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: 94Citation - Scopus: 106Distribution of Simple Phenols, Phenolic Acids and Flavonoids in Turkish Monovarietal Extra Virgin Olive Oils for Two Harvest Years(Elsevier Ltd., 2009) Ocakoğlu, Derya; Tokatlı, Figen; Özen, Fatma Banu; Korel, FigenMonovarietal extra virgin olive oils extracted from six dominant and economically important Turkish olive cultivars (memecik, erkence, domat, nizip-yaglik, gemlik, ayvalik) were examined for their simple phenolics, phenolic acids and flavonoid compounds over 2005 and 2006 harvest years. Total phenol contents, oxidative stabilities and chromatic ordinates as colour parameters were also measured. The most typical phenolic compounds that were identified in both years are hydroxytyrosol, tyrosol, vanillic acid, p-coumaric acid, cinnamic acid, luteolin, and apigenin. Multivariate data were analysed by principal component and partial least square-discriminant analyses. It was observed that phenolic profiles of olive oils depended highly on harvest season. In addition, oils of different olive cultivars have different distribution of phenols. No significant correlation was observed between oxidative stability and phenolic compounds. Increase in peroxide value over an accelerated oxidation period of 11 days showed weak correlations with total phenol content, vanillin, syringic acid and colour parameter a*, as 0.56, 0.55, -0.42, and 0.51, respectively, in terms of correlation coefficient r.Article Citation - WoS: 115Citation - Scopus: 135Antioxidant Activity and Phenolic Content of Fresh and Dry Nuts With or Without the Seed Coat(Academic Press Inc., 2009) Arcan, İskender; Yemenicioğlu, AhmetTotal antioxidant activities based on ABTS free radical scavenging activity and phenolic content of fresh or dry hazelnuts, walnuts and pistachios assayed with their seed coats changed between 3063 and 11,076 μmol trolox equivalents/100 g d.w. and 256 and 755 mg gallic acid equivalents/100 g d.w., respectively. The walnuts used in this study showed the highest antioxidant activity, followed by pistachios and hazelnuts. The removal of seed coat reduced the total antioxidant activity of hazelnuts, walnuts and pistachios almost 36, 90 and 55%, respectively. The total antioxidant activities of investigated fresh and dry nuts are not considerably different. However, phenolic content and antioxidant activity in hydrophilic and ethanolic fractions obtained by successive extraction of nuts showed some variation. The antioxidant activity in 1-serving portion of fresh or dry walnuts is equivalent to that in almost 2-serving portions of black tea, and 1.2-1.7-serving portions of green and Earl Grey tea. One-serving portions of dry hazelnuts and fresh or dry pistachios contained antioxidant activity equivalent to that in 0.7-1-serving portions of black tea. The antioxidant activity measurements correlated with phenolic content (r2 = 0.70). This study showed the potential of using fresh or dry nuts to develop functional foods with high antioxidant activity.Article Citation - WoS: 86Citation - Scopus: 102Total Antioxidant Activity and Total Phenolic Contents in Different Turkish Eggplant (solanum Melongena L.) Cultivars(Taylor and Francis Ltd., 2009) Ökmen, Bilal; Şığva, Hasan Özgür; Mutlu, Sevgi; Doğanlar, Sami; Yemenicioğlu, Ahmet; Frary, AnneIn this study, total water soluble antioxidant activity and phenolic content of 26 eggplant (Solanum melongena L.) cultivars were investigated. Total water soluble antioxidant activity of the cultivars varied from 2664 to 8247 molTrolox/kg, which is a 3.1-fold difference. Cultivars also showed significant variation for total phenolic contents ranging from 615 to 1376 mg/kg, a 2.2-fold difference. The two traits were significantly correlated and results of this study suggested that breeders can use the information to develop eggplant cultivars with high antioxidant activity.Article Citation - WoS: 46Citation - Scopus: 53Extracellular Enzyme Production and Enterotoxigenic Gene Profiles of Bacillus Cereus and Bacillus Thuringiensis Strains Isolated From Cheese in Turkey(Elsevier Ltd., 2009) Molva, Çelenk; Sudağıdan, Mert; Okuklu, BurcuThe aim of the present study was to investigate the biochemical characteristics, extracellular enzyme production and enterotoxigenic genes contents of 6 Bacillus cereus and 22 Bacillus thuringiensis strains, isolated from 100 cheese samples in Turkey. Crystal morphologies of B. thuringiensis strains were found either spherical (n = 12) or spherical and irregular-shaped (n = 10) by phase contrast microscopy. B. cereus and B. thuringiensis strains were found to produce extracellular enzymes, respectively: gelatinase (83% and 91%), DNase (83% and 77%), lecithinase (83% and 95%), protease on skim milk agar (100% and 100%), protease on milk agar (100% and 91%), protease on casein agar (83% and 77%), xylanase (100% and 45%), and cellulase (0% and 41%), and amylase (83% and 27%). All of the strains, except for Bt-D1, hydrolyzed Tween 20 (96%), but not Tween 80 or tributyrin. Pectinolytic activity was obtained to be the least frequent (4%). PCR analysis showed that all strains contained nheA, nheB, nheC and hblD genes. The hblA and hblC genes were present in 2 and 4 of B. thuringiensis strains, respectively. The bceT gene was detected in 1 B. cereus and 9 B. thuringiensis strains. The entFM gene was detected more frequently in B. thuringiensis (82%) than in B. cereus strains (50%). To our knowledge, this is the first report about the isolation and identification of enterotoxigenic B. cereus and B. thuringiensis strains from cheese samples in Turkey.Article Citation - WoS: 231Citation - Scopus: 264Detection of Adulteration of Extra-Virgin Olive Oil by Chemometric Analysis of Mid-Infrared Spectral Data(Elsevier Ltd., 2009) Gürdeniz, Gözde; Özen, Fatma BanuThis study focuses on the detection and quantification of extra-virgin olive oil adulteration with different edible oils using mid-infrared (IR) spectroscopy with chemometrics. Mid-IR spectra were manipulated with wavelet compression previous to principal component analysis (PCA). Detection limit of adulteration was determined as 5% for corn-sunflower binary mixture, cottonseed and rapeseed oils. For quantification of adulteration, mid-IR spectral data were manipulated with orthogonal signal correction (OSC) and wavelet compression before partial least square (PLS) analysis. The results revealed that models predict the adulterants, corn-sunflower binary mixture, cottonseed and rapeseed oils, in olive oil with error limits of 1.04, 1.4 and 1.32, respectively. Furthermore, the data were analysed with a general PCA model and PLS discriminant analysis (PLS-DA) to observe the efficiency of the model to detect adulteration regardless of the type of adulterant oil. In this case, detection limit for adulteration is determined as 10%.Article Citation - WoS: 12Citation - Scopus: 14Identification and Bioactivity of Native Strains of Bacillus Thuringiensis From Grain-Related Habitats in Turkey(Elsevier Ltd., 2008) Apaydın, Özgür; Çınar, Çelenk; Turanlı, Ferit; Harsa, Hayriye Şebnem; Güneş, HaticeA native collection of Bacillus thuringiensis (Bt) strains originated from grain-related habitats in Turkey was characterized according to serotype, cry1 gene content, and bioactivity against Ephestia kuehniella (Lepidoptera: Phycitidae) and Spodoptera littoralis (Lepidoptera: Noctuidae). Twenty-three different serotypes as well as 24 unknown serotypes were obtained from 56 positively agglutinated strains with previously characterized antisera. Most common serovars were sotto, kim, and tochigiensis with the percentages of 14, 14, and 13, respectively. Among the cry1 gene-positive 36 strains, cry1E (100%), cry1Aa (94%), cry1Ac (92%), and cry1D (83%) genes were the most abundant. Bioactivity tests with 56 Bt strains carrying cry1, cry2, and/or cry9 genes indicated that all of them resulted in growth retardation or inhibition of larvae of both E. kuehniella and S. littoralis; however, only one strain, 85PPb (serovar morrisoni), caused high mortality in both insects (84% and 100%, respectively). Different crystal morphology was observed for the strain 85PPb and the standard strain B. thuringiensis subsp. morrisoni. Finally, no correlation was found among serotype, cry gene content and biotoxicity of Bt strains in the collection.Article Citation - WoS: 51Citation - Scopus: 58Rheological Properties of Liquid Egg Products (leps)(Taylor and Francis Ltd., 2008) Atılgan, Mehmet Reşat; Ünlütürk, SevcanRheological properties were determined at 4°C (refrigerated temperature), 25°C (room temperature), 60°C (pasteurization temperature) for liquid whole egg (LWE) and liquid egg yolk (LEY) and 4, 25, 55.6°C for liquid egg white (LEW) by using concentric cylinder viscometer. The shear rate range was 8 to 53.7 s-1 for LEW and LWE, and 1 to 34 s-1 for LEY. Selected physical properties (e.g., density) of LEPs were studied at broad range of temperatures from 4°C to 60°C. All liquid egg products (LEPs) exhibited mildly shear thinning (pseudoplastic) behavior. Experimental data of LWE and LEW successfully fitted Herschel-Bulkley model, LEY data were well described by power law model. LEW and LWE showed thixotropy and time-dependency at their pasteurization temperatures (55.6°C for LEW, 60°C for LWE) and considered being time-independent below these temperatures. LEY exhibited time-dependent behavior at 4°C and 60°C. But its rheological behavior showed no thixotropy and time-dependency at room temperature. The density of all three products decreased with increasing temperature. Density data were correlated by polynomial models (r2 > 0.99).Article Citation - WoS: 124Citation - Scopus: 144Use of Uv-C Radiation as a Non-Thermal Process for Liquid Egg Products (lep)(Elsevier Ltd., 2008) Ünlütürk, Sevcan; Atılgan, Mehmet Reşat; Baysal, Ayşe Handan; Tarı, CananThe efficacy of short wave ultraviolet light (UV-C) as a non-thermal process for liquid egg products (LEP) was investigated. Non-pathogenic Escherichia coli strain (ATCC 8739), which shows lower sensitivity to UV-C light than E. coli O157:H7 and Salmonella typhimurium, was chosen as a target microorganism. The inactivation of UV resistant strain of E. coli in LEP was examined by evaluating the effects of depth of liquid food medium (0.5, 0.3 and 0.153 cm), UV light intensity (1.314, 0.709 and 0.383 mW/cm2) and exposure time (0, 5, 10, and 20 min) by using a collimated beam apparatus. The best reduction (>2-log) was achieved in liquid egg white (LEW) when the fluid depth and UV intensity were 0.153 cm and 1.314 mW/cm2, respectively. Maximum inactivation was 0.675-log CFU/ml in liquid egg yolk (LEY) and 0.316-log CFU/ml in liquid whole egg (LWE) at the same conditions. The kinetics of UV inactivation of E. coli in LEP was nonlinear. Our results emphasize that UV-C radiation can be used as a pre-treatment process or combined with mild heat treatment to reduce the adverse effects of thermal pasteurization of LEP.Article Citation - WoS: 120Citation - Scopus: 135Authentication of Pomegranate Juice Concentrate Using Ftir Spectroscopy and Chemometrics(Elsevier Ltd., 2008) Vardin, Hasan; Tay, Abdullatif; Özen, Fatma Banu; Mauer, LisaFourier transform infrared (FTIR) spectroscopy and chemometric techniques were used to detect the adulteration of pomegranate juice concentrate (PJC) with grape juice concentrate (GJC). The main differences between PJC and GJC infrared spectra occurred in the 1780-1685 cm-1 region, which corresponds to C{double bond, long}O stretching. Principal component analysis of the spectra was used to: (1) differentiate pure PJC and GJC samples and (2) classify adulterated (containing 2-14% vol/vol GJC) and pure PJC samples. Two principal components explained 99% of the variability in each of these applications. Partial least square analysis of the spectra resulted in prediction of the GJC adulterant concentration in PJC with a correlation coefficient, R2, of 0.9751. Partial least square analysis of spectra could also predict % titratable acidity and total solids in PJC with correlation coefficients of 0.9114 and 0.9916, respectively. Therefore, FTIR and chemometrics provide a useful approach for authenticating pomegranate juice concentrate.
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