Interference of Saturated Fats in the Determination of Low Levels of trans Fats (below 0.5%) by Infrared Spectroscopy

Abstract

The mandate to label food products with the content of total trans fatty acids has led to an increase in demand for sensitive and accurate methodologies for the rapid quantitation of trans fats. Unfortunately, the latest official infrared (IR) spectroscopic method lacks the required sensitivity. A more sensitive IR procedure that requires the measurement of the height of the second derivative (2D) of the trans absorption band at 966 cm -1 was recently proposed; however, a reported inconsistency at low trans levels between GC (0% of total fat) and IR (1.2% of total fat) results for a fully hydrogenated vegetable oil could not be reconciled, and triggered further investigations. For the first time, we recognize and report the presence of weak interference bands (962-956 cm -1 ) attributed to saturated fats in the IR spectra of trans fats; these interference bands have an adverse impact on the sensitivity and accuracy of the IR determination at low trans levels (£0.5% of total fat). Therefore, weak spectral features observed at energies below the one expected for trans bands (966 cm -1 ) in test samples high in saturated fat (coconut oil and cocoa butter) must not be mistaken for trans bands. Tristearin TL Trilaurin TM Trimyristin TP Tripalmitin TA Triarachidin Since trans fat labeling requirements became mandatory in the US, Canada and many other countries [1], there has been an urgent need for accurate analytical methodologies that would facilitate the verification of compliance with the various regulations. The determination of total trans fatty acids by IR has been a widely used procedure [2] that has been standardized [3-6]. Its importance stems from the fact that the C-H out-of-plane deformation band observed at 966 cm -1 is uniquely characteristic of isolated double bonds with trans configuration. These double bonds are found in trans-monoenes, and in methylene-interrupted and non-methylene-interrupted trans,trans-dienes, mono-trans-dienes, and mono-trans-trienes. All these different fatty acids exhibit that same absorption band at 966 cm -1 regardless of chain length or position of the isolated trans double bond. Thus measuring the intensity of the absorption of the trans band effectively adds up all the different fatty acids containing isolated M. M. Mossoba (&) Food and Drug Administration, Abbreviations IR Infrared HSBO Hydrogenated soybean oil TS

Assessment of Trans Fatty Acid Level in French Fries from Various Fast Food Outlets in Karachi, Pakistan

“…PLS is a multivariate analysis technique that accurately measures components in the presence of interfering absorptions [14]. The trans values of the samples were estimated with the PLS calibration model (Fig.…”

“…Two different sampling times on the same day were selected to monitor the quality of frying oil. Oil that is reused many times for deep frying undergoes changes in physical characteristics and chemical composition, affecting the quality of the fried foods [14]. Due to repeated use of the same oil, the color of some of the oil samples changed from light to dark.…”

“…A total of 32 scans at a resolution of 4 cm −1 were collected. The reference background material used was air [14]. The cell was warmed to about 65 ± 2 °C in order for standards and samples to remain melted during analysis.…”

Quantitative Gas Chromatographic Method for the Analysis of cis and trans Fatty Acid in Margarines

“…The association between dietary consumption of some cis/trans FAs and increased risk of cardiovascular disease has led to the implementation in several countries of new regulations requiring the declaration of FAs including TFA content on the labels of dietary fats and oils products (Wassell & Young 2007). Accordingly, accurate methods for measurement of cis and trans FAs with adequate sensitivity and accuracy are needed to achieve those objectives (Backholer & Peeters 2012;Mossoba et al 2007).…”

Application of a Portable Handheld Infrared Spectrometer for Quantitation of trans Fat in Edible Oils

“…Established IR methods such as AOCS Cd 14d-99 and AOAC 2000.10 use band area at 966 cm -1 to measure trans fatty acid content, although these methods have limits of quantitation around 5% trans. This limitation has been overcome by a new methodology which measures the height of the negative second derivative of the trans absorbance band [4] which is sensitive below 2% trans.…”