No abstract

The structures of six commercial hydrolyzable tannins, chestnut, oak, tara, sumach, chinese gall, and turkey gall tannins have been examined by matrixassisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry. Their oligomeric structures and structure distributions have been defined. Degradation products of rather different structure than what previously reported were present. Different galloyl glucose monomers were observed for chestnut and oak tannin extracts and in chinese gall gallotannin extract. Combination of positive-and negative-mode MALDI-TOF showed that most galloyl residues of the galloyl glucose chains were stripped from a skeletal glucose chain. Oligomers, in some cases up to 16 or 17 glucose units long, almost totally stripped of galloyl residues were observed. This indicated that a wide distribution up to very long gaIloylglucose chains exist in most commercial hydrolyzable tannin extracts. This indicated that these commercial tannin extracts are mainly composed of long galloyl glucose chains of mixed di-, tri-, and pentagalloyl glucose repeating units being present in the same chain. The presence of long glucose chains where most of the galloyl residues have been stripped indicates that their linkage may be sugar residue to sugar residue. Commercial tara and turkey gall tannins have been shown to be mainly polygallic oligomers of up to eight gallic acid residues linked to each other in a chain. Commercial sumach extract revealed itself a more complex mixture of glucose oligomers up to 13 repeating units.

No abstract

High molar mass wood tannin extracts are complex mixtures that are distributed in both molar mass and chemical composition. Hydrolysable tannins from tara, Turkey gall, and chestnut woods were analyzed and compared using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Although MALDI-TOF MS reveals the oligomer structure of the tannins, this method cannot distinguish between isomers with isobaric masses and, therefore, ambiguous structural assignments were made in a number of cases. To determine the actual microstructures present, MALDI-TOF-CID (collision induced dissociation) experiments were conducted. MALDI-TOF-CID enables monomer sequence determination and positive assignments of isobaric structures can be made

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An experimental study has been conducted to determine the combined effects of different extraction conditions and precipitation method on the yield and quality of high methoxyl pectin from lemon peels. Pectin was extracted using different mineral acids (HCl, HNO3 and H2SO4) at four concentration levels (0.025; 0.05; 0.1 and 0.2 m), at 70 °C for 4 h. The soluble pectin was precipitated by iso-propanol or by an aluminium sulphate, Al 2(SO 4) 3, solution at pH 4. The extraction with HCl and HNO 3, at the highest concentrations investigated, followed by aluminium precipitation led to the best results in terms of yield (22-25%), quality and gelling power of pectin with a remarkable decrease of alcohol consumption as compared to the alcoholic precipitation under the same extracting conditions

No abstract

New, green and cheap rigid foams presenting outstanding performances for thermal insulation are described. Such ultralightweight cellular materials are mainly based on renewable chemicals: tannin and furfuryl alcohol, are very easy to produce and have thermal conductivity as low as 38 mW/m/K. Compared to previously reported tannin-based foams, these new materials are much "greener" and present improved resistance to compression and to water. Especially the formaldehyde, formerly used as cross-linking agent of tannins but known as a volatile and harmful chemical, could be successfully removed from the formulation. The as-obtained, 2 nd generation, tannin-based foams are totally stable and have an expected interest for thermal insulation of buildings.