Прегледај по Аутор "Marjanović-Balaban, Željka"
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- СтавкаCHROMATOGRAPHIC SEPARATION OF GLUTENIN WITH HIGH MOLECULAR WEIGHT FROM WHEAT FLOUR(KEY, 2020) Gojković Cvjetković, Vesna; Grujić, Radoslav; Marjanović-Balaban, ŽeljkaGlutenins with high molecular weight (HMW glutenins) are one of the glutenin's fractions. They play a key role in the formation of the gluten elasticity property and contribute to the formation of large glutenin polymers. The aim of this study was to investigate the effect of solvent type and column temperature on the chromatographic separation of HMW glutenins from wheat flour. For HMW glutenins extraction, 50% (v/v) ethanol, 1-propanol and isopropanol was used to which Tris-HCl (0.05 mol/L, Ph = 7.5), urea (2 mol/L) and dithioerythritol (1%) were added. The high performance liquid chromatography (HPLC) method (HPLC Agilent Technologies 1260 Infinity, Zorbax 300SB-C3 column) was used for protein separation at a column temperature 40, 45 and 50 0C. Absorbance measurements were performed at 210 nm and 280 nm. The effect of the solvents tested on the separation of HMW glutenins was shown by determining the number of observed peaks (proteins) on the chromatogram and calculating the relative concentration of HMW in the total number of glutenins from wheat flour (RC). After the extraction of glutenin proteins with 50% (v/v) ethanol, the highest number of proteins at 210 nm was observed when the column temperature was 45 0C and 50 0C (Xsr = 6.17 and RC1 = 17.76% and RC2 = 27.07%) and the lowest number at a column temperature of 40 0C (Xsr = 4, RC = 13.43%). By extraction with 50% (v/v) 1-propanol, the highest number of proteins was observed at column temperatures of 40 0C and 45 0C (Xsr = 5.17 and RC1 = 28.22% and RC2 = 31.70%, respectively) and the lowest number at 50 0C (Xsr = 4.67, RC = 34.68%) and by extraction with 50% (v/v) isopropanol the highest number of proteins was observed at a column temperature of 50 0C (Xsr = 7.17, RC = 23.61%) and the lowest number at 45 0C (Xsr = 5.83, RC = 10.67%). After the extraction of glutenin proteins with 50% (v/v) ethanol and detection at a wavelength of 280 nm, the highest number of proteins was observed at a column temperature of 45 0C (Xsr = 8.33, RC = 36.49%), and the lowest at 40 0C (Xsr = 5.50, RC = 32.57%). In the case of protein extraction with 50% (v/v) 1-propanol, the highest number of HMW glutenins was observed at 40 0C (Xsr = 7.83, RC = 61.62%) and the lowest at 50 0C (Xsr = 4.67, RC = 39.18%). When extraction was performed with 50% (v/v) isopropanol, the highest number of proteins was observed at a column temperature of 45 °C (Xsr = 7.33, RC = 21.66%), and the lowest number at a column temperature of 40 0C and 50 0C (Xsr = 7.00, RC1 = 28.64%, RC2 = 34.22%). Based on the obtained results it can be seen that the highest number of proteins was observed with 50% (v/v) ethanol (Xsr = 8.33)
- СтавкаCOMPARISON OF METHODS FOR DETERMINING THE FALSIFICATION OF MILK(KEY, 2017) Vujadinović, Dragan; Beribaka, Mirjana; Vukić, Milan; Marjanović-Balaban, ŽeljkaFalsification of milk creates many difficulties in the dairy industry. Diluting milk with water can cause changes in the chemical composition, nutritional, hygienic and technological quality of milk. The aim of this study was to evaluate the possibility of applying the standard method for milk analysis for determining the presence of added water in sterilized milk products. Samples were prepared by diluting the milk with distilled water in the range from 5 to 50%, with a gradient of 5% and monitoring the impact of water on the relevant physical and chemical indicators of milk. Standard methods for milk analysis were performed, such as: determination of fat content, density, viscosity, acidity and sensory evaluation. Analysis of milk samples prepared with the proper dilution has shown that the average value of the freezing point of the milk samples ranged from -0.484 0C to -0.25 0C. Determination of the fat content showed that the fat content was constantly decreasing, from 3% (5% H2O) to 1.48% (50% H2O). With the increased proportion of water in milk, the density and viscosity were reduced, and pH value was slightly increased. Sensory evaluation was only partially accurate. In addition to cryoscopy, as a reliable method for determining the presence of added water in milk, some other methods have also proven to be reliable, such as: determination of fat content, density, viscosity and acidity.
- СтавкаEFFECTS OF INCUBATION CONDITION AND DIFFERENT STARTER STRAINS FOR THE PRODUCTION OF NITRITES FROM NATURAL NITRATE SOURCES(KEY, 2016) Vujadinović, Dragan; Beribaka, Mirjana; Vukić, Milan; Marjanović-Balaban, ŽeljkaNitrates and nitrites are used in production of meat products and they play an important role as preservatives, but also in the formation of characteristic red color and taste of the meat. Vegetable products represent a significant potential as a natural source of nitrate for producing organic cooked meat products. The aim of this paper was to investigate the effect of temperature changes on the degree and speed of reduction of nitrates to nitrite salts, using different starter strains of microorganisms. Staphylococcus carnosus was used as nitro-reducing starter culture for the first model, and S. carnosus in combination with Lactobacillus sakei, for the second model. Celery powder was used as a natural source of nitrate salts. Both models were incubated in the temperature range from 20 0C to 40 0C with a temperature gradient of 2 0C, for 24 and 48 hours. A method for determining nitrite is defined by the international standard ISO 2918:1999. Obtained values of nitrite concentrations were used to calculate the degree and speed of reduction of nitrates to nitrites. The degree and speed of a chemical reaction increase with increasing temperature. The final concentration of nitrite salts after 24 hours of incubation for the first model was 85 ± 2 ppm at 40 0C and for the same model after 48 hours of incubation, 100 ± 10 ppm (40 0C). The second model showed similar patterns of increase, 81 ± 9 ppm (24h, 40 0C) and 83 ± 10 ppm (24h, 40 0C). The concentration of nitrite salts, the degree and speed of reduction of nitrate salts after 48 hours of incubation was increased, compared to the concentration of nitrite salts after incubation for 24 hours, in both models. The starter culture in which it was used only S. carnosus, proved to be more efficient when it comes to the reduction of nitrates
- СтавкаGliadin proteins from wheat flour the optimal determination conditions by ELISA(2021) Marjanović-Balaban, Željka; Gojković Cvjetković, Vesna; Grujić, RadoslavIntroduction. The number of people with celiac disease is rapidly increasing. Gluten, is one of the most common food allergens, consists of two fractions: gliadins and glutenins. The research objective was to determine the optimal conditions for estimating gliadins by using enzyme-linked immunosorbent assay (ELISA). Study objects and methods. The experiment involved wheat flour samples (0.10, 0.20, 0.25, 0.50, and 1.0 g) suspended in different solvents (ethanol, methanol, 1-propanol, and isopropanol) of different concentrations (40, 50, 60, 70, 80, and 90% v/v). The samples were diluted with Tris buffer in ratios of 1:50, 1:100, 1:150, and 1:200. The gliadin test was performed using a Gliadin/Gluten Biotech commercial ELISA kit (Immunolab). Results and discussion. The optimal conditions for determining gliadin proteins that provided the highest gliadin concentration were: solvent – 70% v/v ethanol, extract:Tris buffer ratio – 1:50, and sample weight – 1.0 g. Conclusion. The obtained results can be of great importance to determine gliadin/gluten concentrations in food products by rapid analysis methods.
- СтавкаSeparation of gliadins from wheat flour by capillary gel electrophoresis: optimal conditions(Kemerovo State University, 2020) Grujić, Radoslav; Gojković Cvjetković, Vesna; Marjanović-Balaban, ŽeljkaIntroduction. Gliadin proteins are one of the gluten fractions. They are soluble in alcoholic solution and divided into four groups (α + β, γ, ω1.2, and ω5-gliadins). In this paper gliadins were extracted from wheat flour, and optimal conditions for their separation were determined. Study objects and methods. The separation was performed by capillary gel electrophoresis on Agilent apparatus, CE 7100 (a capillary with an inner diameter of 50 μm, a total length of 33 cm, and an effective length of 23.50 cm). In order to determine the optimal conditions, different solvent concentrations (50, 60, and 70% ethanol), capillary temperatures (20, 25, 30, 35, and 40°C), and electrode voltages (–14.5, –16.5, –17.5 and –18.5 kV) were applied. Migration time and relative concentration of each protein molecules within gliadin fractions in the electrophoregram were analysed using Agilent ChemStation Software. Results and discussion. The optimal conditions for gliadin separation were: solvent 70% (v/v) ethanol, capillary temperature of 25°C, and electrode voltage of –16.5 kV. Under these conditions, the total proteins were indetified as Xav = 23.50, including α + β gliadin fraction (Xav = 7.50 and relative concentration RC = 28.29%), γ-gliadins (Xav = 5.00, RC = 26.66%), ω1.2-gliadins (Xav = 4.33, RC = 14.93%), and ω5-gliadins (Xav = 6.67, RC = 30.98%). Conclusion. The results of the research can be of fundamental importance in the study of gluten proteins and the influence of technological procedures on their change and the possibility of reducing the allergic effect of gluten during processing.
- СтавкаTHE EFFECT OF THE DURATION OF SEPARATION AND WAVELENGTHS OF ABSORBANCE’S MEASUREMENT ON THE EFFECTIVENESS OF ELECTROPHORETIC SEPARATION OF GLIADINS BY GCE(2022) Gojković Cvjetković, Vesna; Grujić, Radoslav; Marjanović-Balaban, ŽeljkaGliadins are one of the gluten components which are present in most wheat products. Based on their mobility in acidic polyacrylamide gel electrophoresis (A-PAGE), gliadins are divided into α+β, γ, ω1.2, and ω5 classes. Gliadins are allergenic proteins which play a key role in celiac disease pathogenesis. Considering that the number of people with celiac disease is increasing, the aim of this study was to examine how different duration of analysis (30, 35 and 40 minutes) and wavelengths (200, 210 and 230 nm) effect the gliadin separation effectiveness by glassy carbon electrode (GCE). We examined the effect of duration of capillary gel electrophoresis (GCE) separation (30, 35 and 40 minutes) and measurement of absorbance at different wavelengths (200, 210, and 230 nm) on the effectiveness of electrophoretic separation by capillary gel electrophoresis, with the aim of faster identification and quantification of gliadin proteins. Separation of gliadin proteins by GCE was performed on an Agilent, CE 7100 apparatus. SDS-MW analysis kit, PA 800 plus (2015 Beckman Coulter, USA) was used. Based on the obtained results the optimal duration of GCE separation was 30 minutes, because the number of observed proteins is the highest and the effectiveness of electrophoretic separation is the best (Xav = 23.50). A wavelength of 200 nm proved to be the best wavelength. By measuring the absorbance at this wavelength, the total number of observed proteins is Xav=18.33. In this study a duration of 30 minutes and a wavelength of 200 nm proved to be optimal. As the duration of analysis increases, the number of proteins decreases
- СтавкаTHE INFLUENCE OF EXTRACTION CONDITIONS AND CHROMATOGRAPHIC SEPARATION ON THE ABILITY OF IDENTIFYING GLIADINS FROM THE WHEAT FLOUR(Consulting and Training Centre, KEY, 2019) Gojković, Vesna; Marjanović-Balaban, Željka; Grujić, Radoslav; Vujadinović, Dragan; Vukić, MilanCereal proteins play an important role in the humans’ and animals’ diet, due to their nutritional composition and functional properties in food production. One of these proteins is gluten. It contains protein components that are present as monomers and interconnected by disulfide bonding polymers. Based on their solubility in an aqueous alcohol, gluten proteins are divided into soluble gliadins and insoluble glutenins. Apart from the beneficial nutritional composition and importance in food production, gluten also causes adverse health effects in susceptible individuals, such as celiac disease. In this paper, gliadin proteins have been analyzed in wheat flour by high-pressure liquid chromatography of reversed phases (RP-HPLC). The influence of different concentrations of ethanol (30%, 40% and 50%) and column temperature (40 C, 45 C and 50 C) was investigated to achieve better chromatographic separation and identification of gliadin proteins. The chromatographic separation of gliadin proteins was carried out on the column Zorbax 300 SB-C3 (Agilent) and the Agilent Technologies 1260 Infinity HPLC apparatus has been used. After extraction gliadin proteins with 30% (v/v) ethanol, the number of identified proteins was 20, after extraction with 40% (v/v) ethanol was 21 and with 50% (v/v) ethanol was 24, at a temperature of 40 C. By increasing the column temperature (45 oC and 50 oC), the number of identified proteins after extraction with 30% ethanol was 17 and 20, after extraction with 40% ethanol was 25 and 24, and after extraction with 50% ethanol was 26 and 24. Based on the obtained results, the largest number of gliadin proteins was identified by extraction with 50% ethanol and at a column temperature of 45 C. By increasing the column temperature to 50 oC, the number of identified proteins decreases.