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Pre-treatment Effect on Physical and Microbial Parameters of Smoked Baltic Sprats
2021
Puke, Santa | Galoburda, Ruta
Smoked sprats are delicious and nutritionally valuable product. Besides protein, it contains high amount of unsaturated fatty acids and fat soluble vitamins. Nowadays, human interest for fish product consumption is increasing. It leads to the demand for increased shelf life of the smoked sprats. One way to prolong the shelf life is to use some pre-treatment prior to smoking. The aim of study was to analyse the effect of pre-treatment on smoked Baltic sprat quality and microbiological parameters. Various compositions of brine using salts (NaCl, CaCl₂) and acetic acid in different proportions were used for fresh sprat pre-treatment. Pre-treatment had the influence on physical parameters; pre-treated samples had higher salt and lower moisture content, and lower pH, which allowed prolonging the shelf life of smoked sprats. The highest pH was in the control sample 6.6, and it allowed growth of yeasts, moulds, Pseudomonas spp., and mesophilic and facultative anaerobic microorganisms. The results demonstrated that after two-week storage of the smoked sprats the growth of moulds (1×10² CFU g⁻¹) was observed only for smoked sprats without pre-treatment (control sample), indicating the positive effect of pre-treatment. Salmonella spp., Clostridium perfingens, Listeria monocytogenes, and Escherichia coli were not detected in any of the analysed samples. After pre-treatment in brine, containing combination of NaCl and CaCl₂, smoked fish had darker colour compared to control sample or sample with sodium chloride only. Any of applied pre-treatments, except brine containing NaCl, made firmer texture of the smoked fish.
Afficher plus [+] Moins [-]The Efficiency of Different Wood Coatings against Water Surface Absorption
2021
Iejavs, Jānis | Ruļuks, Oskars | Laiveniece, Laura | Jakovļevs, Vilnis | Pugovičs, Kārlis | Liše, Sigita | Spulle, Uldis
In the market of the Latvia different wood surface coating materials suitable for use in outdoor conditions are offered, but available information on the efficiency of these against direct water exposure is insufficient. For structural timber building elements, such as glued laminated timber (GLT), the surface coating should be applied taking into account technological, visual or colour changes (ISO 7724:1984) and – last, but not least – economic aspects are considered. Wood surfaces coated with coating materials, such as varnishes, paints, etc. can stabilize some properties such as movement of moisture content, dimensional changes and attack by microorganisms and fungi. The changes in the moisture content of timber may influence such important parameters as mechanical properties and the total life time of the structural timber elements. A study has been conducted with the aim of assessing the efficiency of coating materials used for wood protection against water absorption. In this study, six different commercial coating products used for the treatment of spruce (Picea Abies L. Karst.) and pine (Pinus Sylvestris L.) samples were tested. The efficiency of different coating substances was assessed using two modified test methods according to the standards EN 382-2 (1994) and EN 927-5 (2006), determining the surface water absorption after immersion in water for 24 h and the dynamics of water absorption of the glued laminated timber for 696 h kept in water. As a result of the study, it has been ascertained that organic solvent-based commercial coating products are more efficient against short-term and long-term wood water absorption compared to oil-based coating materials.
Afficher plus [+] Moins [-]Disparity in Discolouration of Thermally Modified Wood Exposed to Solar and Artificial Ultraviolet Irradiation
2016
Cirule, Dace | Kuka, Edgars | Antons, Andis
Artificial weathering is a widely used method for predicting wood behaviour during its service life. A study was carried out to compare the colour change of thermally modified aspen (Populus tremula L.) and grey alder (Alnus incana (L.) Moench) wood during natural solar and artificial ultra violet (UV) irradiation. Thermally modified wood specimens were exposed for 30 h to artificial UV irradiation at two different intensities, i.e.1.36 W m⁻² at 340 nm and 0.68 W m⁻² at 340 nm, as well as to solar irradiation outdoors and indoors. After 2.5, 5 and 10 h exposure, colour parameters and reflectance spectra (360–740 nm) were determined. Colour was expressed in accordance with the CIELAB colour model as colour parameters L*, a*, b*. The total colour change ΔEab was calculated from colour parameter differences ΔL*, Δa*, Δb*. The colour changes caused by solar and artificial UV irradiation had a similar pattern for both thermally modified hardwood species under study. Changes in the individual colour parameters in the course of the experiment altered their direction, which implies that discolouration of thermally modified wood is a complicated and dynamic process with various and different chemical transformations in wood chromophores. Colour and reflectance changes had similar trends for different intensities of the same type of irradiation, but they differed for various irradiation types – natural solar or artificial UV irradiation. Greater discolouration was detected for the specimens exposed to both solar irradiations - outdoors and indoors. The results suggest that the fluorescent lamps of the UVA-340 type, which only imitate well the sunlight UV spectrum from 290 nm to 365 nm, do not fully simulate the changes in thermally modified wood induced by solar radiation.
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