Comparative studies on the in-ground and above-ground durability of European oak heartwood (Quercus petraea Liebl. and Quercus robur L.)

The durability of European oak (Quercus petraea Liebl. and Quercus robur L.) is controversially discussed since a long time. While it is classified as a “durable” timber species (durability class 2, according to EN 350-2), results from different studies indicated a lower durability. Therefore comparative studies with sessile oak and English oak were carried out including laboratory resistance tests against different basidiomycetes, soil box tests against soft rot and other soil-inhabiting micro-organisms, as well as in-ground and above-ground field trials at different test sites. Both oak species were rated “non-durable” (durability class 5, DC 5) in soil box tests and in-ground field trials and “slightly durable” (DC 4) in above-ground field trials. Solely results from laboratory tests with pure basidiomycete cultures led to partly better estimates (“very durable” to “moderately durable” DC 1-3), but did not represent the organisms responsible for decay in the field. For oak, EN 350-2 reflects only laboratory results but not the performance of the material in real field situations.     

Durability of European oak (Quercus petraea and Quercus robur) against white rot fungi (Coriolus versicolor): relations with phenol extractives

Knowledge on wood natural durability is required in order to be able to decide if we can use a certain type of wood outdoors. For instance, when used outside, oak wood is subjected to the leaching of its water-soluble substances. In this case the resistance of European oak wood is considered to be durable according to the European Standard EN 350-2. However, so far we do not exactly know the real impact of the leaching phenomenon on the resistance of oak wood and the importance of chemical contents. Nevertheless, our study has indicated that some individuals may contain highly durable wood characteristics even after the leaching process (i.e. 33% of very durable wood was still very durable after the leaching test). Chemical analysis has demonstrated that the presence of phenolic compounds are positively correlated with durability. This means that higher proportions of phenol confer higher resistance on wood. After the leaching test, which involves a washout of water soluble compounds, 70% of the trees demonstrate a decline in durability (after the leaching test 75% of the very durable wood dropped to a durable class; whereas, 25% of the wood in the same class still kept their very durable status). This experiment clearly shows the influence of the leaching phenomena and its important role on durability in oak wood. The results show also that 18% of the oak samples could be considered as very durable even after leaching.     

Application of high-frequency densitometry to detect changes in early- and latewood density of oak (Quercus robur L.) due to thermal modification

The aim of the present investigation was the identification of changes in the density of oak (Quercus robur L.) due to the influence of thermal modification. The reduction of the density was recorded by High-Frequency Densitometry and compared to measurements based on the gravimetric method. To identify changes in density, the initial density and the density after thermal treatment were determined using the same sample. In conclusion, results from the High-Frequency Densitometry Method show smaller deviations than those from gravimetric method. In addition, High-Frequency Densitometry provides reasonably good results with respect to the localisation of changes in density within an annual ring. As expected, in contrast to the Gravimetric Method the High-Frequency Densitometry Method were proved to be applicable to localise the change of the tree-ring density. It can be summarized that the measurement of the local density change can be realized by High-Frequency Densitometry. The density of earlywood was significantly more reduced due to thermal modification than the density of latewood.     

Antimicrobial and antioxidative enrichment of oak (Quercus robur) bark by rotation planar extraction using ExtraChrom

The multifunctional ExtraChrom instrument was used in the extraction of antimicrobial and radical scavenging components from oak (Quercus robur L.) bark. Milled and sieved oak bark was extracted with 80% (v/v) methanol solution in water on the ExtraChrom instrument using step-gradient in the preparative separation. Extracts were tested using agar diffusion method on Staphylococcus aureus, Enterobacter aerogenes and Candida albicans. Some extracts showed moderate bactericidal, fungicidal, bacteriostatic and fungistatic activity. The composition related to activity of the fractions and extracts was screened simultaneously by thin-layer chromatography (TLC) detected by UV and by spraying the plate with radical scavenging reagent 1,1-diphenyl-2-picrylhydrazyl (DPPH) to detect antioxidant activity. Thus, we could demonstrate the antiradical and antimicrobial activity of oak beneficial in the storage of wine against the oxidation and human microbial exposure.     

Durability of European oak (Quercus spp.) in ground contact – A case study on fence posts in service

The durability of European oak (Quercus spp.) is under debate for a long time. In contrast to its classification as ‘‘durable’’ timber species according to EN 350-2 (CEN 1994), results from different comparative studies have clearly shown a lower durability, especially for in-ground exposures. To highlight this conflict more detailed, a case study on oak fence posts, which had been in service for 5, 10, 20, 30, and 60 years, was carried out. The posts were examined in terms of decay type and intensity, remaining cross section, wood moisture content, and different characteristics of the adjacent soil. The durability of the oak posts was affected by high variation. Posts prematurely failing after only five years were found as well as posts still serviceable after 60 years. Different findings of the study have the potential to increase the understanding of durability aspects in the future and might be considered for calibration and adaption of field and laboratory test methods in the future: The ground line turned out to be not the most severe exposure for posts, although it is generally assumed to be. Furthermore, no significant negative impact of remaining sapwood portions on the durability of the heartwood was found, but the important role of radial cracks for the initiation of decay became apparent. In this regard further potentially important factors for the in-ground durability are size and shape of timber components.     

Effect of extracts of oak (Quercus petraea) bark,oak leaves,aloe vera (Curacao aloe), coconut shell and wine on the colloidal stability of milk and concentrated milk

Addition of aloe vera extract, non-dialyzable red wine residue or aqueous methanol extracts of oak bark, oak leaves or coconut shell increased the heat stability of skim milk (at 140°C) and concentrated milk (at 120°C) and retarded rennet coagulation, but had no effect on the alcohol stability of milk. The calcium ion concentration in milk was reduced by the addition of these extracts but calcium chelation does not appear to be the exclusive mechanism responsible for promoting micellar stability. The extracts contained a high concentration of polyphenols, which are highly reactive and may be the active agents in the extracts, responsible for the enhanced stability of casein micelles.     

Comparative studies on the artificial drying of normal and semi-naked beans (Vicia faba L.)

Small-scale tests were carried out to compare the drying behaviour of beans (Vicia faba L.), which had been bred with part of the seed coat missing, with that of normal beans possessing intact testas. Results showed drying behaviour for the ‘semi-naked’ and normal types to be similar, irrespective of whether the drying was started when the beans were very moist at 35–45% moisture content or moderately moist at around 20% moisture content.     

Ethyl carbamate in the production and aging of cachaça in oak (Quercus sp.) and amburana (Amburana cearensis) barrels

There are residual organic and inorganic contaminants in the cachaça production chain. Among the organic contaminants, ethyl carbamate has been widely studied. It is formed naturally during the fermentation processes and can be found in many foods and beverages such as bread, yoghurt, wine, beer and especially in fermented–distilled beverages such as whiskey, rum, vodka, grappa, cachaça and tiquira. The objective of this study was to identify and quantify ethyl carbamate during the steps of the production process and aging of cachaça in oak (Quercus sp) and amburana (Amburana cearensis) barrels. The cane used for cachaça production, as well as the process for obtaining the fermentation broth, did not affect the formation of ethyl carbamate, as it was not detected. Carbamate was detected in low concentrations, but was not quantified, in the fermentation, distillation and aging steps. Copyright © 2014 The Institute of Brewing & Distilling     

烘烤强度和木纹理对橡木（Quercus petraea）心材多酚和香气的影响

考察不同烘烤程度对不同纹理橡木心材试样中低分子质量酚酸和挥发性物质含量的影响,结果表明烘烤过程将会改变橡木心材的物质组成,并通过相应的化学反应增加挥发性物质的含量。同时,在不考虑烘烤强度条件下,供试的细纹理橡木心材试样含有较高的挥发性物质含量,例如顺/反橡木内脂、顺/反异丁子香酚、呋喃醛、紫丁香醇,以及芥子醛、松柏醛、香草醛和丁香醛等低分子质量酚类化合物,而中纹理和粗纹理的样品则表现出较高的总酚、总单宁水平,以及较高的鞣花酸和没食子酸含量。此外,主成分分析显示,中纹理和细纹理样品的中度和重度烘烤处理与橡木心材试样的挥发性物质含量有较大的正相关性,而粗纹理的未烘烤和轻度烘烤样品则与试样中总单宁和阿魏酸含量呈正相关。     

Radial variation of total phenol content in beech (Fagus sylvatica L.) wood with and without red heartwood

A comparative study of the radial distribution of the total phenol contents has been carried out on two Beech (Fagus sylvatica L.) discs, one with red heartwood and the other without red heartwood. The wood disc samples were investigated immediately after felling and at the different stages of room-drying. In the disc without red heartwood the concentrations increased from the bark towards the pith. In the disc with red heartwood the total phenol concentration rose steeply in front of the colour boundary, but this could only be measured in the fresh tissues. This suggests, that in these tissues either the formation of phenols (accumulation) is more intense or that special phenols are also formed. Beyond the boundary the concentration decreased dramatically. After drying of the wood samples the concentration decreased in all wood parts of the discs, but the amount of this is the highest in the white tissues next to the red heartwood. The results prove that the transformation of the phenols in the white tissues next to the colour boundary takes place faster.     

Comparative studies of some properties of undehulled, mechanically dehulled and manually dehulled cowpea (Vigna unguiculata Walp. L.) flours

A comparative evaluation was made of some physico‐chemical and rheological characteristics of undehulled, manually dehulled and mechanically dehulled cowpea (Vigna unguiculata Walp. L.) flours from brown and white varieties of the legume. The flours were used to prepare steamed bean paste, ‘Moinmoin’, which was analysed for some sensory parameters. Dehulling and dehulling methods had no appreciable influence on the physical characteristics and proximate composition of the flours, except ash content, which was slightly higher in undehulled flour samples. Amylograph pasting characteristics of the flours showed varying trends because of dehulling method and/or presence of seed coats. ‘Moinmoin’ samples prepared from the flours received similar ratings for all sensory attributes, with no significant differences (P < 0.01 and P < 0.05), except for the low‐rated (poorer) colour of the undehulled brown product.     

The effect of oak tannin (Quercus robur) and hops (Humulus lupulus) on dietary nitrogen efficiency,methane emission,and milk fatty acid composition of dairy cows fed a low-protein diet including linseed

The objective of this study was to test the effects of inclusion of hop pellets (HP) and oak tannin extracts (OT) alone or in combination on N efficiency, methane (CH₄) emission, and milk production and composition in 2 experiments with dairy cows fed low-N rations supplemented with linseed. In both experiments, 6 lactating Holstein cows were assigned to 3 dietary treatments in a 3 × 3 duplicated Latin square design (21-d periods). Cows were fed a total mixed ration at a restricted level to meet their nutrient requirements. In experiment 1, 169 g dry matter (DM) of OT or 56 g DM of HP was included separately in the control diet (C1). In experiment 2, the additives were included together (OT-HP) in the control diet (C2) similar to C1. Diet C2 was compared with a control without linseed (C0). In experiment 1, the supplementation of the control diet with OT decreased urinary N excretion by 12%. In experiment 2, the combination of OT and HP decreased urinary N by 7%. Oak tannin extracts and HP alone or in combination did not influence the daily enteric CH₄ production of cows. Cows fed diet C0 produced 17% more enteric CH₄ daily than those fed diet C2. Intake of diet C2, which contained 6.7% extruded linseed on a DM basis (experiment 2), decreased the sum of 6:0 to 14:0 fatty acids (?16%) and palmitic acid (?26%) and increased the stearic acid (+50%), oleic acid (+36%), vaccenic acid (trans-11 18:1; +285%), rumenic acid (cis-9,trans-11 18:2; +235%), and α-linolenic acid (+100%) in milk fat. The supplementation of diet C2 with the OT-HP mixture further improved the milk's fatty acid composition. Intake of the OT alone increased α-linolenic acid by 17.7% (experiment 1). The results of this study show that at the economically acceptable dose we tested, hops had no effect on urinary N excretion, CH₄ emission, milk production, and milk composition. By contrast, supplementation of diets with oak tannin extract can be considered for reducing urinary N excretion. The combination of oak tannin and hops had no more effect than oak tannin alone except on the milk fatty acid profile, which was favorably influenced from a nutritional point of view.     

Biological,chemical and technological characteristics of waterlogged archaeological piles (<Emphasis Type="Italic">Quercus petraea</Emphasis> (Matt.)Liebl.) of a medieval bridge foundation in Bavaria

The biological, chemical and technological study of waterlogged archaeological piles of oak wood (Quercus petraea (Matt.)Liebl.) of a medieval bridge in Bavaria was primarily undertaken in the context of finding an adequate drying method to assure stable long-term conditions while presenting the archaeological finds in a local history museum. There was a unique chance to study the oak wood preservation of five generations of a bridge foundation from one and the same place. According to the dendrochronological dating of the felling dates of the oaks, the first identified generation is already medieval with an earliest date of 1447, followed by the second generation at about 1572, with the third one at about 1658, the fourth one at about 1727 and the youngest one at about 1787. The experienced selection of the trees in the forest and the subsequent careful manufacture of the piles without any sapwood and obviously their immediate application allowed for studying the alteration of the wood characteristics with increasing years of underground pile exposure. The light microscopical study did not reveal remarkable structural alterations of lignin and cellulose. Microbial activities of erosion bacteria and soft rot could only be detected within the uppermost rounded part of some piles and in their periphery. However, it was informative to see how green and wet manufactured oak wood responds as a sensitive ion-exchange system underground. The iron ions penetrated particularly into the outer heartwood and reacted with the special accessory compounds, such as tannins, essentially within the parenchyma cells. However, the radial distinct gradient had no notable difference between the fifth generation (1787) and the older ones. The uptake of Si-, Ca- and Mg-ions significantly represents an influx with a radial penetration even to the pith. Surprisingly, the monomeric K-ions, which are present in the green woody tissue with a mean value of 330 ppm moved radially out of the wood, down to about 10% compared to the beginning of the underground exposure. Moreover, the shift of the original pH value of about 3.6 of the heartwood to finally a mean of pH 4.6 clearly underlines a correlated efflux effect, which might slightly chemically alter the woody tissue. The changes of the chemical and technological characteristics such as basic density, compression strength, sorption behavior, shrinkage, and ash content actually indicate that over the centuries some change in the chemical characteristics of the heartwood must have occurred.     

超临界CO2萃取与传统方法提取鸦胆子油实验比较

应用超临界C02萃取法（SCFE）和溶剂法提取鸦胆子油，对两种提取方法制备的鸦胆子油进行了得率、制备工艺、外观评价和化学组成等方面的对比实验，结果表明：SCFE方法萃取的鸦胆子油得率为18．26％，溶剂法的得率为20．25％，两种萃取方法所得鸦胆子油的主要脂肪酸组成为油酸、亚油酸、棕榈酸和硬脂酸。体外试验表明鸦胆子油对肝癌和鼻咽癌有较好的抑制作用。     

Effect of drying conditions on tannin,fibre and lignin levels in mature oak (Quercus incana) leaves

Oak (Quercus incana Roxb) leaves are rich in tannins and produce adverse effects when fed to livestock. The effects of shade and sun drying and oven drying at 60°C and 90°C for different lengths of time (24 to 72 h) on total phenolics, condensed tannins, protein precipitation capacity, degree of polymerisation, specific activity (protein bound per unit tannins), fibre-linked proanthocyanidins, acid and neutral detergent fibres and lignin levels in mature oak leaves were studied. Removal/inactivation of tannins was not observed on wilting or drying under several conditions. Similarly the drying conditions had no effect on fibre composition. The adverse effects on feeding fresh or dried oak leaves are expected to be of similar magnitude.     

Effect of cooking on the composition of beans (Phaseolus vulgaris L.) and chickpeas (Cicer arietinum L.)

The effect of cooking on levels of nutrients and anti-nutritional factors in beans and chickpeas was investigated. Significant (p < 0.05) variation existed among the beans and chickpeas with respect to their crude protein, starch, soluble dietary fiber (SDF), insoluble dietary fiber (IDF), total dietary fiber (TDF), resistant starch (RS), trypsin inhibitor activity (TIA), mineral, phytic acid, tannin, sucrose and oligosaccharide (raffinose, stachyose and verbascose) contents. Cooking beans and chickpeas in water significantly increased protein, starch, SDF, IDF, TDF, Mn and P contents (on a dry weight basis), whereas reduced ash, K, Mg, TIA, tannin, sucrose and oligosaccharide contents were observed. Colored beans (black, cranberry, dark red kidney, pinto and small red bean) contained tannins, whereas little tannin in white-colored beans (great northern and white pea bean) and chickpeas (Desi and Kabuli type) was detected.     

啤酒花总黄酮测定方法的比较研究

以高效液相色谱法对啤酒花总黄酮含量的测定结果作为评判标准（相对准确值）,比较与评价AlCl3分光光度法、Al(NO3)3分光光度法和硼氢化钠/氯醌分光光度法3 种比色法测定酒花总黄酮含量的准确性。结果表明,高效液相色谱法测定酒花总黄酮含量为（12.73±0.26） mg/g;AlCl3法测得总黄酮含量为（13.66±0.45）mg/g,与高效液相色谱法偏差率为7.3%;而Al(NO3)3法测定结果为（43.53±1.16）mg/g,与高效液相色谱法的偏差率为241.9%;硼氢化钠/氯醌法测定结果为（70.25±1.42）mg/g,与高效液相色谱法的偏差率为451.8%。提出AlCl3分光光度法比其他2 种比色法更适用于酒花总黄酮含量的测定,该方法误差小,准确性好。     

Influence of phenolic compounds in heartwood of Silver fir (Abies alba Mill.) on the equilibrium moisture content

Experiments were undertaken to differentiate between sapwood and uncolored (light) heartwood of Silver fir (Abies alba Mill.). Paired samples of sapwood and heartwood were removed from five randomly selected healthy trees without wetwood, aged over 170 years, and (a) the percent of extractives, (b) the amount of total soluble phenols and (c) the equilibrium moisture content (EMC) at three relative humidities (RH) were determined. The percentage of extractives and the amount of total soluble phenols in the heartwood were significantly higher and EMC lower than in the sapwood. The effect of extractives on the EMC was most marked in the upper range of the RH.