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Öğe CHANGES IN beta-CAROTENE, CHLOROPHYLL AND COLOR OF SPINACH PUREE DURING OHMIC HEATING(Wiley-Blackwell Publishing, Inc, 2010) Yildiz, H.; Icier, F.; Baysal, T.The spinach puree was heated from 30C to prescribed temperatures (60, 70, 80 or 90C) ohmically and conventionally. Ohmic heating was performed by application of four different voltage gradients in the range of 10-40 V/cm, while conventional heating was conducted at constant temperature in a water bath. Although ohmic heating time required from 30 to 70C was similar for water heating (129 +/- 7 s) and ohmic heating by 20 V/cm (127 +/- 2 s), faster heating (51 +/- 0.5 s) could be obtained as the voltage gradient for ohmic heating increased to 30 V/cm. Ohmic heating caused browning more than conventional water heating for the same temperature range. The effect of voltage gradient applied was not found statistically significant on chlorophyll (total, a and b), beta-carotene and color values (L, a, b, Lb/a, Lba, hue angle) (P < 0.05). On the other hand, temperature (60, 70, 80 or 90C) at constant voltage gradient (30 V/cm) affected color values of spinach puree (P < 0.05), whereas holding time (0 and 600 s) at constant temperature increased chlorophyll-a and beta-carotene contents (P < 0.05). This increase could be caused by the possible enhancing effect of ohmic heating on beta-carotene biosynthesis and formation of chlorophyll derivatives. It was concluded that ohmic heating could be applied to vegetable purees, resulting in high retention of color attributes and beta-carotene. PRACTICAL APPLICATIONS The present study suggests that ohmic heating could be used to heat the spinach puree faster than conventional heating by adjusting voltage gradient. Moreover, this treatment resulted in high retention of color attributes. In this study, detailed information was given about the effects of ohmic heating parameters such as temperature, voltage gradient and holding time on chlorophyll, beta-carotene and color values of spinach puree. There are no published data in the open literature about effects of ohmic heating on beta-carotene and chlorophyll, to the authors' knowledge. These data could be used in designing of ohmic heating units for functional foods.Öğe Changes on rheological properties of pomegranate (Punica granatum L., cv. Hicaznar) juices during concentration process(Bulgarian Acad Science, 2014) Cevik, M.; Sabanci, S.; Icier, F.; Yildiz, H.The investigation of the changes on rheological properties during evaporation process could diminish the severe effects of thermal processing at any individual soluble solids content. In this study, the rheological properties of pomegranate juices at different soluble solids content (20, 30, 40 and 50 %) during concentration process applied by using the rotary evaporator were determined. Rheological measurements were conducted in the range of 0-264 s(-1) shear rates by using the concentric cylinder type viscometer. It was found expectedly that apparent viscosity increased as the soluble solids content increased. The apparent viscosity was 0.0024 +/- 0.0001 Pa. s for raw pomegranate juices (15.73 +/- 0.30 % soluble solids) while it increased to 0.01342 +/- 0.0003 Pa. s for the concentrated juice having 50 % soluble solids contents. Four different rheological models were applied to find the suitable model best fitting the experimental data; Newton model, Power Law model, Bingham model and Herschel-Bulkley model. The statistical criteria having highest regression coefficient, lowest root mean square error and lowest chi-square were chosen for selection of best model for fitting. It was determined that the Power law model was best described the experimental shear stress-shear rate relation for pomegranate juices at different concentrations. It was predicted that the consistency coefficient of pomegranate juice increased from 0.005 Pa.s(n) to 0.013 Pa. sn as the soluble solid content was increased from 20 % to 50 %. The rheological data obtained in this study could serve valuable data for calculation of changes in flow behaviors of pomegranate juice in pumping systems depending of their concentration.Öğe Effect of ohmic treatment on quality characteristic of meat: A review(Elsevier Sci Ltd, 2013) Yildiz-Turp, G.; Sengun, I. Y.; Kendirci, P.; Icier, F.Ohmic cooking, a well-known electro-heating technique, provides an alternative method for cooking meat products due to its ability for rapid heat generation. Ohmic heating uses the resistance of meat products to convert the electric energy into heat. The rate of heat generation depends on the voltage gradient applied and the electrical conductivity of the meat product. The advantages of ohmic cooking over conventional heating include shorter processing times, higher yields, and less power consumption while still maintaining the colour and nutritional value of meat products. In recent years, ohmic cooking has increasingly drawn interest from the meat industry as a method to ensure the quality and the safety of meat products. The present paper reviews the effects of ohmic cooking on the physical, chemical, sensory, and microbiological quality characteristics and toxicological properties of meat and meat products. (c) 2012 Elsevier Ltd. All rights reserved.Öğe Effect of ohmic treatment on quality characteristic of meat: A review(Elsevier Sci Ltd, 2013) Yildiz-Turp, G.; Sengun, I. Y.; Kendirci, P.; Icier, F.Ohmic cooking, a well-known electro-heating technique, provides an alternative method for cooking meat products due to its ability for rapid heat generation. Ohmic heating uses the resistance of meat products to convert the electric energy into heat. The rate of heat generation depends on the voltage gradient applied and the electrical conductivity of the meat product. The advantages of ohmic cooking over conventional heating include shorter processing times, higher yields, and less power consumption while still maintaining the colour and nutritional value of meat products. In recent years, ohmic cooking has increasingly drawn interest from the meat industry as a method to ensure the quality and the safety of meat products. The present paper reviews the effects of ohmic cooking on the physical, chemical, sensory, and microbiological quality characteristics and toxicological properties of meat and meat products. (c) 2012 Elsevier Ltd. All rights reserved.Öğe The effects of ultrasound application durations on the rheological properties of tomato (Lycopersicon Esculentum) juice(Bulgarian Acad Science, 2014) Sabanci, S.; Cevik, M.; Icier, F.In this study, effects of ultrasound application durations on the rheological properties of tomato juice were investigated. Tomato juice having 6.18 +/- 0.04 % soluble solid contents was ultrasonicated using a 1500 W ultrasonic processor at a constant frequency of 20 kHz for different application durations (0, 5 and 10 min). The empirical data for tomato juice samples obtained from the viscometer (Brookfield LVDV II Pro, USA) were converted into viscosity function. Rheological properties of juice at 20 degrees C were determined by fitting shear stress-shear rate data to some rheological models (Newtonian, Bingham, Power Law, Herschel Bulkley). It was found that samples showed Non-Newtonian fluid (pseudoplastic) behavior. As the ultrasonic application duration increased the apparent viscosity of the tomato juice increased. Herschel Bulkley model was the best model for all application durations investigated (For raw juice and chi-square (chi(2)) 0.203, root mean square error (RMSE) 0.045, Regression coefficient (R-2) 0.995; for 5 min: chi(2) = 0.219, RMSE = 0.053, R-2 = 0.994 and for 10 min: chi(2) = 0.225, RMSE = 0.056, R-2 = 0.994). Rheological data obtained in this study showed the importance of ultrasonic application duration. Application time should be optimized for ultrasonic processing of tomato juices by considering pumping requirements and changes on quality attributes.Öğe Exergoeconomic analysis of ultrasound-assisted extraction of tannins from acorn fruit(Elsevier Ltd, 2024) Döner, D.; Icier, F.Acorn fruit (AF) is a valuable yet tannin-rich forest byproduct. The removal of bitter-tasting tannins is essential for its use as food. This study investigated exergoeconomic analysis of ultrasound-assisted extraction (USAE) with varying amplitudes (20%-60%-100%) and duty cycle conditions (20%-60%-100%) to extract tannins from AF. Conventional solvent extraction (CSE) was used as comparison. AF, mixed with water (1:10 w/v), subjected to ultrasound until tannin content reached 0.0274 mg TAE/mg DM. The study evaluates process conditions' impact on performance and tannin's unit extraction cost. Exergoeconomic analysis was conducted by considering the exergy values, operating costs, investment costs, and extraction time. CSE requires 300 min for target tannin content, while USAE reduces this time to 40-fold. The highest energy efficiency (84.44 ± 2.97) and exergy efficiency (83.68 ± 3.61) were determined at 20% amplitude-20% duty cycle. USAE reduces extraction costs by 25% compared to CSE. USAE has the potential for rapid tannin extraction and cost reduction. © 2023 Elsevier LtdÖğe Ohmic and Conventional Heating of Pomegranate Juice: Effects on Rheology, Color, and Total Phenolics(Sage Publications Ltd, 2009) Yildiz, H.; Bozkurt, H.; Icier, F.Ohmic heating is an alternative fast-heating method especially for liquid foods. In this study, pomegranate juice samples, prepared by two different extraction methods, were heated ohmically by matching the same thermal history, with that of the conventional method. The ohmic heating application was conducted by changing the voltage gradient (10-40 V/cm) at 50 Hz. The samples were heated from 20 degrees C to 90 degrees C and held at 90 degrees C for different treatment times (0, 3, 6, 9 or 12 min). Although rheological properties, color, and total phenolic content (TPC) values changed at the initial heating up period, there were no significant changes during holding period (p<0.05). Non-Newtonian (power law) rheology model had higher regression coefficient than Newtonian model, and the extraction method affected the consistency of pomegranate juice samples (p<0.05). Color values of juice extracted from arils (APJ) was better than that of juice extracted from whole fruits (PPJ), as PPJ contained higher amount of TPC (p<0.05). Since the heating method did not affect the rheological properties, color, and TPC values, it could be said that there was no electrical effect rather than thermal effects during ohmic heating of pomegranate juice. Ohmic heating could be recommended as an alternative fast-heating method for fruit juices.Öğe Ohmic and Conventional Heating of Pomegranate Juice: Effects on Rheology, Color, and Total Phenolics(Sage Publications Ltd, 2009) Yildiz, H.; Bozkurt, H.; Icier, F.Ohmic heating is an alternative fast-heating method especially for liquid foods. In this study, pomegranate juice samples, prepared by two different extraction methods, were heated ohmically by matching the same thermal history, with that of the conventional method. The ohmic heating application was conducted by changing the voltage gradient (10-40 V/cm) at 50 Hz. The samples were heated from 20 degrees C to 90 degrees C and held at 90 degrees C for different treatment times (0, 3, 6, 9 or 12 min). Although rheological properties, color, and total phenolic content (TPC) values changed at the initial heating up period, there were no significant changes during holding period (p<0.05). Non-Newtonian (power law) rheology model had higher regression coefficient than Newtonian model, and the extraction method affected the consistency of pomegranate juice samples (p<0.05). Color values of juice extracted from arils (APJ) was better than that of juice extracted from whole fruits (PPJ), as PPJ contained higher amount of TPC (p<0.05). Since the heating method did not affect the rheological properties, color, and TPC values, it could be said that there was no electrical effect rather than thermal effects during ohmic heating of pomegranate juice. Ohmic heating could be recommended as an alternative fast-heating method for fruit juices.Öğe Ohmic thawing of frozen ground meat(Bulgarian Acad Science, 2014) Celebi, C.; Icier, F.In this study, the applicability of ohmic heating on tempering of the frozen ground meat was investigated. Ground beef meat has been shaped as a block of 1 cm 7 cm 10 cm in a specially designed container, and then frozen at air blast freezer (-30 degrees C). It was aimed to reach the center temperature of the frozen block meat to +20 degrees C from -18 degrees C. The ohmic tempering was performed by the application of different voltage gradients (10, 15 and 20 V cm(-1)) whereas conventional tempering was performed at controlled conditions in the refrigerator (4 degrees C). The effects of the thawing method and the voltage gradient on tempering time, temperature distribution, color and pH were investigated. As the voltage gradient increased, the tempering time decreased in the range of 92-95 % comparing to conventional tempering. Average initial thawing temperature was measured as -1.1 degrees C for the samples. At the end of the tempering, the cold point of the ground meat was 0 degrees C while the minimum temperature value of surface were -4.7 degrees C, -3.3 degrees C and -3.4 degrees C for 10, 15 and 20 V cm(-1) voltage gradients, respectively. Similarly, the thawing method and the voltage gradient affected the color properties (L*, a*, b*, Hue angle, chroma and total colour differences), significantly (p<0.05). The value of a*, which is important for meat samples, was similar for conventional thawing and ohmic thawing applied at 10 V cm(-1). It is thought that the results of this study will provide data for the scaling up of the industrial ohmic tempering or thawing systems and give useful insights to further studies on these subjects.Öğe Processing of Fruits and Fruit Juices by Novel Electrotechnologies(Springer, 2012) Evrendilek, G. Akdemir; Baysal, T.; Icier, F.; Yildiz, H.; Demirdoven, A.; Bozkurt, H.Recent demands from consumers for fresh-like quality foods with less and/or no artificial additives have introduced innovative processing technologies. These technologies due to their potential for food processing with preservation of important properties may cause to introduce new products in the market, to improve the competitiveness of the food, to eliminate the use of some artificial food additives, and to reduce energy cost. Pulsed electric fields for microbial and enzyme inactivation, shelf-life extension, moderate electric fields for yield and extraction, and ohmic heating are among these novel technologies that are based on the application of electric current on food materials. It has been well established that these technologies can successfully be applied to different food products. Among all, fruit juices have special importance due to the suitability of their physical properties to be processed by the electrotechnologies. This article covers the fundamentals of these technologies, their current use, research activities, and trends.
