Određivanje brzine korozije austentnih čelika u rastvorima kalcijum-hipohlorita

This paper presents the results of testing the corrosion resistance of austenitic chromium-nickel steel X6 CrNiTi 18-10 and X6 CrNiNb 18-10 in solutions of calcium hypochlorite. For the tests were used potentiodynamic measurement methods. By graphical method of linear polarization, corrosion currents and corrosion potential were obtained on the intersection of the Tafel real E = f(log i) on the basis of potentiodynamic curves for the examined steels. The comparative method to determine the corrosion current density is the polarization resistance method. Based on corrosion currents were calculated corrosion rate of tested steel. Anodic polarization curves for both austenitic steel in the investigated solutions were shot in the interval of stationary potential of up to + 2.5V, to determine the areas of activity. Test results show that with increasing of calcium hypochlorite solution concentration, increase the pH of the solution and the concentration of active chlorine which causes a reduction in the corrosion resistance of the tested steel. These steels are resistant to corrosion in a 1% solution, stable in 10% solutions, and less resistant in 50% suspensions of calcium hypochlorite.U ovom radu dati su rezultati ispitivanja korozione otpornosti austenitnih hrom-nikl čelika Č 4572 i Č 4583 u rastvorima kalcijum-hipohloriita. Za ispitivanja su korišćene potenciodinamičke metode merenja. Grafičkom metodom linearne polarizacije koroziona struja i korozioni potencijal dobijani su u preseku Tafelovih pravih E = f(log i) na osnovu potenciodinamičkih krivih za ispitivane čelike. Komparativna metoda za određivanje korozione struje je metoda polarizacionog otpora. Na osnovu korozionih struja, izračunate su brzine korozije ispitivanih čelika. Anodne polarizacione krive za oba austenitna čelika u ispitivanim rastvorima snimane su u intervalu potencijala od stacionarnog do +2,5V, da bi se odredila područja aktivnosti. Rezultati ispitivanja pokazuju da sa porastom koncentracije rastvora kalcijum-hipohlorita, raste rN vrednost rastvora i koncentracija aktivnog hlora što izaziva smanjenje korozione otpornosti ispitivanih čelika. Ovi čelici su otporni na koroziju u 1% - nim rastvorima, postojani u 10% - nim rastvorima i manje otporni u 50% - nim suspenzijama kalcijum - hipohlorita

Gliadin Proteins in Muffins with Quinoa Flour

Partial replacement of wheat flour in foodstuffs is of great importance in the food industry. Muffins are a type of semi-sweet cake that is traditionally made from wheat flour. They are especially favored by children and senior citizens. Muffins have a long shelf life, which also contributes to their popularity. However, gluten, the main protein in wheat flour, is commonly associated with celiac disease. Gluten consists of two fractions: gliadins and glutenins. In this experiment, the original muffins contained 100% wheat flour. Then, we replaced a portion of wheat flour with 25, 50, and 75% quinoa flour. The samples were stored for 0, 2, and 4 weeks. After that, gliadin proteins were extracted with 70% (v/v) ethanol. We separated gliadin using a high-performance liquid chromatograph (Agilent Technologies 1260 Infinity, USA) and measured the total amount of gliadin protein and the amount of gliadin proteins per fraction. The absorbance tests were conducted at 210 nm. The gliadin protein content was significantly reduced to the wheat vs. quinoa ratio of 50:50 because quinoa is gluten-free, even though it is rich in protein. During the storage time of 0, 2, and 4 weeks, the protein content fell down in the samples with the wheat vs. quinoa ratios of 100:0, 75:25, and 50:50. However, the muffins with 25% wheat flour and 75% quinoa demonstrated an increase in gliadin content. The results obtained could be a good starting point for the development of high-fiber, gluten-free, and more nutritionally valuable muffins