Biopolymer films and coatings are generally designed using biological materials such as proteins,... more Biopolymer films and coatings are generally designed using biological materials such as proteins, polysaccharides, lipids and their derivatives. The use of plasticizers is also required to improve the mechanical properties (tensile strength and elongation) of the films. For application of films to food systems, it is important for the developed films to possess favorable mechanical and permeability characteristics. Therefore, knowledge of optimum conditions where the water vapor permeability (WVP) is minimized while the mechanical properties are enhanced would be significant depending on the application of the edible films. In this study, the effects of glycerol, as a plasticizer, and methylcellulose (MC) ratios on WVP and mechanical properties of the whey protein films were investigated. Optimum properties of edible films were obtained by applying the complex method optimization algorithm to this multiobjective function problem, and glycerol to total polymer ratio (MC and whey protein concentrate [WPC]) of 0.356 and 0.45 was found for the films with MC : WPC ratios of 0.3 and 0.8, respectively. With respect to the results of this study, it might be concluded that optimum conditions for different edible film-forming agents can be determined via the use of a good experimental design.
All the positively charged proteins in whey were bound simultaneously to a cation exchange column... more All the positively charged proteins in whey were bound simultaneously to a cation exchange column, rinsed free of contaminants and then eluted selectively to produce different fractions. Three different elution procedures were used: (1) a single elution buffer to make whey protein isolate (WPI); (2) two elution buffers to make alpha-lactalbumin (ALA) and WPI depleted in ALA; and (3) four
ABSTRACT: With the use of Fourier Transform Infrared (FTIR) analysis applied to methylcellulose (... more ABSTRACT: With the use of Fourier Transform Infrared (FTIR) analysis applied to methylcellulose (MC) films, the hydrogen bonding formation between MC-MC molecules and between MC and a series of different-molecular-weight PEGs was studied. The spectra of the films were interpreted in terms of the symmetry distortion of hydroxyl stretch at 3466.5 cm-1, which is the measure of hydrogen bonding interactions in the polymer matrix. The symmetry distortion was determined to be affected by the MC concentration, indicating the presence of intra- and intermolecular hydrogen bonding between MC molecules. Neither ethanol nor its concentration influenced the symmetry distortion. A competition for hydrogen bonding via hydroxyl groups between MC-MC and MC-PEG occurred when PEG was incorporated into the polymer matrix.
Desorption isotherms of unblanched and blanched red peppers were experimentally obtained at 30C. ... more Desorption isotherms of unblanched and blanched red peppers were experimentally obtained at 30C. The desorption data were exploited to estimate equilibrium moisture contents of the peppers at drying temperatures other than 30C by using a semi-empirical method. Red pepper samples were dried in a tunnel-type drier with an air velocity of 2 m/s at 50C, 60C, 70C, and 80C. The blanched samples dried faster than the unblanched ones. The drying behavior of unblanched and blanched samples was characterized by falling rate period, and constant and falling rate drying periods, respectively. The interphase mass and heat transfer coefficients of the blanched sample during the constant rate period were not affected by temperature and estimated to be 1.94*10−3 kg mol/s. m2 and 57.3 W/m2. K, respectively. Effective moisture diffusivity was estimated between 6.83*10−10−17.4*10−10 m2/s for the unblanched sample and 11.4*10−10−31.0*10−10 m2/s for the blanched sample within the given temperature range. Effect of temperature on the diffusivity was described by an Arrhenius-type equation with an activation energy of 28.4 kJ/mol for the unblanched pepper and 33.3 kJ/mol for the blanched pepper.
Surface of polystyrene beads was modified by poly(phe-lys) for invertase immobilisation. The opti... more Surface of polystyrene beads was modified by poly(phe-lys) for invertase immobilisation. The optimum immobilisation conditions of invertase were; 0.01% (w/v) poly(phe-lys), 2% (v/v) glutaraldehyde at 25 °C and pH 4.5. The kinetics of sucrose hydrolysis by free and immobilised invertase in a batch reactor at pH 4.5 and 55 °C gave Km and Vmax values for sucrose with free and immobilised invertase of 81, 114 mM and 10.1, 9.2 μmol glucose/min.mg enzyme, respectively. The deactivation rate constants of free and immobilised invertase were 0.0347 and 0.0098 min−1, respectively.
Biopolymer films and coatings are generally designed using biological materials such as proteins,... more Biopolymer films and coatings are generally designed using biological materials such as proteins, polysaccharides, lipids and their derivatives. The use of plasticizers is also required to improve the mechanical properties (tensile strength and elongation) of the films. For application of films to food systems, it is important for the developed films to possess favorable mechanical and permeability characteristics. Therefore, knowledge of optimum conditions where the water vapor permeability (WVP) is minimized while the mechanical properties are enhanced would be significant depending on the application of the edible films. In this study, the effects of glycerol, as a plasticizer, and methylcellulose (MC) ratios on WVP and mechanical properties of the whey protein films were investigated. Optimum properties of edible films were obtained by applying the complex method optimization algorithm to this multiobjective function problem, and glycerol to total polymer ratio (MC and whey protein concentrate [WPC]) of 0.356 and 0.45 was found for the films with MC : WPC ratios of 0.3 and 0.8, respectively. With respect to the results of this study, it might be concluded that optimum conditions for different edible film-forming agents can be determined via the use of a good experimental design.
All the positively charged proteins in whey were bound simultaneously to a cation exchange column... more All the positively charged proteins in whey were bound simultaneously to a cation exchange column, rinsed free of contaminants and then eluted selectively to produce different fractions. Three different elution procedures were used: (1) a single elution buffer to make whey protein isolate (WPI); (2) two elution buffers to make alpha-lactalbumin (ALA) and WPI depleted in ALA; and (3) four
ABSTRACT: With the use of Fourier Transform Infrared (FTIR) analysis applied to methylcellulose (... more ABSTRACT: With the use of Fourier Transform Infrared (FTIR) analysis applied to methylcellulose (MC) films, the hydrogen bonding formation between MC-MC molecules and between MC and a series of different-molecular-weight PEGs was studied. The spectra of the films were interpreted in terms of the symmetry distortion of hydroxyl stretch at 3466.5 cm-1, which is the measure of hydrogen bonding interactions in the polymer matrix. The symmetry distortion was determined to be affected by the MC concentration, indicating the presence of intra- and intermolecular hydrogen bonding between MC molecules. Neither ethanol nor its concentration influenced the symmetry distortion. A competition for hydrogen bonding via hydroxyl groups between MC-MC and MC-PEG occurred when PEG was incorporated into the polymer matrix.
Desorption isotherms of unblanched and blanched red peppers were experimentally obtained at 30C. ... more Desorption isotherms of unblanched and blanched red peppers were experimentally obtained at 30C. The desorption data were exploited to estimate equilibrium moisture contents of the peppers at drying temperatures other than 30C by using a semi-empirical method. Red pepper samples were dried in a tunnel-type drier with an air velocity of 2 m/s at 50C, 60C, 70C, and 80C. The blanched samples dried faster than the unblanched ones. The drying behavior of unblanched and blanched samples was characterized by falling rate period, and constant and falling rate drying periods, respectively. The interphase mass and heat transfer coefficients of the blanched sample during the constant rate period were not affected by temperature and estimated to be 1.94*10−3 kg mol/s. m2 and 57.3 W/m2. K, respectively. Effective moisture diffusivity was estimated between 6.83*10−10−17.4*10−10 m2/s for the unblanched sample and 11.4*10−10−31.0*10−10 m2/s for the blanched sample within the given temperature range. Effect of temperature on the diffusivity was described by an Arrhenius-type equation with an activation energy of 28.4 kJ/mol for the unblanched pepper and 33.3 kJ/mol for the blanched pepper.
Surface of polystyrene beads was modified by poly(phe-lys) for invertase immobilisation. The opti... more Surface of polystyrene beads was modified by poly(phe-lys) for invertase immobilisation. The optimum immobilisation conditions of invertase were; 0.01% (w/v) poly(phe-lys), 2% (v/v) glutaraldehyde at 25 °C and pH 4.5. The kinetics of sucrose hydrolysis by free and immobilised invertase in a batch reactor at pH 4.5 and 55 °C gave Km and Vmax values for sucrose with free and immobilised invertase of 81, 114 mM and 10.1, 9.2 μmol glucose/min.mg enzyme, respectively. The deactivation rate constants of free and immobilised invertase were 0.0347 and 0.0098 min−1, respectively.
Uploads
Papers by nazan turhan