Monitoring of heat‐induced degradation of edible oils by proton NMR

The degradation process of edible oils of very different nature, submitted to 190 °C with aeration, is studied by means of ¹H nuclear magnetic resonance (NMR). In this study, no primary oxidation products, such as hydroperoxides, are detected, the signals of aldehydes being the first to be observed in the ¹H NMR spectra. Differences between this degradation process and those occurring at 70 °C with aeration or under microwave action are discussed, not only in relation to the degradation rate of the different acyl groups, but also in relation to the nature and proportions of some of the degradation products generated. Oils rich in oleic acyl groups are not only more resistant to degradation than oils rich in linoleic and linolenic acyl groups, but also produce lower proportions of toxic aldehydes.     

Nanopatterned UV curable hydrogels for biomedical applications

With an increasing use of emerging patterning technologies such as UV-NIL in biotechnological applications there is at the same time a raising demand for new material for such applications. Here we present a PEG based precursor mixed with a photoinitiator to make it UV sensitive as a new material aimed at biotechnological applications. Using HSQ patterned quartz stamps we observed excellent pattern replication indicating good flow properties of the resist. We were able to obtain imprints with <20 nm residual layer. The PEG based resist has hydrogel properties and it swelling in water was observed by AFM.     

Interface‐Assisted Sign Inversion of Magnetoresistance in Spin Valves Based on Novel Lanthanide Quinoline Molecules

Molecules are proposed to be an efficient medium to host spin‐polarized carriers, due to their weak spin relaxation mechanisms. While relatively long spin lifetimes are measured in molecular devices, the most promising route toward device functionalization is to use the chemical versatility of molecules to achieve a deterministic control and manipulation of the electron spin. Here, by combining magnetotransport experiments with element‐specific X‐ray absorption spectroscopy, this study shows the ability of molecules to modify spin‐dependent properties at the interface level via metal–molecule hybridization pathways. In particular, it is described how the formation of hybrid states determines the spin polarization at the relevant spin valve interfaces, allowing the control of macroscopic device parameters such as the sign and magnitude of the magnetoresistance. These results consolidate the application of the spinterface concept in a fully functional device platform.     

Oxidation process of oils with high content of linoleic acyl groups and formation of toxic hydroperoxy‐ and hydroxyalkenals. A study by 1H nuclear magnetic resonance

The oxidation process of sunflower and corn oils at 70 °C with circulating air has been studied by means of ¹H nuclear magnetic resonance (NMR). The changes produced in the two oils are compared not only in relation to the rate of degradation of acyl groups but also with reference to both the rate of formation and degradation of primary oxidation products as well as the rate of formation of secondary oxidation products such as aldehydes. Special attention is paid to the evolution of the different kinds of aldehydes formed throughout the process. The great ability of these oils to produce geno‐ and cytotoxic aldehydes under the above conditions is proved. Moreover, peroxide and anisidine values of corn oil throughout its oxidation process have also been determined and the results obtained have been compared with those provided by the ¹H NMR spectra, showing good agreement. Copyright © 2005 Society of Chemical Industry     

Formation of hydroperoxy‐ and hydroxyalkenals during thermal oxidative degradation of sesame oil monitored by proton NMR

The usefulness of ¹H nuclear magnetic resonance (NMR) for studying oil oxidation processes was tested. Refined sesame oil was submitted to oxidative conditions at 70 °C with circulating air, and the status of the sample was studied daily by ¹H NMR. This technique permits the determination of the proportions of the acyl groups in the oil throughout the oxidation process and, at the same time, allows monitoring of the formation and degradation of primary oxidation compounds, as well as of the formation of secondary oxidation products. Generation of the geno‐ and cyto‐toxic oxygenated aldehydes 4‐hydroxy‐, 4‐hydroperoxy‐ and 4,5‐epoxy‐trans‐2‐alkenal was proved.     

Rapid simultaneous determination by proton NMR of unsaturation and composition of acyl groups in vegetable oils

¹H NMR spectra of 66 samples of edible oils from 14 different botanical origins were acquired. Assignment of signal spectra to the different types of hydrogen atoms was made and the areas of the signals determined. Considering that the area of the signals of the spectra is proportional to the number of hydrogen atoms of each type in the sample, it is possible to calculate not only the iodine value, but also the proportion of different acyl groups from the data. Determination of both parameters requires only a few minutes and one spectroscopic run. Classical methodology however, requires two separate wet methods for determining the unsaturation degree (iodine value) and the proportions of different acyl groups; both of them involve chemical transformations of the sample and considerable time and cost. Determination of acyl group proportions in samples by ¹H NMR, which was validated with mixtures of standard triglycerides, provides accurate results and is able to detect small differences between samples of very similar composition.     

1H nuclear magnetic resonance as a fast tool for determining the composition of acyl chains in acylglycerol mixtures

Several samples containing different proportions of standard compounds such as tristearin, triolein, trilinolein, and trilinolenin, covering a broad range of compositions, some similar to those of edible oils, were prepared by weight. The ¹H nuclear magnetic resonance (NMR) spectra of these samples were recorded and their signals were assigned. It was shown that concentrations of linolenic acyl groups close to 0.4% or higher can be detected by this technique. The area of 5 discrete proton signals of the spectrum was determined. Considering the ratio between this area and the concentration of the corresponding types of hydrogen atoms in the sample, equations calculating the proportions of the acyl groups were deduced. The high level of agreement between data coming from ¹H NMR spectra and data obtained by weight shows the usefulness of this methodology. In addition, it has the advantage that it is very fast and simple in comparison with the classical methods, and does not require a chemical modification of the sample. For this reason, the described method constitutes a valuable alternative for the determination of the proportions of different acyl groups in acylglycerol mixtures, such as, for example, oils and fats.     

Interactions between arbuscular mycorrhizal fungi and Trichoderma harzianum and their effects on Fusarium wilt in melon plants grown in seedling nurseries

BACKGROUND: Biological control through the use of Trichoderma spp. and arbuscular mycorrhizal fungi (AMF) could contribute to a reduction of the inputs of environmentally damaging agrochemical products. The objective of this study was to evaluate the interactions between four AMF (Glomus intraradices, Glomus mosseae, Glomus claroideum and Glomus constrictum) and Trichoderma harzianum for their effects on melon plant growth and biocontrol of Fusarium wilt in seedling nurseries. RESULTS: AMF colonisation decreased fresh plant weight, which was unaffected by the presence of T. harzianum. Dual inoculation resulted in a decrease in fresh weight compared with AMF‐inoculated plants, except for G. intraradices. AMF colonisation level varied with the AM endophyte and was increased by T. harzianum, except in G. mosseae‐inoculated plants. Negative effects of AMF on T. harzianum colony‐forming units were found, except with G. intraradices. AMF alone were less effective than T. harzianum in suppressing disease development. Combined inoculation resulted in a general synergistic effect on disease control. CONCLUSION: Selection of the appropriate AMF species and its combination with T. harzianum were significant both in the formation and effectiveness of AM symbiosis and the reduction of Fusarium wilt incidence in melon plants. The combination of G. intraradices and T. harzianum provided better results than any other tested. Copyright © 2009 Society of Chemical Industry