Food Engineering / Gıda Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/12

Browse

Filters

2006 - 200982010 - 2019222020 - 20246

Settings

Author: search.filters.author.Ünlütürk, Sevcan

Search Results

Now showing 1 - 10 of 36
  • Article
    Effect of Partial Replacement of Sucrose With Stevia and Sucralose on the Physicochemical and Structural-Mechanical Properties of Apple Marmalade
    (2024) Berk, Berkay; Şirin, Pınar; Ünlütürk, Sevcan
    In this study, low-sugar apple marmalade formulations were developed by partial replacement of sucrose with stevia and sucralose. Their rheological, textural, physicochemical properties and microstructures were evaluated. The concentration of sweeteners was found to have a significant effect on the physicochemical and rheological properties of the formulations. The hardness of marmalades decreased with addition of sweeteners. Herschel–Bulkley model was found to be the best model describing rheological behavior. The consistency index decreased with increasing sweeteners substitution, whereas the flow behavior index showed an increasing trend with the increase of the sweeteners content. Additionally, the microstructure of marmalades with sweetener substitution exhibited a porous structure in the gel network. The increase in sucralose concentration resulted in more surface deformation resulting in weaker gel formation than stevia. Marmalade prepared with 50% stevia substitution was found the best combination and resulted in good sensory properties like marmalade samples containing 500 g sugar.
  • Research Project
    UV ışın yayan diyotların (UV-LEDs)taze sıkılmış elma suyunun pastörizasyonunda alternatif bir teknoloji olarak kullanılabilirliğinin araştırılması
    (TÜBİTAK - Türkiye Bilimsel ve Teknolojik Araştırma Kurumu, 2014) Ünlütürk, Sevcan
    Bu proje kapsamında, UV-LED lamba ışınlarının taze sıkılmış bulanık elma suyunun (ES) pastörizasyonunda alternatif bir teknoloji olarak kullanılabilirliği araştırılmıştır. Projenin ilk aşamasında UV-LED lambaların kullanıldığı masa üstü statik bir ünite tasarlanıp yaptırılmıştır. “Starking Delecious çeşidi” elmalardan elde edilen elma suyu örneklerinin fiziksel, kimyasal ve optik özellikleri (pH, suda çözünür kuru madde (°Brix), bulanıklık (NTU), renk (L*, a*, b*), absorbans katsayısı (cm-1 ), toplam asitlik, ve askorbik asit içeriği belirlenmiştir. 24,712280nm (19,184254nm) absorbans katsayısına ve 908,5 NTU bulanıklık değerine sahip bulanık elma suyu, 280 nm ve 254 nm dalga boylarına sahip 4 adet UV LED lamba kullanılarak 40 dakika boyunca UV ışınlarına maruz bırakılmıştır. 280 nm dalga boyuna sahip lambalar kullanıldığında, pastörize edilmiş bulanık elma suyuna inoküle edilen E. coli K12 suşunda maximum 2,0 log azalma (771,6 mJ/cm2 UV dozda) sağlandığı, 254 nm dalga boyunda lambalar kullanıldığı durumda ise maximum 1,64 log azalma (708 mJ/cm2 UV dozda) sağlanmıştır. 280/365 nm kombine dalga boyunda uygulanan UV işlemi, elma suyundaki poifenoloksidaz enziminin %66,19`ını inaktive edebilmişken, 254 nm ve 280 nm`de uygulanan UV işlemi %29,53 ve %43,65 oranında bir inaktivasyon sağlamıştır. Reaktivasyon denemeleri sonucunda, oda sıcaklığında ve gün ışığına maruz kalan elma suyunda, proses sonrası (280/365 nm, 40 dak.) zarar gören E. coli hücrelerinin sayısı, 4 saat sonunda sadece % 15,68 artmıştır. UV işlemine tabii tutulan elma sularının mikrobiyal raf ömrü maximum 14 gün iken kontrol örnekleri 7 gün içinde bozulmuştur. Pastörize edilen örneklerde ise mikrobiyal gelişme olmamıştır. Kontrol, UV işlemine tabii tutulmuş ve pastörize edilmiş örneklerin renk değerleri arasında önemli farklılık olduğu görülmüş ancak depolama süresi boyunca (14 gün) örneklerin renk değerlerinde önemli bir değişim gözlenmemiştir (p<0,05). Aynı şekilde örneklerin polifenoloksidaz enzim aktivitesinde depolama süresince önemli bir farklılık tespit edilmemiştir (p<0,05).
  • Research Project
    Sıvı Yumurta Ürünlerinin Ultraviole (uv) Işık ile Dezenfeksiyonu
    (2007) Ünlütürk, Sevcan; Tarı, Canan; Korel, Figen
    Bu projede, UV ışığın sıvı yumurta ürünlerinde inaktivasyon etkisinin olup olmadığı tespit edilmeye çalışılmıştır. Bu amaçla hem laboratuvar tipi hem de pilot ölçekli UV cihazı kullanarak, sabit UV dozajında ve farklı tatbik sürelerinde dezenfekte edilen sıvı yumurta ürünlerinde pH, absorbans, renk, bulanıklık gibi fiziksel ölçümlerle beraber toplam canlı sayımı , Salmonella, ve E. Coli gibi mikrobiyolojik analizler yapılmıştır. Labarotuvar tipi UV cihazı ile yapılan biyodozimetrik çalışmalar sonucunda, en iyi logaritmik mikrobiyal azalman ı n (> 2-log) yumurta beyazında sağlandığı ortaya konmuştur. Sürekli sistemde inaktivasyon etkisinin, biyodozimetrik denemelere göre çok daha düşük olduğu görülmüştür. Bunun sonucunda, kullanılan pilot tipi UV reaktörün tasarımında değişiklikler yapılması gerektiği ortaya konmuş ve gerekli öneriler getirilmiştir.
  • Research Project
  • Book Part
    Citation - Scopus: 8
    Uv Processing and Storage of Liquid and Solid Foods: Quality, Microbial, Enzymatic, Nutritional, Organoleptic, Composition and Properties Effects
    (Elsevier, 2021) Hakgüder Taze, Bengi; Pelvan Akgün, Merve; Yıldız, Semanur; Kaya, Zehra; Ünlütürk, Sevcan
    Non-thermal food processing technologies have been explored extensively in recent years in order to develop food products with extended shelf life as well as preserved nutritional and organoleptic characteristics in accordance with the changing consumer demands (Falguera et al., 2011a; Sanchez-Moreno et al., 2009). Ultraviolet (UV) irradiation is one of the non-thermal processes that can be applied to reduce the microbial load in liquid foods and surfaces, and to sterilize food packages and packaging materials, and environments involved in food processes (Jimenez-Sanchez et al., 2017a; Bintsis et al., 2000). UV light is subdivided into three regions as short-wave UV (UV-C, 200 and 280 nm), medium-wave UV (UV-B, 280 to 315 nm), and long wave UV (UV-A, 315 to 400 nm). The different types of effects on microorganisms can be caused by UV light of different wavelengths. The effectiveness of UV light on microorganisms results primarily from the fact that DNA molecules absorb UV photons between 200 and 300 nm, with peak absorption around 260–265 nm. This causes DNA damage by altering the nucleotide base pairing, thereby creating new linkages between adjacent nucleotides, particularly between pyrimidine bases, on the same DNA strand and ultimately results in cell death (Zimmer and Slawson, 2002). Peak et al. (1984) proposed that the dimer formation is not the only requirement to damage the DNA. Absorption of different wavelength photons by different molecular groups in the long DNA molecule can damage or destroy these bond groups. Thus, different bonds in the DNA can be affected with photons of different energy (Neister, 2014).
  • Article
    Citation - WoS: 69
    Citation - Scopus: 88
    Shelf Life Extension of Strawberry Juice by Equivalent Ultrasound, High Pressure, and Pulsed Electric Fields Processes
    (Elsevier, 2021) Yıldız, Semanur; Pokhrel, Prashant Raj; Ünlütürk, Sevcan; Barbosa-Canovas, Gustavo V.
    Nonthermal processing technologies have focused on the production of safe, fresh-like and high quality food products very much in line with current consumer demands. It is a high priority to maintain the quality attributes of the food during its shelf life. In this study; microbial stability, physicochemical properties and phytochemical characteristics of strawberry juice (SJ) pasteurized by ultrasonication (US) (55 degrees C, 0.29 W/mL acoustic energy density, 120 mu m amplitude, 3 min), high pressure processing (HPP) (300 MPa, 1 min), and pulsed electric fields (PEF) (35 kV/cm, 27 mu s) were evaluated during 42 days of storage at 4.C in comparison with conventional thermal pasteurization as a reference treatment (72 degrees C, 15 s). The nonthermal processes were equivalent in terms of E. coli inactivation since the selected processing conditions previously led to almost identical inactivation level (at least 5-log) of inoculated E. coli. Thus, the current study demonstrates how these equivalent US, HPP, and PEF treatments differ from each other in terms of their effect on SJ natural microbiota and quality characteristics during refrigerated storage. Results showed that US, HPP, and heat treatment ensured the microbial stability of SJ for at least 42 days while PEF extended the shelf life of SJ by at least 28 days based on the natural microbiota. No significant difference was found for the total soluble solids of the processed samples (p > 0.05) whereas acidity and pH of the samples varied during the storage period (p < 0.05). Immediately after processing, the total phenolic contents and antioxidant activities of SJ were better retained by HPP and PEF compared to thermal pasteurization. Furthermore, HPP and PEF significantly increased total anthocyanin content of SJ by 15 and 17% with respect to untreated SJ (p < 0.05). Phytochemical characteristics of processed SJ started to decrease after 7 days of storage irrespective of treatment type. HPP treated juices showed significantly higher levels of total anthocyanin and antioxidant activity at the final day of storage. Principal component and cluster analysis showed that the processed SJ samples had higher similarity to the untreated fresh SJ during storage up to 14 days, while the samples beyond this storage period clustered together and discriminated from the rest indicating a decreased similarity to the fresh juice. This study rendered simultaneous evaluation of several quality characteristics during storage of pasteurized strawberry juice based on the equivalent processing approach and multivariate data analysis. Under the selected processing conditions, HPP was the best option to extend the shelf life of SJ and enhance its phytochemical characteristics.
  • Article
    Citation - WoS: 41
    Citation - Scopus: 43
    Changes in Quality Characteristics of Strawberry Juice After Equivalent High Pressure, Ultrasound, and Pulsed Electric Fields Processes
    (Springer Verlag, 2020) Yıldız, Semanur; Pokhrel, Prashant Raj; Ünlütürk, Sevcan; Barbosa-Canovas, Gustavo V.
    Understanding the efficacy of viable emerging technologies in preserving overall quality attributes and antioxidant characteristics of fruit juices is of great interest. This study aimed to evaluate the effect of high pressure (HP), ultrasound (US), and pulsed electric fields (PEF) processes on natural microbiota inactivation, as well as changes in physicochemical attributes and phytochemical content of strawberry juice (SJ). HP at 300 MPa (1 min), US at 55 degrees C (3 min) and 517.1 mW/mL acoustic energy density, and PEF at 35 kV/cm (27 mu s) using monopolar square pulses with 2 mu s pulse width were applied, and then compared with a conventional thermal pasteurization treatment (72 degrees C, 15 s). The nonthermal processes were equivalent in terms ofEscherichia coli(E. coli) inactivation since the selected processing conditions led to almost identical inactivation level (at least 5-log) of inoculatedE. coli. The current study analyzes why these equivalent processes had different effect on SJ quality. All treatments significantly reduced the initial natural microbiota (i.e., total mesophilic aerobic bacteria and yeast-molds) below 2 log CFU/mL. No significant changes were observed on the total soluble solid content (7.83-8.00 degrees Brix), titratable acidity (0.79-0.84 g/100 mL), and pH (3.45-3.50; except in sonication) between SJ processed samples and the untreated ones (p > 0.05). HPP and PEF significantly promoted higher retention of total phenolic content (TPC) and radical scavenging activity (RSA) than thermal pasteurization, and significantly enhanced total anthocyanin content (TAC) compared with unprocessed SJ. HPP and PEF increased the TPC (4-5%), RSA (18-19%), and TAC (15-17%) in comparison with unprocessed SJ. Multivariate data analysis tools, i.e., principal component analysis (PCA) and hierarchical cluster analysis (HCA), were successfully applied for discrimination and classification of SJ samples based on the similarities or differences among physicochemical and phytochemical characteristics. PCA and HCA indicated that HPP- and PEF-treated samples had similar enhanced properties in terms of phytochemical content and were superior to sonicated, thermally pasteurized, and unprocessed samples. The multivariate data analysis methods were very useful to compare and classify SJ quality characteristics as a function of the processing technology. This study demonstrated that the application of the equivalent processing approach may reveal new opportunities to produce equivalent or even enhanced quality fruit juices.
  • Article
    Citation - WoS: 21
    Citation - Scopus: 28
    Effectiveness of Pulsed Light Treatments Assisted by Mild Heat on Saccharomyces Cerevisiae Inactivation in Verjuice and Evaluation of Its Quality During Storage
    (Elsevier, 2020) Martin Belloso, Olga; Soliva Fortuny, Robert; Kaya, Zehra; Ünlütürk, Sevcan
    The effects of pulsed light (PL) processing parameters such as depth of juice layer (1, 3, 5 mm), distance from the lamp (5, 10 cm) and number of pulses (0-50 pulses) on the inactivation of Saccharomyces cerevisiae in verjuice, a clarified beverage obtained from freshly-squeezed unripe grapes, were investigated. A reduction of 0.96 +/- 0.27 log CFU/mL was achieved by applying a dose of 34 J/cm(2) (1-mm layer depth, 5-cm distance, 50 pulses). PL was combined with mild heating (MH) at 43, 45 and 47 degrees C to increase its inactivation efficacy. Pasteurization was achieved by applying 17 J/cm(2) at 45 degrees C (PLMH45-3) and 6.12 J/cm(2) at 47 degrees C (PLMH47-3) to a 3-mm juice layer with S. cerevisiae reductions of 5.10 +/- 0.24 and 5.06 +/- 0.08 log CFU/mL, respectively. Quality properties of PLMH47-3-pasteurized verjuice were monitored during 6 weeks of storage at refrigerated (5 degrees C) and room temperature (25 degrees C), The results were compared to those of untreated and thermally pasteurized (72 degrees C/18 s) samples. Untreated juice spoiled within 2 weeks at 25 degrees C. No growth was detected in other conditions for 6 weeks. Among quality characteristics, only optical properties changed slightly during storage. It was concluded that mild MH-assisted pulsed light treatments have potential for verjuice pasteurization compared to conventional thermal pasteurization due to the better preservation of its fresh-like characteristics.
  • Article
    Uv-c Uygulamasının Sıvı Yumurta Beyazının Mikrobiyolojik Kalitesi Üzerine Etkisi
    (Gıda Teknolojisi Derneği, 2010) Ünlütürk, Sevcan; Baysal, Ayşe Handan; Atılgan, Mehmet R.
    Sıvı yumurta beyazı, kabuğundan ayrılmış yarı geçirgen (opak) görünümlü yumurta ürünüdür. Sıvı yumurta beyazı, düşük sıcaklık ve kısa sürelerde pastörize edilerek dayanıklı hale getirilmektedir. Ancak yüksek protein içeriği nedeni ile ısıl işlem ürün kalitesini olumsuz yönde etkilemektedir. Bu çalışma, ısıl işleme alternatif olarak öne sürülen UV-C ışınlama yöntemiyle sıvı yumurta beyazının mikrobiyolojik kalitesinin incelenmesini kapsamaktadır. Bu amaçla; yumurta beyazı örnekleri, E. coli 0157-.H7 (ATCC 700728), L. innocua (NRRL-B 33314) ve E. coli K-12 (ATCC 25253) ile inoküle edilerek belli dozlarda UV-C ışın uygulamasına tabi tutulmuştur. Denemeler 0-100 mJ/cm2UV doz aralığı ve 1.315 mW/cm2 UV şiddetinde, laboratuvar ölçekli UV dezenfeksiyon cihazı kullanılarak gerçekleştirilmiştir. Elde edilen sonuçlara göre, E. coli 0157:H7, E. coli K-12 ve L. innocua sayılarında maksimum 3.206±0.777 log, 2.719±0.63 log ve 2.624±0.268 log kob/mL azalma saptanmıştır. Sıvı yumurta beyazı üretiminde, UV-C ışınlarının bir ön işlem olarak kullanılabileceği ve ürünün mikrobiyolojik stâbilitesini artırılabileceği sonucuna varılmıştır.
  • Article
    Citation - WoS: 42
    Citation - Scopus: 53
    Effects of Ultraviolet-Light Emitting Diodes (uv-Leds) on Microbial Inactivation and Quality Attributes of Mixed Beverage Made From Blend of Carrot, Carob, Ginger, Grape and Lemon Juice
    (Elsevier Ltd., 2021) Baykuş, Gökçen; Pelvan Akgün, Merve; Ünlütürk, Sevcan
    Efficacy of ultraviolet light-emitting diodes (UV-LEDs) with peak and coupled emissions at 280, 365 and 280/365 nm on inactivation of E. coli K12 in mixed beverage (MB) was investigated. MB comprised of 31.6% carrot, 44.3% carob, 8.7% grape, 10.2% ginger, and 5.2% lemon juice. The impact of UV-LEDs on some physicochemical and phytochemical properties of MB was compared to that of heat treatment (70 °C, 120 s). While, UV-LED irradiation using coupled 280/365 nm for 40 min resulted in the highest inactivation of E. coli K12 (>4 log) out of tested wavelengths, the number of mesophilic bacteria (TAC), and yeast and molds (YM) in mixed beverage were reduced by 2.59 log CFU/mL (from 5.69 log CFU/mL of initial load), and 0.17 log CFU/mL (from 3.28 log CFU/mL of the initial load), respectively. Although, the color parameters slightly changed after irradiation, the color of MB did not show visual difference (?E = 0.94) compared to untreated samples. UV-LED treatment caused a significant increase in total phenolic compound (1.75-fold) and antioxidant capacity (4.60 fold) compared to heat-treated samples (p < 0.05). UV-LED treatment caused a decrease in carotenoid content (71.3%) lower than that of heat-treated samples (88.9%), indicating that UV-LED irradiation preserved the total carotenoid content better than the heat treatment. Industrial relevance: Light-emitting diodes (LEDs) are new sources of ultraviolet light utilized for non-thermal processing of foods. In this study, a static bench top unit was designed to investigate the efficacy of UV-LEDs with different treatment times and peak emissions by considering the inactivation of E. coli K12 in newly formulated mixed drink (MB). UV-LED irradiation of MB using coupled 280/365 nm for 40 min provided the highest microbial inactivation and preserved bioactive compounds better than the heat treatment. It can be proposed as an effective method for the processing of fruit juices which is rich in bioactive constituents. © 2020 Elsevier Ltd