Concentrations Of Trans Isomers Research Articles

Highly stable platinum monolith catalyst for the hydrogenation of vegetable oil

In the present work, a novel structured platinum catalyst where the Pt is supported on an anodized aluminum monolith was studied for the hydrogenation of sunflower oil. The catalytic tests were carried out in a monolithic stirred semi-batch reactor at temperatures between 433 and 473 K, and hydrogen pressures from 2.7 to 5.4 atm. The monoliths were prepared using H2PtCl6 and Pt(C5H7O2)2 metal precursors and characterized by temperature programmed reduction, N2 adsorption isotherms, H2 chemisorption, scanning electronic microscopy, inductively coupled plasma-atomic emission spectroscopy, and ultrasound adherence tests. Response surface methodology was used to study the relationship between the process variables and C = C conversion, concentration of trans-isomers and selectivity toward monosaturated (S1) and saturated (S2) fatty acids.The catalysts showed to be active, reaching a conversion of 18% at 120 min. The H2PtCl6 impregnated monolith exhibited low selectivity towards trans-isomer formation, maintaining its initial catalyst activity after 40 consecutive uses, without modifications on S1 and S2. The results indicated that platinum monolith catalysts could be an affordable alternative to commercial Ni catalysts, removing the filtration and bleaching stages, hence reducing the processing costs.

Photo-Isomerization Kinetics of Azobenzene Containing Surfactant Conjugated with Polyelectrolyte.

Ionic complexation of azobenzene-containing surfactants with any type of oppositely charged soft objects allows for making them photo-responsive in terms of their size, shape and surface energy. Investigation of the photo-isomerization kinetic and isomer composition at a photo-stationary state of the photo-sensitive surfactant conjugated with charged objects is a necessary prerequisite for understanding the structural response of photo-sensitive complexes. Here, we report on photo-isomerization kinetics of a photo-sensitive surfactant in the presence of poly(acrylic acid, sodium salt). We show that the photo-isomerization of the azobenzene-containing cationic surfactant is slower in a polymer complex compared to being purely dissolved in aqueous solution. In a photo-stationary state, the ratio between the trans and cis isomers is shifted to a higher trans-isomer concentration for all irradiation wavelengths. This is explained by the formation of surfactant aggregates near the polyelectrolyte chains at concentrations much lower than the bulk critical micelle concentration and inhibition of the photo-isomerization kinetics due to steric hindrance within the densely packed aggregates.

Hydrogenation of plant oil over a palladium catalyst supported on activated diatomite

A possibility of lowering the formation of trans-isomers during hydrogenation of plant oil over a low-loaded palladium catalyst supported on activated diatomite was studied. The comparison to the commercial nickel catalyst led to establish that the activated diatomite is a promising support of the catalyst for hydrogenation of plant oil. Palladium particles of 2–10 nm in size (3–6 nm particles predominated) were shown to be uniformly distributed over the support surface. It was shown experimentally that the Pd catalyst was more active and selective at low temperature than the nickel catalyst to provide two-fold decrease in the concentration of trans-isomers in the hydrogenated fat.

Can concentrations of trans octadecenoic acids in milk fat be used to predict methane yields of dairy cows?

There is a need to develop simple, accurate methods for predicting methane emissions, yields and intensities of dairy cows. Several studies have focussed on the relationship between the concentrations of trans-10 plus trans-11 C18:1 fatty acids in milk fat and methane yield. The aim of the present study was to perform a meta-analysis to quantify relationships between the concentrations of various trans isomers of C18:1 in milk fat and methane emissions (g/day), methane yield (g/kg dry-matter intake) and methane intensity (g/kg energy-corrected milk yield). Data were from seven experiments encompassing 23 different diets and 220 observations of milk fatty acid concentrations and methane emissions. Univariate linear mixed-effects regression models were fitted to the data with the linear term as a fixed effect and with experiment and observation within experiment as random effects. Concentrations of trans-9, trans-10, trans-11 and trans-10 plus trans-11 isomers of C18:1 were poorly related to methane emissions, yields and intensities, with the best relationships being between trans-10 C18:1 and methane emissions (R2 = 0.356), trans-10 C18:1 and methane yield (R2 = 0.265) and trans-10 plus trans-11 C18:1 and methane intensity (R2 = 0.124). The data indicated that the relationships between trans-10 C18:1 and methane metrics were not linear, but were biphasic and better described by an exponential model. However, even exponential models poorly fitted the data. It is concluded that the concentrations of trans isomers of C18:1 have limited potential to accurately predict methane emissions, yields or intensities of dairy cows.

Thermal Deterioration of the Trans-/Cis-Ratio of Bittering Agents of Commercial Beers

The use of reduced isomerised hop extracts to achieve both bitterness and light stability became very popular during the last decade. Changes during storage in four hop extracts and seven commercial lager beers are studied using HPLC and spectrophotometric techniques. The degradation of the iso-α-acids and tetrahydro iso-α-acids as a function of time is represented by the ratio, in percentage, of the sum of trans-isomer concentration to the sum of the cis-isomer concentration (T/C). The results provided conclusive evidence that the gradual decreased of bitterness intensity in beer was due to the degradation of iso-α-acids, notably to the instability of the trans-iso-α-acids. When the beers were stored for 14 days at 45°C the decrease of the T/C average varied from 8.6 to 14.0%, except in lemon beer, in which case, T/C decreased 36.9%. The results allowed us to infer that in open storage and/or warm conditions the deterioration of beer was critical above 35°C. On the other hand, the results showed that tetrahydro iso-α-acids remained unaltered.

Complex chromatographic determination of the adulteration of dairy products: A new approach

A new approach to complex chromatographic determination of the adulteration of dairy products was proposed, based on the determination of not only the total fatty acid composition but also the composition of the sterol fraction and the concentration of trans-isomers of fatty acids. Procedures for the chromatographic identification of low-fat dairy products were developed, including the extraction of a water-milkalcohol emulsion with a hexane-ether mixture followed by the chromatographic determination of the sterol fraction and trans-isomers.

Dynamics of photoinduced dichroism and birefringence in optically thick azopolymers

Dynamics of photoinduced dichroism and birefringence have been studied experimentally and theoretically (with the help of the Dumont model) by using some comb-shaped azopolymers. It is shown that the dynamics of trans-isomer concentration and their angular distribution anisotropy can be restored from the experimentally found dichroism dynamics, with the concentration and anisotropy being averaged over the thickness for optically thick samples. At the initial stage of photoinduced anisotropy when the active role of the polymer matrix can be neglected, the experimental time dependence of dichroism is shown to comply well with the Dumont model even if the orientation memory is neglected, provided that only a part of trans-isomers participates in trans-isomerisation.

Dynamics of optically induced dichroism (theory and experiment)

The dynamics of photoinduced dichroism has been experimentally and theoretically (on the basis of the Dumont model) investigated in several ridge-shaped azopolymers. This dynamics was used to reconstruct the dynamics of change in the concentration of trans-isomers and anisotropy of their angular distribution, thickness-averaged for optically thick samples. It is shown that, at the beginning of illumination, the experimental dependences of dichroism are described well within the Dumont model, even disregarding the orientational memory, on the assumption that only some part of trans-isomers are involved in trans-cis isomerization.

Effects of dietary n-6:n-3 fatty acid ratio on feed intake, digestibility, and fatty acid profiles of the ruminal contents, liver, and muscle of growing lambs

This study investigated the effect of modifying the n-6:n-3 fatty acid ratio (FAR) of diets using linseed, soybean, and cottonseed oils on apparent digestibility, ruminal fermentation characteristics, growth performance, key circulating hormones, and the fatty acid profile of ruminal digesta, liver, and fore-shank muscle of growing lambs fed a high concentrate diet. Forty individually housed Katadhin Dorper lambs (average of 20.0 kg of BW) were fed Bermudagrass hay in ad libitum amounts and concentrates at 3.7% of BW daily. The concentrate contained 68.9% corn, 23.8% soybean meal, 3.3% limestone, and 4.0% oil supplements (DM basis). The treatments consisted of dietary n-6:n-3 FAR of 2.3:1, 8.8:1, 12.8:1, and 15.6:1. After feeding for 35 d in metabolism crates, lambs were slaughtered 15 h after feeding, and samples of ruminal digesta, blood, liver, and foreshank tissue were collected. Increasing dietary n-6:n-3 FAR did not affect the intake of DM nor the apparent digestibility of DM, ether extract, NDF, or ADF, but did increase apparent digestibility of CP (linear, P < 0.05). Concentrations of ruminal butyrate increased linearly (P < 0.05) with increasing dietary n-6:n-3 FAR, whereas the valerate concentration decreased linearly (P < 0.001). Concentrations of plasma insulin and IGF-I were not affected by dietary n-6:n-3 FAR. Concentrations of C18:3n-3 increased linearly (P < 0.001), whereas that of C18:2n-6 decreased linearly (P < 0.001) in ruminal digesta with decreasing dietary n-6:n-3 FAR. Concentrations of transisomers of fatty acids in ruminal digesta did not change. Proportions of C18:0 in liver and foreshank muscle were unchanged by diet. The proportion of trans11 C18:1 and cis-9 trans11 CLA decreased (P < 0.05) in liver but increased (P < 0.05) in foreshank muscle as dietary n-6:n-3 FAR decreased. Proportions of all measured n-3 fatty acids were greater in liver when diets contained more C18:3n-3 from linseed oil. By decreasing the dietary n-6:n-3 FAR, the proportions of n-6 fatty acids in foreshank muscle decreased dramatically; specifically, C18:2n-6 decreased linearly (P < 0.001) from 28.0 to 16.5% and C20:4n-6 decreased linearly (P < 0.001) from 14.7 to 8.6%. Although feeding a diet that contained more n-3 fatty acids increased the n-3 fatty acid concentration of muscle, the ratio of PUFA to SFA was decreased.