Comparative Gas Chromatographic–Mass Spectrometric Evaluation of Hop (Humulus lupulus L.) Essential Oils and Extracts Obtained Using Different Sample Preparation Methods

The main aim of investigations was to identify chemotypes and determine differences between some domestic hop varieties and wild hops, which were collected from some regions of Lithuania and cultivated at the same edafoclimatic conditions in hops collection of Kaunas Botanical Garden of Vytautas Magnus University. One of objectives was to compare essential oils of hops (2 years harvest) by the evaluation of volatiles content. Among the main components of hop essential oils monoterpenes (β-myrcene) and sesquiterpenes (α-humulene and β-caryophyllene) were determined using gas chromatography coupled with mass spectrometry (GC-MS). Retention parameters (t _R, calculated retention index, and Kovats retention index) and m/z value of molecular ion for selected compounds from hop essential oils were determined. Samples were prepared by applying solid phase microextraction (SPME), supercritical fluid extraction (SFE) and accelerated solvent extraction (ASE). The steam distillation was used to obtain hop essential oils. The chemometric comparison of domestic and wild hops based on GC-MS analysis data was carried out. The obtained statistical results allow us to classify the investigated wild forms and domestic varieties of hops according to the similarities of their chemotypes. The concentration of β-myrcene, α-humulene in hop essential oils obtained from cones 2 years harvests is much higher than other volatile organic compounds (15.2–23.7 % in total contribution). In analysed essential oils β-farnesene is a constituent in higher quantity of hop essential oils obtained from cones from second time harvest than from cones from first harvest. This can be explained by the year-to-year vegetation conditions difference.     

Supply-chain transparency within industrialized construction projects

This paper addresses those issues relating to the integration of information flows in relation to material management throughout the construction industry supply-chain. Based on a case study, it shows how to bridge any gaps between those information systems used within the design, prefabrication, and on-site construction processes.     

Zirconium dioxide refractory erosion in an ionized combustion product flow

Erosion is considered for zirconium refractories in a hot gas flow. Additional ionization of the flow with 1% of atomic potassium in terms of the mass of combustion products increases the wear, and also causes diffusion in the structure. Consequently, local accumulations of carbon occur in the intergranular zones of a coarse-grained specimen. __________ Translated from Novye Ogneupory, No. 1, pp. 49–53, January, 2008.     

Stability and transformation of products formed from dimeric dehydroascorbic acid at low pH

Dehydroascorbic acid dimer (DDHA) is the commercially available form of oxidised vitamin C. When DDHA enters an aqueous environment, it will interact with water, but the details of this process are not well defined. Hydration of DDHA was analyzed as a function of concentration, pH and temperature. Above pH 5 only hydrated dehydroascorbic acid monomer (DHA) and its degradation product 2,3-diketogulonic acid (DKG) were observed. At pH lower than 4 and in MilliQ water, relatively stable hydrated dimeric species were additionally detected. They are intermediates formed from DDHA and transformed into DKG, either directly or through DHA. A lower temperature of dissolution favours the formation of hydrated dimeric products, while the concentration of DDHA has no effect on their yield. All products were separated chromatographically and analyzed by three detectors: diode array, refractive index and electrospray ionisation mass spectrometry. The stability and transformations of products were studied in the mixture and in the isolated fractions. Two initially formed monohydrated products are transformed to a dihydrated product that is degraded to DHA and DKG. Once formed, the dihydrated product and one of the monohydrated products are sufficiently stable to be identified at neutral pH. All three hydrated products are interconvertible and can be also formed after dissolution of dried DHA.     

Physical Properties of Non-Agglomerated Cocoa Drink Powder Mixtures Containing Various Types of Sugar and Sweetener

Characterization of flow properties represents a crucial step in the production of powdered composite mixtures. Mixing of cocoa powders with different sugars is the first step in the production of this type of beverages, which leads to a change in the mixtures flow properties. The objective of this work was firstly to determine the physical properties of non-agglomerated powdered cocoa and sugar mixtures and, after that, to determine which physical properties of cocoa powders are influenced by sugar addition and in what way they are influenced by sugars. Mixtures were formulated by two cocoa powders containing different amounts of fat and 11 different kinds of sugar or sweetener. A significant change was found in the median diameter, poured bulk density, compression and decompression force of the mixtures compared to the sole components’ physical properties. All the mixtures display a decreasing compaction coefficient with increase of flow speed, which indicates that these powder mixtures flow more freely at higher transport speeds. An increase of cake height ratio was detected in all the mixtures, indicating that all the mixtures were susceptible to caking and that they formed a strong cake. Insolubility of the mixtures was influenced significantly by the median diameter of the sugar particles added to the mixture. Addition of sugars and sweeteners to the cocoa powder reduced the red and yellow colour components, but the type of sugar or sweetener did not produce a considerable difference in the colour of the cocoa drink mixtures.     

Total Hydroxycinnamic Acids Assay: Prevalidation and Application on Lamiaceae Species

In this work, qualitative and quantitative analyses of total hydroxycinnamic acid (THA) derivatives in leaves, flowers and aerial parts of 32 Lamiaceae species were carried out. HPTLC analysis of plant material indicated rosmarinic acid as the main phenolic acid in 22 Lamiaceae plant extracts, while chlorogenic acid predominated in other 10 investigated species. Determination of THA in different medicinal plants was performed by colorimetric methods using chromogenic system of HCl-NaNO₂–Na₂MoO₄–NaOH and two standards: rosmarinic acid (R-THA procedure) and chlorogenic acid (C-THA procedure). Performance characteristics of THA assay were established, and the quality of the analytical procedures was evaluated using valuable prevalidation strategy. Good quality of the measurements at the lower analyte level, excellent resolution of blank and analyte signals, homogenous data material, ideal linear calibration and analytical evaluation functions, very low limit of detection [L _D(R-THA)?=?0.53 μg; L _D(C-THD)?=?1.75 μg] and limit of quantitation [L _Q(R-THD)?=?1.76 μg; L _Q(C-THD)?=?4.21 μg], and high precision and accuracy confirmed the high quality of investigated procedures as valuable tools in THA analysis. Application of these prevalidated, simple and rapid analytical methods revealed that the studied Lamiaceae plants differ greatly in their THA contents, ranging from 1.95 % (Acinos arvensis) to 11.03 % (Satureja subspicata). The results obtained from qualitative and quantitative analysis provided new information regarding phytochemical characterization of Lamiaceae species originating from Croatia and highlighted members of the genus Micromeria, Origanum, Melissa and Satureja as rich sources of hydroxycinnamic acids.