The influence of material properties on the amount of twist of spruce wood during kiln drying

The development of twist in Norway spruce boards (Picea abies Karst.) during normal temperature kiln drying was researched. Tangentially oriented boards were sawn from diametrical radial planks, from which the basic wood properties, i.e. linear shrinkage and grain angle, were determined. The unrestrained boards were kiln dried using a selected drying schedule. During the controlled drying process the moisture content (MC) and twist of the boards were measured. Twist was generally induced by the shrinkage of wood below the fibre saturation point, and increased in proportional to the decrease in MC. The earlier appearance of twist, with regard to MC and drying time, was confirmed in the case of boards sawn from the central part of logs. The final twist amounted to between 10 and 20°/m in the case of boards close to the pith, and decreased to less than 4°/m in the case of boards sawn at a radius of 70 mm from the centre of the logs. Ring curvature had the highest impact on the final twist of the dried boards, followed by grain angle and tangential shrinkage.     

Influence of compounding conditions,treatment of wood particles with fire-retardants and artificial weathering on properties of wood-polymer composites for façade applications

European Journal of Wood and Wood Products - Various fire-retardants (FR) for the pre-treatment of wood flour, for example, ammonium polyphosphate and different formulations based on phosphorus-...     

Water retention of wood particles – characterization of polarity and particle size

The basic principle of methods measuring water retention of fibre pulp was adapted for a new method to prove differences in polarity and particle size of wooden particles used for particle board production. With this new method, particles come into contact with the liquid for a short time. Besides the laboratory method, appropriate data analyses of the weight-time curves, including the calculation of a novel polarity coefficient are introduced. The measurement signal was found to be most significantly influenced by the particle properties at the equilibrium of liquid charge and discharge, as well as within the asymptotic levelling phase around 30 s of testing. With increasing particle size, water retention values of both native and thermally modified particles decrease due to reduced specific particle surface. Thermally modified particles show significantly lower water retention values in the range of ?28 to ?46 % and higher variability which is thought to be related to reduced polarity. The method proved to be quick, easy to handle and reproducible.     

Microwave testing of moist and oven-dry wood to evaluate grain angle,density, moisture content and the dielectric constant of spruce from 8 GHz to 12 GHz

The scope of this work is to discuss the challenges and demonstrate the potential of microwave testing for applications in the wood processing industry. Microwave technology benefits from the anisotropic dielectric properties of wood to simultaneously identify grain angle, density, and moisture content of wood. Therefore, the theory of free space transmission measurement is thoroughly discussed with emphasis on the characteristics of (and how to deal with) reflections occurring in real measurements. A more sophisticated calculation method for the derivation of the desired physical wood properties is presented. The advantages of a modern laboratory style setup are shown and its possible transition in an industrial-style application is discussed. Moist (moisture content 7.6–14%) and oven-dry spruce samples are tested. The detection of grain angle for moist and oven-dry wood yields an RMSE (root-mean-squared-error) of 0.14° and 0.4°, respectively. Moisture content is evaluated with density- and thickness-independent methods. Adapted regression models are proposed yielding an RMSE for moisture content of 0.45% for a single frequency measurement. The promising advantages of wood moisture estimation with frequency sweeps instead of fixed frequency signals are discussed and demonstrated for all samples (RMSE 0.39%). The dielectric constant of moist and oven dry spruce in the range from 8 to 12 GHz is evaluated in respect to density, moisture content and temperature. The respective constants ε′, ε′′, and tan(δ) are formulated in a general form via a non-linear regression and compared to existing data in literature.     

Role of precursors on the kinetics of acrylamide formation and elimination under low moisture conditions using a multiresponse approach – Part II: Competitive reactions

The effect of addition of amino acids, other than asparagine, on the kinetics of acrylamide formation and elimination reactions was investigated under low moisture conditions using equimolar asparagine-glucose-amino acid model systems, heated at temperatures between 120 and 200 °C. To this end, glutamine and cysteine were selected. A mechanistic model was proposed, composed of the basic reactions occurring in an asparagine-glucose control system on the one hand and of extra reactions in which the additional amino acids are assumed to be involved. Using this model, multiresponse modelling was applied on the responses measured (the same as before plus the concentration of the second amino acids added). In order to test the consistency of the basic model and to elucidate the mechanism(s) by which the additional amino acids act on acrylamide formation and elimination, the kinetic parameters for the different reaction steps of the basic model were fixed to the values estimated for the control system. Addition of glutamine had a slightly increasing effect on the yield of acrylamide, resulting in a significant increased rate constant for acrylamide formation and elimination. Cysteine on the contrary, had a pronounced reducing effect (>99%) on the acrylamide yield, which can mainly be attributed to an additional acrylamide elimination reaction which is dependent on the cysteine concentration.     

Role of precursors on the kinetics of acrylamide formation and elimination under low moisture conditions using a multiresponse approach – Part I: Effect of the type of sugar

The effect of type of sugar on the kinetics of acrylamide formation and elimination reactions was investigated under low moisture conditions using equimolar asparagine–sugar model systems, heated at temperatures between 120 and 200 °C. The monosaccharides glucose and fructose and the disaccharide sucrose were selected to study this effect. A mechanistic model was used as a basis for multiresponse modelling of the different responses measured (acrylamide, glucose, fructose, sucrose, asparagine, aspartic acid and melanoidins). In spite of the higher acrylamide yield per mol initial asparagine for sucrose over fructose to glucose, the kinetic parameters estimated for acrylamide formation revealed that the type of sugar, monosaccharide or disaccharide, had only a limited effect on this reaction. The corresponding activation energy, however, was significantly lower in case the disaccharide sucrose was added. An opposite trend was observed for the acrylamide elimination rate constant, being significantly higher for the system with sucrose, whereas the temperature dependence of this rate constant remained unaffected by the type of sugar available under the reaction conditions considered.     

Effects of wood flour modification on the fire retardancy of wood–plastic composites

Wood–plastic composites (WPC) are materials that combine the properties of wood and plastics. Both are flammable organic materials. Fire safety is considered to be an important issue especially in construction applications. In this research, the fire safety of WPC material is improved by using modification chemicals for wood flour treatment. The effectiveness of the modification is studied with a cone calorimeter device. Mechanical properties and water absorption are also examined. Scanning electron microscopy is used for analyzing the interfacial adhesion of the fiber and matrix. The results show that the fire performance of WPC material can be enhanced through wood modification, which can also improve the moisture uptake performance and the interfacial adhesion of the material. However the mechanical properties decrease as a result of modification with the used fire retardants.     

Influence of processing conditions on reducing γ-aminobutyric acid content during fortified milk production

The work studied the effects of processing conditions on the γ-aminobutyric acid (GABA) loss during fortified milk production. Bovine milk or their proteins/lactose fractions (0.66% whey protein and 2.6% casein or 4.9% lactose, w/v) containing 0.05–1.0% added γ-aminobutyric acid (w/w, based on bulk milk or these fractions) were subjected to a simulated milk technological process as following the sequential preheating (25–60 °C), homogenization (0–20 MPa), and pasteurization (62 °C/30 min, 72 °C/15 s, 95 °C/5 min, and 138 °C/2 s) or their unit processes to treat GABA. The resulting samples were characterized through GABA and lactose concentrations under various processing conditions. The amine and carboxyl groups and the structural characteristics of the resulting protein (lactose) were also examined through their concentrations (for lactose) and mass/spectral analyses, respectively. The results showed that the increase in temperature significantly promoted a reduction in GABA content. Whey protein fractions than caseins were primarily responsible for inducing GABA, whereas lactose had no remarkable effect on it. The rationale for GABA reduction is potential reactions with milk proteins/lactose, which preliminarily confirmed by the measurement of protein modification and lactose mass spectrometry.     

Use of acacia barrique barrels – Influence on the quality of Malvazija from Istria wines

In order to improve Malvazija from Istria wine quality, we used two types of barrels: oak (of French and Croatian origin) and acacia (of Croatian origin). After 12 months ageing period all of the wines were analysed chemically and sensorially. Results showed marked differences between oak and acacia aged wines, especially in simple volatile phenol and oak lactones concentrations. During the ageing period a significant increase in furfural, 5-methylfurfural, guaiacol, eugenol and trans-eugenol was noticed. Results pointed out the importance of choosing the right barrels (oak or acacia) and time of leaving the wine in the barrels to achieve the desired goal. The highest rated wines were made in acacia barrels.     

Influence of human gastric juice on oxidation of marine lipids – in vitro study

This study evaluates whether marine lipids can oxidise in acidic stomach environment and whether authentic gastric juice has the potential to act as a pro- or anti-oxidative medium. Oxidation of herring lipids in emulsions and liposomes was followed in in vitro digestion models containing authentic human gastric juice, and compared to models containing hydrochloric acid solution. Peroxide value, concentration of thiobarbituric acid reactive substances and oxygen uptake rate increased in all the models during 2.5 h incubation at pH 4 and 37 °C in darkness. The markers showed no difference between oxidation in gastric juice and hydrochloric acid solution. Gastric juice reduced the prooxidant activity of iron ions measured as oxygen uptake rate, but did not reduce the activity of methemoglobin. Berry juice, green tea, red wine, and caffeic acid reduced oxygen uptake in the acidic environments while coffee, ascorbic acid and orange juice increased oxidation. Beverages accompanying foods containing marine lipids will therefore affect the course of post-prandial lipid oxidation.     

Enhanced water resistance of extruded wood–polypropylene composites based on alternative wood sources

Polypropylene wood flour composites made from short-rotation coppice (SRC) and low valued beech wood (Fagus sylvatica) were investigated with respect to their suitability for use in the production of wood–polymer composites (WPC). An industrial wood source consisting of spruce wood flour (Picea abies) was used as reference material. All composites were compounded on a co-rotating twin screw extruder containing either 60 or 70 wt% wood flour. Consolidation was done by profile extrusion. Mechanical and physical properties of the composites were investigated. The wood sources were characterized concerning their particle length and shape by the use of a dynamic optical particle analysis system. X-ray microtomography (µ-CT) was used to study the dispersion of wood particles and the internal composite structure. However, all composites based on alternative wood sources showed an equivalent performance regarding mechanical properties compared to the composite reference. Composites containing beech wood flour showed notably reduced water absorption rates, whereas the composites based on SRC wood flour revealed significantly reduced moisture content compared to reference composites. A different particle length distribution was depicted between the industrial wood source and three other investigated wood sources. Moreover, all wood flour sources were characterized by a mean aspect ratio up to 3:1. The X-ray microtomography illustrated morphological differences between composites. Based on the X-ray images, an alignment along the melt flow and a decent encapsulation by polypropylene were shown.     

Influence of different extraction conditions on the detection of glycinin and β-conglycinin in model processed foods by ELISA

ABSTRACT

The presence of undeclared soy proteins in food can cause severe reactions in soy allergic individuals. The extraction of target proteins from processed foods is a crucial step in allergen detection by immunoassays, as only successfully extracted target proteins can be detected by the specific antibodies. The effectiveness was studied of different conditions (type of buffer, temperature and time of incubation) on the extraction of total protein, and concentration of glycinin and β-conglycinin from different food matrices. The yields were determined using a soy protein isolate and three processed foods (sausage, bread and pâté) incurred with soy proteins. The yields were affected by the processing of analysed products and the composition and pH of the extraction buffers. Neutral and alkaline buffers (pH from 7.4 to 10.6) exhibited good protein extraction capacity and detectability of the specific target proteins. Denaturing additives and highly alkaline buffer (pH 12) extracted more crude protein but they were incompatible with the ELISA assay. Overall, the best results were obtained using phosphate (pH 7.4) and Tris/HCl (pH 8.5) buffers in the presence of 0.5 M NaCl. Crude protein yield of food extracts did not correlate with that of glycinin and β-conglycinin, whereas a good relationship was found between the yields of the two proteins.     

Influence of storage conditions on aroma compounds in coffee pads using static headspace GC–MS

Static headspace gas chromatography coupled to mass spectrometry (SHGC–MS) was used to identify aroma compounds in coffee pad powder. Based on the peak areas of these aroma compounds, the influence of the type of original package on the time of evolution was studied. Statistical ANOVA indicated that coffee pads which were individually packed and hermetically sealed lost less aroma compounds than did pads which were enclosed together in an open package. In addition, coffee pads from an open package were stored in closed plastic bottles at two different temperatures. Storing the pads at 4 °C instead of keeping them at room temperature had a positive influence on the evolution of aroma compounds with time.     

Influence of milk pre-heating conditions on casein–whey protein interactions and skim milk concentrate viscosity

The viscosity of concentrates (50–55% total solids) prepared from skim milk heated (5 min at 80 or 90 °C) at pH 6.5 and 6.7 was examined. The extent of heat-induced whey protein denaturation increased with increasing temperature and pH. More denatured whey protein and κ-casein were found in the serum phase of milk heated at higher pH. The viscosity of milk concentrates increased considerably with increasing pH at concentration and increasing heating temperature, whereas the distribution of denatured whey proteins and κ-casein between the serum and micellar phase only marginally influenced concentrate viscosity. Skim milk concentrate viscosity thus appears to be governed primarily by volume fraction and interactions of particles, which are governed primarily by concentration factor, the extent of whey protein denaturation and pH. Control and optimization of these factors can facilitate control over skim milk concentrate viscosity and energy efficiency in spray-drying.     

Up-milling and down-milling wood with different grain orientations – theoretical background and general appearance of the chips

Peripheral milling with up-milling and down-milling techniques is very well known from a geometrical point of view. However, in processing anisotropic materials such as wood these geometrical aspects imply relevant differences when machining. In fact milling anisotropic materials leads to different cutting geometries when up-milling or down-milling and when changing the depth of cut. This results in a relative orientation of the grain depending on the process adopted. In this paper the geometrical interactions between tool and wood grain have been analysed theoretically and supported by experimental evidence. To achieve this result, Douglas fir has been processed with different depths of cut and grain orientations, the resulting chips have been collected and analysed. The experiments show how a shift of the cutting phenomenon and the chip type can be observed to support the theoretical background.     

Influence of temperature and environmental conditions on aflatoxin contamination in maize collected from different regions of Pakistan during 2016–2019

Aspergillus and their associated metabolites like aflatoxins (AFs) are one of the extremely significant contaminants that affect food production around the world. This species decreases yield and grains quality under suitable environmental conditions. AFs were identified in various food commodities, have been recognized as carcinogenic, mutagenic, teratogenic and immunosuppressive. From 2016 to 2019, a total of 324 samples of maize were obtained from diverse areas of Pakistan and examined for AFs level. AFs were determined using an HPLC validated method through post-column derivatization and fluorescence detection. This study also focused on the effect of climatic conditions on AF production. The total AFs (B₁+B₂+G₁+G₂) were detected in 267 (82.4%) samples, ranged between 0.69 and 356.7 μg/kg with a mean of 15.27 ± 0.82 μg/kg. A total of 182 (56.2%) and 85 (26.2%) samples had AFs level above the maximum acceptable limit as accepted by European Union (EU) and United States of America (USA), respectively. The outcomes of the existing study indicated that the climatic situations in the examined areas had a great impact on AFs contamination. Significant differences were found between AFs contamination levels in the samples collected in different months (p < 0.05). The most contaminated samples were identified in July, August and September as the climatic conditions favored the AF production. These outcomes suggested that the food commodities must be regularly examined in order to prevent the health of human and animal from the hazardous effects produced by AFs contamination.     

Physical and nutritional conditions for optimized production of bacteriocins by lactic acid bacteria – A review

ABSTRACT

There has been an increasing debate about the use of synthetic chemical compounds and the consequences of their use in food preservation. In this context, the utilization of some natural compounds produced by bacteria, showing an inhibitory effect against microorganisms associated with food contamination, have gained attention as preservation technology. In order to improve the production and yield costs of bacteriocins, detailed studies are necessary to determine the conditions that allow an optimized production and extraction of bacteriocins from lactic acid bacteria (LAB). In this context, this article aims to discuss the information regarding the main factors that influence bacteriocin production by LAB. The biosynthesis of bacteriocins can be influenced by various culture conditions, such as the composition of the medium, pH, temperature and growth kinetics of the microorganisms. One of the limiting factors for the use of bacteriocins on a large scale in food preservation is the economic factor. In order for the production costs of bacteriocins to be reduced, making them attractive, it is necessary to know the optimum parameters of production, thus maximizing productivity and making costs more attractive.     

Properties of furfurylated wood (Pinus?pinaster)

Sapwood samples of Pinus pinaster wood were treated with a?70% furfuryl alcohol mixture. Weight percent gain (WPG), equilibrium moisture content, dimensional stability, MOE, bending strength, hardness, density and durability were determined. WPG was on average 38%. Equilibrium moisture content decreased more than?40%. Dimensional stability increased reaching an ASE of?45%. MOE was little affected by the treatment but bending strength increased by about?6%. Hardness increased by about?50%, and density by?37%. Mass loss due to Postia placenta and Coniophora puteana decreased by?96% and?86%, respectively. Furfurylation of Pinus pinaster wood shows an interesting potential to improve the wood quality for solid timber products.