Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 153Citation - Scopus: 192Development of Cellulose Acetate Based Antimicrobial Food Packaging Materials for Controlled Release of Lysozyme(Elsevier Ltd., 2009) Gemili, Seyhun; Yemenicioğlu, Ahmet; Alsoy Altınkaya, SacideAntimicrobial packaging materials were obtained by incorporation of lysozyme into cellulose acetate (CA) films. In order to achieve controlled release of lysozyme, the structure of the films was changed from highly asymmetric and porous to dense by modulating the composition of the initial casting solution. The highest release rate, soluble lysozyme activity and antimicrobial activity were obtained with the film prepared from 5% CA solution including 1.5% lysozyme. Increasing CA content in the casting solution decreased the porosity of the films, hence, reduced the release rate, maximum released lysozyme activities and the antimicrobial activities of the films. In contrast, immobilized lysozyme activities and the tensile strength of the films increased. The incorporation of lysozyme did not cause significant reductions in tensile strength and elongation at break values except in films prepared with 15% CA. This study showed the good potential of asymmetric CA films to achieve controlled release in antimicrobial packaging.Article Citation - WoS: 87Citation - Scopus: 111Development of Antioxidant Food Packaging Materials With Controlled Release Properties(Elsevier Ltd., 2010) Gemili, Seyhun; Yemenicioğlu, Ahmet; Alsoy Altınkaya, SacideIn this study, cellulose acetate (CA) films with different morphological features were prepared in order to control the release rates of low molecular weight natural antioxidants, L-ascorbic acid and L-tyrosine. Increasing CA content in the casting solution decreased the average pore size and porosity of the films, thus, reduced the diffusion rates of both antioxidants through the films. Although both antioxidants have similar molecular weights, L-tyrosine released into water much more slowly than L-ascorbic acid. The highest antioxidant activity in release test solutions was observed with highly porous L-tyrosine containing films. However, when the porosity of the films reduced, the antioxidant activity of L-ascorbic acid released into solution was found to be higher due to trapping of significant amount of L-tyrosine in dense films. The use of different antioxidants caused different changes in morphological and mechanical properties of the CA films. Varying the structural features of the films with the preparation conditions or using different surfaces of the films allowed the controlled release of each antioxidant. © 2009 Elsevier Ltd. All rights reserved.Article Citation - WoS: 105Citation - Scopus: 133Water Vapor and Oxygen-Barrier Performance of Corn-Zein Coated Polypropylene Films(Elsevier Ltd., 2010) Tıhmınlıoğlu, Funda; Atik, İsa Doğan; Özen, BanuA novel corn-zein coating structure on polypropylene (PP) films was developed to examine its feasibility as an alternative water vapor and oxygen-barrier for flexible packaging industry. The barrier properties of the resulting films were evaluated as affected by coating formulation (solvent, corn-zein, plasticizer concentration and plasticizer type). Corn-zein with different amounts (5% and 15%) was dissolved in 70% and 95% aqueous ethanol solution at 50 °C, respectively. Solutions of corn-zein plasticized by polyethylene glycol (PEG) and glycerol (GLY) with various levels (20% and 50%) were applied on corona-discharged-treated PP by using solvent-casting method. The significant improvements in water vapor and oxygen-barrier properties of uncoated PP films were obtained with corn-zein coating. Water vapor permeability (WVP) of the coated films decreased significantly with increasing corn-zein concentration. The application of plasticized corn-zein coating on PP films showed nearly more than three order of reduction in oxygen permeability (OP). The high water vapor and oxygen-barriers were obtained for films coated with coating formulation consisting of higher amounts of corn-zein plasticized by GLY. The statistical analysis defined the key parameters of coating formulation that had major effect on the final properties of coated PP films as corn-zein, plasticizer concentration, and plasticizer type. © 2009 Elsevier Ltd. All rights reserved.Article Citation - WoS: 46Citation - Scopus: 52Effect of Enzyme Location on Activity and Stability of Trypsin and Urease Immobilized on Porous Membranes by Using Layer-By Self-Assembly of Polyelectrolyte(Elsevier Ltd., 2010) Guedidi, Sadika; Yürekli, Yılmaz; Deratani, André; Déjardin, Philippe; Innocent, Christophe; Alsoy Altınkaya, Sacide; Roudesli, Sadok; Yemenicioğlu, AhmetThe layer-by-layer (LbL) self-assembly of polyelectrolyte is one of the simplest ways to immobilize enzyme on membrane. In this paper, the immobilization of trypsin (TRY) and urease (URE) on polyacrylonitrile based membranes using the LbL assembly technique was presented. The studied systems consisted in bilayered assemblies with the enzyme layer as the outer layer and trilayered assemblies with the enzyme layer as the inner sandwiched layer. The membrane pore size was chosen so that the smaller enzyme TRY was mainly immobilized within the membrane and confined in the porous membrane structure while URE immobilization mainly took place at the membrane surface. No dramatic difference on reactivity was evidenced between these two enzyme locations. The catalytic activity of immobilized enzymes was found to be lower than the free ones in solution but their stability was dramatically enhanced. The higher activity was observed when the enzyme is deposited as the outer layer of the LbL assembly. On the other hand, the more stable catalytic membranes were obtained when the outer layer consists of a polyelectrolyte covering the enzyme layer. © 2010 Elsevier B.V.Article Citation - WoS: 21Citation - Scopus: 32Separation of Whey Components by Using Ceramic Composite Membranes(Elsevier Ltd., 2006) Erdem, İlker; Çiftçioğlu, Muhsin; Harsa, Hayriye ŞebnemCeramic supports were prepared from alumina powder and dip-coated with zirconia sol. The ceramic composite membranes prepared were characterized with respect to their microstructure/pore structures. The supports were 40% porous of which 87% were open pores. The average particle size of the sol particles was 35 nm. The prepared membrane has good protein lactose separation properties with a relatively high protein content (PR ∼80%) and with relatively low lactose retention (LR ∼7%). The permeate flux value was around 40 l/m2h. These results indicate the possibility of the preparation of ceramic composite membranes for separation of whey components with higher yields.Article Citation - WoS: 35Citation - Scopus: 39Optimisation of the Effect of Colemanite as a New Synergistic Agent in an Intumescent System(Elsevier Ltd., 2006) Atikler, Ulaş; Demir, Hasan; Tokatlı, Figen; Tıhmınlıoğlu, Funda; Balköse, Devrim; Ülkü, SemraAn intumescent system including ammonium polyphosphate (APP) as an acid source and blowing agent, pentaerythritol (PER) as a carbonific agent and colemanite as a synergistic agent is used to enhance flame retardancy of polypropylene (FR-PP). In order to investigate the synergism between colemanite and the flame retardant materials (APP and PER), D-optimal mixture design was employed. The limiting oxygen index (LOI) and amount of residue (AoR) were accepted as response 1 and response 2, respectively. Applying D-optimal strategy, 18 experiments were performed. Filler content was fixed at 30 wt% of total amounts of flame retardant PP composites. Constraints were determined according to the ratio of APP/PER ranging between 1 and 3. Statistical analysis of the cubic model revealed that lack of fit (LoF) was not significant for the cubic and linear model for both responses. The model suggested an optimum composite formulation with concentration levels 65% of APP, 28% of PER and 7% of colemanite that gives an LOI of 40.3. The experimental LOI and AoR of optimum formulation were achieved as 39.3 and 21.4 with 2.5% and 2.2% errors, respectively.