Food Engineering / Gıda Mühendisliği
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Article Citation - WoS: 69Citation - Scopus: 88Shelf 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: 41Citation - Scopus: 43Changes 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: 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 Citation - WoS: 42Citation - Scopus: 53Effects 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, SevcanEfficacy 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 LtdArticle 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.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.Article Citation - WoS: 81Citation - Scopus: 115Effects of Ultraviolet Light Emitting Diodes (leds) on Microbial and Enzyme Inactivation of Apple Juice(Elsevier Ltd., 2017) Pelvan Akgün, Merve; Ünlütürk, SevcanIn this study, the effects of Ultraviolet light-emitting diodes (UV-LEDs) on the inactivation of E. coli K12 (ATCC 25253), an indicator organism of E. coli O157:H7, and polyphneoloxidase (PPO) in cloudy apple juice (CAJ) were investigated. The clear (AJ) and cloudy apple juice were exposed to UV rays for 40 min by using a UV device composed of four UV-LEDs with peak emissions at 254 and 280 nm and coupled emissions as follows: 254/365, 254/405, 280/365, 280/405 and 254/280/365/405 nm. UV-LEDs at 254 nm achieved 1.6 ± 0.1 log10 CFU/mL inactivation of E. coli K12 at UV dose of 707.2 mJ/cm2. The highest inactivation of E. coli K12 (2.0 ± 0.1 log10 CFU/mL and 2.0 ± 0.4 log10 CFU/mL) was achieved when the cloudy apple juice was treated with both 280 nm and 280/365 nm UV-LEDs. For clear apple juice the highest inactivation 4.4 log10 CFU/mL obtained for E. coli K12 was achieved using 4 lamps emitting light at 280 nm for 40 min exposure time. For the same treatment time, the experiments using a combination of lamps emitting light at 280 and 365 nm (2lamp/2lamp) were resulted in 3.9 ± 0.2 log10 CFU/mL reductions. UV-A and UV-C rays in combination showed a better inactivation effect on PPO than UV-C rays used separately. Residual activity of PPO in CAJ was reduced to 32.58% when treated with UV-LED in combination of UV-C (280 nm) and UV-A (365 nm) rays. Additionally, the total color change (ΔE) of CAJ subjected to combined UV-LED irradiation at 280/365 nm was the lowest compared to other studied processing conditions. This study provides key implications for the future application of UV-LEDs to fruit juice pasteurization.Article Citation - WoS: 42Citation - Scopus: 55Processing of Clear and Turbid Grape Juice by a Continuous Flow Uv System(Elsevier Ltd, 2016) Kaya, Z.; Unluturk, S.The inactivation of inoculated (S. cerevisiae) and spoilage microorganisms, i.e. yeasts and lactic acid bacteria (LAB), in clear and turbid grape juice was investigated using a pilot scale UV system. The biodosimetry method was used for UV dose prediction in a continuous flow UV reactor. Weibull model was applied for fitting the inactivation data. The flow rates (774, 820 ml/min) in this system were very close to the ones used in fruit juice processing. S. cerevisiae in clear juice was reduced by 3.39 ± 0.04 at 65.50 mJ/cm2 of UV dose. 1.54 ± 0.04 and 1.64 ± 0.03 log CFU/ml reductions were obtained for spoilage yeasts and LAB in turbid juice at UV dose of 78.56 and 67.97 mJ/cm2, respectively. The soluble solids (°Brix) and pH of grape juice samples were not affected by UV-C treatment (p > 0.05). Although the color parameters slightly were changed after irradiation, the color of PCGJ and FSTGJ did not show visual difference compared to the untreated samples. Industrial relevance: UV light has a potential to reduce the levels of microbial contamination in liquid foods. Although grape juice has many beneficial health effects, it has a fairly short shelf life. Therefore, pasteurization is required. But the thermal pasteurization has some undesired effects on the juice quality. Consumer demands for high quality fruit juice with fresh-like characteristics have markedly expanded in recent years. In the current study, the microbial inactivation efficiency of a pilot scale UV system for non-thermal treatment of clear and turbid grape juice was evaluated under conservative conditions. Most of the physicochemical properties of grape juice samples were not significantly affected from UV-C treatment (p > 0.05). This would be a major advantage in the processing of nutritious juice products. © 2015 Elsevier Ltd. All rights reserved.Article Citation - WoS: 82Citation - Scopus: 103Effect of Uv-C Irradiation and Heat Treatment on the Shelf Life Stability of a Lemon-Melon Juice Blend: Multivariate Statistical Approach(Elsevier Ltd., 2015) Kaya, Zehra; Yıldız, Semanur; Ünlütürk, SevcanHeat treatment and UV-C irradiation of lemon and melon juice (LMJ) blends were comparatively evaluated by examining their impact on E. coli K12 (ATCC 25253) and their physicochemical properties, i.e., total soluble solids (TSS), pH, titratable acidity (TA), color, turbidity and absorbance coefficient, both immediately after processing and during 30 days of refrigerated storage. The newly formulated LMJ blend containing 12% (v/v) lemon juice (pH 3.92 ± 0.01) scored the highest in the consumer acceptance test. Upon UV-C irradiation (2.461 J/mL) and heat treatment (72 °C, 71 s), the E. coli K12 population in LMJ blend was reduced by > 6 log10 CFU/mL. Principal component analysis (PCA) and hierarchical cluster analyses (HCA) showed a clear discrimination among the physicochemical properties of the control and the UV-C and heat-treated LMJ blends during storage, suggesting that UV-C irradiation has a comparable effect on microbial stability at 4 °C and better quality preservation performance than heat treatment. Industrial relevance Melon juice has many beneficial health effects. It has high sugar content, pH (5.6-6.0) and a fairly short shelf life. Therefore, pasteurization is required. But the thermal pasteurization has some undesired effects on the juice quality. Consumer demands for high quality fruit juice with fresh-like characteristics has markedly expanded in recent years. In this study, an alternative lemon-melon juice (LMJ) blend formulation was developed, and pasteurized using both UV-C irradiation and mild heat treatment. The shelf life stability of pasteurized LMJ blends was assessed by means of principal component analysis and hierarchical cluster analysis. The shelf life of LMJ blends treated by both methods was increased from 2 days to 30 days. The multivariate data analysis was successfully applied as a tool for an overall evaluation of the shelf-life of the product. UV-C irradiation has a comparable effect on microbial stability at 4 °C and better quality preservation performance than heat treatment for obtaining both shelf-stable and fresh-like LMJ blends. This would be a major advantage in processing of nutritious juice products.