Chemical investigations on boiling process waters in face veneer production

Boiling processes in veneer industry generate large amounts of process water replete with dissolved wood extractives. In the present study the chemical composition of boiling waters from 18 industrially treated wood species were investigated. Contamination levels of the boiling waters varied within a wide range depending on the different extractive contents of the processed wood species and operational conditions. Boiling wood species with high extractives content, heated over several days at temperatures above 80 °C, generate highly loaded waste waters with chemical oxygen demands (CODs) of up to 7000  mg l^-1. The determination of the elemental composition, using optical emission spectrometry (ICP-OES), showed iron contents of up to 10 mg l^-1. Phenolic compounds were in a range of 40 to 900 mg l^-1. Flavonoid compounds and phenolic acids were identified in the boiling waters by liquid chromatography (RP-HPLC-UV). The results confirm the need for water treatment facilities to establish a recycling process and to avoid discolourations of the wood by accumulated wood extractives.     

Effects of high pressure treatment on physicochemical characteristics of fresh sea bass (Dicentrarchus labrax)

The effects of high pressure (HP) treatment (pressure: 220–250–330 MPA; holding time: 5 and 10 min; temperature: 3, 7, 15 and 25°C) on physicochemical characteristics (colour, thiobarbituric acid, trimethylamine nitrogen values) of fresh sea bass fillets were investigated. HP-treated sea bass fillets had higher lightness (Hunter L*) values than untreated sea bass fillets; the magnitude of changes increased with treatment pressure. HP-induced changes in colour generally imparted a cooked sample. The TBA value of HP treated sea bass samples (except 220–330 MPa, 3°C for 5 min) were found to be insignificant (P > 0.05) or significantly (P < 0.05) lower than the untreated samples. TMA-N content of HP treated at 220–250–330 MPa, 3–7–25°C for 10 min sea bass samples were found to insignificant according to the untreated samples. The results obtained from this study showed that the quality of high pressure treated sea bass is best preserved at 220 MPa, 25°C for 5 min.     

Developing treatment protocols for disinfesting pine wood product using radio frequency energy

Numerous non-native insect pests are moved around the world via international trade and have caused major forestry losses, especially for pine trees. The purpose of this research was to study a potential application of radio frequency (RF) heating for disinfesting pine wood products to reduce forestry damage caused by exotic pests. A pilot-scale 6 kW, 27.12 MHz RF system was used to develop a treatment protocol for disinfesting pine wood products based on the heating uniformity studies. The results showed that the heating time needed was only 6.7 min to heat the wood blocks (250?×?400?×?60 mm³) with moisture content of 13.3% d.b. from 25 to 60?°C using RF energy, but 320 min to reach 56.2?°C using hot air at 60?°C with 1.6 m/s. Based on the heating uniformity study, the best condition occurred when the lower wood moisture content was used and the wood width approached the RF electrode one. The RF treatment protocol was finally developed to combine RF energy with forced hot air at 60?°C, movement of conveyor at 7.4 m/h and holding at 60?°C hot air for 1 min. Wood quality was not affected significantly by the RF treatments because quality parameters of treated wood samples were similar to those of controls. The RF treatment may provide a rapid, effective and environmentally friendly method to disinfest wood products.     

Changes in dimensional stability and mechanical properties of Eucalyptus pellita by melamine–urea–formaldehyde resin impregnation and heat treatment

This study investigated the influence of heat treatment on the dimensional stability and mechanical properties of untreated and low molecular weight melamine–urea–formaldehyde (MUF) resin treated Eucalyptus pellita wood. Wood samples were heat treated under vacuum atmosphere in laboratory conditions at temperatures between 160 and 240 °C for 2–10 h. The results showed that anti-shrink efficiency and anti-swelling efficiency of MUF resin-impregnated heat-treated eucalypt wood were improved by up to 47 and 49 % at 240 °C for 10 h separately, which were greater than those of heat-treated wood. In relation to mechanical properties, the modulus of elasticity and modulus of rupture decreased with increasing temperature and time, but the reduction of properties appeared to be smaller for MUF resin-impregnated heat-treated wood. Therefore, heat treatment combined with resin treatment of eucalypt wood shows potential to improve the wood quality of solid wood products.     

Contact thermal post-treatment of oriented strandboard to improve dimensional stability: A preliminary study

The oriented strandboard (OSB) has less dimensional stability than plywood, but they are competitive panels and have been used for similar ends. The wood-water relation variables, such as thickness swelling and water absorption, express this OSB dimensional instability and can be explained by two main factors: wood hygroscopicity and imposed hot-pressing stresses. The objective of this present paper was to propose a thermal post-treatment as a method to improve OSB dimensional stability by decreasing wood hygroscopicity and releasing hot-pressing stress. OSB panels from Pinus taedawood were produced in laboratory, and their characteristics were: single layer, 0.8 g/cm³; 8% phenolic resin and without wax. The OSB panels were treated in a laboratory press at 250 °C for about 4, 7 and 10 minutes. The wood-water relation variables, thickness swelling (TS), water absorption (WA), equilibrium moisture content (EMC) and springback or permanent thickness swelling (PTS) were determined and compared with untreated panels. The results showed that the proposed thermal treatment was effective to reduce TS, EMC and PTS, but didn’t affect WA which was affected by panel density reduction. The longer the treatment the higher the dimensional stability, and panel weight loss could be used as predictive variable for the efficiency of the treatment.     

Effect of additives on mesophilic α-amylase and its application in the desizing of cotton fabrics

An investigation was carried out on thermal stability of α-amylase. The influence of various additives (calcium acetate, sodium lactate, L-histidine, and water-soluble chitosan) on the stability of α-amylase was studied. Results showed the inactivation behavior of α-amylase with or without additives all followed the first-order kinetics. All additives (Ca2+, sodium lactate, L-histidine, and water-soluble chitosan) displayed good stabilizing effect on α-amylase lower than 80 °C, and only water-soluble chitosan had an efficient stabilizing effect on α-amylase when the treatment temperature exceeds 80 °C. All additives improved the catalytic activity of α-amylase at 70–90 °C, and the appearance of water-soluble chitosan increased the catalytic activity of α-amylase at 90 °C sharply. A desizing ratio of 68.42% was obtained by treating the cotton fabrics in the buffer solution at 100 °C without α-amylase. To obtain a desizing ratio exceed 95% when fabrics were treated at 100 °C for 10 min, the addition of water-soluble chitosan saves 2/3 α-amylase dosage. Moreover, water-soluble chitosan showed a further improvement in desizing effect than the additive of calcium acetate.     

Heat-induced conversion of gingerols to shogaols in ginger as affected by heat type (dry or moist heat), sample type (fresh or dried), temperature and time

The impact of heat type, sample type, temperature and time on the heat-induced conversion of gingerols to shogaols in ginger were studied by an UHPLC–ESI–MS/MS. Heat treatments greatly induced the conversion of gingerols to shogaols in ginger. As the temperature increased, the faster conversion of gingerols into shogaols were observed. However, the efficiency of the heat-induced conversion differed greatly with the heat types. Moist heat treatment induced significantly higher quantity of shogaols than dry heat treatment. The moist heat treatment at 120 °C for 360 min induced the highest conversion, reaching to 2991 mg 6-shogaol per kg ginger. In addition, dry-heat induced conversion was affected by the sample type. The dry-heat treatment on dried powder induced significantly higher quantity of shogaols than that on sliced fresh ginger. This represents the first systematic comparative study on the heat and sample types on the heat-induced conversion of gingerols into shogaols in ginger.     

Study of rosin softening point through thermal treatment for a better understanding of maritime pine exudation

The temperature of pine rosin softening point was studied to better understand the phenomenon of resin exudation on the surface of pine boards. This problem may decrease strongly the aesthetical performance of wood used outside and is an important concern for the industry. To perform a reliable measurement of rosin properties with a small amount of sample, differential scanning calorimetry (DSC) and thermo mechanical analysis (TMA) techniques were investigated and the results compared. DSC curves on industrial rosin and acetone rosin extractives from maritime pine show a behavior similar to a glass transition in polymers. TMA measurements carried out on the same industrial rosin showed that the softening point is in the midpoint of the transition phase observed by DSC. The softening point temperature is about 45 °C for industrial rosin and about 50 °C for rosin extractives from maritime pine boards. These values are significantly lower than those usually found on other rosins measured by the ASTM E28-14 standard using the ring-and-ball method. When using heat treatment, it was observed for the first time that the thermal history of the sample can change its softening point temperature. With these results, it could be possible to develop a new strategy to reduce rosin exudation for exterior wood siding.     

Stevioside and Stevia-sweetener in food: application, stability and interaction with food ingredients

The stability of the natural sweetener stevioside during different processing and storage conditions as well as the effects of its interaction with water-soluble vitamins, food relevant organic acids and other common low calorie sweeteners and its application in coffee and tea beverages were evaluated. Incubation of the solid sweetener stevioside at elevated temperatures for 1 h showed good stability up to 120°C, whilst at temperatures exceeding 140°C forced decomposition was noticed. In aqueous solutions stevioside is remarkable stable in a pH range 2–10 under thermal treatment up to 80°C, however, under strong acidic conditions (pH 1) a significant decrease in the stevioside concentration was detected. Up to 4 h incubation of stevioside with individual water-soluble vitamins in aqueous solution at 80°C showed no significant changes in regard to stevioside and the B-vitamins, whereas a protective effect of stevioside on the degradation of ascorbic acid was observed resulting in a significant delayed degradation rate. In the presence of other individual low calorie sweeteners practically no interaction was found at room temperature after 4 months incubation in aqueous media. Stability studies of stevioside in solutions of organic acids showed a tendency towards enhanced decomposition of the sweetener at lower pH values depending on the acidic medium. In a stevioside-sweetened coffee and tea beverage, practically, no significant chances neither in caffeine content nor in stevioside content could be noticed. Furthermore an overview of already performed studies in literature about the Stevia-sweetener stevioside and rebaudioside A is given.     

Effect of oil type, temperature and time on moisture properties of hot oil-treated wood

This paper focuses on the moisture properties of wood treated in palm oil-, soy oil- and slack wax for different processing times and temperatures. Also, the relative importance of oil uptake and thermal modification on the wood moisture properties is investigated. Slack wax was better than palm oil or soy oil in improving the moisture performance of thermally treated wood, and treatment at 220 °C was superior to treatment at 200 °C, with 4 h being generally better than 2 h treatment. Water absorption in samples treated with wax at 100 °C or 160 °C was similar to that in samples treated at high temperatures while improved anti-shrink efficiencies (ASE) and lower hygroscopicities occurred only for the high temperature treatments. Chloroform extracted samples treated at high temperature with palm oil or soy oil had relatively similar hygroscopicity and ASE properties compared to unextracted samples, but had greatly increased water absorption properties. These results confirm that chemical reactions in wood resulting from the heat treatment account for the main improvements of wood properties in reduced hygroscopicity and improved dimensional stability, while the oil absorbed by wood reduces the rate of water absorption.     

The water absorption of sapwood and heartwood of Scots pine and Norway spruce heat-treated at 170 °C, 190 °C, 210 °C and 230 °C

Heat-treatment changes the chemical and physical properties of wood. Wood polymers are degraded, dimensional stability is enhanced, equilibrium moisture content is lowered, colour darkens and biological durability is increased. The properties of heat-treated wood have been researched considerably, but the differences between sapwood and heartwood have not been reported separately. In this research, water absorption differences between sapwood and heartwood of Scots pine and Norway spruce heat-treated at temperatures 170 °C, 190 °C, 210 °C and 230 °C were investigated. The results were compared to industrially kiln-dried reference samples. Water absorption was determined with a floating test based on the EN 927-5 standard. The heartwood of both wood species absorbed less water than sapwood. Heat-treatment evidently decreased the water absorption of spruce and pine heartwood. The higher the heat-treating temperature, the lower the amount of absorbed moisture. However, a very interesting exception was pine sapwood, whose water absorption actually increased with heat-treatment after the three lowest heat-treatment temperatures compared to the reference material. Water absorption did not decrease until the heat-treatment temperature was 230 °C.     

Influence of temperature of thermal treatment on surface densification of spruce

Spruce (Picea abies L. Karst) wood lamellae, thermally treated at 170, 190, 210 and 230 °C were surface densified by compression at a temperature of 150 °C to three degrees of compression. Immediate springback, set recovery, mechanical properties in 3-point flexure, Brinell hardness and density profiles measurements were used to determine the effect of thermal treatment on the properties of surface densified wood. The highest immediate springback occurred in wood specimens thermally treated at the highest temperature (230 °C) and decreased with decreasing thermal treatment temperature. The untreated samples had the highest set recovery, which decreased with the temperature of thermal treatment. The surface densification increased hardness and bending strength. The highest increase was in the case of untreated wood and decreased with the temperature of thermal treatment. The modulus of elasticity (MOE) and modulus of rupture (MOR) of surface densified wood decreased with increasing thermal treatment temperature. The trend was similar for specimens which were thermally treated but not surface densified. Surface densification increased the density of the specimens in the first few millimetres below the surface. The highest density was achieved in untreated specimens and the lowest in specimens thermally treated at the highest temperature.     

Development of schedule to steaming prior to drying and its effects on <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> × <Emphasis Type="Italic">E. urophylla</Emphasis> wood

To investigate the influence of moisture content (MC) and steaming temperature on defects developing during steaming prior to kiln drying, mass loss, heat transfer, microstructures, extractives, and chemical transformation of Eucalyptus grandis?×?E. urophylla specimens (with moisture content of 120, 70, 60, 50, 40, 30, 20%) were observed in this study. Specimens of each experimental moisture content were steamed at 80, 100, and 120?°C for 4 h after pre-heating at atmospheric pressure, respectively. Results revealed that it was most beneficial to conduct steaming at 100?°C when the moisture content was approximately 50% after air drying when stagewise heating-up and continuous steaming schedule were adopted. Under this condition, there was a notable decrease in defects including edge bends, surface splits, and inner splits. Steaming was also a drying period characterized by various extents of mass loss. Changes in microstructures and extractive contents proved the increasing permeability of steamed wood. Deacetylation and crosslinking reactions happened in the hemicellulose of the sample materials, which contributed to the loss of hemicellulose after treatment.     

Cutting forces in bandsaw processing of oak and beech wood as affected by wood moisture content and cutting directions

Cutting forces in bandsaw processing of oak and beech wood were measured at two levels of wood moisture content (about 12 % and FSP) for four cutting directions (90°–90°, 90°–0°, 0°–90° and 90°–45°). A constant cutting speed of 40 m/s and a feed rate of 20 m/min were applied. A piezoelectric dynamometer (KISTLER type 9257A) mounted on the carriage of the vertical bandsaw machine (ESTERER model EB 1400) was used to measure the parallel, normal and lateral cutting forces. Results revealed that all cutting forces depend on the wood moisture content and cutting direction. The greatest parallel force was observed for oak wood at 12 % MC for 90°–90° cutting direction (44 N/mm) whereas the lowest one was for beech wood at 30 % MC for 0°–90° cutting direction (20 N/mm). In contrast to the little change of lateral force at various cutting directions, the change in parallel force was significant.     

Chemical analysis of heat treated softwoods

Heat treatment of wood has been found an effective method to improve dimensional stability and durability against biodegradation. A two-stage heat treatment of wood at relatively mild conditions (<200 °C) was investigated by using different chemical analysing methods, such as a wood chemical component analysis, CHNO-elemental analysis, UV-spectroscopy, and analysis of the acetyl and free hydroxyl group content. The results of this study contribute to a better understanding of the typical reaction mechanisms occurring and of the effect of heat treatment on the properties of wood, as described in previous 13C-NMR and FTIR studies of heat treated wood.     

The properties of Moso bamboo heat-treated with silicon oil

Bamboo is very vulnerable to mold fungi, which greatly limits its applications. In this paper, moso bamboo was heat-treated with silicon oil at temperatures of 160, 175, and 190 °C for a duration of 2 h. The physical–mechanical properties and mold resistance were investigated. The chemical action of silicon oil within bamboo was analyzed by FTIR spectroscopy on bamboo samples before and after the oil heat treatment. The results showed that the hygroscopicity and the dimensional stability of bamboo were effectively improved by the oil heat treatment. The MOR of oil heat-treated bamboo increased as it was treated at 165 and 175 °C due to the oil uptake, but its MOR decreased as the treated temperature increased to 190 °C; at this temperature the degradation of chemical components should be considered. Mold grew more slowly on the oil heat-treated bamboo than untreated bamboo, and the performance of mold resistance was also effectively improved. In addition, the presence and chemical action of silicon oil were also examined through a comparison of FTIR spectrum of untreated control and 175 °C oil heat-treated bamboo.     

Effects of silver nanoparticles and fungal degradation on density and chemical composition of heat-treated poplar wood (Populous euroamerica)

Effects of silver nanoparticles and fungal degradation on the weight loss and chemical composition of heat-treated poplar wood were studied. Wood blocks were impregnated with a 400 ppm nanosilver suspension under 3 bar pressure for 20 min using Lowry process (edited empty cell). Heat-treatment was carried out at 135, 160 and 185 °C. Specimens were divided into 4 groups; control, nanosilver impregnated, heat-treated and impregnated- heat treated specimens (135, 160 and 185 °C). All samples from the internal and superficial parts of the blocks were exposed to the white rot fungus Trametes versicolor. The results of heat-treated samples indicated higher amount of Klason lignin and extractives, but lower holocellulose and cellulose content. Furthermore, heat-treatment illustrated an increasing effect on the fungal resistance. For all the properties, significant difference was found between the internal and superficial test specimens. Nanosilver impregnation had an intensifying effect on the results of the heat-treatment.     

Phytosanitary treatment of European pallets by microwave: developing a program to ensure compliance with ISPM 15 and monitoring its efficacy on the house longhorn beetle (Hylotrupes bajulus L.)

Microwave heating was recently approved by the FAO as a significantly effective phytosanitary treatment for wood packaging material. According to ISPM 15 (FAO 2009), the target organisms are eradicated if a temperature higher than 60 °C is maintained for 60 s across the entire profile of the board (i.e. 60 °C/60 s). A study using pallet boards was carried out in order to set up a treatment program that would meet ISPM 15 requirements in terms of wood temperature and insect mortality. A 4 m-long industrial tunnel oven (maximum power of 28.8 kW) was used to carry out the experiments. Temperature was measured by means of a VarioCAM^® infrared camera. The most relevant results found were: (i) achieving a mean temperature of 63.2 °C (Populus sp.) or 64.8 °C (Pinus sylvestris L.) on the upper surface of 22 mm-thick boards enabled compliance with FAO requirements (i.e. 60 °C/60 s), whatever the moisture content, basic density and initial temperature of the wood (provided the latter exceeded 0 °C); (ii) larvae >150 mg represented the most microwave-resistant life stage of Hylotrupes bajulus L.; (iii) the mortality rate of the larvae was influenced by the moisture content of the boards. Using the Gompertz model, the upper surface temperature was estimated that would be needed to achieve a 99.99683 % mortality rate (the Probit 9 mortality level of efficacy) for the most microwave-resistant life stage of H. bajulus. This temperature was estimated to be 46.8 and 57 °C for wood with >50 and <25 % moisture content, respectively.     

Characteristics of Pleurotus sp. TD36 and its ability to reduce wood extractives in pretreatment for pulping

Lipophilic extractives of wood cause pitch deposition during pulp and paper production, leading to serious economic losses and environmental pollution. Natural seasoning of wood material before pulping can reduce wood extractives, but there is no control of the pulp yield and quality. Pretreatment of the wood chips with selected fungi is regarded as better controlled seasoning with effective removal of problematic extractives. Commercially available fungal preparations are effective mostly for softwood, but not quite suitable for Acacia mangium and hybrid hardwood—the main pulpwood of Vietnam. In this paper, a fungal isolate TD36 was identified as white-rot basidiomycete Pleurotus sp. TD36 based on the biological characteristics and phylogenetic analysis. Having high activity of ligninolytic enzymes, amylase and protease, Pleurotus sp. TD36 was able to degrade lignin-like compounds (guaiacol, Remazol Brilliant Blue), starch and casein. Degradation of wood extractives was evaluated by laccase and sterol esterase assays of the fungus in shake flask cultures and in pretreatment of Acacia wood chips. Favorable conditions for wood pretreatment were selected, including: inoculum size, 1% v/w; wood moisture, 60% v/w; temperature, 28–30 °C and 30 days. Under such conditions, Pleurotus sp. TD36 removed about 68?±?2.75% of wood acetone extractives soluble in chloroform. Of that, about 73–89% of fatty acids and fatty alcohols, 76% of free sterols and 63% of sterol ester, were removed. Fungal pretreatment did not significantly affect the cellulose content of wood and Kraft pulp yield.

     

The Effects of Subcritical Water Treatment on Antioxidant Activity of Golden Oyster Mushroom

Subcritical water (SCW) extraction of golden oyster mushroom (GOM) was carried out at various temperatures (50, 100, 150, 200, 250, and 300 °C) for 10, 30, and 60 min, and the antioxidant and certain physiological activities of the extracts were evaluated. SCW treatment of GOM increased the antioxidant activity of the extracts. The SCW extraction of GOM at 250 °C for 60 min or 300 °C for 30 min showed relatively high levels of total phenolic content, 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity, and reducing power. The β-glucan content was the highest when SCW extraction was carried at 200 °C for 60 min, while the highest 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical scavenging activity occurred at 300 °C for 60 min. These results indicate that the temperature and time of SCW extraction significantly affect the antioxidant activity as well as the nutraceutical compound levels of GOM extracts.