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Pectic substances from red beet(Beta vulgaris conditiva).Part I.Structural analysis of rhamnogalacturonan I usingenzymic degradation and methylation analysisG.R.Strasser,R.Amado`*Swiss Federal Institute of Technology,Institute of Food Science,ETH-Zentrum,Schmelzbergstrasse9,CH-8092Zurich,SwitzerlandAccepted2March2000AbstractCell wall material from ripe red beet(Beta vulgaris L.var.conditiva)was isolated as alcohol insoluble residue(AIR).The chelator-soluble pectin obtained by cyclohexane-trans-1,2-diaminotetraacetate(CDTA)extraction of the AIR was fractionated by anion exchange chromatography(AEC).The main fraction was further fractionated by gelfiltration chromatography(GFC).Fractions from both chromatographic systems were stepwise degraded by endo-polygalacturonase,endo-b-(134)-d-galactanase,endo-a-(135)-l-arabinanase and a-l-arabinofuranosidase.Degradation products were fractionated by GFC or by AEC.Polymeric fractions were investigated by methylation analysis after carbodiimide-activated reduction with NaBD4.Selected fractions were additionally methylated with trideuteromethyliodide to enable the detection of O-methyl substituted sugars.The results indicate that the CDTA-soluble pectins of red beet cell walls are composed of three different sub-units:a homogalacturonan,which accounts for about75%,a highly ramified rhamnogalacturonan I(RG-I)and a typical rhamnogalacturonan II(RG-II).RG-I consists of a highly ramified backbone composed of nearly equal amounts of rhamnose and galacturonic acid.Side chains,mainly arabinans,galactans and type-II arabino-galactans are attached to the RG-I backbone.Some arabinans are connected via short galactan chains directly or indirectly to this backbone.Type-II arabinogalactans are formed by“inner”chains consisting of(133)-linked galactans and short“outer”chains composed of an average number of one to three(136)-linked galactose residues.Terminal arabinofuranoses are linked via the O-3-position to galactose residues.Nearly all non-reducing ends consist of glucuronic acid.Approximately65%of the glucuronic acid residues are substituted by a methyl ether group and approximately10%,most probably,by a terminally linked rhamnose.᭧2001 Elsevier Science Ltd.All rights reserved.Keywords:Red beet pectic substances;Rhamnogalacturonan I;Characterisation1.IntroductionPectins are a group of polysaccharides from the primary cell wall and the middle lamella of higher plants(Carpita& Gibeaut,1993;John&Dey,1986;McCann et al.,1995). Changes in the texture of fruits and vegetables and in the properties of their products are related to changes in pectic components.Pectins comprise a family of acidic polymers, like homogalacturonans and rhamnogalacturonans with several neutral polymers such as arabinans,galactans and arabinogalactans attached to them.They have been exten-sively investigated for their structure and functions within the plant cell wall using chemical analysis and enzymic degradation.Rhamnogalacturonan I(RG-I)is a poly-saccharide solubilised from plant cell walls after treatment with polygalacturonase(PG).The RG-I polymer is composed of alternating l-rhamnose and d-galacturonic acid residues.l-Arabinosyl-and d-galactosyl-rich side chains are attached to this backbone.Occasionally the side chains are terminated by l-fucosyl,d-glucuronosyl or4-O-methyl-d-glucuronosyl residues(Albersheim,Darvill, O’Neill,Schols&Voragen,1996).The aim of our work was the characterisation of the chelator-soluble pectic substances from ripe red beet(Beta vulgaris L.var.conditiva).For this purpose the alcohol-insoluble residue(AIR)was extracted with cyclohexane-trans-1,2-diaminotetraacetate(CDTA),the extracts were fractionated and characterised using enzymic degradation and methylation analysis.The isolation procedure and the characterisation of an RG-I are described below. The characterisation of an RG-II from ripe red beet willCarbohydrate Polymers44(2001)63–70 0144-8617/01/$-see front matter᭧2001Elsevier Science Ltd.All rights reserved.PII:S0144-8617(00)/locate/carbpol*Corresponding author.Tel.:ϩ41-1632-32-91;fax:ϩ41-1632-11-23. E-mail address:renato.amado@ilw.agrl.ethz.ch(R.Amado`).be described in part II of this paper (Strasser &Amado`,2000).2.Experimental2.1.Isolation of pectic materialCell wall material from ripe red beet of the variety Red Ace F1was isolated as AIR.15kg of red beets were peeled,cut into small pieces and blended in 90%boiling ethanol for 10min.The residue was homogenised with a commercial Waring blendor,filtered (Polyestergaze Polynom,Schweiz.Seidenfabrik AG,Zurich,CH),and washed 11times with 70%ethanol.AIR (30g dry weight)was stirred in 3.0l of 50mM 1,2-diaminocyclohexane-N ,N ,N H ,N H -tetraacetic acid (CDTA)solution (pH 6.5)at 20ЊC for 6h.The residue was removed by filtration through a D3glass filter funnel and washed with water.The residue was re-extracted under the same conditions for 2h.The washings from both extractions were combined,filtered (0.45m m,Millipore)and dialysed (Servapor 44146,Serva &Co,Heidelberg,G)first against tap water (3days),and then against de-ionised water (4days).After exhaustive dialysis the extract wasconcentrated under vacuum and freeze-dried (fraction:CDTAS,Fig.1).2.2.Fractionation of CDTASAnion exchange chromatography (AEC)and gel filtration chromatography (GFC)were performed as described earlier(Strasser,Wechsler &Amado`,1996).Fractions IE0.0M,IE0.1M,IE0.2M,IE1.0M,and GF1,GF2,GF3,respec-tively,were pooled (Fig.1).2.3.Enzymic degradation with polygalacturonase The methyl ester and O-acetyl groups were saponified prior to enzymic degradation with 150ml 0.05M NaOH at 0ЊC for 14h.The pH was corrected to 4.5with 0.1M acetic acid containing 0.01%NaN 3.Fraction IE0.2M and the GF x -fractions (1.0g)were incubated separately with a PG (90IU,pH 4.5,35ЊC,6h),heated to inactivate the enzyme (100ЊC,10min),filtered (0.45m m,Millipore)and fractionated by GFC (Sephacryl S-300HR,Pharmacia,95×2:6cm :A pH 5.0sodium acetate buffer (0.05M,containing 0.01%NaN 3)was used as eluent at a flow-rate of 1.8ml/min.The separations were monitored with a HP 1037A RI-Detector (30ЊC).The corresponding fractions were pooled.High molecular weight fractions were dialysed and freeze-dried (fractions:PG1,PG2and GF x PG1,GF x PG2,respectively,Fig.1).The PG used for these degra-dation experiments had been purified and characterised by Elgorriaga (1994).2.4.Enzymic degradation by an endo-a -(135)-l -arabinanase or an endo-b -(134)-d -galactanase PG1-and PG1GF x -samples (100mg in 30ml 0.02M sodium acetate buffer,containing 0.01%NaN 3)were either incubated with endo-arabinanase (gift from Novo Nordisk A/S,Bagsvaerd,DK;50IU,pH 5.5,35ЊC,12h)or endo-galactanase (Megazyme Ltd,Boronia,AUS;60IU,pH 4.5,45ЊC,5h).The solutions were filtered (0.45m m,Millipore)after inactivation of the enzyme (100ЊC,10min)and frac-tionated by AEC (DEAE-Sepharose CL-6B,Pharmacia,35×2:6cm using 170ml 0.02M and 200ml 0.8M sodium acetate buffer (pH 5.0M,0.01%NaN 3)for elution.Two fractions were collected,dialysed and freeze-dried (neutral fractions:An or Gn,ionic fractions:Ai or Gi,Fig.1).2.5.Enzymic degradation by a -l -arabinofuranosidase or by a combination of endo-arabinanase and a -l -arabinofuranosidasePG1Gi-and GF x PG1Ai-samples (90mg,30ml in 0.05M sodium acetate buffer,containing 0.01%NaN 3)were incu-bated with arabinofuranosidase (gift from Novo Nordisk A/S,Bagsvaerd,DK;60IU,pH 4.5,40ЊC,5h,additional 40IU,40ЊC,48h)or by arabinanase and arabinofuranosidase (50mg GF x PG1AiAF1-sample in 30ml 0.05M sodiumG.R.Strasser,R.Amado`/Carbohydrate Polymers 44(2001)63–7064Fig.1.Scheme for the isolation and fractionation of pectic substances from red beet cell wall material by CDTA-extraction,AEC,GFC and treatment with different pectin-degrading enzymes.acetate buffer containing0.01%NaN3,33IU and40IU,pH 5.0,40ЊC,48h).The solutions werefiltered(0.45m m, Millipore)after inactivation of the enzymes(100ЊC, 10min)and fractionated by GFC(Sephacryl S-200, Pharmacia,95×2:6cm using0.05M sodium acetate buffer(pH5.0containing0.01%NaN3)at aflow-rate of 1.8ml/min.The separations were monitored using a HP 1037A RI-Detector(30ЊC).The corresponding fractions were pooled.High molecular weight fractions were dialysed (SpectraPor3Membranes,Socochim SA,Lausanne,CH) and freeze-dried(fractions:AF1,Fig.1).2.6.Analytical methodsNeutral sugars and uronic acids of enzymatically non-treated samples were determined by GC as alditol–acetates (Blakeney,Harris,Henry&Stone,1983)and photo-metrically by the m-hydroxy-diphenyl method(Blumen-krantz&Asboe-Hansen,1973),respectively.Analysis of the glycosidic linkages in polysaccharides was performed by methylation analysis after carbodiimide-activated reduc-tion with NaBD4.Carbodiimide-activated reduction was carried out by a method developed by Kim and Carpita (1992)and modified by Wechsler(1997).Methylation analysis was performed based on Harris,Henry,Blakeney and Stone(1984)and Kvernheim(1987),as modified by Wechsler(1997).The fraction PG1GiAF1was additionally methylated using CD3I instead of CH3I.2.7.Partial acid hydrolysis of RG-IA solution of fraction PG1Ai(40mg)in2M trifluoroacetic acid(TFA,3ml)was treated at100ЊC for1h(An,O’Neill, Albersheim&Darvill,1994).The solvent was removed by co-distillation with2-propanol.A solution of the residue in water (1ml)was applied to a DEAE-Sepharose CL-6B column (Pharmacia,35×2:6cm :The column was eluted with water(100ml),and then with1.5%formic acid(200ml). The solvent of the acidic fraction was removed by co-distillation with2-propanol.2.8.Purification of the acidic oligosaccharides obtained by partial acid hydrolysisThe acidic oligosaccharides were purified using a semi-preparative CarboPac PA-100column(9×250mm; Dionex).The column was eluted at4ml/min with a gradient of NaOAc in100mM NaOH as follows:0–50mM NaOAc (0–5min),50–150mM NaOAc(5–20min),150–200mM NaOAc(20–30min),350–400mM NaOAc(30–35min), 0.9mM NaOAc(35–40min).The column was re-equili-brated in100mM NaOH for15min prior to the next injec-tion.The column eluent was split,25%going through a pulsed electrochemical detector(gold working electrode) and75%collected by an automatic fraction collector (LKB Superrac2211,Pharmacia).Fractions were desalted by an anion self-regenerating supressor(ASRS-I,Dionex) and dried by co-distillation with2-propanol.2.9.Glycosyl-residue composition analysisThe sample was hydrolysed in2M TFA(1ml)at120ЊC for1h.The solvent was removed by co-distillation with2-propanol.A solution of the residue in water(1ml)was analysed using a CarboPac PA-100column(4×250mm; Dionex)equipped with a pulsed electrochemical detec-tor(gold working electrode).The column was eluted at 1ml/min with a gradient as follows:100–0mM NaOH (0–0.1min),0–100mM NaOH(0.1–20min),0–250mM NaOAc in100mM NaOH(20–50min),0.9mM NaOAc in 0.1M NaOH(50–55min).The column was re-equilibrated in100mM NaOH for15min prior to the next injection.G.R.Strasser,R.Amado`/Carbohydrate Polymers44(2001)63–7065Fig.2.GFC(Sephacryl S-300HR)of CDTA-soluble red beet pectin fractions after degradation with a purified PG.3.Results and discussion3.1.CDTA-soluble pectinsRed beet pectins isolated by CDTA from the AIR were fractionated by AEC and GFC.Besides galacturonic acid, arabinose and galactose,typical residues known to be present in side chains of pectins(arabinan,galactan,and type-II arabinogalactan)were detected in the CDTA extract and in the fractions obtained by AEC and GFC.In addition, sugars indicating the presence of RG-II such as1,3H-Api,T-Fuc,1,3,4-Fuc and1,3-Rha p were detected as well.The results of these investigations are summarised in the paper by Strasser et al.(1996).Incubation of the different chro-matographic fractions with various enzymes followed by chromatographic fractionation of the degradation products (Fig.1)led to a more detailed insight into the structure of CDTA-soluble pectic substances.3.2.Degradation by PG and fractionation by GFC Samples degraded by PG yielded three fractions each (PG1,PG2and PG3,Fig.2).PG3-fractions were analysed by HPAEC-PAD,and were shown to be composed of mono-, di-and trigalacturonic acid.This fraction was quantitatively predominant and indicated the presence of large homoga-lacturonan domains in the CDTA-soluble pectic substances of red beet.PG2-fractions contained high amounts of1,3H-Api p,T-2-O-Me-Fuc p,T-2-O-Me-Xyl p,1,3,4-Fuc p and 1,2-GlcA p,indicating the presence of an RG-II in the inter-mediate molecular weight fraction obtained by GFC(results are presented in part II of this study,Strasser&Amado`, 2000).Results of the methylation analyses of the PG1-frac-tions are presented in Table1.All fractions contain high amounts of arabinose.The high molecular weight fraction GF1PG1contains more and considerably more branched arabinans than the two fractions with lower molecular weights,GF2PG1and GF3PG1.1,3-Gal p,1,6-Gal p and 1,3,6-Gal p residues indicate the presence of type-II arabino-galactan.Smaller molecules seem to contain more type-II arabinogalactan than larger molecules.Furthermore, surprisingly high values of terminally linked glucuronic acid were detected.The results obtained with the PG1-frac-tions strongly suggest the presence of RG-I-like structures in the not or only slightly PG-sensitive part of CDTA-solu-ble pectins from red beet.The absence of1,3H-Api p,1,3,4-Fuc p and1,2-GlcA p in the PG1-fractions clearly indicate that they are not contaminated with RG-II.3.3.Degradation of PG1-fractions by arabinanase or galactanaseTreatment of the different PG1-fractions by arabinanase or by galactanase led to a release of neutral polysaccharides. Methylation analysis of fractions obtained by AEC showed similar results for the ionic fractions(Ai and Gi)compared to their educts.Only slightly smaller amounts of arabinose could be detected(results not presented).The neutral frac-tions removed by either arabinanase(An)or galactanase (Gn)showed the presence of an arabinan in all the PG1-fractions(Table1).This result suggests that some arabinans are linked directly or indirectly through a galactan to the pectic backbone.The arabinan removed by arabinanase was much more branched(resistant against further degradation) than the arabinan removed by galactanase.These results are consistent with the results published by Sakamoto and Sakai (1995),who found a fraction similar to our Gn-fraction in sugar beet pectin containing95%of arabinose.Furthermore de Vries,den Uijl,Voragen,Rombouts and Pilnik(1983) have isolated fragments of arabinogalactans with side-chains consisting of arabinans with a degree of polymerisa-tion of about25from apple pectins by treatment with a galactanase.Yamada,Kiyohara,Cyong and Otsuka(1987) found some arabinans directly attached to a1,4-linked galactan chain.For CDTA-soluble pectins from red beet the amount of galactose remained nearly unchanged.There-fore,it can be concluded that the linking galactans must be relatively short.Arabinans liberated by the arabinanase treatment contained about97mol%arabinose,thus indicat-ing that essentially no other sugars are attached to the outer regions(non reducing ends)of the arabinans.3.4.Treatment of PG1Gi-and GFxPG1Ai-fractions by an arabinofuranosidase and by a combination of arabinanase and arabinofuranosidaseDegradation by arabinofuranosidase removed most term-inally linked arabinose(Table2),whereas the linear1,5-linked arabinofuranose remained nearly unchanged.This might be because of sterical inaccessibility.Similar results are described in the literature(Cheetham,Cheung&Evans, 1993;McCleary,1989;Renard,Voragen,Thibault&Pilnik, 1991).A dramatic change was observed for the patterns of the galactose residues.Since the arabinofuranosidase removed only single arabinose residues(as shown by HPAEC-PAD)this result indicates that arabinose residues were originally linked to galactans.The sum of galactose residues remained constant and is calculated to100mol% (Table3).From Table3it can easily be concluded that the removal of arabinose leads to a decrease of1,3,6-Gal p,1,4-Gal p and1,3-Gal p residues,which became1,6-Gal p and T-Gal p,respectively.These results suggest the arabinose resi-dues in type-II arabinogalactans to be linked to the position O-3in galactans.Moreover the proportion of1,6-Gal p (outer side-chains of type-II arabinogalactan)to1,3,6-Gal p(branching points of type-II arabinogalactan)allows the estimation of an average number of residues within an outer side-chain of type-II arabinogalactan.In CDTA-solu-ble pectins of red beet approx.1.5–2.11,6-linked galactose residues are linked to approx.50%of the O-6-position of a 1,3-linked galactan chain(inner chain).The decrease of the residue1,4-Gal p is an additional clue to the existence of arabinans linked through galactans.G.R.Strasser,R.Amado`/Carbohydrate Polymers44(2001)63–70 66Most of the remaining arabinose residues were removed by simultaneous incubation with arabinanase and arabino-furanosidase(Table2).The removal of arabinose led to an enrichment of the other sugars.However,fucose,xylose, glucose and mannose were not affected,and are thus believed not to be part of the RG-I present in red beet. Rhamnose was mainly present as terminal-,1,2-or1,2,4-linked residue.The ratio of1,2,4-Rha p to arabinose was much higher than one suggesting that most O-4-positions of rhamnose are substituted by galactose.During the differ-ent enzymatic degradation steps the ratio of the backbone sugars1,2-Rha p and1,2,4-Rha p remained nearly unchanged in all samples,indicating that sugars attached to the O-4-position of rhamnose were not removed.In all samples T-Rha p was found in almost equal amounts to1,4-GlcA p suggesting a terminal disaccharide Rha p-(134)-GlcA p-(13as was described to be present in type-II arabinoga-lactan(Mollard&Joseleau,1994;Pellerin,Vidal,Williams &Brillouet,1995).Remarkably high amounts of terminally linked glucuronic acid residues were present in the enriched samples,probably attached to galactans(see below).Link-age analysis of the fraction PG1GiAF1using CD3I showed that two-thirds of the glucuronic acid residues were originally methylated at position O-4.Galacturonic acid was found in approx.equal amounts to the sum of 1,2-Rha p and1,2,4-Rha p,thus indicating the presence of an alternating rhamnogalacturonan backbone.Considerable amounts of1,3,4-GalA p were shown to be present in all samples.The almost total absence of xylose suggests that the1,3,4-GalA p-residues are not part of a xylogalacturonan. Glucuronic acid does not seem to be a substituent either(see below).Because of the remaining residues,galactose as well as arabinose might possibly be attached to the O-3-position of galacturonic acid.Both linkages are already described to be present within the plant kingdom(Guillon&Thibault, 1989;Samuelson et al.,1996).3.5.Semipreparative HPAEC-PAD fractionation and structural characterisation of the acidic material released by partial acid hydrolysis of fraction PG1GiAF1The acidic material released by partial acid hydrolysis of PG1GiAF1was isolated by AEC and then fractionated by HPAEC using a semipreparative CarboPac PA-100column (Fig.3).Some fractions were pooled,desalted using a supressor and analysed for their glycosyl residues by analy-tical HPAEC-PAD(Table4).The values for each sugar and for each pool were calculated to the corresponding concen-tration of the respective sugar at a specific retention time. These results were graphically compared with the original HPAEC-PAD-chromatogram(Fig.3).Peak A is composed of rhamnose and galacturonic acid.G.R.Strasser,R.Amado`/Carbohydrate Polymers44(2001)63–7067 Table1Glycosyl-linkage composition(mol%)of red beet RG-I-fractions obtained by enzymic treatment with PG,arabinanase and galactanase(indication of the different fractions,see text and Fig.1)PG1GF1PG1GF2PG1GF3PG1PG1Gn PG1An GF1PG1An GF2PG1n GF3PG1An T-Ara f24.326.724.724.225.638.438.838.939.3T-Ara p0.30.30.30.40.20.20.30.50.31,2-Ara f0.50.30.60.70.40.3 1.00.40.51,3-Ara f 2.2 2.5 2.1 2.0 2.1 3.2 1.6 3.4 3.51,5-Ara f18.620.819.318.944.222.022.822.622.11,2,5-Ara f 2.2 1.7 2.6 2.7 2.5 1.1 1.1 1.2 1.31,3,5-Ara f12.215.411.810.318.830.529.928.628.71,2,3,5-Ara f 2.1 2.0 1.5 1.8 1.8 3.5 3.3 2.9 3.1T-Gal p 1.8 2.7 2.6 2.10.40.10.10.10.01,3-Gal p 3.0 1.7 2.6 3.40.80.00.00.50.11,4-Gal p 3.9 5.4 4.1 3.00.40.50.20.60.51,6-Gal p 1.8 1.7 2.2 2.20.30.00.00.00.01,3,4-Gal p0.00.20.00.10.00.00.00.00.01,3,6-Gal p9.4 3.510.413.5 1.30.10.30.10.01,4-Glc p0.60.30.30.30.70.20.30.30.21,4-Man p0.00.00.00.00.00.00.30.20.3T-Rha p0.50.8 1.0 1.00.00.00.00.00.01,2-Rha p 1.5 1.5 1.3 1.30.00.00.00.00.01,2,4-Rha p 2.7 2.3 1.9 2.10.20.00.00.00.01,4-Xyl p0.20.00.10.00.10.00.00.00.01,4-GalA p 5.7 4.4 2.9 2.10.20.00.00.00.01,2,4-GalA p0.20.20.20.20.00.00.00.00.01,3,4-GalA p 1.2 1.5 1.40.90.00.00.00.00.0T-GlcA p 4.2 3.3 5.6 6.20.00.00.00.00.01,4-GlcA p0.60.40.60.70.00.00.00.00.0Total100100100100100100100100100Yield(%)13111515424201610This peak is assumed to consist of the dimer a -d -GalA p –(132)-a -Rha p ,which was confirmed by the formation of peak A during hydrolysis of peak F (see below).Peaks B and C contain more or less exclusively galactose and 4-O-methylglucuronic acid.Considering the results obtained by the linkage analysis,the measured retention time and the comparison with results by An et al.(1994),led to the conclusion that these peaks contain dimers composed of 4-O-Me–GlcA–Gal.The type of linkage of these dimers remains unknown.Peaks D and E contain galactose and glucuronic acid and suggest the presence of dimers of GlcA–Gal.In addition,peak D contains some monomeric galacturonic acid,which elutes at exactly the same retention time.The surpris-ingly high amounts of glucuronic acid (peak E)and 4-O-methylglucuronic acid (peak C)can also be explained by the presence of free monomeric uronic acids that co-elute with the dimers.Peak F contains predominantly rhamnose and galacturonic paring with the results obtained by An et al.(1994),peak F couldcorrespond to the tetramer a -d -GalA p –(132)-a -Rha p –(134)-a -d -GalA p –(132)-a -Rha p .In summary,these results demonstrate that 4-O-methylglucuronic and glucuronic acid are exclusively attached to galactose.G.R.Strasser,R.Amado`/Carbohydrate Polymers 44(2001)63–7068Table 3Galactose residues of PG-treated red beet RG-I-fractions before and after arabinofuranosidase degradation (indication of the different fractions,see text and Fig.1)GF1PG1GF2PG1GF3PG1AiAF1Differ.Ai AF1Differ.Ai AF1Differ.T-Gal p 172371014491241,3-Gal p 107Ϫ31210Ϫ21812Ϫ51,4-Gal p 3533Ϫ21815Ϫ3129Ϫ31,6-Gal p 11251493828940311,2,4-Gal p 0000000001,3,4-Gal p 10Ϫ10000001,3,6-Gal p 2612Ϫ145123Ϫ285327Ϫ26Total100100100100100100Table 2Glycosyl-linkage composition (mol%)of red beet RG-I-fractions obtained by enzymic treatment with PG ϩarabinofuranosidase and PG ϩarabinofuranosidase ϩarabinanase,respectively (indication of the different fractions,see text and Fig.1)GF1PG1AiAF1GF2PG1AiAF1GF3PG1AiAF1GF1PG1AAF1GF2PG1AAF1GF3PG1AAF1T-Ara f 4.8 3.9 3.9 2.3 2.5 2.9T-Ara p 0.30.30.30.20.20.31,2-Ara f 0.7 1.1 1.70.7 1.0 1.11,3-Ara f 4.4 3.1 2.1 1.6 1.2 1.91,5-Ara f 17.410.5 4.4 1.4 1.4 3.91,2,5-Ara f 1.6 1.70.00.00.30.31,3,5-Ara f 2.2 1.60.90.40.00.81,2,3,5-Ara f 0.00.10.10.00.00.1T-Fuc p 0.00.10.00.20.10.0T-Gal p 8.0 6.67.210.88.28.31,3-Gal p 2.4 4.67.1 3.9 6.1 6.91,4-Gal p 11.17.0 5.214.58.0 5.41,6-Gal p 8.517.322.912.120.323.21,2,4-Gal p 0.00.00.00.00.00.71,3,6-Gal p 3.910.715.5 5.512.515.91,4-Glc p 0.60.40.30.30.70.51,6-Man p 0.00.00.00.00.00.2T-Rha p 1.1 1.5 1.7 1.2 1.9 1.91,2-Rha p 2.8 2.9 1.7 4.6 2.9 1.41,3-Rha p 0.30.00.00.00.00.01,2,3-Rha p 0.20.00.00.00.00.01,2,4-Rha p 8.1 6.1 4.710.48.1 4.41,2,3,4-Rha p 0.20.10.10.60.20.1T-Xyl p 0.20.10.00.00.10.01,4-Xyl p 0.20.10.10.20.00.0T-GalA p 0.00.00.00.50.00.01,4-GalA p 8.6 5.0 3.411.1 5.4 3.21,2,4-GalA p 0.50.40.20.60.50.21,3,4-GalA p 3.7 2.6 1.9 5.1 3.2 2.01,4,6-GalA p 0.00.00.00.50.00.0T-GlcA p 7.310.912.810.013.512.91,4-GlcA p 0.8 1.4 1.7 1.1 1.7 1.7Total 100.0100.0100.0100.0100.0100.0Yield (%)555460878079Oligosaccharides containing 4-O-methylglucuronic acid or glucuronic acid do not contain galacturonic acid or rhamnose.4.ConclusionIncubation of CDTA-soluble pectic substances of red beet with a PG yielded an enzyme-resistant fraction.Linkage analyses indicated the presence of an RG-I.The ratio of rhamnose to galacturonic acid and the results obtained using partial hydrolysis and semipreparative HPAEC-PAD suggest the presence of an alternating rhamnogalacturonan backbone.This backbone is highly ramified,since two-thirds of the rhamnose residues are branched.Side chains consisting of arabinans,galactans and type-II arabinogalac-tans are attached to the RG-backbone.Arabinans have been shown to have an a -(135)-linked backbone.Single arabinose residues or small oligoarabinans are attached to the backbone at the O-3-position,and to a lower extent at the O-2-position.Some of the arabinans are indirectly attached through small galactans to the pectic backbone.Short b -(134)galactan chains have been shown to occur in red beet RG-I as well.Most of them are attached directly to the pectic backbone.Type-II arabinogalactans are the most complex side chains within red beet RG-I pectins.They consist of anG.R.Strasser,R.Amado `/Carbohydrate Polymers 44(2001)63–7069Table 4Monosaccharide composition of acidic material released from a PG ϩgalactanase ϩarabinofuranosidase-treated red beet RG-I-fraction after partial acid hydrolysis and HPAEC-PAD fractionation (indication of the different fractions,see text)Pool number P1P2P3P4P5P6P7P8P9P10P11P12P13P14Rha 6550010000000072Gal142828183166641410141937166Me-GluA 081634330164011111GalA 18420010035100048GlcA 00112111471559101Total391324422789781212022359727129Total/fract.1)204444117849277571232522Num./fract.2)23221233433356Fig.3.HPAEC-PAD chromatograms of acidic material released from a (PG ϩgalactanase ϩarabinofuranosidase)-treated red beet RG-I-fraction after partialacid hydrolysis (bold line),compared to calculated sugar concentrations at specific retention times (thin lines).inner chain composed of b-(133)-linked galactose residues.Approximately50%of the galactose residues are substitutedat the O-6-position by short outer side chains consisting of b-(136)-linked galactose residues(average:1–3resi-dues).Some of these outer side chains are substituted byterminally linked glucuronic acid.Further work is needed tofigure out the type and position of the glycosidic linkagebetween glucuronic acid and galactose(a-or b-,(133)-,(134)-or(136)-linked,respectively).The resultsobtained in this study suggest the presence of at least twodifferently linked glucuronic acid residues in red beet RG-I.Approximately65%of the glucuronic acid residues aresubstituted by a methyl ether group and approx.10%aremost probably substituted by terminally linked rhamnoseresidues.Further work is needed to elucidate thefine struc-ture of red beet RG-I.AcknowledgementsWe thank Novo-Nordisk A/S,(Bagsvaerd,DK)for thegenerous gift of enzymes.ReferencesAlbersheim,P.,Darvill,A.G.,O’Neill,M.A.,Schols,H.A.,&Voragen,A.G.J.(1996).An hypothesis:the same six polysaccharides arecomponents of the primary cell walls of all higher plants.In J.Visser &A.G.J.Voragen,Pectins and pectinases(pp.47–55).Amsterdam: Elsevier.An,J.,O’Neill,M.A.,Albersheim,P.,&Darvill,A.G.(1994).Isolation and structural characterization of b-d-glucosyluronic acid and4-O-methyl-b-d-glucosyluronic acid-containing oligosaccharides from the cell-wall pectic polysaccharide,rhamnogalacturonan I.Carbohydrate Research,252,235–243.Blakeney,A.B.,Harris,P.J.,Henry,R.J.,&Stone,B.A.(1983).A simple and rapid preparation of alditol acetates for monosaccharide analysis.Carbohydrate Research,113,291–299.Blumenkrantz,N.,&Asboe-Hansen,G.(1973).New method for quantita-tive determination of uronic acids.Analytical Biochemistry,54,484–489.Carpita,N.C.,&Gibeaut,D.M.(1993).Structural models of primary cell walls inflowering plants:consistency of molecular structure with the physical properties of the walls during growth.The Plant Journal,3,1–30.Cheetham,N.W.H.,Cheung,P.C.-K.,&Evans,A.J.(1993).Structure of the principal non-starch polysaccharide from cotyledons of Lupinus angustifolius(cultivar Gungurru).Carbohydrate Polymers,22,37–47. Elgorriaga,M.(1994).Enzymkinetische Untersuchungen zum Abbauver-halten einer gereinigten Endo-Polygalacturonase von Aspergillus niger.PhD thesis No.10660,ETH Zurich.Guillon,F.,&Thibault,J.F.(1989).Enzymatic hydrolysis of the hairy fragments of sugar-beet pectin.Carbohydrate Research,190,97–108. Harris,P.J.,Henry,R.J.,Blakeney,A.B.,&Stone,B.A.(1984).An improved procedure for the methylation analysis of oligosaccharides and polysaccharides.Carbohydrate Research,127,59–73.John,M.A.,&Dey,P.M.(1986).Postharvest changes in fruit cell wall.Advances in Food Research,30,139–193.Kim,J.-B.,&Carpita,N.C.(1992).Changes in esterification of the uronic acid groups of cell wall polysaccharides during elongation of maize coleoptiles.Plant Physiology,98,646–653.Kvernheim,A.L.(1987).Methylation analysis of polysaccharides with butyllithium in dimethyl sulfoxide.Acta Chemica Scandinavica Series B,41,150–152.McCann,M.C.,Roberts,K.,Wilson,R.H.,Gidley,M.J.,Gibeaut,D.M., Kim,J.B.,&Carpita,N.C.(1995).Old and new ways to probe plant cell-wall architecture.Canadian Journal of Botany,73,103–113. McCleary,B.V.(1989).Novel and selective substrates for the assay of endo-arabinanase.In G.O.Phillips,P.A.Williams&D.J.Wedlock Gums and stabilisers for the food industry(pp.291–298).vol.5.Oxford:Oxford University Press.Mollard,A.,&Joseleau,J.-P.(1994).Acacia senegal cells cultured in suspension secrete a hydroxyproline-deficient arabinogalactan-protein.Plant Physiology and Biochemistry,32,703–709.Pellerin,P.,Vidal,S.,Williams,P.,&Brillouet,J.-M.(1995).Character-ization offive type II arabinogalactan-protein fractions from red wine of increasing uronic acid content.Carbohydrate Research,277,135–143. Renard,C.M.G.C.,Voragen,A.G.J.,Thibault,J.-F.,&Pilnik,W.(1991).Comparison between enzymatically and chemically extracted pectins from apple cell walls.Animal Feed Science and Technology,32,69–75. Sakamoto,T.,&Sakai,T.(1995).Analysis of structure of sugar-beet pectin by enzymatic methods.Phytochemistry,39,821–823. Samuelson,A.B.,Paulsen,B.S.,Wold,J.K.,Otsuka,H.,Kiyohara,H., Yamada,H.,&Knutsen,S.H.(1996).Characterisation of a biologically active pectin from Plantago major L.Carbohydrate Polymers,30,37–44.Strasser,G.R.,&Amado`,R.(2000).Pectic substances from Red Beet(Beta vulgaris conditiva).Part II.Structural characterisation of rhamnogalac-turonan II(in preparation).Strasser,G.R.,Wechsler,D.E.,&Amado`,R.(1996).Structural features of pectic polysaccharides of red beet(Beta vulgaris conditiva).In J.Visser &A.G.J.Voragen,Pectins and pectinases(pp.631–636).Amsterdam: Elsevier.de Vries,J.A.,den Uijl,C.H.,Voragen,A.G.J.,Rombouts,F.M.,& Pilnik,W.(1983).Structural features of the neutral sugar side chains of apple pectic substances.Carbohydrate Polymers,3,193–205. Wechsler D.E.(1997).Charakterisierung der Struktur von Pektinen wa¨hrend der Reifung und Lagerung von A¨pfeln.PhD thesis.ETH No.12044,Zurich.Yamada,H.,Kiyohara,H.,Cyong,J.-C.,&Otsuka,Y.(1987).Structural characterization of an anti-complementary arabinogalactan from the roots of Angelica acutiloba Kitagawa.Carbohydrate Research,159, 275–291.G.R.Strasser,R.Amado`/Carbohydrate Polymers44(2001)63–70 70。

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carbohydrate polymers影响因子

carbohydrate polymers影响因子

carbohydrate polymers影响因子Carbohydrate polymers, commonly referred to as “starch,” is an important macronutrient found in plants. The macromolecules of carbohydrate polymers play a vital role in human health and nutrition as an energy source and as a structural component of plant cells. Additionally, carbohydrate polymers are also utilized in various industries for a variety of uses.The primary factor that affects the macromolecular structure of carbohydrate polymers is the source of the raw material. Starch can be derived from a variety of plant sources such as corn, wheat, potatoes, and rice and the macromolecular structure of the starch molecules differs accordingly. The size, shape, and arrangement of the macromolecules are of distinct importance since they are intimately associated with the biochemical and nutraceutical properties of starch molecules.In general, starch molecules are primarily based on two distinct types of macromolecules, amylose and amylopectin. Amylose is composed of straight-chain glucose molecules, while amylopectin is composed of branched glucose molecules. The ratio of amylose to amylopectin can vary significantly between different sources which may have an influence on properties such as solubility, viscosity, swelling, and water absorption and retention capacities.Another factor that affects the macromolecular structure of carbohydrate polymers is the chemical processing methods employed. Starch molecules can be modified by enzymatic processing and other chemical treatments resulting in different physical characteristics such as increased solubility and stability, improved sensitivity to water and lower viscosity. Chemical processing can also be used to produce a gelling agent when carbohydrates are treated with anionic detergents.Lastly, the environment in which starch molecules are processed can also have an impact on their macromolecular structure. For instance, changes in temperature and pH levels can alter the structure of the molecules. In addition, other environmental conditions such as the presence of light, oxygen, and ultraviolet radiation can also affect the conformation of the molecules.In conclusion, there are a variety of different factors which can influence the macromolecular structure of carbohydrate polymers. Depending on the source of starch, the chemical processing methods employed and the environment in which it is processed, the physical properties and properties associated with nutritional and functional features ofstarch can be altered. Therefore, it is important to understand the interactions between these factors in order to develop novel products with appropriate qualities.。

Urea and ethanolamine as a mixed plasticizer for thermoplastic starch

Urea and ethanolamine as a mixed plasticizer for thermoplastic starch

Urea and ethanolamine as a mixed plasticizer for thermoplastic starchX.F.Ma,J.G.Yu *,J.J.WanSchool of Science,Tianjn University,Tianjin 300072,ChinaReceived 17October 2005;received in revised form 15November 2005;accepted 23November 2005Available online 18January 2006AbstractMixtures of urea and ethanolamine were used as plasticizers for preparing thermoplastic starch (TPS)in a single-screw extruder.The interaction between urea/ethanolamine and starch was investigated using Fourier Transform Infrared (FT-IR).Glass transition temperature of TPS was tested by Differential scanning calorimetry (DSC).Both FT-IR and DSC proved that the mixture of urea and ethanolamine could form more stable and strong hydrogen bonds with starch molecules than the conventional plasticizer,glycerol.By Scanning Electron Microscope (SEM)native starch granules were proved to transfer to a continuous phase.The thermal stability,mechanical properties and starch retrogradation behavior were also studied by TG (Thermal Gross),tensile testing and X-ray Diffraction (XRD),respectively.TPS plasticized by urea (15wt/wt%)and ethanolamine (15wt/wt%)showed a better thermal stability and mechanical properties than conventional TPS plasticized by glycerol.Moreover,the tensile stress,strain and Energy Break,respectively,reached 9.00MPa,34.4%and 1.34N m.At the same time,this mixed plasticizer could effectively restrain the retrogradation of starch and urea.q 2005Elsevier Ltd.All rights reserved.Keywords:Thermoplastic starch;Retrogradation;Ethanolamine;Urea1.IntroductionMuch effort (Averous,Fauconnier,Moro,&Fringant,2000;Fang &Hanna,2001;Martin &Averous,2001)had recently been made to develop biodegradable materials because of the worldwide environment and resources problems resulted from petroleum-derived plastics.Starch,a natural renewable polysaccharide obtained from a great variety of crops,was one of the promising raw materials for the production of biodegradable plastics (Petersen,Væggemose,&Bertelsen,1999).However,native starch commonly existed in granule structure with about 15–45%crystallinity (Zobel,1998),and starch-based materials were susceptible to aging and starch re-crystallization (retrogradation).TPS plasticized with glycerol,a conventional TPS,was thought to tend to retrogradation after being stored for a period of time,and this retrogradation embrittled TPS (Van Soest &Knooren,1997).Urea was proven to prevent starch retrogradation.It was,however,a solid with little internal flexibility and hence urea-plasticized TPS became rigid and brittle (Stein &Greene,1997).It was hypothesized that the introduction of another plasticizer for starch,which was a good solvent for urea,prevented urea from separating out.Preliminary studies in our laboratory had shown that Ethanolamine could availably suppress the retrogradation of thermoplastic starch and make thermoplastic starch more flexible,but the tensile failure stress was weaker than the conventional glycerol-plasticized TPS (GPTPS).In this paper,a combination of urea and ethanola-mine would effectively restrain TPS retrogradation,improve mechanical properties of TPS and prevent urea from separating out.It was suspected,therefore,that this mixture might be a better plasticizer for starch.In this paper,GPTPS was regarded as the reference.The hydrogen bonding interaction between urea/ethanolamine and starch using FT-IR was described.And the properties of TPS plasticized by urea and ethanolamine,such as thermal stability,starch retrogradation behavior and mechanical properties,were also studied.2.Experimental section 2.1.MaterialsCornstarch (10%moisture)was obtained from Langfang Starch Company (Langfang,Heibei,China).The plasticizers (Chemical Purity),glycerol,ethanolamine and urea,wereCarbohydrate Polymers 64(2006)267–273/locate/carbpol0144-8617/$-see front matter q 2005Elsevier Ltd.All rights reserved.doi:10.1016/j.carbpol.2005.11.042*Corresponding author.Tel.:C 862227406144;fax:C 862227403475.E-mail address:maxiaofei@ (J.G.Yu).purchased from Tianjin Chemical Reagent Factory (Tianjin,China).2.2.PlasticizationThe plasticizers were blended (3000rpm,2min)with cornstarch in the High Speed Mixer GH-100Y (made in China),and then stored overnight.The ratio of plasticizers and cornstarch (wt/wt)was 30:100.When two plasticizers were used together,another step for the pre-mixture of them was required.GPTPS,urea-plasticized TPS (UPTPS),ethanola-mine-plasticized TPS (EPTPS)and urea/ethanolamine-plasti-cized TPS (UEPTPS)were prepared as following:the mixtures were manually fed into the single screw Plastic Extruder SJ-25(s)(Screw Ratio L /D Z 25:1,made in China)with a screw speed of 20rpm.The temperature profile along the extruder barrel was 120,130,130,1108C (from feed zone to die).The die was a round sheet with the diameter 3mm holes.The contents of materials in this paper were all referred to weight contents.2.3.Fourier transform infrared (FT-IR)spectroscopy The IR spectra were measured with BIO-RAD FTS3000IR Spectrum Scanner.The extruded TPS strips were pressured to the transparent slices with the thickness of around 0.2mm in the Flat Sulfuration Machine,and tested by the transmission method.2.4.Scanning electron microscope (SEM)The native starch and the fracture surfaces of extruded TPS strips were performed with Scanning Electron Microscope Philips XL-3,operating at an acceleration voltage of 20kV.Native starch powders were suspended in acetone.The suspension drops were drawn on the glass flake,dried for removing the acetone,and then vacuum coated with gold for SEM.TPS strip samples were cooled in liquid nitrogen,and then broken.The fracture faces were vacuum coated with gold for SEM.2.5.Thermal analysis (TG)TPS was cut into small pieces,which were tested by ZRY-ZP thermal analysis instrument (Beijing Plastic Machinery Factory,Beijing,China).The samples were about 5–10mg in a sealed aluminum pan,the scope of testing temperature was from the room temperature to 5008C and the heated rate was 158C/min.2.6.Differential scanning calorimetry (DSC)DSC measurements were carried out in a Perkin–Elmer DSC-7(Perkin–Elmer Cetus,Norwalk,CT).Calibration was based on pure indium.An empty pan was used as reference.Prior to analysis,samples were placed at room temperature (RH 33%)for 1week.Samples were scanned at a rateofFig.1.The styles of the most possible hydrogen bonds in EPTPS,UPTPS and GPTPS.12001150110010501000950900t r a n s m i t t a n c e102010801157114911471146114910761073107410771017101410131015e dc baWavenumber/cm –1Fig.2.The FT-IR spectra of TPS with different plasticizers:(a)native starch;(b)TPS containing 30%glycerol;(c)TPS containing 30%urea;(d)TPS containing 10%urea and 15%ethanolamine;(e)TPS containing 30%ethanolamine.X.F.Ma et al./Carbohydrate Polymers 64(2006)267–273268108C/min in sealed pan.Glass transition temperatures were determined from resulting thermograms as the midpoint between onset and end temperatures of step changes in heat flow observed during heating and identified as second-order transitions.2.7.X-ray diffractometryThe extruded TPS strips were pressured at 10MPa with the Flat Sulfuration Machine.After a period of storage time at several RHs,the slices were placed in a sample holder for X-ray diffractometry.The powders were packed tightly in the sample holder.X-ray diffraction patterns were recorded in the reflection mode in angular range 10–308(2q )at the ambient temperature by a BDX3300diffractometer,operated at theCu K a wavelength of 1.542A˚.The radiation from the anode,operating at 36KV and 20mA,monochromized with a 15m m nickel foil.The diffractometer was equipped with 18divergence slit,a 16mm beam bask,a 0.2mm receiving slit and a 18scatter slit.Radiation was detected with a proportional detector.2.8.Mechanical testingSamples of 8cm !3mm in size were cut from the extruded strips,pressured with the Flat Sulfuration Machine.The Testometric AX M350-10KN Materials Testing Machine was operated and a crosshead speed of 10mm/min was used for tensile testing (ISO 1184–1983standard).The data was averages of 5–8specimens.Fig.3.SEM micrograph of native starch granules and the fracture face of TPS.X.F.Ma et al./Carbohydrate Polymers 64(2006)267–2732693.Results and discussion3.1.The hydrogen bonding interactionNative starch contained two different molecular structures:the linear (1,4)-linked a -D -glucan amylose and highly (1,6)-branched a -D -glucan amylopectin (Garci’a-Alonso,Jime’ne-z-Escrig,Mart’in-Carron,Bravo,&Saura-Calixto,1999).There was a lot of hydrogen interaction in native starch,which restrained the movement of starch molecules and made it difficult to process starch without plasticizers.Under the action of high temperature,shear and plasticizers,starch could be processed into a mouldable thermoplastic,a material knownas thermoplastic starch (TPS)(Forssell,Mikkila¨,Moates,&Parker,1997).During the thermoplastic process,added plasticizers and water contained in native starch played an indispensable role (Hulleman,Janssen,&Feil,1998),because the plasticizers could form the hydrogen bonds with starch,take the place of the strong action between hydroxyl groups of starch molecules,and make starch thermoplastic.OH groups in ethanolamine,O a C and NH 2groups in urea and OH groups in glycerol could form hydrogen bonds with starch.The styles of the most possible hydrogen bonds in EPTPS,UPTPS and GPTPS were shown in Fig.1.Formation of homogeneous TPS was a result of strong interactions by hydrogen bonds between starch and plastici-zers.The analysis of FTIR spectra of the blends enabledhydrogen bond interactions to be identified (Ma &Yu,2004).Moreover,the lower the peak frequency of C–O group in starch was,the stronger the interaction between starch and plasticizers was.FT-IR spectra for TPS with different plasticizers were shown in Fig.2.There were three characteristic peaks of starch between 990and 1160cm K 1,attributed to C–O bond stretching.The peaks at around 1150and 1080cm K 1were characteristic of C–O–H in starch,while the peak between 990and 1030cm K 1was characteristic of the anhydroglucose ring O–C stretch (Fang,Fowler,Tomkinson,&Hill,2002).As shown in Fig.2,compared to three characteristic peaks of native starch,those of TPS located at the lower wave number,and the double-peak appeared at between 990and 1030cm K 1in c,d and e instead of the single peak of native starch (a in Fig.2),because glycerol,ethanolamine,urea and the mixture (urea and ethanolamine)could form the stable hydrogen bonds with both O of C–O–H and O of anhydroglucose ring O–C in starch molecules.Therefore,this phenomenon should be related to the stability and intensity of hydrogen bonds,newly formed between urea/ethanolamine and C–O group of starch.The more stable and strong the hydrogen bonds were,the more the correlative peaks shifted and the peak styles changed (Pawlak,&Mucha,2003).Therefore,as revealed by FT-IR,the mixture of 15%urea and 15%ethanolamine could form stronger interaction with starch than glycerol or ethanolamine.3.2.Scanning electron microscopy (SEM)The mixture of urea and ethanolamine could form stable hydrogen bond with starch by the analysis of FTIR spectra because ethanolamine and urea weakened the hydrogen bond of the intermolecular and intramolecular in native starch.Due to the high shear and temperature conditions with the action of plasticizer,native starch granules were molten or physically broken up into small fragments.A continuous phase was predicated to be formed under shear and pressure as a pared with native starch granules (in Fig.3a),the microcosmic morphology of the extruded TPS was shown in Fig.3b–e.As shown in Fig.3c,urea crystal separated out in UPTPS,while urea crystal of UEPTPS (urea/ethanolamine wt 15/15%)was invisible in Fig.3e.As a good solvent for urea,ethanolamine and water in starch could dissolve urea and prevent crystallization of urea,which generally made TPS materials rigid and brittle.1002003004005000.20.40.60.81.0M a s s C h a n g eTemperature (˚C)d cb e aFig.4.The TG curves of several TPS.(a)TPS containing 30%glycerol;(b)TPS containing 30%urea;(c)TPS containing 15%urea and 15%ethanolamine;(d)TPS containing 10%urea and 20%ethanolamine;(e)TPS containing 30%ethanolamine.Table 1The effect of the proportion of urea/ethanolamine on the onset of decomposition and mass loss at onset temperature in several in the TG experiments of TPS Plasticizers (wt/wt)Urea/ethanolamine 30%/0%15%/15%10%/20%0%/30%Glycerol 30%Onset temperature (8C)292.8300.8301.2295.9292.5Mass loss (%)16.217.217.923.318.8Midpoint temperature (8C)310.1328.4320.8316.4314.2X.F.Ma et al./Carbohydrate Polymers 64(2006)267–2732703.3.Thermal stabilityFig.4presented the TG experimental results.The behavior of the mass loss curves was similar in several TPS.Because the boiling points of the plasticizer outclassed 1008C,the mass loss below 1008C was mainly ascribed to water loss.And the mass loss from 1008C to the onset temperature was related to the volatilization of both water and plasticizers.So the difference in the decomposition onset and mass loss at onset temperature was mainly due to the different volatility of several plasticizers in TPS.As shown in Fig.4a,b and e,ethanolamine molecule was more volatile than glycerol and urea.However,the mixtures of urea and ethanolamine were able to improve the onset of decomposition and reduce mass loss at onset temperature (compared with Fig.4c–e).The volatility of both ethanolamine and urea was reduced,because ethanolamine was a good solvent for urea,and the mixtures of urea and ethanolamine could form the strong interaction with starch.In the view of onset temperature and midpoint decompo-sition temperature (as shown in Table 1),the proper proportional mixture of urea and ethanolamine (for instance,20wt/wt%urea/10wt/wt%ethanolamine and 15wt/wt%urea/15wt/wt%ethanolamine)could obviously ameliorate TPS thermal stability.3.4.Differential scanning calorimetry (DSC)The DSC measurements served to determine the relaxa-tional transition of the TPS.The glass transition temperature,T g was shown in Fig.5,DSC curves of TPS.T g of GPTPS,EPTPS and UPTPS were,respectively,28,25and 458C,while T g of UEPTPS containing 15%urea and 15%ethanolamine was 378C,located between EPTPS and UPTPS.This evolution could be ascribed to the strong interactions between the starch and plasticizer.In TPS the strong hydrogen bonds formed between plasticizers and starch,which decreased starch chain mobility and consequently increased the matrix glass tran-sition.In the views of T g ,as the plasticizer,this mixture of 15%urea and 15%ethanolamine could form stronger interactionwith starch than glycerol or ethanolamine.This result was similar to FT-IR result.3.5.RetrogradationThe X-ray diffraction patterns of TPS,platicized by glycerol,ethanolamine and urea,were shown in Fig.6.There were no crystals of native starch in newly prepared TPS.In thermoplastic process ethanolamine and/or urea molecules entered into starch granules,then should replace starch intermolecular and intramolecular hydrogen bonds and destruct the crystal of native starch.So their effect was the same as glycerol.When these TPS were stored at RH50%for 25days,TPS showed no obvious crystal peaks except GPTPS in Fig.6.As it was well known,GPTPS,prone to retrogradation,showed a V H style crystal peak (Van Soest &Vliegenthart,1997)(e in Fig.7).AccordingH e a t F l o w (m W /m g )Temperature (˚C)Fig.5.DSC curves of TPS.101520253035I n t e n s i t yfe d c b a 2 thetaFig.6.TPS after thermoplastic process.(a)native starch;(b)GPTPS;(c)EPTPS;(d)UEPTPS (urea/ethanolamine,15/15);(e)UEPTPS (urea/ethano-lamine,25/5);(f)UPTPS.101520253022.48e d c b a 2 thetaI n t e n s i t yFig.7.The diffractograms of TPS stored at RH50%for 25days.(a)EPTPS;(b)TPS containing 15%urea and 15%ethanolamine;(c)TPS containing 25%urea and 5%ethanolamine;(d)UPTPS;(e)GPTPS.X.F.Ma et al./Carbohydrate Polymers 64(2006)267–273271to J.J.G van Soest (Van Soest,Hulleman,de Wit,&Vliegenthart,1996),V H type was a single-helical structure ‘Inclusion Complex’,made up of amylose and glycerol.Urea and ethanolamine could restrain starch retrogradation,because they could form more strong and stable hydrogen bonds with starch than glycerol according to FT-IR and DSC analysis,and then prevent starch molecules from interacting and crystallizing again.The mixed plasticizers of urea and ethanolamine could also effectively suppress the retrogradation of TPS (b and c in Fig.7),as urea did.The crystal peaks (c and d in Fig.7)at around 22.58were ascribed to urea crystallinity.When the ratio of ethanola-mine to urea reached above 1,UEPTPS would become a stable system without the separating of urea.3.6.Mechanical testingThe stress–strain curves of TPS,which were plasticized with only urea,ethanolamine,glycerol or the mixture of urea and ethanolamine with different proportions,and then stored at RH Z 33%for 1week after thermoplastic process,were shown in Fig.8.The stress–strain diagrams of thematerials showed the typical pattern of rubbery starch plastic materials reported previously (Van Soest &Knooren,1997)except UEPTPS1.The plots were essentially linear at low strain and curved towards the strain axis at higher strains.TPS plasticized by only urea was a brittle glassy material but rigid.Urea could destroy the interaction of starch molecules more effectively than ethanolamine and glycerol during thermoplastic process,and then starch molecules were so flexible that starch molecules were packed too tightly without enough space for the segmental motion at room temperature.It was necessary for starch segmental motion to employ additional force,even up to the break strength of TPS,so UPTPS was brittle but rigid.A quantity of ethanolamine,substituting part of urea,could dilute this effect and improve the toughness (UEPTPS 3,UEPTPS 4and UEPTPS 5in Fig.8).Ethanolamine could make cooled TPS retain enough free volume for the segmental motion,so EPTPS was tough but weak (UEPTPS 7in Fig.8).The mixture of ethanolamine and urea in the appropriate proportion (UEPTPS 4in Fig.8)appeared to increase the elongation at break.The effects of the mixed proportion of urea and ethanola-mine (maintaining a constant total contents of 30%)on UEPTPS mechanical properties were shown in Fig.8and Table 2.For TPS plasticized by urea alone,stress peak was 12.55MPa and Youngs modulus was up to 1664MPa,but strain peak and Energy Break were only 5.7%and 0.32N m respectively.A small quantity of ethanolamine (10%)could improve the strain and Energy Break of TPS well,but stress and modulus dropped much.For EPTPS,stress,Youngs modulus and Energy Break were low although strain could reach 61.6%.Fig.8indicated that the superfluous ethanolamine intenerated TPS while the redundant urea rigidified and embrittled TPS.The most appropriate weight proportion was 15%urea and15%ethanolamine.This TPS showed good mechanical properties with the highest values of Energy Break as well as the favored stress,strain and Youngs modulus.The mechanical parameters of TPS plasticized by 15%urea and 15%ethanolamine were compared with those of TPS plasticized by glycerol (30wt/wt%)as listed in Table 3.The former was superior to TPS plasticized by glycerol (30wt/wt%)in mechanical properties except strain peak when they were stored at RH Z 33%for 1week.10203040506070024********GPTPS s t r e s s /M P astrain/%UEPTPS1UEPTPS2UEPTPS3UEPTPS4UEPTPS5UEPTPS6UEPTPS7Fig.8.The stress–strain curves of several TPS plasticized with different plasticizers UEPTPS1-7denoted UEPTPS with the following proportion of urea and ethanolamine.Table 2The effect of the proportion of urea and ethanolamine contents on the mechanical properties of UEPTPSStarch/ethanolamine/ureaStress (MPa)Strain (%)Youngs moduls (MPa)Break energy (N m)UEPTPS 1100/0/3012.55 5.716640.32UEPTPS 2100/5/2510.2010.43370.44UEPTPS 3100/10/209.4413.03150.97UEPTPS 4100/15/159.0034.4236 1.34UEPTPS 100/20/10 5.739.71340.92UEPTPS 6100/5/25 4.250.61020.85UEPTPS 7100/30/03.161.6570.75X.F.Ma et al./Carbohydrate Polymers 64(2006)267–2732724.ConclusionMixtures of urea and ethanolamine used as a plasticizer could obviously ameliorate thermal stability,mechanical properties and retrogradation of TPS.These phenomena could be explained by the following two reasons.First,as proved by FT-IR and DSC analysis,the mixture of urea and ethanolamine could form more stable and strong hydrogen bonds with the hydroxyl group of starch molecules than the conventional plasticizer,glycerol.Second,ethanolamine was a good solvent for urea and then both of them could exist in molecular form in TPS.With effectively restraining starch retrogradation,TPS plasticized by urea(15wt/wt%)and ethanolamine(15wt/wt%)showed a better thermal stability and mechanical properties.Moreover,the tensile stress,strain and Energy Break could respectively reach9.00MPa,34.4% and1.34N m.ReferencesAverous,L.,Fauconnier,N.,Moro,L.,&Fringant,C.(2000).Blends of thermoplastic starch and polyesteramide:Processing and properties.Journal of Applied Polymer Science,76(7),1117–1128.Fang,J.M.,Fowler,P.A.,Tomkinson,J.,&Hill,C.A.S.(2002).The preparation and characterisation of a series of chemically modified potato starches.Carbohydrate Polymers,47(3),245–252.Fang,Q.,&Hanna,M.A.(2001).Characteristics of biodegradable Mater-Bi w-starch based foams as affected by ingredient formulations.Industrial Crops and Products,13(3),219–227.Forssell,P.M.,Mikkila¨,J.M.,Moates,G.K.,&Parker,R.(1997).Phase and glass transition behaviour of concentrated barley starch–glycerol–water mixtures,a model for thermoplastic starch.Carbohydrate Polymers,34(4), 275–282.Garci’a-Alonso,A.,Jime’nez-Escrig,A.,Mart’in-Carron,N.,Bravo,L.,& Saura-Calixto,F.(1999).Assessment of some parameters involved in the gelatinization and retrogration of starch.Food Chemistry,66(2),181–187. Hulleman,S.H.D.,Janssen,F.H.P.,&Feil,H.(1998).The role of water during plasticization of native starches.Polymer,39(10),2043–2048. Ma,X.F.,&Yu,J.G.(2004).The effects of plasticizers containing amide groups on the properties of thermoplastic starch.Starch,56(11),545–551. Martin,O.,&Averous,L.(2001).Poly(lactic acid):Plasticization and properties of biodegradable multiphase systems.Polymer,42(14),6209–6219.Pawlak,A.,&Mucha,M.(2003).Thermogravimetric and FTIR studies of chitosan blends.Thermochimica Acta,396,153–166.Petersen,K.,Væggemose,N.P.,&Bertelsen,G.(1999).Potential of biobased materials for food packaging.Trends in Food Science and Technology, 10(2),52–68.Stein,T.M.,&Greene,R.V.(1997).Amino acids as plasticizers for starch-based plastics.Starch/Sta¨rke,49(6),245–249.Van Soest,J.J.G.,Hulleman,S.H.D.,de Wit,D.,&Vliegenthart,J.F.G.(1996).Crystallinity in starch bioplastics.Industrial Crops and Products, 5(1),11–22.Van Soest,J.J.G.,&Knooren,N.(1997).Influence of glycerol and water content on the structure and properties of extruded starch plastic sheets during aging.Journal of Applied Polymer Science,64(7),1411–1422. Van Soest,J.J.G.,&Vliegenthart,J.F.G.(1997).Crystallinity in starch plastics:Consequences for material properties.Trends in Biotechnology, 15(6),208–213.Zobel,H.F.(1998).Molecules to granules:A comprehensive starch review.Starch/Sta¨rke,40,44–50.Table3The mechanical parameters of TPS plasticized by urea(15wt/wt%)and ethanolamine(15wt/wt%)(1)and by glycerol(30wt/wt%)alone(2)stored at RH Z33%for1weekStress peak (MPa)Strainpeak(%)Stressyield(MsPa)Strainyield(%)Energybreak(N m)Youngsmodulus(MPa)19.0034.4 6.717.4 1.342362 4.6350.5 3.60 3.3 1.05184X.F.Ma et al./Carbohydrate Polymers64(2006)267–273273。

Carbohydrate Polymers 23 (1994) 89 103

Carbohydrate Polymers 23 (1994) 89 103


nature and concentration of cations present in the solution (see, for example, Clark & Ross-Murphy, 1987). Significant interactions also occur with proteins (e.g. in milk) and hydrocolloids such as starch, locust bean gum, guar gum, etc_ (Descamps et al_, 1986). On the basis of these properties, carrageenans are used extensively in the food industry as viscosity/gel or texture enhancers, stabilizers, etc. (Christensen, 1964). The same properties are utilized by the pharmaceutical/ cosmetic industry, in lotions, creams, toothpaste, cough preparations, etc_ Due to its widespread use, extensive toxicological evaluation of carrageenan has been carried out. The major problem that has been identified involves low molecular weight ( < 20 000 g/mole) fractions which can cause lesions. Degraded carrageenan is in fact used to induce ulcerative colitis in the colon in guinea-pigs as an experimental model to study the effects of pharmacological and therapeutic agents
长纤维树脂(产品资料)

长纤维树脂(产品资料)

長繊維強化熱可塑性樹脂长纤维 树脂TM TMPLASTR ON长纤维树脂 的概念30,000 25,000 弯曲模量 (MPa) 20,000 15,000 10,000 5,000非強化熱可塑性樹脂®Metal FRP GMT长纤维树脂 长纤维树脂短繊維強化 熱可塑性樹脂0 0 20 40 60 夏氏衝 夏氏衝撃強度 (kJ/m２) 80 100与短繊維強化樹脂制造工艺的区别■历来短繊維制造工艺■長繊維制造工艺长纤维树脂 粒子内繊維长纤维树脂® 短繊維強化樹脂®和粒子同样长度的繊維状态生産時の混錬により繊維が破砕长纤维树脂 成形品中的繊維和ＰＡ６-ＧＦ４０齿轮成形品的比較®长纤维强化 长纤维强化短繊維強化齿轮的牙齿尖端也分布了长纤维树脂残存繊維長度和強化効果1.0 0.9 0.8Ｆ　繊 維 強 化 効 果 係 数0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.0 1.0 2.0 3.0 4.0 5.0 短繊維強化樹脂 長繊維強化樹脂繊維長（ｍｍ）长纤维树脂 粒子长度与成形工艺6mm 11mm 射出成形 射出挤 射出挤出 15mm 50mm 溶融圧縮®GF：玻纤 ： CF：碳纤 ： SF：钢纤 ： AF：合成纤维 ：合成纤维长纤维树脂 的规格GF CFSF AF GF CF SF AF®Nylon6,66,12PPSGF CF SF AFGF CF SF AFAlloyGFSFPP HDPEGF长纤维树脂 长纤维树脂PCSFTMPBTABSGF SFTPUGFCF长纤维树脂 的種類玻纤 碳纤 合成纤维 合成纤维 钢纤 有机物（ 纶纤维） 有机物（芳纶纤维）®长纤维树脂 的種類•●•強化规 強化规格/ 玻纤・碳纤与玻纤和碳纤相比，有高刚性和高冲击强度。

同时，具有耐疲劳 与持久性的特点。

作为一种使用材料，适合代替金属，FRP等等。