Effect of pH Control with Acetic Acid/Sodium Acetate Buffer on Hot-water Extraction of Poplar Wood

Poplar wood chips were extracted in an acetic acid/sodium acetate(SA/AA)buffer solution at 180ºC for 60 minutes,with a solid-to-liquid ratio of 1:6,to investigate the effect of pH on the extraction performance in terms of chemical compositions of the extract.The pH was controlled by varying the concentrations of sodium acetate and acetic acid in the buffer system.Results showed that the SA/AA system could promote the dissolution of hemicellulose,obtaining more oligosaccharides and monosaccharides,and could also inhibit the excessive decomposition of monosaccharides.When extracting poplar wood chips in a SA/AA system of pH=3.7,the yield of oligosaccharides was the highest,while the contents of furfural and hydroxymethyl furfural decreased by 25%and 30%,respectively,compared to conventional water extraction systems.Moreover,the amount of lignin extracted in the S/AA process was also higher than that in a conventional hot water extraction process.

Determination of saccharin in preserved fruits by High Performance Liquid Chromatography

Quantitative analysis of saccharin in preserved fruits was performed by High Performance Liquid Chromatography （HPLC）. The separation was observed on a reversed phase ODS C）8 column （4.6 × 250 mm）. Mobile phase system consisted of ammonium acetate buffer： Methanol （60：40 v/v） at a flow rate of 1.0 mL.min^-1, and UV detector was set at 235 nm. The calibration curve of saccharin was linear in the concentration range between 1 to 100 mg·L^-1）, while the detection limit of saccharin was found to be 0.08 mg.L^-1. The mean value of recovery was 98.24% with standard deviation of0.32% （n=12）. The proposed method was successfully applied to determine the amount of saccharin in 12 preserved fruits, commercially available in Chiang Mai local markets. The results showed that the saccharin contents were found in the range of 6.22-78.60 mg.kg^-1.

Structural Changes of Poplar Wood Lignin in Hydrothermal pretreatment in Acetic Acid-Sodium Acetate system

Hydrothermal pretreatment of poplar wood chips was performed in an acetic acid/sodium acetate buffer medium.To characterize the structural changes of lignin in the pretreatment process,milled wood lignin(MWL)was isolated from both the un-treated and treated poplar wood chips,and analyzed by ^(1)H-NMR,^(13)C-NMR,^(31)P-NMR,FT-IR,and GPC-MALLS.Results showed that the lignin in the pretreated wood chips had more phenolic OH groups,less aliphatic OH groups,higher molecular weight,and narrower polydispersity,in comparison with the lignin in the un-treated wood.The acetic acid-sodium acetate buffer pretreatment facilitated the removal of-OCH_(3) groups and the cleavage of the inter-unit linkages ofβ-O-4 bond in the lignin.Furthermore,the re-polymerization of lignin in the acetic acid-sodium acetate buffer pretreatment was found to be less than that in autohydrolysis.