Industrial validation of fourier transform infrared trans and lodine value analyses of fats and oils

Abstract

A Fourier transform infrared (FTIR) edible oil analysis package designed to simultaneously analyze for trans content, cis content, iodine value (IV), and saponification number (SN) of neat fats and oils by using calibrations based on pure triglycerides and derived by application of partial-least-squares (PLS) regression was assessed and validated. More than 100 hydrogenated rapeseed and soybean samples were analyzed by using the edible oil analysis package as well as the newly proposed modification of the AOCS IR trans method with trielaidin in a trans-free oil as a basis for calibration. In addition, ~1/3 of the samples were subsequently reanalyzed by gas chromatography (GC) for IV and trans content. The PLS approach predicted somewhat higher trans values than the modified AOCS IR method, which was traced to a combination of the inclusion of trilinolelaidin in the calibration set and the effects of baseline fluctuations. Eliminating trilinolelaidin from the triglyceride standards and the use of second-derivative spectra to remove baseline fluctuations produced excellent concurrence between the PLS and modified AOCS IR methods (mean difference of 0.61% trans). Excellent internal consistency was obtained between the IV and cis and trans data provided by the edible oil analysis package, and the relationship was close to that theoretically expected [IV = 0.86 (cis + trans)]. The IV data calculated for the GC-analyzed samples matched the PLS IV predictions within 1 IV unit. The trans results obtained by both IR methods were linearly related to the GC data; however, as is commonly observed, the GC values were significantly lower than the IR values, the GC and IR data being related by a slope factor of 0.88, with an SD of ~0.80. The concurrence between the trans data obtained by the two FTIR methods, and between the FTIR and GC-IV data, as well as the internal consistency of the IV, cis and trans FTIR predictions, provides strong experimental evidence that the edible oil analytical package measures all three variables accurately. JAOCS 75, 33-39 (1998).

Extinguishment of Cooking Oil Fires by Water Mist Fire Suppression Systems

“…These new components were produced due to the hydroperoxidation of the double bonds in the cooking oil. In the 1725 cm -1 to 1600 cm -1 spectral region (see Figure 6b), a shoulder appeared at wavenumber 1689 cm -1 in the oil sampled at 350 o C. This represents a typical carbonyl double bond of saturated aldehydes, such as hexanal generated by degradation of hydroperoxides [19]. In the trans region, 1050 to 900 cm -1 (see Figure 6c), there was a bimodal band/double peak at 997 cm -1 and 972 cm -1 that is a characteristic of trans double bonds generated by the collapse of hydroperoxides.…”

“…As shown in Figure 6a, a strong and broad peak of associated O-H groups appeared in the region of 3700 to 3100 cm -1 with a maximum at ~3430 cm -1 . This band indicates that hydroperoxides and hydroperoxide-degradation products, such as low molecular weight acids, alcohols, aldehydes and ketones, were formed in the heated oil [19]. These new components were produced due to the hydroperoxidation of the double bonds in the cooking oil.…”

“…These features may result from the presence of β-unsaturated aldehydes in the degraded fatty acid chains that are still bound to glycerol. Most of the new components produced in the oil during heating period, such as shortchain alcohols, aldehydes and acids, have relatively low boiling points and low auto-ignition temperatures, compared with the parent triglycerides [19,20]. New components, such as glycerol and mono-and di-glycerides, produced by hydrolytic degradation due to the discharge of water mist into overheated oil could accumulate in the oil because of their relatively high boiling points [19,20].…”

“…Most of the new components produced in the oil during heating period, such as shortchain alcohols, aldehydes and acids, have relatively low boiling points and low auto-ignition temperatures, compared with the parent triglycerides [19,20]. New components, such as glycerol and mono-and di-glycerides, produced by hydrolytic degradation due to the discharge of water mist into overheated oil could accumulate in the oil because of their relatively high boiling points [19,20]. These components can undergo further hydrolysis in the hot oil to produce acrolein that has a low boiling point and a low auto-ignition temperature [19][20][21][22][23].…”

“…New components, such as glycerol and mono-and di-glycerides, produced by hydrolytic degradation due to the discharge of water mist into overheated oil could accumulate in the oil because of their relatively high boiling points [19,20]. These components can undergo further hydrolysis in the hot oil to produce acrolein that has a low boiling point and a low auto-ignition temperature [19][20][21][22][23]. Therefore, after undergoing a certain period of heating and suppression, the cooking oil has a strong propensity for re-ignition due to the change in oil compositions.…”