determination of lower moisture levels and attempting to account for matrix effects. FTIR spectroscopy in conjunction with the attenuated total reflectance (ATR) technique was applied to the determination of moisture in crude palm oil (Che Man and Mighani, 2000), palm oil derived soaps (Rohman and Che Man, 2009), and olive oil (Cerretani et al, 2010). These applications involved the development of product-specific partial-least-squares (PLS) calibration models, requiring extensive calibration effort, while the inherently short pathlengths associated with ATR accessories limit the sensitivity of the methods.…”