Enhanced Quantitative Extraction and HPLC Determination of Hop and Beer Bitter Acids

A pleasant and consistent bitterness is an essential flavour attribute of beer. Hop‐derived iso‐α‐acids are largely responsible for beer bitterness and accurate determination of these primary flavour compounds is very important in relation to quality control. The most widely used way to determine beer bitterness is based on spectrophotometry, measuring the absorbance of an iso‐octane extract of acidified beer. However, this approach is far from specific as it measures all of the extracted compounds, including non‐bittering principles. For that particular reason, High Performance Liquid Chromatography (HPLC) is increasingly applied for the quantitative determination of hop‐derived iso‐α‐acids and, if present, reduced iso‐α‐acids. However, to obtain accurate data on beer bitterness profiles, both quantitative sample preparation and state‐of‐the‐art HPLC are essential. In this paper, several extraction procedures based on solid phase extraction (SPE) and liquid‐liquid extraction (LLE), respectively, were evaluated and an optimised extraction methodology using H₃PO₄ for sample acidification prior to extraction is presented. The proposed extraction/HPLC methodology allows for the quantitative recovery and analysis of hop‐derived beer bitterness.     

Assessing the origin and fate of Cr, Ni, Cu, Zn, Pb, and V in industrial polluted soil by combined microspectroscopic techniques and bulk extraction methods

The major geochemical forms of Cr, Ni, Cu, Zn, Pb, and V in a soil from an industrial polluted site in the south of Italy were determined by means of synchrotron X-ray microanalytical techniques such as coupled micro-X-ray fluorescence/micro-X-ray diffraction and micro-X-ray absorption near edge structure spectroscopy in combination with bulk extraction methods (sequential extraction procedures, EDTA extractions, and toxicity leaching characteristic procedure tests). Cr, Ni, Zn, and Cu were found in spinel-type geochemical forms (chromite, trevorite, franklinite, zincochromite, and cuprospinel) and often in association with magnetite and hematite. Vwas mainly present as V(V) associated with iron-oxides or in the form of volborthite [Cu3(OH)2V2O7.2H2O]. Pb was speciated as minium (Pb3O4), lanarkite [Pb2O(SO4)], and, in association with Cr(VI), as crocoite (PbCrO4). In general, despite a high total concentration, metals appear to be speciated for the most part as rather insoluble geochemical forms. However, particular attention should be paid to Zn, Cu, V, and Pb that show non-negligible mobilizable fractions. On the basis of the geochemical forms identified, among others, two major former industrial activities were tentatively ascribed as being responsible for the observed major pollution: polyvinyl chloride and cement-asbestos productions.     

Practical application of dynamic temperature profiles to estimate the parameters of the square root model

Optimal experimental design for parameter estimation (OED/PE) is a promising method to improve parameter estimation accuracy and minimise experimental effort in the field of predictive microbiology. In this paper, the OED/PE methodology was applied on two practical examples: the growth of Bacillus cereus and Enterobacter cloacae in liquid whole egg product. Both strains were recovered from samples of a commercial product. The goal of the modelling exercise was to quantify the influence of temperature on bacterial growth. The Baranyi-model for bacterial growth combined with the Ratkowsky square root model to describe temperature dependence was used. Using this model, a temperature step profile was calculated based on the optimal D-criterion. The model was then fitted against the experimental bacterial growth curve measured under the dynamic temperature conditions. This process was repeated until the parameters could be estimated with sufficient accuracy, apparent by the model prediction errors. For B. cereus, prior information could be extracted from the literature, allowing calculating a dynamic temperature profile directly. Two-step profiles were sufficient to obtain a good estimation for the model parameters. No prior information could be found for E. cloacae. Therefore, a limited series of static experiments had to be conducted to obtain usable prior model parameters estimates. Only one dynamic experiment was then needed to achieve a good estimation.     

Treatment of gas-phase methanol in conventional biofilters packed with lava rock

The performance of laboratory scale methanol-degrading biofilters packed with lava rock was checked during almost 1 yr under different conditions. The biomass concentration and biomass adaptation of the inoculum dramatically affected the start-up and the performance of the systems during the first stages of operation. A fast start-up was obtained when using concentrated and adapted inocula, while diluted or non-adapted inocula proved to be much less efficient. The performance of the reactor during long-term operation was significantly affected by the toxic load and moisture content of the gas. Critical loads between 120 and 280 g/m(3)h were reached during different phases of the study. The reactor had a high stability to EBRT changes when working at values between 48.0 and 91.1s, showing little or no negative effect when decreasing the EBRT. Hardly any difference was observed regarding performance when using either a downflow or upflow feed, although slightly better results were obtained when working in a downflow mode.     

Crystallization of model fat blends containing symmetric and asymmetric monounsaturated triacylglycerols

In this study, the crystallization and melting properties of four different fat blends with the same saturated fat content (30%) but with different ratios of symmetric and asymmetric monounsaturated triacylglycerols were investigated using pNMR, DSC and polarized light microscopy. Blends were either palmitic (P) or stearic (S) based, and were combinations of SatOSat‐rich (Sat = saturated, O = oleic) and SatSatO‐rich vegetable oils with high‐oleic sunflower oil. The DSC results demonstrate that there was almost no difference in crystallization mechanism and crystallization rate between the two P‐based blends. Both blends showed a two‐step crystallization, which can be explained by polymorphism. Stop‐and‐return DSC results suggested an initial crystallization into an unstable polymorph followed by polymorphic transition during the crystallization. For the S‐based blends there was a clear difference between the SOS‐rich and the SSO‐rich blend, with a slower crystallization for the SSO‐rich blend. Possibly, this can be explained by fractional crystallization. The microstructure did not differ greatly between the blends. Directly after crystallization, the crystals of the SSO‐rich blend were slightly larger than the crystals of the SOS‐rich blend.     

Structure Determination of the Top‐Loop of the Conserved 3′‐Terminal Secondary Structure in the Genome of Flaviviruses

To what extent small differences in RNA sequences (mutations) can have a profound impact on biology remains an intriguing question. This effect can be studied by using untranslated RNA regions as a model. We have studied the influence of mutations on the structure of an RNA hairpin that occurs in the 3′‐untranslated region (UTR) of Flaviviridae, and is known to have a large impact on the vector dependency of flaviviruses. Three related RNA sequences were studied by NMR spectroscopy. The selected sequences represent each one of the three clusters in the flavivirus genes (mosquito‐borne, tick‐borne, and no‐known‐vector viruses). A new strategy was used to obtain chemical shift signatures of carbonyl atoms in unlabeled uridine nucleobases to characterize their involvement in hydrogen bonding. Clear differences occur in the structures and stacking pattern of the three RNA hairpins. The observed differences cannot be predicted based on sequence analysis. A different biology can be correlated with a different RNA tertiary structure. The underlying biological mechanism, however, remains to be studied.     

Phase Composition During Palm Olein Fractionation and its Effect on Soft PMF and Superolein Quality

Refined palm olein was dry fractionated via three different cooling programs on laboratory-scale fractionation equipment. The enrichment and depletion of the main triacylglycerols in the liquid and solid phase was plotted as a function of the crystallization degree of the oil. It was shown that for the given conditions and palm olein composition, the initial crystals mainly consisted of PPP, diacylglycerols, POP and PLP. At higher crystallization degrees, a sharp viscosity increase in the crystal suspension was primarily related to an obvious decrease of POP but also of POS in the recovered superolein, while the general crystallization rate of the system remained unchanged. Rather than a change in crystallization rate of POP, a change in the ratio between the crystallizing monounsaturated triacylglycerols is linked with the high viscosity of the crystal slurry. For a comparable degree of crystallization, the superolein of the more viscous crystal slurry, obtained through a membrane press filtration up to 15 bar, was more unsaturated than the superolein filtered from the less viscous slurry. Consequently, the high unsaturation in the corresponding soft palm mid fraction is only the result of an incomplete phase separation, and not due to an increased intersolubility of unsaturated triacylglycerols in the crystals.     

Design and verification of a model secondary clarifier for activated sludge

A model clarifier was designed using conventional methods for the surface calculation and an alternative pathway for the determination of the height and constructed accordingly. In addition, a new approach was used to evaluate the necessary scraper speed in comparison to full-scale clarifiers. Scaling effects were taken into account. The model clarifier was first tested by tracer experiments. Conductivity measurements were used for the clarification zone, whereas the thickening zone was tested using pyrene as an organic tracer compound. Finally, the behaviour of the model clarifier was compared with a full-scale settler. The results indicated that operation of the model clarifier was representative of full-scale behaviour, except for severe overloads. Hence, the small-scale clarifier qualified as a model for small-scale studies and could be installed on large-scale plants to monitor more transparently plant performance and sludge behaviour     

Landscape as framework for integrating local subsistence and ecotourism: a case study in Zimbabwe

Ecotourism can be a solution for mitigating the negative environmental and socio-economic impacts of new developments in fragile environments. Before planning an ecotourist project, it is necessary to consider an area that not only covers the margins of the development zone, but also a wider perimeter of physically and culturally related landscape parts. This paper describes an approach to the demarcation and analysis of an expanded zone around a new reservoir near Bulawayo, larger than an originally designated narrow natural fringe. The concept gains in many ways, in landscape diversity, in cultural assets and in interaction with local residents to whom ecotourisms should be profitable in the first place.