Effect of β-cyclodextrin on antioxidant activity of coumaric acids

Inclusion complexes of o-, m- and p-coumaric acid (CA) with β-cyclodextrin (βCD) were prepared in stoichiometric ratios (1:1) and stability constants and antioxidant activity of the complexes were studied. The apparent stability constants in aqueous solution of 0.39 × 10³ M⁻¹, 2.81 × 10³ M⁻¹ and 49 × 10³ M⁻¹ for o-, m- and p-CA complexes, respectively, were determined by phase solubility tests. Different analytical techniques (IR, MS) in combination with different solvent washing procedures, were used for confirmation of the nature of the inclusion complexes. Dioxan was a suitable solvent for removal of only free CA and CA adsorbed on the surface of the βCD, while methanol removed absorbed, included and free CA from the complexes. In the case of o- and m-CA–βCD complexes, antioxidant activity was significantly increased while, in p-CA–βCD, it remained unchanged. The impact of complex structure on antioxidant activity of CA isomers was clarified.     

Tribochemical Conversions of Zinc Dialkyldithiophosphate (ZDDP) Under Extremely Different Pressure Conditions

The authors performed ball-on-disk and four-ball tests. The former gave much less severe conditions than the latter. A ZDDP-containing package, blended with a mineral base oil, was tested. Completely different mechanisms of ZDDP conversions were observed. During ball-on-disk tests, ZDDP undergoes partial tribochemical decomposition. It results in a modification of the surface of test specimens—organic compounds are produced and zinc atoms diffuse into the surface. During four-ball tests, advanced structural decomposition of ZDDP takes place—S and P take part in tribochemical reactions. Probably inorganic compounds are produced, whereas there is a lack of a layer of organic ones adsorbed on the surface. The generation of inorganic compounds results from chemical reactions of decomposed ZDDP with the surface of steel specimens as well as diffusion of some elements (e.g. S) into the surface. Good antiseizure properties of such inorganic structures help to improve the tribological characteristics under severe test conditions.     

The Use of a Novel Ferulic Acid Esterase from Lactobacillus acidophilus K1 for the Release of Phenolic Acids from Brewer's Spent Grain

In this work, an extracellular ferulic acid esterase was produced in bioreactor cultivations of Lactobacillus acidophilus K1 strain. The enzyme was partially purified using ultrafiltration (10 kDa), dialysis (4–6 kDa) and Fast Protein Liquid Chromatography (Sepharose CM, Sephacryl S‐300). A considerable increment of enzyme activity (31‐fold) in the final preparation was achieved. Two distinct bands (approx. 21.5 kDa and 39 kDa) were obtained after SDS‐PAGE. A high similarity of the purified enzyme (LC‐MS/MS analysis) to tannase and ferulic acid esterase from Burkholderia ambifaria MEX‐5 was obtained. The optimal pH and temperature for the enzyme activity were 6.3 and 37°C, respectively. The enzyme preparation effectively released phenolic acids (mainly ferulic and p‐coumaric acid) from brewer's spent grain. This novel enzyme preparation can be used for the utilisation of a valuable and inexpensive by‐product of the brewing industry.     

Influence of the chemical structure on the thermal degradation of the glucosinolates in broccoli sprouts

Glucosinolates are secondary plant metabolites occurring in Brassica vegetables. Food processing significantly reduces glucosinolate content, among other things due to thermal degradation. As there is only little information about thermal glucosinolate breakdown, the influence of the chemical structure as well as the influence of different pH to thermal degradation of individual glucosinolates was studied by analysing desulphoglucosinolates with HPLC-DAD. Thermal degradation was forced by heating broccoli sprouts at 130 °C in dry medium, whereas the influence of the pH was studied by cooking at 100 °C in aqueous medium. Within each group of glucosinolates differences in thermal degradation were revealed. Within the sulphur containing aliphatic glucosinolates the oxidative state of the sulphur atom as well as the side chain length influenced the reactivity. Among the indole glucosinolates great differences in stability were observed. A hydroxyl function in the side chain generally seems to destabilise glucosinolates. Glucosinolates were most stable towards thermal treatment in neutral and slightly acidic medium, whereas they degraded more rapidly in basic medium.     

The effect of temperature and radiation on flavonol aglycones and flavonol glycosides of kale (Brassica oleracea var. sabellica)

The winter crop kale has a complex profile of different glycosylated and acylated flavonol glycosides which may be affected by global warming. To the best of our knowledge, compound–climate relationships for flavonol aglycones and flavonol glycosides were established for the first time. The investigated 10 major flavonol glycosides responded structure-dependent in the investigated temperature range between 0 and 12 °C and the photosynthetic active radiation range between 4 and 20 mol m⁻² d⁻¹, e.g. the decrease in temperature led to an increase in sinapic acid monoacylated and diacylated quercetin glycosides, while the sinapic acid monoacylated kaempferol glycosides showed a maximum at 4.5 °C. Furthermore, the hydroxycinnamic acid residues and the different number of glucose moieties in the 7-O position affected the response of kaempferol triglucosides. Consequently, global warming would result in lower concentrations of antioxidant-relevant quercetin glycosides in winter crops, suggesting a production at e.g. higher altitudes due to lower temperature.     

Yeast ecology in French cider and black olive natural fermentations

In this study, rDNA ITS restriction analysis was used to identify yeasts from two naturally fermented products: French ciders and black olives. In cider musts and bottled ciders, the PCR-RFLP method generated 15 different ITS/RFLP profiles for a total of 208 isolates. The predominant yeasts corresponded to Saccharomyces bayanus, Saccharomyces cerevisiae, Lachancea cidri and Dekkera anomala. Three identified species: Candida sake, Candida tropicalis and Kluyveromyces marxianus had never been described before in ciders. For the black olive fermentation, the method allowed for identification of 11 profiles for a total of 137 isolates. A sequential apparition of yeasts was observed with Pichia anomala, Candida boidinii and Debaryomyces etchellsii being the predominant species. Four isolates did not correspond to any known species based on the sequencing of the D1/D2 region of the 26S rRNA gene. By using the rDNA ITS method, valuable information on yeast population biodiversity and dynamics in the naturally fermented food products studied was obtained.     

Phytate degradation by human gut isolated Bifidobacterium pseudocatenulatum ATCC27919 and its probiotic potential

The growing awareness of the relationship between diet and health has led to an increasing demand for food products that support health above and beyond providing basic nutrition. Probiotics are live organisms present in foods, which yield health benefits related to their interactions with the gastrointestinal tract. Phytases are a subgroup of phosphatases that catalyse the desphosphorylation of phytate, which reduces its negative impact on mineral bioavailability, and generates lower inositol phosphates. The aims of this investigation were to (i) study the ability of the probiotic candidate Bifidobacterium pseudocatenulatum to degrade phytate in synthetic medium, to (ii) identify the lower inositol phosphates generated, to (iii) study its survival under conditions mimicking gastrointestinal passage and finally to (iv) assess adhesion of the bacteria to Caco-2 cells. The first steps of InsP₆ degradation by B. pseudocatenulatum phytate-degrading enzyme/s were preferentially initiated at the DL-6-position and 5-position of the myo-inositol ring. It suggests that the main InsP₆ degradation pathway by B. pseudocatenulatum by sequential removal of phosphate groups was D/L-Ins(1,2,3,4,5)P₅ or D/L-Ins(1,2,3,4,6)P₅; D/L-Ins(1,2,3,4)P₄; to finally Ins(1,2,3)P₃ and D/L-Ins(1,2,4)P₃/D/L-Ins(1,3,4)P₃. This human strain also showed a notable tolerance to bile as well as a selective adhesion capacity (adhesion to control surfaces was zero), to human intestinal Caco-2 cells comparable to the commercial probiotic B. lactis. The phytate-degrading activity constitutes a novel metabolic trait which could contribute to the improvement of mineral absorption in the intestine as a nutritional probiotic feature with potential trophic effect in human gut.     

Oxidation und Aufkohlung hochlegierter Werkstoffe für Crackrohre – Teil 2: Das Aufkohlungsverhalten in sauerstoff- und kohlenstoffhaltigen Atmosphären hoher Kohlenstoffaktivität

Oxidation and Carburization of High Alloyed Materials for Cracking Tubes – Part 2: The Carburization Behaviour in Oxygen and Carbon Containing Atmospheres with High Carbon Activity Carburization tests have been carried out with the casting materials (German Designation) Werkstoff-Nr. 1.4848, 1.4857, 2.4813 and an experimental 25/20/5-CrNiSi melt, and with the wrought materials Werkstoff Nr. 1.4301 and 1.4848 in CO-CO₂ mixtures with a_c = 1, and in humid natural gas with a_c > 1 between 1000 and 1200° C. At temperatures below appr. 1050° C oxide layers formed are analogous to those formed in air (substrate/Cr₂O₃/(Mn, Fe)Cr₂O₄) which prevent carburization. Carburization takes place only after the protective oxide layer has been destroyed. In this context several mechanisms of destruction must be considered, i.e. (a) by chemical reaction (transformation of oxide into carbide, reduction of oxide), (b) by mechanical stresses (temperature fluctuation, growth of graphite layers, creep deformation). Reduction processes are encountered with Fe-rich oxide layers only. Scale layers rich in chromium oxide are transformed into carbide above appr. 1050° C in gases with a_c = 1, depending on the CO partial pressure. The rate of this transformation strongly depends on carbon activity in the gas phase. When graphite is deposited on the surface the transformation occurs at a high rate, while it is rather slow even at a_c = 1 when no graphite is deposited. Deposited graphite may have a mechanically destructive effect, too, because it penetrates into cracks and pores in the oxide layer and thus produces spalling of oxide particles. When the surface of the cast material is porous particles of the substrate may become detached, too. This goes to explain the poor behaviour of tubes with as cast surfaces in cracking reactors. The positive effect of silicon is due to the formation of protective silica layers between metal and Cr₂O₃ and metal and external carbide layer respectively. In order to form a continuous silica layer the Si content in the material must not be below a cricital value.     

“Smart” polymeric nanospheres as new materials for possible biomedical applications

Novel random terpolymers of N-isopropylacrylamide (NIPAM), sodium 2-acrylamido-2-methyl-1-propanesulfonate (AMPS), and cinnamoyloxyethylmethacrylate (CEMA) were synthesized by free radical copolymerization using AIBN as an initiator. Five terpolymers were obtained by copolymerization of the monomer mixtures containing a fixed amount of 10 mol % of AMPS while the content of CEMA ranged from 5 to 25 mol % and was changed in 5 mol % increments. The terpolymers obtained are water-soluble. Because of their amphiphilic nature they undergo self-organization in the aqueous solution with the formation of micelles capable of solubilizing sparingly water soluble organic compounds, such as drugs. The terpolymers are susceptible to three external stimuli, i.e. temperature, ionic strength and UV light. Due to the presence of NIPAM in the terpolymers they display the lower critical solution temperature (LCST), the presence of AMPS makes them sensitive to the ionic strength of the solution, while the light-responsiveness of the terpolymers is due to the presence of cinnamoyl chromophores, which undergo photodimerization when irradiated with UV light at about 280 nm. Application of any of these stimuli alone or in combination with other stimuli allows changing the copolymer properties in a controlled way.     

A new strategy to improve alkyd/acrylic compatibilization in waterborne hybrid dispersions

Grafting of alkyd resin to the acrylic polymer is needed to fully exploit the possibilities of these hybrids; but in the current technology, grafting is accompanied by an important reduction of the unsaturated groups of the alkyds, which adversely affects the curing of the film and its properties. A novel strategy that overcomes these limitations is presented. The strategy is based on the use of alkyd resin functionalized with methacrylic groups, that substantially improved the incorporation of the resin to the growing acrylic polymer chain, and the polymer particle homogeneity, without decreasing the degree of unsaturation in the alkyd resin.