Food Engineering / Gıda Mühendisliği
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Book Part Citation - Scopus: 8Uv 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, SevcanNon-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: 21Citation - Scopus: 28Effectiveness 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, SevcanThe 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: 17Citation - Scopus: 23Pasteurization of Verjuice by Uv-C Irradiation and Mild Heat Treatment(Wiley, 2019) Kaya, Zehra; Ünlütürk, SevcanVerjuice 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: 52Citation - Scopus: 69Identification 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, VThe 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: 7Citation - Scopus: 8Impact of Irradiation on the Microbial Ecology of Foods(Wiley, 2016) Ünlütürk, Sevcan; Ünlütürk, SevcanArticle Citation - WoS: 3Citation - Scopus: 5Assessing 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, ZehraOnion (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: 12Effects 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, NurcanCheese 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: 21Citation - Scopus: 25Milk 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, NurcanFat 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.Article Citation - WoS: 22Citation - Scopus: 28Effect of Postharvest Uv-C Treatment on the Microbial Quality of ‘şalak’ Apricot(Elsevier Ltd., 2018) Hakgüder Taze, Bengi; Ünlütürk, SevcanInactivation of natural flora found on cv. ‘Şalak’ apricot surfaces was investigated using a newly designed UV-C treatment system equipped with four UV lamps and a rotating roller bearing. Multiple Point Source Summation (MPSS) Model was used to estimate UV light intensity field in this processing chamber. Although MPSS model over-predicted the UV intensity data, light intensity profile showed a good agreement with the radiometric measurements. UV-C treatment of apricots resulted in 3-log reduction in the number of total mesophilic aerobic bacteria (TAPC) at 32.3 W m−2 of average UV light intensity for 16 min at 31.01 kJ m−2 of UV dose whereas 2.38-log reduction was achieved for yeast and mould count (YMC) after 4 min of UV exposure at 7.75 kJ m−2 of UV dose. On the other hand, complete inactivation of coliform bacteria was observed after all treatments. Statistical analysis indicated that further extension of the exposure time did not cause any significant effect on the inactivation of natural flora of apricot surfaces. Additionally, the inactivation data obtained for TAPC and YMC were modelled by using log-linear regression, Biphasic model, log-linear + tail, Weibull model, Weibull + tail, double Weibull and biphasic + shoulder models. The inactivation kinetics of TAPC and YMC were best described by log linear + tail model with the smallest root mean squared error (RMSE) and the highest regression coefficient (R2 > 0.90). These results suggest that UV-C treatment can be applied to control the natural flora on cv. ‘Şalak’ apricots. Use of a rotating roller bearing is highly appreciated in UV-C systems to provide equal radiation among fruit surfaces.
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