Cell wall compositions of raw and cooked corms of taro (Colocasia esculenta)

The monosaccharide compositions of parenchyma cell walls of raw and cooked corms of taro, Colocasia esculenta cv Tausala Pink, were determined. The cell wall constituents were sequentially extracted using CDTA, Na₂CO₃, 1 M KOH, 4 M KOH and water to leave a final residue (α‐cellulose). The monosaccharide compositions of the cell walls and cell wall fractions from the raw and cooked corms were consistent with the presence in these cell walls of large amounts of cellulose and pectic polysaccharides. The monosaccharide composition of the cell walls of the raw corms resembled the monosaccharide compositions of primary cell walls of other non‐commelinoid monocotyledons and dicotyledons. Cooking of the corms resulted in alteration of the cell walls, with solubilisation of pectic polysaccharides occurring earlier in the sequential fractionation and possibly changes in the extractability of xyloglucans and/or xylans. © 2000 Society of Chemical Industry     

Effect of tissue type and variety on cell wall chemistry of onion (Allium cepa L.)

The purpose of this study was a comparative examination of the cell wall chemistry of component tissues of different varieties of onions (Allium cepa L. cv Sturon, Durco, Hysam, Grano de Oro and Caribo). Cold alcohol-insoluble residues (CAIRs) were prepared and were extracted sequentially with water, imidazole, CDTA, Na₂CO₃ and 0.5 M KOH to leave a residue. These were analysed for their carbohydrate compositions. On a whole organ basis, the cell wall carbohydrate composition was similar for each variety studied, and no significant change resulted from commercial storage, with or without sprout suppressant. However, there were significant differences in the carbohydrate composition of cell walls from different tissues. Cell walls of inner leaf bases contained galactoserich pectic polysaccharides. Outer layers had progressively less pectic galactose, and the outer brown skin contained virtually none. This was accompanied by changes in water- and CDTA-soluble polysaccharides and may be related to the dry and protective nature of the non-lignified outer skin. The differences in cell walls from different tissues provide the basis for developing processing methods for exploiting onion waste.     

Developmental and ripening-related effects on the cell wall of apricot (Prunus armeniaca) fruit

Alcohol-insoluble residues (AIRs) were prepared from apricots at six stages during development/ripening on the tree. To investigate the changes in cell wall polymers, and in particular those affecting pectic polysaccharides, the AIR preparations were sequentially extracted with water, cyclohexane-trans-1,2-diamine-N,N,N′,N′-tetraacetate (CDTA) and Na₂CO₃. A significant proportion of initially Na₂CO₃-soluble pectic polysaccharides became water- and CDTA-soluble during the ripening process. In terms of composition, a significant decrease in galactose and uronic acid content was detected in all the extractions, whereas the percentage of arabinose increased in both water and CDTA-soluble polymers but decreased in the Na₂CO₃-extracted polysaccharides. The ability of pectic polysaccharides to cross-link was diminished during ripening due to an overall increase in the concentration of Na⁺ or K⁺ associated with the AIRs. This was accompanied by a decrease in the amounts of Ca²⁺ and Mg²⁺. The decrease in pectic galactans and the inhibition of pectin cross-linking detected within the pectic backbone are probably linked to the softening process observed during apricot ripening. © 1998 SCI.     

The roles of cell wall polymers and intracellular components in the thermal softening of cassava roots

Cassava varieties Iapar 19 – Pioneira (short cooking time, domestic vegetable), Taquari (medium-to-long cooking time, domestic vegetable), and Branca de Santa Catarina (long cooking time, industrial vegetable), were selected in order to investigate the cell wall and compositional basis for these textural differences. Pioneira had lower levels of Ca²⁺ and Mg²⁺, and higher levels of phytic acid and monovalent cations than the longer cooking time varieties. Detailed cell wall analysis indicated that the longer cooking Branca cultivar had higher levels of chelator-insoluble pectic polysaccharides. The potential causative roles of these different features were evaluated using vortex-induced cell separation (VICS) studies. Time to achieve the complete VICS of Branca cultivar was reduced to that of Pioneira with externally-supplied chelating agents (CDTA) and Na₂CO₃. Taquari roots did not respond in this way indicating a different biochemical basis for the maintenance of cell adhesion. The results are discussed in relation to the thermal stability of texture in these cassava varieties.     

Ferulic Acid Dehydrodimers in the Cell Walls of Beta vulgaris and their Possible Role in Texture

Sugarbeet, a form of Beta vulgaris var vulgaris, fails to soften completely after heating at 100°C for several hours. This is due to thermal stability of the cell–wall polymers involved in cell–cell adhesion. In contrast, beetroot softens within 25–30 min due to a relatively rapid increase in the ability of the cells to separate. Information concerning the cell–wall polymers responsible for cell–cell adhesion was obtained by subjecting sugarbeet and beetroot tissues to a range of chemical and biochemical treatments designed to cleave cell–wall chemical bonds selectively. Treatment of sugarbeet tissues with chelating agents, weak base (Na₂CO₃, 0·05 M ) or a purified, specific endoxylanase did not facilitate vortex-induced cell separation. However, this could be induced after extraction in dilute, cold alkali (0·05–0·1 M KOH) or dilute, hot acid (0·1 M TFA, 100°C). Tissues from beetroot behaved similarly. Furthermore, the cell walls of sugarbeet and beetroot were similar in yield and neutral carbohydrate composition; the cell–wall-galacturonic acid content of beetroot was 50% higher as compared with sugarbeet. They were also rich in ferulic acid (FA) and its derivatives (6–7 mg g^-1 CWM), and exhibited pH-dependent autofluorescence which disappeared during alkali-induced cell separation. In sugarbeet, over 20% of the FA was in dimer form. In beetroot, however, the value was only 10%. The main FA dimers were 8-O-4′DiFA and 8,5′DiFA (benzofuran form). The results indicate that the degree of thermal stability of cell–cell adhesion and, therefore, texture in Beta vulgaris tissues is related to the degree of FA-cross linking between pectic polysaccharides. © 1997 SCI.     

Enzymatic changes in pectic polysaccharides related to the beneficial effect of soaking on bean cooking time

BACKGROUND: Cooking time decreases when beans are soaked first. However, the molecular basis of this decrease remains unclear. To determine the mechanisms involved, changes in both pectic polysaccharides and cell wall enzymes were monitored during soaking. Two cultivars and one breeding line were studied. RESULTS: Soaking increased the activity of the cell wall enzymes rhamnogalacturonase, galactanase and polygalacturonase. Their activity in the cell wall was detected as changes in chemical composition of pectic polysaccharides. Rhamnose content decreased but galactose and uronic acid contents increased in the polysaccharides of soaked beans. A decrease in the average molecular weight of the pectin fraction was induced during soaking. The decrease in rhamnose and the polygalacturonase activity were associated (r = 0.933, P = 0.01, and r = 0.725, P = 0.01, respectively) with shorter cooking time after soaking. CONCLUSION: Pectic cell wall enzymes are responsible for the changes in rhamnogalacturonan I and polygalacturonan induced during soaking and constitute the biochemical factors that give bean cell walls new polysaccharide arrangements. Rhamnogalacturonan I is dispersed throughout the entire cell wall and interacts with cellulose and hemicellulose fibres, resulting in a higher rate of pectic polysaccharide thermosolubility and, therefore, a shorter cooking time. Copyright © 2011 Society of Chemical Industry     

Role of pectic polysaccharides in structural integrity of apple cell wall material

Texture modulating properties of aqueous dispersions of apple cell wall material differed from those of tomato or kiwifruit, particularly under high shear. It was previously hypothesized that this may be due to the fact that the apple cell wall showed less in vivo solubilization of pectic polysaccharides during ripening compared to tomato or kiwifruit. However, in vitro solubilization of the pectic polysaccharide content of apple CWM by endo-polygalacturonase and/or extraction with 0.05 M sodium carbonate, did not affect the loss in wall integrity shown by tomato or kiwifruit CWMs under shear. In addition, the pectin-depleted residue after Na₂CO₃ extraction possessed better water retaining and viscosity generating properties than the original cell wall material. Following treatment of apple CWM with cellulase, the viscosity of suspensions decreased, emphasising the role that the cellulose–hemicellulose network plays in the water-retaining capacity of the cell wall. Residue from CWM after cellulase treatment consisted of ∼85% pectic polysaccharides. Surprisingly, the integrity of these “cellulose-free” walls was maintained after shear. It is concluded that differences in structural properties of the CWMs of apple compared to kiwifruit or tomato are not simply related to pectin solubilization but to a fundamental difference in the architecture of the apple cell wall.     

The thermomechanical properties of carrot cell wall material

The effect of temperature and moisture on the fabrication of pressed carrot cell wall specimens for Dynamic Mechanical Thermal Analysis was assessed. Results obtained from the water extractability of the material showed that more cell wall material became solubilised when moisture and temperature of the different treatments were increased. Chemical analysis revealed that this involved an increase in the water-soluble uronic acid components. Furthermore, more water-soluble neutral monosaccharides were observed, represented principally by galactose, rhamnose, arabinose and glucose. Pectic polysaccharides became more water soluble when isolated carrot cell wall was pressed at 100°C with a water content 800 g kg⁻¹ (wet weight basis). A molecular weight fraction centred at 100000 Da was observed in the severely pressed material (100°C, 800 g kg⁻¹ water) but was barely present in the mildly pressed (30°C, 500 g kg⁻¹ water) and unpressed specimens, consistent with depolymerisation and solubilisation. In contrast to the chemical modifications, the bending modulus, E′, of the pressed carrot cell wall material remained unchanged for the cell wall specimens moulded under different conditions, consistent with small changes in molecular weight. Pressed cell wall material was stiffer than pressed freeze-dried carrot which could be due to the plasticising role of the intracellular components. The stiffness of both cell wall and freeze-dried carrot specimens decreased with plasticisation by water in the range 10–500 g kg⁻¹. © 1998 Society of Chemical Industry.     

Cell wall modifications during cooking of potatoes and sweet potatoes

Sweet potato (Ipomoea batatas L) tissue, when cooked at 70 °C to activate β‐amylase and break down starch, takes on a distinctive firm, brittle texture and does not show the cell separation that occurs in, for example, cooked potato (Solanum tuberosum L). Similar cooking conditions increase firmness in other plants by activating pectin methyl esterase which de‐esterifies pectic polysaccharides and protects them from thermal depolymerisation. We therefore isolated cell walls from both potatoes and sweet potatoes cooked at 70 °C and 100 °C and determined the remaining degree of methyl esterification of their pectins. Pectins from both species were demethylated to a similar extent at 70 °C and 100 °C. Since cooking sweet potato at 100 °C induced cell separation and softening, it is concluded that β‐amylase is rapidly inactivated at that temperature and swollen starch distends and separates the cells, whereas the firm texture obtained by cooking that species at 70 °C is not the result of pectin demethylation but is caused by the breakdown of starch to oligomers that can escape from the cell. © 2000 Society of Chemical Industry     

Effect of high pressure/high temperature processing on cell wall pectic substances in relation to firmness of carrot tissue

Thermal processing for food preservation results in undesired softening of fruits and vegetables. To explore the potential of high pressure sterilization in food processing, the effects of combined high pressure/high temperature (HP/HT) treatments on carrot pectic polysaccharides and the related textural properties were investigated and compared with that of samples thermally processed at atmospheric pressure. Disks of fresh carrot (Daucus carota var. Yukon) tissue were subjected to three different treatments (80 °C–0.1 MPa, 100 °C–0.1 MPa and 80 °C–600 MPa) for varying time intervals. Subsequently, the residual texture and microstructural changes of the carrots were evaluated. Alcohol-insoluble residues were prepared from the samples and sequentially fractionated with water, cyclohexane-trans-1,2-diamine tetra-acetic acid (CDTA) and Na₂CO₃ solutions. Thermal treatments at 0.1 MPa caused extensive tissue softening. This was marked by increased cell separation, an increase in water soluble pectin (WSP) paralleled by a decrease in chelator (CSP) and sodium carbonate (NSP) soluble pectin. HP/HT treated carrots showed minimal softening and negligible changes in intercellular adhesion. This was accompanied by a significant reduction in the degree of methyl esterification of pectin, low WSP in contrast to the high CSP and NSP fractions, minor changes in the different pectin fractions during treatment, and a substantial amount of pectin in the fractionation residue. There was a clear difference between HP/HT and thermally processed carrot pectin; HP/HT showing pronounced texture preservation.     

Texture of Chinese water chestnut: Involvement of cell wall phenolics

Chinese water chestnuts (CWC) fail to soften during cooking. This is due to thermal stability of cell wall polymers involved in cell-cell adhesion. Information concerning these polymers was obtained by subjecting CWC tissues to a range of chemical and biochemical treatments designed to cleave selectively cell wall chemical bonds. Neither chelating agents nor weak base (Na₂CO₃, 0·05 M ) facilitated vortex-induced cell separation (VICS) in fresh or canned tissues. However, VICS could be induced after extraction in dilute, cold alkali (0·1 M KOH), dilute hot acid, or a purified, specific endoxylanase. The CWC cell walls also exhibited considerable pH-dependent autofluorescence which originated mainly from ferulic acid and its derivatives. This disappeared during alkali-induced VICS. The results are consistent with the involvement of ferulic acid-containing cell wall hemicelluloses in the thermal stability of cell-cell adhesion and therefore texture in CWC tissues.     

Characterisation of Rosa Mosqueta seeds: cell wall polysaccharide composition and light microscopy observations

The utilisation of enzymes for the extraction of vegetable oils from seeds has been a topic of growing interest in recent years. Knowledge of the cell wall polysaccharide composition is important to select the enzyme(s) necessary for the most effective degradation of the cell walls. The purpose of the present work is to characterise the seeds of Rosa Mosqueta (Rosa aff rubiginosa) by light microscopy (where several differential staining methods were applied to analyse the seed structure) and by the isolation of cell wall polysaccharide extracts. The mature seed of Rosa Mosqueta has a very thick and structurally complex seed coat comprising heavily lignified tissue. The embryo has two cell layers of remaining endosperm tissue (indicating that this is an exalbuminous seed), two voluminous cotyledons that contain the oil, and bundles of provascular tissues distributed perpendicularly to the transverse axis of the embryo. The major non‐cellulosic polysaccharides from the non‐lignified tissues are glucuronoxylans and pectic polysaccharides; glucans are also present in small amounts. The major non‐cellulosic polysaccharides from the lignified tissues are glucuronoxylans. Concerning the use of enzymes for oil extraction, microscopy and cell wall polysaccharide analysis showed that the use of pectic enzymes followed by a xylanase or a cellulase should be explored. © 2000 Society of Chemical Industry     

Mechanistic insight into common bean pectic polysaccharide changes during storage,soaking and thermal treatment in relation to the hard-to-cook defect

Different mechanisms responsible for the development of the hard-to-cook defect in common beans during storage, their soaking behavior and softening during thermal treatment have been previously suggested. However, these mechanisms have not been sufficiently confirmed by direct molecular evidence. This research aimed at gaining a detailed mechanistic insight into changes occurring in Canadian wonder bean pectic polysaccharides during storage, soaking and/or thermal treatment in different brine solutions in relation to the development and manifestation of the hard-to-cook (HTC) defect. Both fresh or easy-to-cook (ETC) and stored (HTC) bean samples were either soaked or soaked and thermally treated in demineralized water, solutions of Na₂CO₃ and CaCl₂ salts followed by extraction of cell wall materials. Pectic polysaccharide properties examined included sugar composition, degree of methylesterification (DM), extractability and molar mass (MM). The DM of pectin from ETC and HTC beans was similar but low (< 50%). Upon (pre)treatment in a Na₂CO₃ solution, solubilization of pectic polysaccharides, especially the strongly bound chelator- (CEP) and Na₂CO₃- (NEP) extractable pectins was enhanced leading to increased amounts of water extractable pectin (WEP). Also, there was a decrease in high MM polymers paralleled by an increase in β-elimination degradation products. These observations are in line with the fast cooking behavior of beans (pre)treated in a Na₂CO₃ solution. In contrast, (pre)treatment in a CaCl₂ solution hindered softening leading to the failure of the beans to cook. The beans (pre)treated in a CaCl₂ solution showed increased high MM polymers and lack of cell wall separation. Therefore, it can be inferred that development of the hard-to-cook defect in Canadian wonder beans during storage and its manifestation during soaking and subsequent thermal treatment is largely reflected by the pectic polysaccharide properties in line with the pectin hypothesis. Our data suggest the release of Ca⁺⁺ leading to pectin cross-linking and the increase or decrease of β-elimination depolymerization. However, the relatively high amounts of neutral sugars and strongly bound NEP in HTC seeds do not allow to rule out the possible existence of non-Ca⁺⁺ based pectin cross-linking.     

Degradation of carrot (Daucus carota) fibres with cell-wall polysaccharide-degrading enzymes

Carrot Daucus carota L fibres were degraded with two enzyme preparations, SP249 from Aspergillus aculeatus and Celluclast from Trichoderma reesei. The enzymic activities of these complexes indicate that SP249 was particularly active on pectic polymers, and Celluclast could degrade amorphous and crystalline cellulose. A combination of both preparations degraded carrot fibres with a synergistic effect and led to the solubilisation of 95% of the cell-wall polysaccharides. The kinetics of solubilisation of sugars and gel-permeation chromatography of the soluble products show that pectic polymers were rapidly solubilised and then, in a second stage, degraded mainly to monomers, whereas cellulose was more slowly hydrolysed to cellobiose and glucose. Part (67%) of the polysaccharides were saccharified, the residual soluble material being rhamnogalacturonans containing arabinose residues. Residual insoluble fibres (10% of initial weight) were not liquefied and were composed mainly of lignin, proteins and polymers of glucose, xylose and galacturonic acid.     

Characterisation of Chilean hazelnut (Gevuina avellana) tissues: light microscopy and cell wall polysaccharides

By applying several differential staining techniques and light microscopy, the structure and composition of Chilean hazelnut (Gevuina avellana) seeds were analysed. The structure of the G avellana seed is very simple, with a thin, heavily lignified seed coat and two voluminous cotyledons. The embryo food reserves are uniformly distributed over the cotyledon cells. The cell wall polysaccharides were recovered from the alcohol‐insoluble residue by mild treatment with warm chlorite solution and sequential extraction with alkali solutions of increasing concentration. FT‐IR spectra in the 1200–850 cm^?1 region were used together with chemometric techniques to distinguish the hemicellulosic and pectic polysaccharides in the extracts. The most abundant extracts were fractionated by graded precipitation in ethanol. A xyloglucan was identified by ¹H and ¹³C NMR as the major hemicellulosic polysaccharide, with a sugar composition of 4Glc:3.5Xyl:1Gal:0.5Fuc. The hazelnut cell walls are composed of equivalent amounts of pectic polysaccharides, xyloglucans and cellulose. © 2003 Society of Chemical Industry     

Cultivar and Maturity Effects on Muskmelon ( Cucumis melo) Colour,Texture and Cell Wall Polysaccharide Composition

Cell wall polysaccharides (CWP) of two types of melons were isolated and purified. Fractionations were performed using cyclohexanetrans-1,2-diamine tetraacetate (CDTA), Na₂CO₃, guanidinium thiocyanate (GTC) and KOH. Alditol acetate derivatives of neutral sugars from each CWP fraction were prepared and analysed by gas chromatography. Trifluoro-acetic acid insoluble fractions were analysed colorimetrically and uronic acid was determined. The CDTA and Na₂CO₃ fractions were found to be composed of typical pectic materialscontaining primarily galacturonic acid with the neutral sugars arabinose, galactose, rhamnose and a smaller amount of xylose. As maturity increased, CDTA fraction yields increased, though total neutral sugar CWP compositions decreased. GTC and KOH fractions were typical of hemicellulose, and contained principally xylose, glucose, galactose, mannose and fucose, with very small amounts of uronic acid, arabinose and rhamnose. The residues contained principally glucose and galactose, with smaller amounts of mannose, xylose, arabinose and fucose. With the exception of xylose and glucose, all neutral sugars decreased significantly during ripening in both the Cantaloupe and Honey Dew melons. Total uronic acid did not change as maturity increased, except for Cantaloupe, where total uronic acid decreased from the ripe to overripe stages. Relationships between firmness, drip loss and other composition measurements, as well as the total CWP sugar composition, were also determined. Only the CDTA fraction yields were negatively correlated with the changes in firmness of both melons and positively correlated with changes in drip loss as maturity increased.     

Losses of pectic substances during cooking and the effect of water hardness

Differences in the extent of loss of pectic substances from potato (Solanum tuberosum L.) after boiling, steaming and pressure cooking were investigated. Losses were found to be significantly greater (P< 0.001) after boiling than after pressure cooking or steaming. The pectic substance content (g 100 g^?1 dry matter) of potatoes (cv. Pentland Crown) was 2.98 for raw peeled tubers, 0.97 after boiling for 35 min, 1.22 after steaming for 35 min and 1.24 after pressure cooking at 103.4 kPa (15 psi) for 15 min. The roles of cooking time, cooking temperature and heat transfer medium are discussed. The effects of calcium sulphate (at levels typical of ‘hard’ and ‘soft’ water supplies) in the cooking water on losses of pectic substances from potato (Solanum tuberosum L.), carrot (Daucus carota L.), and swede (Brassica napus L. var. napobrassica Peterm.) after boiling and pressure cooking were also investigated. Water hardness did not influence losses during pressure cooking but samples boiled in hard water had decreased losses of pectic substances compared to those boiled in soft water. The increase in retention of pectic substances due to hard water was about 8 % for potatoes (cv. Pentland Dell), about 33 % for sliced carrots (cv. Berlicum, approved maintenance Perfecta) and about 23% for diced swedes (cv. Acme). The interaction of water hardness with cooking method was significant for potato (P< 0.05) and swede (P<0.001) and approaching significance (P=0.055) for carrot.     

Kinetics of thermal softening of potato tissue (cv. Monalisa) by water heating

The temperature dependence of rheological parameters as firmness indicators for potato tissue was determined within the temperature range 50-100 °C using four different objective methods. The rate of thermal softening of potato tissue by water treatment at 50 °C, 90 °C, and 100 °C was consistent with one pseudo first-order kinetic mechanism, while at 70 °C and 80 °C the rate of softening was consistent with two simultaneous pseudo first-order kinetic mechanisms. Kinetic theory was suitable to detect an increase of firmness through heating at 60 °C, mainly between 20 min and 40 min, presumably by pectinesterase activation. This study shows that two substrates S_a and S_b may be involved in providing firmness to potato tissue at 70 °C and 80 °C. For these temperatures, mechanism 1 is more probably due to gelatinization and light cooking, whereas mechanism 2 is more likely to represent the changes of the pectic substances in the cell wall and interlamellar region. At 90 °C and 100 °C the gelatinization process was fast and therefore the simple mechanism fitted presumably reflects the degree of solubilization of the pectic substances. At 50 °C and 60 °C there was practically no gelatinization, so that the simple mechanism fitted presumably represented incipient solubilization of pectic material. In water heating, gelatinization contributes less than the cell wall structure to potato tissue firmness on the basis of either kinetic parameters or microscopic observations. Maximum breaking compression force and modulus of rigidity were the most suitable rheological parameters for studying the softening of potato tissue in water heating.     

Changes in cell wall pectin and pectinase activity in apple and tomato fruits during Penicillium expansum infection

Cell wall pectin degradation in apple and tomato fruit during infection by Penicillium expansum was investigated. In infected apple fruit, a significant decrease in the average molecular mass was observed in pectins extracted with CDTA and also in pectins extracted with Na₂CO₃. In tomato fruits, depolymerisation was also observed in both pectic fractions during infection, the major change being in the pectins extracted with Na₂CO₃. This pectin depolymerisation associated with P. expansum infection can be attributed to the action of pectinases; in apple fruit, a significant increase in polygalacturonase and pectin methylesterase was observed in infected fruits, although in tomato fruit the only increase in enzymatic activity significantly related to the infection was in polygalacturonase. These differences between apple and tomato fruit during fungus infection could be related to differences in cell wall structure and composition and also to the specificity of P. expansum's infection spectrum in each case. In both cases, pectin depolymerisation might increase the porosity of the wall and allow increased access of fungus colonisation and facilitate the progress of the fungal infection. Copyright © 2006 Society of Chemical Industry     

Yield and composition of cell wall residues isolated from various feedstuffs used for non-ruminant farm animals

The contents of cell wall residue were measured in 14 common feedstuffs used for non-ruminant farm animals by utilising a technique involving pronase and α-amylase treatments. Comparison with the contents of neutral detergent fibre (NDF) revealed that the NDF procedure underestimated cell wall contents in the dicotyledonous plant materials. The losses of cell wall material due to the neutral detergent solution were correlated (r=0.931, P<0.01) with the amount of pectic substances present in the cell wall residues of the dicotyledonous plant materials. Cell wall residues were analysed for starch, crude protein, polysaccharides, condensed tannins, sulphuric acid lignin, acetyl bromide lignin, and ash. Condensed tannins in the cell wall residues of sorghum, rapeseed meal and field bean resulted in a large protein contamination (11.3–26.6%) of these residues and to an overestimation of their lignin content. Compositions of polysaccharides are discussed from chemical and nutritonal viewpoints.