Food Engineering / Gıda Mühendisliği

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

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Author: search.filters.author.Ünlütürk, SevcanEnd date: 2019

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  • 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
  • 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: 17
    Citation - Scopus: 23
    Pasteurization of Verjuice by Uv-C Irradiation and Mild Heat Treatment
    (Wiley, 2019) Kaya, Zehra; Ünlütürk, Sevcan
    Verjuice is a highly acidic juice and more prone to yeast spoilage. In this study, the efficacy of individual and combination processes of UV-C irradiation (UV) and mild heat treatment (MH) for pasteurization of verjuice were assessed. Saccharomyces cerevisiae (NRRL Y-139) was selected as the target microorganism and kinetic parameters for MH, UV, and combined UV + MH inactivation treatments were determined. The UV treatment alone at a UV dose of 0.57 J/cm(2) (energy of 2.30 J/mL), provided only 0.54 +/- 0.02 log CFU/mL reduction of S. cerevisiae. In contrast, the combined treatment (UV + MH2) substantially reduced the number of S. cerevisiae in verjuice, 5.16 +/- 0.24 log CFU/mL reduction was achieved at 0.25 J/cm(2) UV dose (energy of 1.01 J/mL) and 51.25 +/- 1.47 degrees C. The percentage of synergism for the UV + MH inactivation of S. cerevisiae in verjuice was maximized at 51.25 degrees C (50.79% of synergistic effect). Inactivation kinetics of S. cerevisiae was best described by Weibull model with the smallest RMSE and AIC values. D value was decreased from 13.66 to 1.94 min when UV was combined with mild heating. The results showed that UV-C light assisted by mild heat treatment can be a potential alternative to thermal pasteurization of verjuice. Practical applications Fruit juices are prone to spoilage by yeasts, molds, and some acid-tolerant bacteria. Saccharomyces cerevisiae is a heat resistant spoilage microorganism and found in some spoiled juices. Thermal pasteurization is widely used for the preservation of fruit juices but results in losses of essential nutrients and changes in physicochemical and organoleptic properties. This study illustrated that the combined UV-C light assisted by mild heat treatment can deliver the required microbial reduction in verjuice. The synergistic effect of two processing methods is suggested for controlling the growth of spoilage microflora of fruit juices.
  • Article
    Citation - WoS: 52
    Citation - Scopus: 69
    Identification of Equivalent Processing Conditions for Pasteurization of Strawberry Juice by High Pressure, Ultrasound, and Pulsed Electric Fields Processing
    (Elsevier, 2019) Yıldız, Semanur; Pokhrel, Prashant Raj; Ünlütürk, Sevcan; Barbosa-Canovas, Gustavo, V
    The objective of this study was to evaluate the effectiveness of high pressure processing (HPP), ultrasound (US) and pulsed electric fields (PEF) for the pasteurization of strawberry juice (SJ). Acid-adapted Escherichia coli was used to inoculate SJ prior to treatment with HPP, US, and PEF. HPP was applied at several pressures (200-400 MPa) up to 2 min while US (120 mu m, 24 kHz) was conducted at 25, 40, and 55 degrees C up to 10 min in continuous pulsing mode. In order to avoid excessive use of SJ, PEF was performed using a model solution (MS) basically composed of citric acid (8 g/L), fructose (35 g/L), glucose (35 g/L), Na2HPO4 (0.2 M) and NaCl (5%) to simulate the SJ electrical conductivity, pH, and total soluble solid (TSS). A face-centered composite design was conducted for PEF processing at different electric field intensities (EFI) (25-35 kV/cm) and treatment times (5-27 mu s). Processing conditions were selected that resulted in 5-log CFU/mL inactivation of E. coli. HPP at 300 MPa for 1 min, and US at 55 degrees C (thermosonication) for 3 min reduced E. coli in SJ by 5.75 +/- 0.52 and 5.69 +/- 0.61 log CFU/mL, respectively. PEF treatment at 35 kV/cm, 27 mu s treatment time, 350 mL/min flow rate, and 2 mu s pulse width in monopolar mode resulted in 5.53 +/- 0.00 log reduction of E. coli in MS. Likewise, E. coli population in SJ was also reduced by 5.16 +/- 0.15 log after applying the same PEF conditions to SJ. No E. coli was detected in SJ subjected to conventional thermal pasteurization at 72 degrees C for 15 s. All technologies reduced the natural microbiota below 2 log CFU/mL in terms of the total aerobic bacteria and yeast-mold counts. Thus, this study identified the equivalent conditions for the SJ pasteurization by three nonthermal processing technologies. Industrial relevance: Consumers have an increasing interest towards fresh-like food products with desirable nutritional and sensorial attributes. High pressure, ultrasound and pulsed electric field are three relevant novel nonthermal technologies as alternatives to conventional thermal treatments. This study identified the processing conditions of these three nonthermal technologies for the pasteurization of strawberry juice based on equivalent inactivation of acid-adapted E. coli. From an industrial point of view, the established processing conditions are useful references for the development of novel berry juices. In addition to microbiological safety, this study on equivalent processing allows direct efficacy and quality comparisons of a given juice pasteurized by the three nonthermal technologies under consideration.
  • Book Part
    Citation - WoS: 7
    Citation - Scopus: 8
    Impact of Irradiation on the Microbial Ecology of Foods
    (Wiley, 2016) Ünlütürk, Sevcan; Ünlütürk, Sevcan
  • Article
    Citation - WoS: 3
    Citation - Scopus: 5
    Assessing the Impact of Non-Thermal and Thermal Treatment on the Shelf-Life of Onion Juice
    (Czech Academy of Agricultural Sciences, 2018) Demir, Hande; Yıldız, Mustafa Kemal; Becerikli, İsmail; Ünlütürk, Sevcan; Kaya, Zehra
    Onion (Allium cepa L.) juice is a marinating agent for meat and fish marination and readily usable sauce for any meal that has onion in its formulation. This study aims to assess the microbiological and physicochemical changes in the onion juice processed by UV-C irradiation (0.5 mm sample depth, 30 min exposure time, 7.5 mW/cm(2) UV incident intensity) and conventional heat treatment (74.5 degrees C, 12 min) during its storage. Microbiological results showed processing by UV-C irradiation or heat treatment under optimum conditions extended the microbial shelf-life of untreated onion juice by minimum 6-times. Total colour change of heat-treated samples was lower than that of untreated and UV-C treated samples for 12 weeks. Also, pH, total titratable acidity, total soluble solids content, turbidity, NEBI and total phenolic content were monitored for 12 weeks. The results of this study will form scientific infrastructure for onion juice manufacturers to decide on the processing method with respect to its shelf-life.
  • Article
    Citation - WoS: 12
    Effects of Fat Reduction on the Stability, Microstructure, Rheological and Color Characteristics of White-Brined Cheese Emulsion With Different Emulsifying Salt Amounts
    (Korean Society for Food Science of Animal Resources, 2018) Urgu, Müge; Ünlütürk, Sevcan; Koca, Nurcan
    Cheese emulsion is an intermediate product for the production of cheese powder and needs to be stable, homogeneous and pumpable characteristics to convey to the spray drier. This study was conducted to evaluate the effects of fat reduction and emulsifying salt (ES) amount in cheese emulsion systems on the physicochemical characteristics. Reduced-fat (RF) and full-fat (FF) white-brined cheese emulsions were produced with different dry matters (DM; 15%-25% excluding ES) and ES concentrations (0%-3% based on cheese weight). Stable cheese emulsion was obtained at lower DM in RF cheese emulsion than that of FF cheese emulsion. Reduction in the amount of ES resulted in instability of both emulsions. Apparent viscosity with pseudoplastic flow behavior significantly increased with the decrease of fat content in stable cheese emulsions. Microstructure of emulsions appeared to be related to the fat content, stability and degree of emulsification. Reduction of fat content caused to get less lightness and more greenness in color, whereas yellowness was significantly decreased by increase in the amount of ES. In conclusion, fat reduction resulted in higher viscosities of cheese emulsion due to inducing the increment of protein, and the addition amount of ES considered as very important factor to produce stable cheese emulsion without protein precipitation or cream separation. Therefore, for preparation of RF cheese emulsion using a variety of white-brined cheese, lower amounts of DM would be suggested in this study to obtain homogenous droplets in the atomizing process of spray drying.
  • Article
    Citation - WoS: 21
    Citation - Scopus: 25
    Milk Fat Substitution by Microparticulated Protein in Reduced-Fat Cheese Emulsion: the Effects on Stability, Microstructure, Rheological and Sensory Properties
    (Korean Society for Food Science of Animal Resources, 2019) Urgu, Müge; Türk, Aylin; Ünlütürk, Sevcan; Kaymak Ertekin, Figen; Koca, Nurcan
    Fat reduction in the formulation of cheese emulsion causes problems in its flowability and functional characteristics during spray-dried cheese powder production. In order to eliminate these problems, the potential of using microparticulated whey protein (MWP) in cheese emulsions was examined in this study. Reduced-fat whitebrined cheese emulsions (RF) with different dry-matters (DM) (15%, 20%, and 25% excluding emulsifying salt) were produced using various MWP concentrations (0%-20% based on cheese DM of emulsion). Their key characteristics were compared to full-fat cheese emulsion (FF). MWP addition had no influence on prevention of the phase separation observed in the instable group (RF 15). The most notable effect of using MWP was a reduction in apparent viscosity of RF which significantly increased by fat reduction. Moreover, increasing the amount of MWP led to a decrease in the values of consistency index and an increase in the values of flow behavior index. On the other hand, using high amounts of MWP made the emulsion more liquid-like compared to full-fat counterpart. MWP utilization also resulted in similar lightness and yellowness parameters in RF as their full-fat counterparts. MWP in RF increased glossiness and flowability scores, while decreased mouth coating scores in sensory analyses. Fat reduction caused a more compact network, while a porous structure similar to FF was observed with MWP addition to RF. In conclusion, MWP showed a good potential for formulation of reducedfat cheese emulsions with rheological and sensorial characteristics suitable to be used as the feeding liquid in the spray drying process.