Isabel Miranda

Wood properties of teak (Tectona grandis) from a mature unmanaged stand in East Timor

The wood quality from 50- to 70-year-old Tectona grandis trees from an unmanaged forest in East Timor was assessed. The aim was to evaluate teak in mature stands that had undergone uncontrolled disturbances, e.g., fire and local community usage. Heartwood represented 91% of the tree radius at a height of 1.7 m, and sapwood contained on average nine rings. The mean ring width showed within-tree and between-tree variability. The chemical compositions of heartwood and sapwood were similar. Within-tree chemical variation occurred only in terms of extractives, which increased from the pith (8.3%) to the heartwood-sapwood transition (12.7%) and decreased in the sapwood (9.2%). Overall, the wood properties of teak from a unmanaged forest in East Timor were comparable to those reported for plantation teaks of other origin: 607 kg/m3 basic density, 3.5% and 5.2% radial and tangential shrinkage, 141 N/mm2 modulus of rupture, 10684 N/mm2 modulus of elasticity, and 50 N/mm2 maximum crushing strength in compression parallel to the grain. Disturbances on individual tree growth arising from the unmanaged status of the stand were evidenced by higher within-tree variability of ring width. However, the longitudinal and radial variations of wood density and mechanical properties were of low magnitude and in a degree that did not negatively impact on timber quality.

Within-Tree Variation in Wood Fibre Biometry And Basic Density of the Urograndis Eucalypt Hybrid (Eucalyptus Grandis × E. Urophylla)

Within-tree variations in fibre length, width, wall thickness and wood basic density of Eucalyptus grandis × E. urophylla (urograndis) were studied in five 6.8-yr-old seedling trees and five 5.6-yr-old trees from one clone from Brazil. Samples were taken at 5%, 25%, 35%, 55%, 65% and 90% of stem height and five radial positions (10%, 30%, 50%, 70% and 90% of radius). The tree average fibre length, width and wall thickness were in seed and clone trees: 0.955 mm and 1.064 mm, 18 μm and 20 μm, 3.6 μm and 4.4 μm respectively. The axial variation of fibre dimensions was very low, while there was a consistent but small increasing trend from pith to periphery. The basic density ranged from 397–464 kg/m3 to 486–495 kg/m3 respectively in seedling and clone trees with a low variation along the stem. In comparison with other eucalypt pulpwood, e.g. E. globulus, the urograndis hybrid showed similar fibre dimensions and lower basic density. Overall the within-tree variation of these wood properties was low and age had a small impact on the variation of density and fibre dimensions.

Kinetics of ASAM and Kraft Pulping of Eucalypt Wood (Eucalyptus globulus)

Summary The kinetics of ASAM and kraft pulping of eucalypt wood (Eucalyptus globulus) were studied in relation to delignification and polysaccharide removal. In comparison to kraft, ASAM pulping had lower mass losses and delignification for the same temperature and reaction times (59.2% at Kappa 25 vs 50.0% at Kappa 17, at 180°C). The ASAM pulps have a higher brightness. ASAM pulping had a short initial period with no mass loss and lignin removal, followed by two reaction phases: a main phase where 61% of lignin was removed (at 180°C) and a subsequent final phase. In comparison to kraft, the main delignification rates of ASAM pulping were approximately 2.5 slower (at 180°C, −1.8 × 10−2 min−1 for ASAM and −4.2 × 10−2 for kraft pulping), and the calculated Arrhenius activation energies were higher (132.4 kJ mol−1 and 83.5 kJ mol−1, respectively). The loss of cellulose was relatively small (12.5 %) and lower than in kraft pulps.

Pulping Yield and Delignification Kinetics of Heartwood and Sapwood of Maritime Pine

Abstract In maritime pine (Pinus pinaster Ait.), heartwood represents a substantial part of the tree stem at final harvest age (80 years) corresponding to 42% at the base of the stem wood diameter and decreasing upward. The rate of heartwood formation was estimated at 0.35 rings/year, beginning at 18 years of age. Differences in the chemical composition between heartwood and sapwood were mainly in the extractives, 19.7% and 5.8%, respectively. The lignin content was 23.1% and 24.5% in the heartwood and sapwood, respectively. Pulping yield of the heartwood was lower than that of the sapwood (40.0% vs. 49.7%) and was negatively correlated with the extractives content. Extraction of heartwood prior to pulping increased the pulp yield and the delignification (lower residual lignin in pulps). Pulping kinetics showed lower yields for heartwood at all pulping stages, the difference occurring especially in the initial reaction phase. However, delignification rate constants were similar for heartwood and sapwood (3.1×10−2 min−1 and 2.7×10−2 min−1 for the main delignification phase for sapwood and heartwood, respectively), with a lower activation energy for sapwood (68.3 vs. 90.0 kJ · mol−1). The presence of heartwood decreases the raw‐material quality for pulping and this should be taken into account when harvesting trees for pulping processes.

Chemical characterization of cork and phloem from Douglas fir outer bark

Abstract Cork and phloem from Pseudotsuga menziesii outer bark were separated, fractionated and the 40- to 60-mesh fractions chemically analyzed. Cork and phloem showed a different grinding behavior with the highest yields for cork and phloem, respectively, for the 40- to 60-mesh fraction (31.4%) and the <0.180-mm fraction (49.2%). Cork chemical composition was (% o.d. mass): ash 0.9%; extractives 29.2% (mostly polar, 23.5%); lignin 16.8%, and suberin 36.2%. Polysaccharides (16.9%) contained glucose (55.4% of total neutral carbohydrates), xylose (13.3%), mannose, arabinose, and galactose as minor components. Lipophilic and suberin extracts from cork and phloem were analyzed by GC-MS, directly and after alkaline hydrolysis. In cork, catechin was the major compound identified in the lipophilic extract, accompanied by ferulic acid and acylglycerols. In phloem, β-sitosterol was the major compound. The content of fatty alcohols and fatty acids increased after hydrolysis confirming their esterification in both extracts. Suberin from P. menziesii cork is rich in saturated ω-hydroxyacids (ω-hydroxyacids 36.2%, α,ω-diacids 18.6%, alkanoic acids 6.2%, and alkanols 8.7%), being different from suberin of Quercus suber where α,ω-diacids are dominant.

Chemical characterization of the bark of Eucalyptus urophylla hybrids in view of their valorization in biorefineries

Abstract Eucalyptus urophylla hybrids are important raw materials for the forest industry in Brazil, and large quantities of barks are available at mill site that may be used for added-value products. The chemical composition of barks of six commercial hybrids clones of E. urophylla×E. grandis, E. urophylla×E. Camaldulensis, and undisclosed E. urophylla hybrids was studied. The hybrids had similar composition, on average (data based on oven dry bark): 16% extractives, mainly corresponding to polar compounds that are soluble in ethanol and water, 19% lignin, 47% polysaccharides, 1% suberin, and 2% ash. The polysaccharides consists mainly of cellulose as indicated by 84% of total neutral monosaccharides in the acid hydrolysate and 10% xylose. The compositions of the lipophilic extracts was determined by GC-MS before and after alkaline hydrolysis. In all the barks, fatty acids, and triterpenes (namely: betulinic and ursolic acids) were the most abundant compounds followed by smaller amounts of sterols, long-chain aliphatic alcohols, phenolic acids, and acylglycerols. The ethanol-water bark extract had a high phenolic content: total phenolics ranged 211–551 mg gallic acid equivalents (GAE) g-1 of extract, tannins 76–184 mg catechin equivalents (CE) g-1 extract, and flavonoids 98–234 mg CE g-1 of extract. The antioxidant activity corresponds to 338 mg Trolox g-1 of extract. Development of high-value products is proposed through an integrated biorefinery approach including valorisation of extractives and targeting for cellulose-based applications.

Pattern recognition as a tool to discriminate softwood and hardwood bark fractions with different particle size

Abstract The aim of this study was to characterize the chemical composition of different granulometric fractions obtained by milling of the bark of two softwood [Norway spruce, Picea abies (L.) Karst., and Scots pine, Pinus sylvestris L.] and two hardwood species (birch, Betula pendula Roth, and eucalypt, Eucalyptus globulus Labill.), and to discriminate between them on the basis of their chemical composition content via pattern recognition techniques [principal component analysis (PCA), cluster analysis (CA), and discriminant analysis (DA)]. Bark chemical composition differed between species, and chemical variables could be used to differentiate between them. Size reduction yields granulometric fractions that are not chemically homogeneous and that can also be discriminated. Therefore, potential applications of bark in valorization programs have to carefully consider the species-specific composition and their size reduction patterns. PCA and CA were adequate tools to characterize the different bark fractions within each species. DA allowed identifying the bark samples according to species and independently from particle size. Pattern recognition statistical methods were shown to be useful tools to analyse bark fractions and chemically discriminate species and fractions.

Chemical characterization and extractives composition of heartwood and sapwood from Quercus faginea

Heartwood and sapwood of Quercus faginea were evaluated in relation to summative chemical composition and non-polar and polar extracts composition, including an assessment of antioxidant properties (DPPH and FRAP). Twenty trees from two sites in Portugal were analysed. Heartwood had approximately two times more solvent extractible compounds than sapwood (on average 19.0% and 9.5%). The lipophilic extractible compounds were below 1%, and most of them were polar e.g. ethanol-soluble compounds corresponded to 65% of total extractives in heartwood and 43% in sapwood. Lignin content was similar in sapwood and heartwood (28.1% and 28.6% of extractive-free wood respectively) as well as the sugar composition. Site did not influence the chemical composition. The lipophilic extractible compounds from both sapwood and heartwood included mainly saturated fatty acids (23.0% and 36.9% respectively) and aromatic compounds were also abundant in sapwood (22.9%). The ethanol-water extractibles had a high content of phenolic substances (558.0 and 319.4 mg GAE/g extract, respectively of heartwood and sapwood). The polyphenolic composition was similar in heartwood and sapwood with higher content of ellagitannins (168.9 and 153.5 mg tannic acid/g of extract in sapwood and heartwood respectively) and very low content of condensed tannins. The antioxidant activity was very high with IC50 of 2.6 μg/ml and 3.3 μg/ml for sapwood and heartwood respectively, as compared to standard antioxidants (IC50 of 3.8 μg/ml for Trolox). The ferric reducing ability was 2.8 and 2.0 mMol Trolox equivalents/g extract of heartwood and sapwood respectively. The variability between trees was low and no differences between the two sites were found. Q. faginea showed a very good potential for cooperage and other applications for which a source of compounds with antioxidant properties is desirable.

FRACTIONING OF BARK OF Pinus pinea BY MILLING AND CHEMICAL CHARACTERIZATION OF THE DIFFERENT FRACTIONS

The bark of stone pine (Pinus pinea) from 50 year old trees grown in Portugal was submitted to grinding and fractioning into different particles sizes. The trees had a thick bark with an average 3,7 cm constituted mainly by the periderm and rhytidome (3,2 cm).The bark fractured easily into particles: yield of fines was low, and 74,0% of the particles were over 2 mm. The chemical composition, as a mass weighed average of all granulometric fractions showed a content of 1,1% ash 20,6% extractives (91% of which polar extractives) 2,2% suberin, 43,0% lignin and 37,6% holocellulose. The percentage of material dissolved by extraction with 1% NaOH was 42,3%. The chemical characterization of the different granulometric fractions showed that extractives were present preferentially in the finest fractions (<80 mesh and 60-80 mesh), representing 34-35%, particularly with enrichment in ethanol soluble extractives, that also showed lower content of lignin. The coarser fractions contained higher proportions of lignin and holocellulose. P. pinea bark grinding and fractionation by particle size may be used to selectively enrich the finest fractions in soluble materials, while the coarser fractions tend to have higher holocellulose content and will be therefore more suitable for carbohydrate related uses.

Copaifera langsdorffii Bark as a Source of Chemicals: Structural and Chemical Characterization

The chemical composition and the anatomy of Copaifera langsdorffii bark are reported here for the first time by studying trees grown in a native forest area in the Amazon region, Brazil. The bark is thin, dark reddish brown, and exfoliates in irregular flakes. It is very dense, showing highly lignified cells and abundant sclereids, and cellular fillings of phenolic nature. It includes a poorly developed rhytidome and a periderm with thin- and thick-walled phellem cells. The mean chemical composition was: ash 3.7%, total extractives 21.3%, mainly corresponding to polar compounds soluble in ethanol and water, suberin 0.8%, and lignin 36.6%. The polysaccharides showed a predominance of glucose and xylose (66.4% and 23.5% of total monosaccharides, respectively). The ethanol-water bark extract had a high content in phenolics: total phenolics 589.2 mg gallic acid/g extract, flavonoids 441.9 mg catechin/g extract, and tannins 54.8 mg catechin/g extract. The antioxidant activity was high, comparable to known antioxidant reference compounds: 720.3 mg Trolox per g of extract or 92.1 mg Trolox per g of bark. After bark grinding, the finest fraction was enriched in polar extractives (40.6%). C. langsdorffii bark is a potential source of functional extractives, therefore representing a valorization of the residual bark obtained during the industrial tree processing for timber.