Effects of hydrocolloid addition and high pressure processing on the rheological properties and microstructure of a commercial ostrich meat product "Yor" (Thai sausage)

"Yor" is a traditional sausage like product widely consumed in Thailand. Its textures are usually set by steaming, in this experiment ultra-high pressure was used to modify the product. Three types of hydrocolloid; carboxymethylcellulose (CMC), locust bean gum (LBG) and xanthan gum, were added to minced ostrich meat batter at concentration of 0-1% and subjected to high pressure 600 Mpa, 50 degrees C, 40 min. The treated samples were analysed for storage (G) and loss (G '') moduli by dynamic oscillatory testing as well as creep compliance for control stress measurement. Their microstructures using confocal microscopy were also examined. Hydrocolloid addition caused a significant (P < 0.05) decrease in both the G' and G '' moduli. However the loss tangent of all samples remained unchanged. Addition of hydrocolloids led to decreases in the gel network formation but appears to function as surfactant materials during the initial mixing stage as shown by the microstructure. Confocal microscopy suggested that the size of the fat droplets decreased with gum addition. The fat droplets were smallest on the addition of xanthan gum and increased in the order CMC, LBG and no added gum, respectively. Creep parameters of ostrich yors with four levels of xanthan gum addition (0.50%, 0.75%, 1.00% and 1.25%) showed an increase in the instantaneous compliance (J(0)), the retarded compliance (J(1)) and retardation time (lambda(1)) but a decrease in the viscosity (eta(0)) with increasing levels of addition. The results also suggested that the larger deformations used during creep testing might be more helpful in assessing the mechanical properties of the product than the small deformations used in oscillatory rheology. (c) 2007 Elsevier Ltd. All rights reserved.

A homo-proline tetrazole as an improved organocatalyst for the asymmetric Michael addition of carbonyl compounds to nitro-olefins

A new homo-proline tetrazole derivative 7 has been prepared and shown to have improved properties for achieving asymmetric Michael addition of carbonyl compounds to nitro-olefins.

Surface structure of thin asymmetric PS-b-PMMA diblock copolymers investigated by atomic force microscopy

Asymmetric poly(styrene-b-methyl methacrylate) (PS-b-PMMA) diblock copolymers of molecular weight M-n = 29,700g mol(-1) (M-PS = 9300 g mol(-1) M-PMMA = 20,100 g mol(-1), PD = 1.15, chi(PS) = 0.323, chi(PMMA) = 0.677) and M-n = 63,900 g mol(-1) (M-PS = 50,500 g mol(-1), M-PMMA = 13,400 g mol(-1), PD = 1.18, chi(PS) = 0.790, chi(PMMA) = 0.210) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. Atomic force microscopy (AFM) was used to investigate the surface structure of thin films, prepared by spin-coating the diblock copolymers on a silicon substrate. We show that the nanostructure of the diblock copolymer depends on the molecular weight and volume fraction of the diblock copolymers. We observed a perpendicular lamellar structure for the high molar mass sample and a hexagonal-packed cylindrical patterning for the lower molar mass one. Small-angle X-ray scattering investigation of these samples without annealing did not reveal any ordered structure. Annealing of PS-b-PMMA samples at 160 degrees C for 24 h led to a change in surface structure.

Asymmetric synthesis of cyclic β-amino acids and cyclic amines via sequential diastereoselective conjugate addition and ring closing metathesis

Diastereoselective conjugate addition of lithium (S)-N-allyl-N-alpha-methylbenzylamide to a range of alpha,beta-unsaturated esters followed by ring closing metathesis is used to afford efficiently a range of substituted cyclic beta-amino esters in high d.e. Alternatively, conjugate addition to alpha,beta-unsaturated Weinreb amides, functional group conversion and ring closing metathesis affords cyclic amines in high d.e. The further application of this methodology to the synthesis of a range of carbocyclic beta-amino esters via conjugate addition, enolate alkylation and ring closing metathesis is also described. Application of this methodology affords, after deprotection, (S)-homoproline, (S)-homopipecolic acid, (S)-coniine and (1S,2S)-trans-pentacin.

Time-resolved gas-phase kinetic study of the germylene addition reaction, GeH2 + C2D2

Time-resolved studies of germylene, GeH2, generated by laser. ash photolysis of 3,4-dimethyl-1-germacyclopent-3-ene, have been carried out to obtain rate coefficients for its bimolecular reaction with C2D2. The reaction was studied in the gas phase, mainly at a total pressure of 1.3 kPa (in SF6 bath gas) at five temperatures in the range 298-558 K. Pressure variation measurements over the range 0.13-13 kPa ( SF6) at 298, 397 and 558 K revealed a small pressure dependence but only at 558 K. After correction for this, the second-order rate coefficients gave the Arrhenius equation: log(k(infinity)/cm(3) molecule(-1) s(-1)) = (-10.96 +/- 0.05) + ( 6.16 +/- 0.37 kJ mol(-1))/RT ln 10 Comparison with the reaction of GeH2 + C2H2 (studied earlier) showed a similar behaviour with almost identical rate coefficients. The lack of a significant isotope effect is consistent with a rate-determining addition process and is explained by irreversible decomposition of the reaction intermediate to give Ge(P-3) + C2H4. This result contrasts with that for GeH2 + C2H4/C2D4 and those for the analogous silylene reactions. The underlying reasons for this are discussed.

Gas-phase kinetics of chlorosilylene reactions II. ClSiH + C2H4: absolute rate measurements and quantum chemical and RRKM calculations for the prototype pi addition reaction

Time-resolved studies of chlorosilylene, ClSiH, generated by the 193 nm laser flash photolysis of 1-chloro-1-silacyclopent-3-ene, are carried out to obtain rate constants for its bimolecular reaction with ethene, C2H4, in the gas-phase. The reaction is studied over the pressure range 0.13-13.3 kPa (with added SF6) at five temperatures in the range 296-562 K. The second order rate constants, obtained by extrapolation to the high pressure limits at each temperature, fitted the Arrhenius equation: log(k(infinity)/cm(3) molecule(-1) s(-1))=(-10.55 +/- 0.10) + (3.86 +/- 0.70) kJ mol(-1)/RT ln10. The Arrhenius parameters correspond to a loose transition state and the rate constant at room temperature is 43% of that for SiH2 + C2H4, showing that the deactivating effect of Cl-for-H substitution in the silylene is not large. Quantum chemical calculations of the potential energy surface for this reaction at the G3MP2//B3LYP level show that, as well as 1-chlorosilirane, ethylchlorosilylene is a viable product. The calculations reveal how the added effect of the Cl atom on the divalent state stabilisation of ClSiH influences the course of this reaction. RRKM calculations of the reaction pressure dependence suggest that ethylchlorosilylene should be the main product. The results are compared and contrasted with those of SiH2 and SiCl2 with C2H4.

Time-resolved gas-phase kinetic study of the germylene addition reaction, CH3C CCH3

Time-resolved kinetic studies of the reaction of germylene, GeH2, generated by laser. ash photolysis of 3,4-dimethyl-1-germacyclopent-3-ene, have been carried out to obtain rate constants for its bimolecular reaction with 2-butyne, CH3C CCH3. The reaction was studied in the gas phase over the pressure range 1-100 Torr in SF6 bath gas, at five temperatures in the range 300-556 K. The second order rate constants obtained by extrapolation to the high pressure limits at each temperature, fitted the Arrhenius equation: log(k(infinity)/cm(3) molecule(-1) s(-1)) = (-10.46 +/- 10.06) + (5.16 +/- 10.47) kJ mol(-1)/ RT ln 10 Calculations of the energy surface of the GeC4H8 reaction system were carried out employing the additivity principle, by combining previous quantum chemical calculations of related reaction systems. These support formation of 1,2-dimethylvinylgermylene (rather than 2,3-dimethylgermirene) as the end product. RRKM calculations of the pressure dependence of the reaction are in reasonable agreement with this finding. The reactions of GeH2 with C2H2 and with CH3CRCCH3 are compared and contrasted.

Photopolymerization of Pluronic F127 diacrylate: a colloid-templated polymerization

Pluronic F127 diacrylate (F127DA) is a bifunctional acrylate and as such it should in principle produce macroscopically cross-linked materials; however, its photopolymerization in water does not lead to 3D-extended hydrogels. The main species present after photopolymerization appear to be cross-linked micelles, which indicates that the micellar morphology of F127DA has a template effect on the polymerization. The structural analogy causes the physical state of precursor and polymerized materials to be very similar for a wide range of concentrations (5–25% wt) and temperatures (10–37 °C). Also the long-range morphology of F127DA appears to have a template effect: samples photopolymerized in a micellar gel state and redispersed at high concentration (25% wt) show a long-range organization that depended on the concentration and therefore on the order of the precursor.

Metal cluster expansion by addition of low valent group 14 reagents: III. Reaction of bis[bis(trimethylsilyl)methyl]tin with M3(CO)12 or its derivatives (M = Fe, Ru, or Os): the crystal and molecular structures of M3(μ-SnR2)2(CO)10(R = CH(SiMe3)2; M = Ru or Os)

The stannylene [SnR2] (R = CH(SiMe3)2) reacts in different ways with the three dodecacarbonyls of the iron triad: [Fe3(CO)12] gives [Fe2(CO)8(μ-SnR2)], [Ru3(CO)12] gives the planar pentametallic cluster [Ru3(CO)10(μ-SnR2)2], for which a full structural analysis is reported, while [Os3(CO)12] fails to react. Different products are also obtained from three nitrile derivatives: [Fe3-(CO)11(MeCN)] gives [Fe2(CO)6(μ-SnR2)2], which has a structure significantly different from that of known Fe2Sn2 clusters, [Ru3(CO)10(MeCN)2] gives the pentametallic cluster described above, while [Os3(CO)10(MeCN)2] gives the isostructural osmium analogue, which shows the unusual feature of a CO group bridging two osmium atoms.

Metal cluster expansion by addition of low-valent group 4B reagents: crystal and molecular structure of [Os3SnH2(CO)10{CH(SiMe3)2}2]; a compound with hydrogen bridging osmium and tin

Cluster expansion of [Os3H2(CO)10] with [SnR2][R = CH(SiMe3)2] take place in high yield to give [Os3SnH2(CO)10R2], the first closed triosmium–main-group metal cluster to be structurally characterized; a novel feature is the presence of a hydrogen atom bridging the tin atom and one of the osmium atoms.

Alkenyl derivatives of the metals. Oxidative addition to intermediate tin(II) alkenyls; isolation, and crystal and molecular structure of n-butyltris(triphenylethenyl)tin(IV)

Reaction of tin(II) chloride with Li(CPhCPh2) at –78 °C in diethyl ether–hexane–tetrahydrofuran affords a deep red solution whose colour fades on warming, and which we believe contains the (unstable) first dialkenyltin(II) species. The latter survives long enough at low temperatures to undergo intermolecular oxidative addition, and one such adduct leads ultimately to the formation of Sn(CPhCPh2)3Bun, which has been fully characterised including a crystal and molecular structure study. The mechanism of formation of the final product has been examined and results are reported.

Effects of addition of phenolic compounds on the acid gelation of milk

Tannic acid (0.1–1%, w/w) and gallic acid (0.3–1%, w/w) were added to skim milk prior to acidification with GDL. The acid gelation of tannic and gallic acid fortified milk had a faster gelation time in comparison with the control gel without phenolic compounds. The addition of tannic acid and gallic acid (up to 0.8%) to the milk resulted in a higher storage modulus (G′), decrease in the water mobility (T2 time) and had no significant effect on the syneresis index (SI). However, the inclusion of 1% gallic acid resulted in a significant decrease in G′, a significant increase in the SI and a wider T2 distribution. Lowering the temperature of the gels from 30 to 5 °C caused the G′ for the gels with gallic and tannic acid to increase significantly in comparison with the control, possibly due to increased hydrogen bonding in the presence of phenolic compounds

Reversible addition of CO to coordinatively unsaturated high-spin iron(II) complexes

Several new coordinatively unsaturated iron(II) complexes of the types [Fe(EN-iPr)X2] (E = P, S, Se; X = Cl, Br) and [Fe(ON-iPr)2X]X containing bidentate EN ligands based on N-(2-pyridinyl)aminophosphines as well as oxo, thio, and seleno derivatives thereof were prepared and characterized by NMR spectroscopy and X-ray crystallography. Mössbauer spectroscopy and magnetization studies confirmed their high-spin nature with magnetic moments very close to 4.9 μB, reflecting the expected four unpaired d-electrons in all these compounds. Stable low-spin carbonyl complexes of the types [Fe(PN-iPr)2(CO)X]X (X = Cl, Br) and cis-CO,cis-Br-[Fe(PN-iPr)(CO)2X2] (X = Br) were obtained by reacting cis-Fe(CO)4X2 with the stronger PN donor ligands, but not with the weaker EN donor ligands (E = O, S, Se). Furthermore, the reactivity of [Fe(PN-iPr)X2] toward CO was investigated by IR spectroscopy. Whereas at room temperature no reaction took place, at −50 °C [Fe(PN-iPr)X2] added readily CO to form, depending on the nature of X, the mono- and dicarbonyl complexes [Fe(PN-iPr)(X)2(CO)] (X = Cl) and [Fe(PN-iPr)(CO)2X2] (X = Cl, Br), respectively. In the case of X = Br, two isomeric dicarbonyl complexes, namely, cis-CO,trans-Br-[Fe(PN-iPr)(CO)2Br2] (major species) and cis-CO,cis-Br-[Fe(PN-iPr)(CO)2Br2] (minor species), are formed. The addition of CO to [Fe(PN-iPr)X2] was investigated in detail by means of DFT/B3LYP calculations. This study strongly supports the experimental findings that at low temperature two isomeric low-spin dicarbonyl complexes are formed. For kinetic reasons cis,trans-[Fe(PN-iPr)(CO)2Br2] releases CO at elevated temperature, re-forming [Fe(PN-iPr)Br2], while the corresponding cis,cis isomer is stable under these conditions.

Effects of seed addition on beetle assemblages during the re-creation of species-rich lowland hay meadows

Species-rich lowland hay meadows are of conservation importance for both plants and invertebrates; however, they have declined in area across Europe as a result of conversion to other land uses and management intensification. The re-creation of these grasslands on ex-arable land provides a valuable approach to increasing the extent and conservation value of this threatened habitat. Over a 3-year period a replicated block design was used to test whether introducing seeds promoted the re-creation of both plant and phytophagous beetle assemblages typical of a target hay meadow. Seeds were harvested from local hay meadows, and applied to experimental plots in the form of either green hay or brush harvesting seeds. Green hay spreading achieved the greatest success in re-creating plant and phytophagous beetle assemblages. While re-creation success increased over time for both taxa, for the phytophagous beetles the greatest increase in re-creation success relative to the establishment year also occurred where green hay was applied. We also considered the phytophagous beetles in terms of functional traits that describe host plant specificity, larval feeding location and dispersal. Phytophagous beetle functional trait composition was most similar to the target hay meadow assemblage where some form of seed addition was used, i.e. hay spreading or brush harvested seeds. This study identified the importance of introducing target plant species as a mechanism to promote the re-creation of phytophagous beetle communities. Seed addition methods (e.g. green hay spreading) are crucial to successful hay meadow re-creation.

Altering peptide fibrillization by polymer conjugation

A strategy is presented that exploits the ability of synthetic polymers of different nature to disturb the strong selfassembly capabilities of amyloid based β-sheet forming peptides. Following a convergent approach, the peptides of interest were synthesized via solid-phase peptide synthesis (SPPS) and the polymers via reversible addition−fragmentation chain transfer (RAFT) polymerization, followed by a copper(I) catalyzed azide− alkyne cycloaddition (CuAAC) to generate the desired peptide− polymer conjugates. This study focuses on a modified version of the core sequence of the β-amyloid peptide (Aβ), Aβ(16−20) (KLVFF). The influence of attaching short poly(Nisopropylacrylamide) and poly(hydroxyethylacrylate) to the peptide sequences on the self-assembly properties of the hybrid materials were studied via infrared spectroscopy, TEM, circular dichroism and SAXS. The findings indicate that attaching these polymers disturbs the strong self-assembly properties of the biomolecules to a certain degree and permits to influence the aggregation of the peptides based on their β-sheets forming abilities. This study presents an innovative route toward targeted and controlled assembly of amyloid-like fibers to drive the formation of polymeric nanomaterials.