Browsing by Author "Uğurlu, S."

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Comparison of a Novel Vacuum-Combined Infrared and Hot-Air Convection Methods for Drying of Deveci (Pyrus Communis L.) Pear Slices
(Plapiqui, 2023) Topuz, F.C.; Uğurlu, S.; Bakkalbaşi, E.
In this study, the quality characteris-tics of pear slices dried in vacuum-combined infrared dryer equipped with a two-way infrared heating (100-300 W infrared power) and convectional dryer (40-70 °C) were comparatively investigated. Increasing in-frared power in vacuum-combined infrared dryer de-creased the drying time. However, the differences be-tween vacuum pressures (100 mmHg and 250 mmHg) were generally negligible. Drying process at 200 and 300 W IP under vacuum was approximately 2 and 2.5-times shorter than conventionally drying at 55 and 70 °C, respectively. Although a very low amount of HMF in dried pear slices by the conventional dryer was detected only at 70 °C after 300 min, high amounts of HMF was detected at 300 W after 120 minutes. The rehydration rate of pear slice dried with vacuum-combined infrared dryer was higher than those of pear slice dried with conventional dryer. Sy-ringic, chlorogenic and ellagic acids were identified in dried pear samples. Chlorogenic acid was found to be the most among phenolic compounds in dried pears. While the ellagic acid was not detected in fresh pear, dried pears had ellagic acid content (8.14-16.93 mg/kg d.m.). It was found that total phenolic content, ABTS and DPPH values of dried pears by vacuum-com-bined infrared dryer was lower than those of dried sample by conventional dryer. The pear slices dried at 300W and 250 mmHg had the highest sensory scores. The results show that the vacuum-combined infrared drying provided a shorter drying time and better sensory quality for dried pear compared to conventional drying. © 2023, Latin American Applied Research. All Rights Reserved.
Investigating the Effects of a Novel Combined Infrared-Vacuum Dryer on the Drying Kinetics and Quality Parameters of Apple Chips
(Iranian Institute of Research and Development in Chemical Industries, 2023) Uğurlu, S.; Aldemir, A.; Bakkalbaşı, E.
In this study, the kinetic and quality parameters of apple chips dried by a novel dryer equipped with two-way infrared heating (180, 275, and 325 W) and vacuum pump systems (100 and 400 mmHg) were investigated. The final drying time of the sample was reduced with the increasing infrared power. However, it significantly decreased with the increasing vacuum pressure at only 180 W. While the rehydration ratio and sugar content decreased at higher infrared power, the degree of browning and 5-hydroxymethylfurfural increased. Apple chips had high HMF contents (205.39-351.30 mg/kg DM). After sensory evaluation, the highest color, crispness, chewiness, taste, and general acceptance values were determined in the apple chips dried at 275 W and 400 mmHg. The results showed that Midilli’s model was the best option to describe the experimental drying data. The effective moisture diffusivity increased with increasing power and ranged from 1.4499 to 2.9362 × 10−8 m2/s. The activation energies of drying kinetics for 100 and 400 mmHg were 40.5507 and 36.5134 kJ/mol, respectively. Results showed that the higher energy efficiency and product quality for apple chips could be obtained with a specially designed infrared vacuum combined dryer (275 W and 400 mmHg). © 2023, Iranian Institute of Research and Development in Chemical Industries. All rights reserved.
Investigation of the Effect of Immersion and Ultrasound Pretreatments on Some Quality Characteristics of Pears Dried in Vacuum-Assisted Double-Sided Infrared Dryer
(Centenary University, 2025) Coşkun Topuz, F.; Uğurlu, S.; Bakkalbaşi, E.
In this study, the effects of different immersion solutions (maltodextrin and ascorbic acid), solution concentrations (7 and 14% for maltodextrin, 0.5 and 1% for ascorbic acid), immersion times (1, 5, and 10 minutes) and ultrasound amplitudes (0%, 50% and 100%) applied as pretreatment on pears dried in a vacuum-assisted two-way infrared dryer were investigated. Moisture, pH, and acidity values of fresh pear were determined as 81.15%, 4.50 and 0.26%, respectively. Glucose, fructose, sucrose, and total sugar values were calculated as 14.76, 26.51, 6.63, and 47.90 g 100g-1 DM, respectively. Total phenolic content amount, DPPH, and ABTS values were found to be 2461.35 mg GAE kg-1 DM, 407.76, and 206.79 mmol Trolox eq. kg-1 DM. Increasing ascorbic acid concentration prevented HMF formation with increasing ultrasound amplitude and duration, while increasing maltodextrin concentration increased HMF content, especially with increasing immersion duration. In terms of individual phenolics, ellagic acid was not detected in fresh pears, while ellagic acid was detected in dry samples together with chlorogenic acid and rutin. As the ultrasound duration applied in pretreatments increased, the amounts of all individual phenolic compounds in the samples, except for rutin, increased. In the sensory evaluation, the highest approval score was obtained from samples kept in 0.5% ascorbic acid solution and 50% ultrasound amplitude for 10 minutes. As a result, it was determined that the quality of pears dried in vacuum-supported two-way infrared dryers could be increased with the pretreatment combinations, and products with low HMF, high phenolic compounds, antioxidant activity, and approval levels could be produced. © 2025, Centenary University. All rights reserved.
Phenolic Content and Antioxidant Activities of Green Walnuts Harvested at Different Periods on the Lake Van Coast
(Centenary University, 2019) Uğurlu, S.; Okumuş, E.; Bakkalbaşi, E.
Walnut (Juglans regia L.) is a nut with high nutritional and economic values. Walnut is commonly used as a functional ingredient in several traditional food products and as a natural source of phytochemicals in pharmacy and cosmetics. Walnut harvested in the immature periods, known as milk walnut, have been used in formulation of some traditional foods. In this study, phenolic composition and antioxidant activities of green walnuts (immature) harvested from 3 different districts (Van Center, Edremit, and Gevas) around Lake Van in 4 different periods (1st June, 15th June, 30th June, and 15th July) were investigated. The total phenolic content, DPPH, and ABTS values of green walnuts were 17842.26-6907.83 mg GAE kg-1, 208.8-49.03 and 208.48-66.97 mmol TE g-1, respectively. Juglone, gallic acid, neochlorogenic acid, and rutin common phenolic compounds were determined in green walnut samples. While the highest total phenolic content and antioxidant activity were observed in green walnuts harvested on 1st June, the highest juglone was determined in samples collected on 30th June. As a result, it was determined that green walnut had high antioxidant activity and phenolic content, especially juglone. The harvesting period considerably affect the phenolic contents of samples. © 2019, Centenary University. All rights reserved.