Interlaboratory study on lipid oxidation during accelerated storage trials with rapeseed and sunflower oil analyzed by conjugated dienes as primary oxidation products

Accelerated storage tests are frequently used to assess the oxidative stability of foods and related systems due to its reproducibility. Various methods and experimental conditions are used to measure lipid oxidation. Differences between laboratories make it necessary to determine the repeatability and reproducibility of oxidation tests performed under the same conditions. The objective of the present interlaboratory study was to evaluate the outcome of a storage test for two different bulk oils, sunflower oil (SFO) and rapeseed oil (RSO), during a period of 9 weeks at 20°C, 30°C, 40°C, and 60°C. Sixteen laboratories were provided with bottled oils and conducted the storage tests according to a detailed protocol. Lipid oxidation was monitored by the formation of conjugated dienes (CD) and the activation energy (E_a) was determined for comparative purposes and statistically evaluated. An increase in CD formation was observed for both oils when the storage temperature was increased in all laboratories. The E_a,1 ranged from 47.9 to 73.3 kJ mol⁻¹ in RSO and from 27.8 to 62.6 kJ mol⁻¹ in SFO, with average values of 58.2 and 46.8 kJ mol⁻¹, respectively. The reproducibility coefficients were 10.9% and 18.2% for RSO and SFO, respectively. Practical applications: In order to compare results on oxidative stability of foods derived from different studies, the reproducibility of storage tests and methods employed to evaluate the oxidation level should be considered. This study provides fundamental data on the reproducibility of lipid oxidation under accelerated storage conditions and defines important parameters to be considered for the conduction of experiments.     

Fast Self-Assembly Dynamics of a β-Sheet Peptide Soft Material

Peptide-based hydrogels are promising biocompatible materials for wound healing, drug delivery, and tissue engineering applications. The physical properties of these nanostructured materials depend strongly on the morphology of the gel network. However, the self-assembly mechanism of the peptides that leads to a distinct network morphology is still a subject of ongoing debate, since complete assembly pathways have not yet been resolved. To unravel the dynamics of the hierarchical self-assembly process of the model β-sheet forming peptide KFE8 (Ac-FKFEFKFE-NH₂)_, high-speed atomic force microscopy (HS-AFM) in liquid is used. It is demonstrated that a fast-growing network, based on small fibrillar aggregates, is formed at a solid–liquid interface, while in bulk solution, a distinct, more prolonged nanotube network emerges from intermediate helical ribbons. Moreover, the transformation between these morphologies has been visualized. It is expected that this new in situ and in real-time methodology will set the path for the in-depth unravelling of the dynamics of other peptide-based self-assembled soft materials, as well as gaining advanced insights into the formation of fibers involved in protein misfolding diseases.     

Selective and Sustainable Production of Sub-terminal Hydroxy Fatty Acids by a Self-Sufficient CYP102 Enzyme from Bacillus Amyloliquefaciens

Enzymatic hydroxylation of fatty acids by Cytochrome P450s (CYPs) offers an eco-friendly route to hydroxy fatty acids (HFAs), high-value oleochemicals with various applications in materials industry and with potential as bioactive compounds. However, instability and poor regioselectivity of CYPs are their main drawbacks. A newly discovered self-sufficient CYP102 enzyme, BAMF0695 from Bacillus amyloliquefaciens DSM 7, exhibits preference for hydroxylation of sub-terminal positions (ω-1, ω-2, and ω-3) of fatty acids. Our studies show that BAMF0695 has a broad temperature optimum (over 70 % of maximal enzymatic activity retained between 20 to 50 °C) and is highly thermostable (T₅₀ >50 °C), affording excellent adaptive compatibility for bioprocesses. We further demonstrate that BAMF0695 can utilize renewable microalgae lipid as a substrate feedstock for HFA production. Moreover, through extensive site-directed and site-saturation mutagenesis, we isolated variants with high regioselectivity, a rare property for CYPs that usually generate complex regioisomer mixtures. BAMF0695 mutants were able to generate a single HFA regiosiomer (ω-1 or ω-2) with selectivities from 75 % up to 91 %, using C12 to C18 fatty acids. Overall, our results demonstrate the potential of a recent CYP and its variants for sustainable and green production of high-value HFAs.     

Monomer Recycling and Repolymerization of Post-Consumer Polyester Textiles

Due to the presence of dyes and additives, textile recycling is challenging, therefore the majority of textile waste is downcycled to low-value products, incinerated or landfilled. In this study, a continuous depolymerization of post-consumer polyester textiles was conducted by alkaline hydrolysis. The degree of depolymerization was assessed and found to be 94 %. After recovering and analyzing the terephthalic acid and ethylene glycol the monomers were successfully polymerized to regain a food grade quality recycled polyethylene terephthalate. The presented recycling approach allows a closed-loop recycling of textiles.     

Gelatinisation and Retrogradation Behaviour of Some Starch Mixtures

Differential scanning calorimetry (DSC) and dynamic rheological measurements were used to characterise the behaviour of potato‐waxy maize, potato‐barley and waxy maize‐barley starch mixtures. Gelatinisation and retrogradation were studied at two starch concentrations, 20% (w/w) and 50% (w/w). In the DSC gelatinisation thermograms of the mixtures it was possible to recognise features of the thermograms of the individual components, indicating that each starch gelatinised independently of the other starch in the mixture. The retrogradation enthalpy was measured in the DSC after four and seven days of storage at 6 °C. The lowest values of retrogradation enthalpy for the mixtures were found for the waxy maize‐barley and potato‐barley mixtures, particularly at 20% starch concentrations and in the ratios 25:75 and 50:50, correspondingly. The retrogradation enthalpy measured for most starch mixtures corresponded to the calculated value, assuming that each starch contributed to the enthalpy according to its proportion in the mixture. Storage and loss moduli were measured for gelatinised starch suspensions during cooling from 90 to 6 °C, and then during a holding period at 6 °C for up to 6 h. The moduli for the mixtures were in most cases in between the values obtained for the individual starches.     

Rational Loading of Linear Multi-Site Receptors with Functional Lanthanide Containers: The Missing Link between Oligomers and Polymers

Although metal-containing organic polymers are becoming essential for modern applications in lighting, catalysis, and electronic devices, very little is known about their controlled metallic loading, which mainly limits their design to empirical mixing followed by characterization and often hampers rational developments. Focusing on the appealing optical and magnetic properties of 4f-block cations, the host–guest reactions leading to linear lanthanidopolymers already display some unexpected dependence of the binding-site affinities on the length of the organic polymer backbone: a drift usually, and erroneously, assigned to intersite cooperativity. Taking advantage of the parameters obtained for the stepwise thermodynamic loading of a series of rigid linear multi-tridentate organic receptors with increasing length, N = 1 (monomer L1), N = 2 (dimer L2), and N = 3 (trimer L3), with [Ln(hfa)3] containers in solution (Ln = trivalent lanthanide cations, hfa⁻ = 1,1,1,5,5,5-hexafluoro-pentane-2,4-dione anion), it is demonstrated here that the site-binding model, based on the Potts–Ising approach, successfully predicts the binding properties of the novel soluble polymer P2 ^N made up of nine successive binding units . An in-depth examination of the photophysical properties of these lanthanidopolymers shows impressive UV→vis downshifting quantum yields for the europium-based red luminescence, which can be modulated by the length of the polymeric chain.     

Highly Tuneable Photochromic Sodalites for Dosimetry,Security Marking and Imaging

Photochromic sodalites are considered for a plethora of possible applications, such as UV indexing and X-ray imaging, but for many of these the materials are yet to be optimized. UV indexing can be improved through incremental adjustment of the activation energy of coloration from 300 to 410 nm through replacement of sulfur with selenium. By combining this and other methods of tuning presented in the literature, the excitation threshold and photochromism color can be tuned independently of one another. The range of possible absorption maxima is expanded to 420–680 nm, or almost the entire visible spectrum. Mixing low-cost and easy-to-synthesize sodalites further broadens the possible range of colors and facilitates development of a unique sodalite mix capable of quantifying the doses of two types of UV radiation simultaneously. Finally, the response to X-rays of these highly tuned sodalites is investigated, and it is found that they can be sensitized to produce clear, high-contrast X-ray images at significantly lower doses of radiation than those required by classic photochromic sodalite, Na₈(AlSiO₄)₆(Cl,S)₂.