Ali Reza Fardin-Kia

Separation of Fatty Acid Methyl Esters by GC-Online Hydrogenation × GC

The separation of fatty acid methyl esters (FAME) provided by a 200 m × 0.25 mm SLB-IL111 capillary column is enhanced by adding a second dimension of separation ((2)D) in a GC × GC design. Rather than employing two GC columns of different polarities or using different elution temperatures, the separation in the two-dimensional space is achieved by altering the chemical structure of selected analytes between the two dimensions of separation. A capillary tube coated with palladium is added between the first dimension of separation ((1)D) column and the cryogenic modulator, providing the reduction of unsaturated FAMEs to their fully saturated forms. The (2)D separation is achieved using a 2.5 m × 0.10 mm SLB-IL111 capillary column and separates FAMEs based solely on their carbon skeleton. The two-dimensional separation can be easily interpreted based on the principle that all the saturated FAMEs lie on a straight diagonal line bisecting the separation plane, while the FAMEs with the same carbon skeleton but differing in the number, geometric configuration or position of double bonds lie on lines parallel to the (1)D time axis. This technique allows the separation of trans fatty acids (FAs) and polyunsaturated FAs (PUFAs) in a single experiment and eliminates the overlap between PUFAs with different chain lengths. To our knowledge, this the first example of GC × GC in which a chemical change is instituted between the two dimensions to alter the relative retentions of components and identify unsaturated FAMEs.

Use of the Chloroplast Gene ycf1 for the Genetic Differentiation of Pine Nuts Obtained from Consumers Experiencing Dysgeusia

Pine nuts are a part of traditional cooking in many parts of the world and have seen a significant increase in availability/use in the United States over the past 10 years. The U.S. Food and Drug Administration (US FDA) field offices received 411 complaints from U.S. consumers over the past three years regarding taste disturbances following the consumption of pine nuts. Using analysis of fatty acids by gas chromatography with flame ionization detection, previous reports have implicated nuts from Pinus armandii (Armand Pine) as the causative species for similar taste disturbances. This method was found to provide insufficient species resolution to link FDA consumer complaint samples to a single species of pine, particularly when samples contained species mixtures of pine nuts. Here we describe a DNA based method for differentiating pine nut samples using the ycf1 chloroplast gene. Although the exact cause of pine nut associated dysgeusia is still not known, we found that 15 of 15 samples from consumer complaints contained at least some Pinus armandii, confirming the apparent association of this species with taste disturbances.

Rapid screening of commercial extra virgin olive oil products for authenticity: Performance of a handheld NIR device

The performance of a handheld near infrared spectroscopic device was evaluated for the rapid screening of extra virgin olive oil for authenticity. Without any sample preparation, the spectra of authentic reference extra virgin olive oils, refined olive oils, potential adulterants consisting of edible oils, extra virgin olive oil spiked with adulterants, and a total of 93 commercial olive oil products were each rapidly (10 s) measured in the transflection mode. The univariate conformity index and the multivariate supervised soft independent modeling of class analogy classification tools were used to differentiate among the various oils investigated. Out of 88 commercial products labeled extra virgin olive oil, 39 (44%) were classified as belonging to the class of authentic extra virgin olive oils. The results were compared to those recently reported for analyses carried out with a benchtop Fourier transform-near infrared spectrometer.

CHAPTER 7:Analysis of Conjugated and Other Fatty Acids

Analysis of conjugated fatty acids (CFA) is both convenient and challenging. Convenient, because CFA have a unique double bond system with chemical properties not common to other fatty acids (FA) that can be used for their selective analysis. Challenging, because CFA exist in many isomeric forms just as other unsaturated FAs, and most FAs have different biological properties. Therefore, the choice of method used depends on whether a selective or a complete analysis of all FAs in any given matrix is desired. For routine analysis, gas chromatography (GC) as their fatty acid methyl esters (FAME) is the method of choice. The choice of the separation column depends on the FA complexity of the matrix and how well CFA isomers separate from other FAMEs and among themselves. Currently, there is no single GC method to analyse all geometric/positional isomers of FAMEs that might occur in natural fats or synthetic mixtures. Analytical techniques can be combined considering the complexity of the matrix, the selectivity of GC columns, choice of supportive techniques, and keeping analyses per sample to a minimum. In this review, the benefits and limitations of different GC columns are evaluated and supported by selective techniques. Combinations of methods are suggested to obtain a comprehensive analysis of as many conjugated and non-conjugated FAs as possible.