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Exposure of beer to light results in the formation of undesirable flavours or complete spoilage. Photo-damaged beerhas a specific, so-called skunky or light-struck flavour (LSF). The compound responsible for LSF is 3-methylbut-2-ene-1-thiol (MBT). Riboflavin (RF) plays a key role in the formation of MBT. It absorbs light in the blue part of thespectrum and transfers excitation energy to isohumulones. This process is accompanied by the decomposition of RF,which causes a decrease in the absorbance of the sample at 450 nm. The decomposition is directly related to theformation of LSF. In this study, the decrease in absorbance associated with the defined illumination of model and realbeer directly in commercial bottles was measured. The decrease in absorbance correlated with the decrease in RFconcentration and the formation of LSF detected by the sensory panel. The Light-Struck Flavour Susceptibility Indexwas introduced as a rate of the beer susceptibility to light degradation and the formation of LSF.

Classical molecular simulation methods were used for a detailed structural description of zirconium 4-sulfophenylphosphonate and zirconium phenylphosphonate 4-sulfophenylphosphonates with general formula Zr(HOSCHPO) (CHPO) ·yHO (x = 0.7-2; y = 0 or 2). First, models describing the structure of zirconium 4-sulfophenylphosphonate (x = 2) were calculated for the hydrated (y = 2) and dehydrated (y = 0) compounds. Subsequently, models for two mixed zirconium phenylphosphonate 4-sulfophenylphosphonates (x = 1.3 and 0.7) were calculated. Optimized models suggest that the presence of water molecules between sulfo groups creates a water-sulfonate layer with a system of hydrogen bonds. We suppose that this arrangement is the reason for a higher proton conductivity of the hydrated samples compared to dehydrated samples. When the water molecules are removed, a small decrease in the basal spacing (around 0.06 Å) is observed. This behavior is confirmed by the simulated models, where no significant changes in the structure on dehydration were observed except the absence of the water molecules and a lower number of hydrogen bonds between two adjacent sulfonate sheets. Due to the good crystallinity of the samples and the presence of sharp non-basal peaks in their X-ray diffraction patterns, Miller indices of the non-basal peaks in the diffraction patterns calculated from the models can be compared with those found in the experimental data. This allowed us to precisely describe for example (15 5-2) planes, from which mutual distances of the phenyl rings were determined to be 2.62 Å. Graphical Abstract Detailed ball and stick view into the interlayer structure of ZrSPhP1.3.

A structural arrangement of sodium, copper, and iron cations intercalated in zirconium 4-sulfophenylphosphonate (ZrSPhP), as a potential material for ion-exchange applications, was suggested by molecular simulation methods. The calculations were focused on a detailed description of the influence of individual cations on mutual positions of the ZrSPhP layers and arrangement of sulfo groups and water molecules. Results of the calculations were compared with experimental measurements (X-ray diffraction, thermogravimetric analysis, and chemical analysis). A very good agreement between the experimental and calculated basal peaks was achieved, and the correspondence for the nonbasal peaks was improved by cell refinement. A model with sodium cations shows that the cations remain immersed between the sulfo groups of the individual sulfo sheets and that the water molecules are homogeneously spread in the interlayer. The copper cations are placed in the interlayer more homogeneously and are shifted from the central part of the interlayer space to the positions close to the sulfo sheets. The iron cations are positioned in the middle of the interlayer. The water molecules remain randomly scattered in the interlayer space, and the sulfo groups are connected with the intercalated cations and water molecules by nonbond interactions.

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