Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 52Citation - Scopus: 55Wheatgrass Juice To Wheat Grass Powder: Encapsulation, Physical and Chemical Characterization(Elsevier Ltd., 2017) Akbaş, Elif; Kilercioğlu, Mete; Önder, Özge Nur; Köker, Alperen; Söyler, Betül; Öztop, Mecit HalilWheatgrass juice (Triticum aestivum L.) is known as a healthy drink due to its high antioxidant activity and phenolic content. In order to avoid the undesirable odor and protect the functional compounds, wheatgrass juice was encapsulated using maltodextrin and whey protein. Antioxidant and phenolic content, mean particle size and distribution, morphology, simulated digestion and thermal stability experiments were conducted on the encapsulated powders. Results showed that antioxidant activity was in between 0.30 and 0.06 mg 2-diphenyl-1-picrylhydrazyl (DPPH)/g powder and phenolic content was 3.52–2.28 mg gallic acid equivalent (GAE)/g powder. Encapsulated powders showed good stability in gastric juice and had 62% higher phenolic content compared to the intestinal fluid within 10 min digestion. Phenolic content of powders was also protected against thermal treatment at 40 °C, 55 °C and 70 °C. Kinetic parameters for degradation of the phenolics were well estimated (R2⩾0.85) using fractional conversion model.Article Citation - WoS: 28Citation - Scopus: 38Bioconversion of Wheat Bran for Polygalacturonase Production by Aspergillus Sojae in Tray Type Solid-State Fermentation(Elsevier Ltd., 2016) Demir, Hande; Tarı, CananWheat bran was tested as the solid substrate for the tray-type solid-state fermentation (SSF) production of polygalacturonase (PG) enzyme by A. sojae mutant strain - a high-PG activity producer. PG production of A. sojae was found to reduce as the thickness of the substrate increase from 8 mm to 14 mm at 90% relative humidity. An interaction between the thickness of the bed and relative humidity of the environment was determined with the help of experimental design and statistical analysis tools. As a result, the PG activity could be enhanced by 31% as the process conditions optimized. Additionally, 11 mm thickness and 70% relative humidity were selected as the PG production favoring conditions with the maximum PG activity of 298 U/g substrate in tray type of SSF without the addition of any nutritive or inducing supplements into wheat bran. The kinetic study conducted in the trays revealed the presence of reduction in the water activity on the 4th day of the SSF process under stated conditions. The productivity of the process conducted under optimized conditions was 3.41 U/g substrate-1 h-1 for the 4th day of the SSF. © 2015 Elsevier Ltd.Article Citation - WoS: 35Citation - Scopus: 41Protection of Lactobacillus Acidophilus Nrrl-B 4495 Under in Vitro Gastrointestinal Conditions With Whey Protein/Pullulan Microcapsules(Elsevier Ltd., 2015) Çabuk, Burcu; Tellioğlu Harsa, ŞebnemIn this research, whey protein/pullulan (WP/pullulan) microcapsules were developed in order to assess its protective effect on the viability of Lactobacillus acidophilus NRRL-B 4495 under in vitro gastrointestinal conditions. Results demonstrated that WP/pullulan microencapsulated cells exhibited significantly (p ≤ 0.05) higher resistance to simulated gastric acid and bile salt. Pullulan incorporation into protein wall matrix resulted in improved survival as compared to free cells after 3 h incubation in simulated gastric solution. Moreover WP/pullulan microcapsules were found to release over 70% of encapsulated L. acidophilus NRRL-B 4495 cells within 1 h. The effect of encapsulation during refrigerated storage was also studied. Free bacteria exhibited 3.96 log reduction while, WP/pullulan encapsulated bacteria showed 1.64 log reduction after 4 weeks of storage.Article Citation - WoS: 18Citation - Scopus: 18Surface Energetics To Assess Biomass Attachment Onto Hydrophobic Interaction Adsorbents in Expanded Beds(Elsevier Ltd., 2009) Vennapusa, Rami Reddy; Tarı, Canan; Cabrera, Rosa; Fernandez-Lahore, MarceloCell-to-support interaction and cell-to-cell aggregation phenomena have been studied in a model system composed of intact yeast cells and Phenyl-Streamline adsorbents. Biomass components and beaded adsorbents were characterized by contact angle determinations with three diagnostic liquids and zeta potential measurements. Subsequently, free energy of interaction vs. distance profiles between interacting surfaces was calculated in the aqueous media provided by operating mobile phases. The effect of pH and ammonium sulphate concentration within the normal operating ranges was evaluated. Calculation indicated that moderate interaction between cell particles and adsorbent beads can develop in the presence of salt. Cell-to-cell aggregation was suspected to occur at high salt concentration and neutral pH. Predictions based on the application of the XDLVO approach were confirmed by independent experimental methods like biomass deposition experiments and laser diffraction spectroscopy. Understanding biomass attachment onto hydrophobic supports can help in alleviating process limitations normally encountered during expanded bed adsorption of bioproducts.Article Citation - WoS: 19Citation - Scopus: 22Optimization of the Associative Growth of Novel Yoghurt Cultures in the Production of Biomass, Ss-Galactosidase and Lactic Acid Using Response Surface Methodology(Elsevier Ltd., 2009) Tarı, Canan; Üstok, Fatma Işık; Harsa, Hayriye ŞebnemThe associative growth of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp. bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey was investigated with respect to lactic acid, biomass and β-galactosidase enzyme production using response surface methodology (RSM). The ratio (St 95/2:Lb 77) of the strains and media formulation had significant effect on all responses (p < 0.001). The predicted enzyme activity (2.14 U mL-1), lactic acid (22.50 g L-1) and biomass (7.11 g L-1) production at optimum conditions were very close to the actual experimental values (2.14 U mL-1, 22.94 g L-1 and 7.86 g L-1, respectively). The optimum conditions were to use these cultures in a ratio of 1.66:1.62 (St 95/2:Lb 77) in a medium containing whey (5%), corn steep liquor (4%), potassium phosphate (2%) and peptone (2%) at 43 °C for 8 h. The associative growth provided 6.4% and 39% more β-galactosidase activity and 8.73% and 44% more lactic acid compared with the results obtained using pure St 95/2 and Lb 77 strains, respectively.Article Citation - WoS: 6Citation - Scopus: 8Segment 10 Based Molecular Epidemiology of Bluetongue Virus (btv) Isolates From Turkey: 1999-2001(Elsevier Ltd., 2009) Özkul, Aykut; Ertürk, Arife; Çalışkan, Elvin; Saraç, Fahriye; Ceylan, Çağatay; Mertens, Peter; Kabaklı, Özden; Dinçer, Ender; Çizmeci, Şirin G.Bluetongue is a significant arbovirus infection that has a negative impact on ruminant productivity in Turkey. Twenty-one Turkish BTV isolates were analyzed phylogenetically, based on genome segment 10 (Seg-10) nucleotide sequences. These analyses were used to explore the epidemiological background of individual isolates from both a regional and global perspective. In the regional analysis, the different BTV strains fell into two groups (Group 1 and Group 2). The Turkish virus isolates were localized in Group 1 which contains two sub-groups. The neighbor-joining analysis revealed that Seg-10 of majority of the Turkish viruses was closely related to certain other virus strains allocated in the eastern lineage. The Seg-10's of two viruses (TR25 and TR26) were more closely related to strains isolated in the Asia-Australia region. These strains belong to the 'eastern' topotype identified by [Maan, S., Maan, N.S., Ross-Smith, N., Batten, C.A., Shaw, A.E., Anthony, S.J., Samuel, A.R., Darpel, K.E., Veronesi, E., Oura, C.A.L., Singh,K.P., Nomikou, K., Potgieter, A.C., Attoui, H., van Rooij, E., van Rijn, P., De Clercq, K., Vandenbussche, F., Zientara, S., Bréard, E., Sailleau, C., Beer, M., Hoffman, B., Mellor, P.S., Mertens, P.P.C., 2008. Sequence analysis of bluetongue virus serotype 8 from the Netherlands 2006 and comparison to other European strains. Virology 377, 308-318]. Comparisons of amino acid sequences deduced from the Seg-10 genes showed a high level of conservation in the NS3/3A proteins from the Turkish viruses. The more frequent amino acid substitutions were identified by multiple alignment analysis, and one of the isolates (TR23) was remarkably found to be genetically quite distinct from the other isolates.Article Citation - WoS: 50Citation - Scopus: 59Characterization of Three-Phase Partitioned Exo-Polygalacturonase From Aspergillus Sojae With Unique Properties(Elsevier Ltd., 2008) Doğan, Nergiz; Tarı, CananExo-polygalacturonase enzyme produced by Aspergillus sojae ATCC 20235 was purified using three-phase partitioning (TPP), an emerging bio-separation technique where a single step as compared to the classical multi-step purification was used. Using this technique, crude enzyme solution (pH 6.6) saturated to 30% (w/v) with ammonium sulphate and with a crude extract to tert-butanol ratio of 1:1 (v/v) at 25 °C resulted in 25.5% recovery of exo-polygalacturonase with a 6.7-fold purification. The purified enzyme was characterized with respect to its activity and stability at various pH and temperature ranges. Optimum pH and temperature for maximum activity were determined as pH 4 and 55 °C. The enzyme was stable at both acidic and alkaline pH for 2 h at 30 °C. The thermal stability study showed that the purified enzyme had an inactivation energy of 68.41 kcal/mol and a half-life (t1/2) value of 3.6 h at 75 °C presenting a large thermal stability. The kinetic constants Km and Vmax using polygalacturonic acid as substrate were 0.75 g l-1 and 1.14 μmol min-1, respectively. SDS-PAGE profiling revealed that the purified exo-polygalacturonase had two bands with the molecular weights of 36 and 53 kDa. The enzyme was completely inhibited in the presence of Mn2+ and SDS and induced significantly by EDTA, glycerol and β-mercaptoethanol.Article Citation - WoS: 52Citation - Scopus: 62Solid-State Production of Polygalacturonase by Aspergillus Sojae Atcc 20235(Elsevier Ltd., 2007) Üstok, Fatma Işık; Tarı, Canan; Göğüş, NihanThe effect of solid substrates, inoculum and incubation time were studied using response surface methodology (RSM) for the production of polygalacturonase enzyme and spores in solid-state fermentation using Aspergillus sojae ATCC 20235. Two-stage optimization procedure was applied using D-optimal and face-centered central composite design (CCD). Crushed maize was chosen as the solid substrate, for maximum polygalacturonase enzyme activity based on D-optimal design. Inoculum and incubation time were determined to have significant effect on enzyme activity and total spore (p < 0.01) based on the results of CCD. A second order polynomial regression model was fitted and was found adequate for individual responses. All two models provided an adequate R2 of 0.9963 (polygalacturonase) and 0.9806 (spores) (p < 0.001). The individual optimum values of inoculum and incubation time for maximum production of the two responses were 2 × 107 total spores and 5-6 days. The predicted enzyme activity (30.55 U/g solid) and spore count (2.23 × 107 spore/ml) were very close to the actual values obtained experimentally (29.093 U/g solid and 2.31 × 107 spore/ml, respectively). The overall optimum region considering the two responses together, overlayed with the individual optima. Solid-state fermentation provided 48% more polygalacturonase activity compared to submerged fermentation under individually optimized conditions.Article Citation - WoS: 61Citation - Scopus: 75Optimization of Biomass, Pellet Size and Polygalacturonase Production by Aspergillus Sojae Atcc 20235 Using Response Surface Methodology(Elsevier Ltd., 2007) Tarı, Canan; Göğüş, Nihan; Tokatlı, FigenA two-step optimization procedure using central composite design with four factors (concentrations of maltrin and corn steep liquor (CSL), agitation speed and inoculation ratio) was used in order to investigate the effect of these parameters on the polygalacturonase (PG) enzyme activity, mycelia growth (biomass) and morphology (pellet size) of Aspergillus sojae ATCC 20235. According to the results of response surface methodology (RSM), initial concentrations of maltrin and CSL and agitation speed were significant (p < 0.05) on both PG enzyme production and biomass formation. As a result of this optimization, maximum PG activity (13.5 U/ml) was achievable at high maltrin (120 g/l), at low CSL (0 g/l), high agitation speed (350 rpm) and high inoculation ratio (2 × 107 total spore). Similarly, maximum biomass (26 g/l) could be obtained under the same conditions with only the difference for higher level of CSL requirement. The diameter of pellets in all optimization experiments ranged between 0.05 and 0.76 cm. The second optimization step improved the PG activity by 74% and the biomass by 40%.Article Citation - WoS: 21Citation - Scopus: 29Partial Purification and Kinetic Characterization of Mushroom Stem Polyphenoloxidase and Determination of Its Storage Stability in Different Lyophilized Forms(Elsevier Ltd., 2007) Şimşek, Şebnem; Yemenicioğlu, AhmetMonophenolase (1011 ± 626 U/g AP) and diphenolase activities (5163 ± 3059 U/g AP) of PPO in acetone powders (APs) of different mushroom stems varied considerably. However, the limited variation of average dipenolase (L-DOPA) to monophenolase (L-tyrosine) activity ratio (5.4 ± 0.7) in crude extracts showed the homogeneity of PPO from different mushroom stems. The change in extraction material or partial purification method (ammonium sulfate or acetone precipitation) did not affect the temperature stability, temperature and pH dependency and Km of monophenolase activity considerably. However, some changes were observed in pH stability and substrate specificity of PPO in different parties of mushroom stems. The most important aspects of mushroom stem PPO are its lower diphenolase to monophenolase activity ratio than mushroom cap PPO, low temperature dependency of activity between 25 and 40 °C (Ea = 30 kJ/mol), broad optimum pH between 6 and 8, but lack of activity pH ≤5, and ability to use phloridzin as substrate. The mushroom stem PPOs partially purified and lyophilized by using sucrose, dextran or alginate showed moderate to high stability at -18 °C for 6-6.5 months. Thus, the mushroom stems obtained as a waste material during mushroom processing may be used as a more homogenous source than whole mushrooms to obtain PPO used for different industrial, clinical or research purposes.