Synthesis and characterization of boehmitic alumina coated graphite by sol–gel method

Non-wettability property makes graphite a good protecting material against the molten metal and/or slag. Properties like high oxidation potential between 600 and 1200 °C and non-wettability with water at room temperatures limits the usage of graphite in castable refractory applications. In this study, sol–gel method, which is a relatively cheaper process, was used. Boehmitic sol was obtained by hydrolyzing and peptiziting the alkoxide AIP (aluminum isopropoxide) used as alumina source. Then natural flake graphite was mixed with the boehmitic solution for coating of graphite. At 120 °C boehmitic sol coated graphite was dried and gelled. Then heat threaded at 550 °C for γ-Al₂O₃ transformation of boehmite. Products that obtained from the studies were characterized with FTIR and XRD tests. Alumina coated graphite samples were made by repeating the same steps and TG analysis were made to investigate the oxidation behaviour of the samples. Finally, SEM–EDS analyses were carried out to investigate the microscopic properties of the alumina coated graphite powders.     

The Effect of the Geometrical Non-Linearity on the Stress Distribution in the Infinite Elastic Body with a Periodically Curved Row of Fibers

In the framework of the piecewise homogeneous body model with the use of the three-dimensional geometrically non-linear exact equations of the theory of elasticity, the method for determination of the stress-strain state in the infinite body containing periodically located row of periodically curved fibers is developed. It is assumed that the midlines of the fibers are in the same plane. With respect to the location of the fibers according to each other the sinphase and antiphase curving cases are considered. Numerical results on the effect of the geometrical non-linearity to the values of the self balanced shear and normal stresses are presented. In particular, it is established that this effect causes to increase (to decrease) the absolute values of these stresses in compression (in tension) along the fibers.     

Effects of four cooking methods on the heavy metal concentrations of sea bass fillets (Dicentrarchus labrax Linne, 1785)

Heavy metals (Pb, Cd, Cr, Co, As, Ni) were analysed in cooked sea bass (Dicentrachus labrax). Different cooking treatments were used (baking, grilling, microwaving and frying). The results obtained were statistically compared with those of raw fish. The Co concentrations were below limits of detection in all samples (<0.05). Furthermore, Cr in fried samples and Ni in raw fish were not detected. Cd was only detected in microwaved samples. The Pb concentrations of microwaved and baked fish were significantly decreased. The As concentrations of fried and microwaved samples were significantly increased. The Cd and As concentrations of the fillets subjected to microwave cooking were 0.741 and 1.41 mg/kg, respectively. However, the As concentration was also significantly increased in fried samples. This value was 2.66 mg/kg. Microwaving and frying are not suitable for sea bass.     

Effect of carotenoids from red pepper and marigold flower on pigmentation,sensory properties and fatty acid composition of rainbow trout

Effects of carotenoid sources on pigmentation, sensory properties and fatty acid composition of rainbow trout (Onchorhynchus mykiss) were investigated. The fish (120.51 ± 0.75 g) were fed with diets containing 1.8% marigold flower, 5% red pepper, 70 mg kg⁻¹ commercial astaxanthin and compared with a control group for 60 days. Commercial astaxanthin provided the highest carotenoid accumulation in the fish, and this was followed by red pepper and marigold flower (p < 0.05). Dietary carotenoid sources did not significantly affect fatty acid composition of the fish fillets. Trout muscle coloured with commercial astaxanthin was more preferred than the others by the sensory panellists.     

Physicochemical characterization of chitosan extracted from Metapenaeus stebbingi shells

In this study, chitosan was extracted from Metapenaeus stebbingi shells. In order to determine physicochemical characteristics of the extracted chitosan, the yield, moisture and ash contents, degree of deacetylation, molecular weight, water and fat binding capacities, apparent viscosity and colour properties were measured using a variety of techniques including Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. In addition, the physicochemical characteristics of the chitosan extracted from M. stebbingi shells were compared to commercial chitosan. The degree of deacetylation was calculated by the titration method and elemental analysis. The molecular weight was determined by viscosimetric methods. The results of the study indicate that shrimp shells are a rich source of chitosan as 17.48% of the shell’s dry weight is consisted of this material. Extracted chitosan exhibited a lower molecular weight, higher degree of deacetylation, higher viscosity and higher water and fat binding capacities compared to the commercial chitosan.     

Proximate composition and mineral contents of the blue crab (Callinectes sapidus) breast meat, claw meat and hepatopancreas

The objective of this study was to determine the nutritional composition of the breast, claw meat and hepatopancreas of the blue crab (Callinectes sapidus). Samples were subjected to proximate (protein, fat, ash and moisture) and calcium, magnesium, phosphorus, potassium and sodium (Ca, Mg, P, K and Na) analyses. Protein, fat, ash and moisture of the breast, claw meat and hepatopancreas of the blue crab averaged 19.05, 0.59, 2.10 and 76.85 g/100 g, respectively. The results have revealed that this species is a rich source of protein, Ca, Mg, P and Na. Claw meat had higher protein concentrations (19.55 g/100 g) than both breast meat and hepatopancreas (18.81 g/100 g). Na was predominant element among minerals analysed. There were significant differences between Ca, Mg, P, K and Na contents of claw, breast meat and hepatopancreas of the blue crab. Information on the nutrient composition is needed to facilitate the processing, utilisation and marketing of blue crab products. Blue crab could balance human nutrition and could be used as an alternative dietary supplement of proteins and mineral matter.     

Effects of season on proximate and fatty acid compositions of two mediterranean fish – the round herring (Etrumeus teres) and tub gurnard (Chelidonichthys lucernus)

The aim of this work was to study the seasonal variation of the proximate and fatty acid compositions in the round herring (Etrumeus teres) and tub gurnard (Chelidonichthys lucernus) caught from the North‐Eastern Mediterranean Sea. Proximate compositions and fatty acid contents of both fish species showed statistically significant seasonal variations (P < 0.05). While the protein contents were at its highest in winter, the lipid contents were at its highest in autumn. The main fatty acids were C16:0 (palmitic acid), C18:0 (stearic acid), C16:1 n‐7 (palmiteoleic acid), 18:1 n‐9c (oleic acid), C20:5 n‐3 (eicosapentaenoic acid) and C22:6 n‐3 (docosahexaenoic acid). The total polyunsaturated fatty acid in round herring was highest in winter, whereas that in tub gurnard was highest in spring.     

Seasonal amino acid profiles and mineral contents of green tiger shrimp (Penaeus semisulcatus De Haan, 1844) and speckled shrimp (Metapenaeus monoceros Fabricus, 1789) from the Eastern Mediterranean

The amino acid and mineral contents of green tiger shrimp (Penaeus semisulcatus) and speckled shrimp (Metapenaeus monoceros) from the North Eastern Mediterranean were determined for each season of the year. For both species, the highest protein values were recorded during the summer (p < 0.05). The most abundant amino acids were, in decreasing order, glutamic acid, aspartic acid, arginine, lysine, leucine, glycine and alanine. The ratio of essential to nonessential amino acids (mean value) for green tiger shrimp and speckled shrimp were 0.60 and 0.59, respectively. Mineral contents of the two species varied with season (p < 0.05), except for the Ca content in green tiger shrimp.     

Effects of brine concentration on shelf-life of hot-smoked tilapia (Oreochromis niloticus) stored at 4 °C

This work evaluated the effect of brine concentration on the shelf-life of hot-smoked tilapia (Oreochromis niloticus) stored at 4 °C. The fish were brined in solutions of 5%, 10%, and 15% NaCl and unsalted fish were used as controls. The fish were then smoked, cooled and stored at 4 °C. Oxidative rancidity measured by the peroxide value (PV), and thiobarbituric acid number (TBA) showed increases with the storage time and also as a result of the increasing salt content in fish muscle. Hot smoked tilapia can be stored safely under refrigerated conditions for over 35 days, and 5% brine was found to be optimal for storage.