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    A Prototype Downdraft Gasifier Design with Mechanical Stirrer for Rice Straw Gasification and Comparative Performance Evaluation for Two Different Airflow Paths
    (Ankara Univ, Fac Agr, 2018) Dalmış, İbrahim Savaş; Kayişo?lu, Birol; Tuğ, Serkan; Aktaş, Türkan; Durgut, Mehmet Recai; Durgut, Figen Tasci
    In this research, a prototype downdraft throatless gasifier was designed with a mechanical stirrer. The gasifier was designed for gasification of rice straw pellets. The diameter of the reactor was 350 mm and a nominal value for the heat power of biomass input was 70 kW. Rice straws which were collected from Thrace Region of Turkey gasified for determination of the designed gasifier performance in Namik Kemal University Biosystem Engineering Laboratories. The effects of airflow path and stirring process on the gasification efficiency during the gasification process were investigated. Temperatures and airflow rates observed and adjusted by controlling the air flow rate in the automation system constantly. Pellets were gasified using two different airflow paths with the same equivalence ratio of 0.2 and these were compared. Air inlet from the top showed better results than air inlet from tuyeres. For the air inlet from the top, the higher heating value of producer gas was determined as 5.047 MJ Nm(-3) and cold gas efficiency was calculated as 65.4%. H-2/CO ratio was found as 1.385 which was higher than the air inlet from tuyeres.
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    Air and Steam Gasification of Almond Biomass
    (Frontiers Media Sa, 2019) McCaffrey, Zach; Thy, Peter; Long, Michael; Oliveira, Melina; Wang, Li; Torres, Lennard; Jenkins, Bryan M.; Aktaş, Türkan
    Experiments were performed on a laboratory scale fluidized bed gasifier to characterize the gasification products of almond shell and hull removed in nut processing operations and to determine the effect of gasifying media on bed agglomeration. The higher heating value of syngas during air gasification of almond biomass ranged from 4 to 6 MJ m(-3) while gas concentrations ranged from 14 to 18% H-2, 3-4% CH4, 43-50% N-2, 16-19% CO, and 16-17% CO2. For steam gasification, higher heating value was 10-12 MJ m(-3) and gas concentrations were 35-40% H-2, 5-7% CH4, 17-21% N-2, 18-21% CO, and 16-18% CO2. The high level of potassium in the almond shells led to strong corrosion and bed agglomeration due to flue gas transport of potassium compounds. These resulting pervasive kalsilite reactions were significantly worse under air gasification than under steam gasification. As a result of prolonged duration and elevated temperature approaching 1,000 degrees C, the corrosinal reaction changes to formation of an adhesive potassium distillate melt locally forming strong bonds. This latter is interpreted as a result of aerosol transported of melt particles.
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    Antioxidant Activity, Some Nutritional and Colour Properties of Vacuum Dried Strawberry Tree (Arbutus Unedo L.) Fruite
    (Termedia Publishing House Ltd, 2011) Orak, Hakime Hülya; Aktaş, Türkan; Yağar, Hülya; İşbilir, Şebnem Selen; Ekinci, Neslihan; Şahin, Füsun H.
    Background. The strawberry tree (Arbutus unedo L.) fruit contains a higher amount of nutrients and bioactive compounds than many other cultivated species, however, the edible use of this fruit is currently not widespread. In this study, the influences of vacuum drying have been investigated in terms of changing of some nutritional characteristics, antioxidant properties, and colour. Material and methods. Fruits were collected from Canakkale province in Turkey and next vacuum dried. Ethyl oleate and water blanching pre-treatments were applied to fruits before drying. Ascorbic acid, reducing sugar, minerals, colour, total phenolic content, DPPH radical scavenging activity, beta-carotene bleaching activity and HMF formation were determined. Results. The EO pretreatment shortened the drying time more than WB and gives a higher beta-carotene bleaching activity, lower HMF and higher yellowness and brightness of external colour characteristics. Conclusions. In this research, the effects of vacuum drying process on the colour, antioxidant activity and nutritional characteristics of fruit have been determined and it has been concluded that the strawberry tree fruit is assessable in food industry by drying due to rich nutritional components, antioxidant activity and attractive colour of the fruit.
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    Bir Torefikasyon Reaktörünün Geliştirilmesi ve Kızıl Meşe “Quercus Rubra” Kullanılarak Farklı Torefikasyon Sıcaklıklarında Elde Edilen Biyokömür Yakıt Özelliklerinin Saptanması
    (Kahramanmaraş Sütçü İmam Üniversitesi, 2019) Aktaş, Türkan; Batur, Tolga
    Bu araştırmada, geleneksel üretime kıyasla daha kaliteli, hızlı ve kontrollü koşullarda biyokömür elde etmek amacıyla bir torefikasyon reaktörünün imalatı ve en uygun torefikasyon sıcaklığının belirlenmesi amaçlanmıştır. Elde edilen örneklerin yakıt özellikleri klasik yöntemlerle (torluk oluşturma ve ticari fırın metodu) elde edilen biyokömür örneklerinin yakıt özellikleri ile karşılaştırılmıştır. Bu amaçla, biyokömür elde etmek için geliştirilmiş reaktör kullanılarak 5 farklı sıcaklıkta (220, 245, 260, 280, 300 °C)  kızıl meşe “Quercus Rubra” örnekleri torefiye edilmiş ve elde edilen örneklerin kısa analizleri yapılarak ısıl değerleri ölçülmüştür. Elde edilen sonuçlar klasik yöntemlerle elde edilmiş olan ve piyasada satılan ticari ürünler ile karşılaştırılmıştır. Analizler sonucu torefiye edilmiş ürünlerde en yüksek ısıl değer, 7135 cal g-1 ile 300 °C’de elde edilmiş örnekte saptanırken, en düşük ısıl değer ise 220 °C’ de elde edilmiş olan örnekte 5421.33 cal g-1 olarak belirlenmiştir. Ayrıca, 300 °C’de elde edilen altı numaralı numune sahip olduğu nem ve kül oranı ile ticari anlamda satışı yapılan piyasa ürününü geride bırakmıştır.  Numunelerde uçucu madde oranları %70-%80 aralığında, sabit karbon oranları ise %20-%25 aralığında saptanmıştır. Uygulama sıcaklığı arttıkça ısıl değerin arttığı, nem ve kül oranının düştüğü saptanmıştır. Nem, kül ve uçucu madde miktarları açısından reaktörden elde edilen örneklerin, geleneksel yöntemlerle elde edilen örneklere kıyasla daha iyi özelliklere sahip olduğu belirlenmiştir. 300 °C' de elde edilmiş olan biyokömür örneklerinin ortalama ısıl değeri (7135 cal g-1) ticari fırından elde edilen biyokömürlerin ısıl değerinden (6003 cal g-1) oldukça yüksek bulunurken,  klasik torluk oluşturma yöntemiyle elde edilen örneklerinkine de oldukça yakın olduğu saptanmıştır.
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    Breaking of apricot pits by using a mechanical system
    (Asian Network for Scientific Information, 2007) Polat, R.; Aktaş, Türkan; Gezer, Isaac; Atay, Ümran; Bilim, H.I.C.
    The objective of this research was to investigate the effects of heating process and warping effect on breaking of apricot pits and obtaining of its kernel without damage. For this aim, heating process (350°C) was applied to apricot pits. Heated pits were fallen onto the rotating disc and they were warped to warping wall by centrifuge effect. Warping velocity was adjusted by changing of rotating disc revolution that was driven by an electric engine. Three different disc revolution namely 400, 500 and 600 min-1 and 4 different moisture contents of apricot pits namely 6.7, 15.5, 22.2 and 31.5% were used in the experiments. As a result, it was found that increasing of moisture content was increased amount of breaking and also sound kernel ratio. Increasing of disc revolution increased ratio of damaged kernel. The highest breaking amount was determined for experiment with heated pits that had 31.5% moisture content and warped with 400 min-1 disk revolution. © 2007 Asian Network for Scientific Information.
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    Çeltik Saplarının Gazlaştırılması Amacıyla Laboratuvar Tipi Bir Gazlaştırıcının Geliştirilmesi ve Denenmesi
    (Namık Kemal Üniversitesi, Ziraat Fakültesi, 2017) Aktaş, Türkan; Dalmış, İbrahim Savaş; Tuğ, Serkan; Dalmış, Figan; Kayişoğlu, Birol
    Bu çalışma kapsamında, Trakya Bölgesi’nde yoğun olarak yetiştirilen çeltik bitkisinin hasattan sonra tarlada kalan saplarının gazlaştırılarak enerji içeriklerinin değerlendirilmesi için laboratuvar tipi bir gazlaştırıcı tasarlanmış ve imalatı yapılmıştır. Bölgeden toplanan çeltik sapları %100 sap ve %15 oranında kömür tozu ile karıştırılmış şekilde peletlenmiş ve peletlerin analizleri yapılmıştır. Gerek hammadde ve gerekse pelet örnekleri için gazlaştırma denemeleri gerçekleştirilmiş ve elde edilen gaz örneklerinin içerikleri belirlenmiştir. Gazlaştırma denemeleri sonucunda, kömür katkısının çeltik sapı peletleri için sentez gaz ısıl değerini arttırdığı (3,686 MJ/Nm3 değerinden 3,71 MJ/Nm3 değerine) ancak özgül gazlaşma hızının da artmasıyla beraber verime etkisinin olumsuz olduğu gözlemlenmiştir (katkısız peletlerde maksimum %61,9, kömür katkılı peletlerde en fazla %57,41). Çeltik sapı peletlerinin içerdiği yüksek silisyum sebebiyle 800?C ve yukarı sıcaklık değerlerinde camlaşma riski taşıdığından dolayı yüksek gazlaşma hızlarına çıkılamamıştır. Peletlenerek enerji yoğunluğu arttırılmış biyokütlenin gazlaştırılması için ise tasarım sorunsuz bir şekilde çalışmış fakat peletlenmemiş, saman halindeki çeltik saplarının gazlaştırılması için reaktör konstrüksiyonunun mevcut şekliyle uygun olmadığı, uygun olması için sürekli biyokütle besleme donanımlarını ilave edilmesi ve ebatlarda değişiklik yapılması gerektiği görülmüştür. Peletlenmemiş çeltik samanı için %37,14 gibi düşük bir verim elde edilmiştir. Aynı şekilde elde edilen singazın ısıl değeride çeltik sapı için oldukça düşük (1.94 MJ/Nm3 ) bulunmuştur.
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    Changes in nutritional properties of sorrel (Rumex acetosa L.) plant dried using different drying methods
    (Scibulcom Ltd., 2017) Eryılmaz Açıkgöz, Funda; Hastürk Şahin, F.; Altan, Deniz Damla; Aktaş, Türkan
    In this study, drying process of sorrel (Rumex acetosa L.) using different drying methods the determination of its quality characteristics was aimed. For these aims, sorrel plants were dried by the methods of convective hot air drying, sun drying, and shadow drying. 40-50-60°C drying temperatures and drying air velocity values of 1-2 m/s were applied for hot air drying experiments. Total amount of phenolic material and antioxidant activity were determined both on fresh and dried plant samples in order to study the effects of drying on nutrient retention. The most appropriate drying method was tried to be determined that will retain the maximum nutrient and quality properties expected from the sorrel samples. According to results of the analyses, the maximum values of phenolics content and antioxidant activity were obtained for the samples dried at conditions of 40°C with 2 m/s air velocity . Dried consumption of sorrel plant was recommended as well as consumption of fresh sorrel.
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    Changes in the drying characteristics and water activity values of selected pistachio cultivars during hot air drying
    (Wiley, 2007) Aktaş, Türkan; Polat, Refik
    The drying characteristics and changing of water activity (A(w)) values of Kirmizi and Siirt pistachio cultivars were determined experimentally as a function of drying air temperature and initial moisture content during hot air drying. The drying experiments were conducted using two levels of initial moisture content (32 and 38%) and three drying air temperatures (40, 50 and 60C) at 1.5 m/s drying air velocity at 12% air relative humidity. The drying curves obtained from the experimental data were then fitted to the 10 different semitheoretical and/or empirical thin-layer drying models. The moisture ratios at any drying time were compared by the Newton, Page, Henderson and Pabis, Logarithmic, Two-term, Wang and Singh, Diffusion approximation, Modified Henderson and Pabis, Verma et al. and Midilli et al. models. The effect of drying air temperature and initial moisture content on the coefficients of the best-suited moisture ratio model were determined by multiple regression method. Root mean square error and reduced chi-square were used for the determination of the best suitable model. In addition to these statistical parameters, the modeling efficiency was also determined. The Modified Henderson and Pabis model was found to be the most suitable for describing the drying behavior of both pistachio cultivars. As a criterion of shelf life, A(w) changes of dried pistachio samples were investigated.
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    Changes of Nutritional and Physical Quality Characteristics During Storage of Osmotic Pretreated Apple Before Hot Air Drying and Sensory Evaluation
    (Wiley-Hindawi, 2013) Aktaş, Türkan; Ülger, Poyraz; Dağlıoğlu, Figen; Hastürk Şahin, Füsun
    The aim of this research was to increase the application of different osmotic dehydration solutions to decrease the drying time, and decrease the loss of quality after drying and during storage of apples. Sucrose and trehalose solutions with 20 and 50 Brix concentrations were applied. Drying experiments were performed at 50, 60 and 70C using a hot air dryer. Changes in color, water activity, vitamin C, dry matter, total phenol content and mechanical properties were determined with 3-month intervals. Trehalose pretreatments, especially with 50 Brix concentration, generally decreased the drying time. Trehalose pretreatment with 20 Brix had better effects on quality characteristics. Texture of the samples pretreated using 50 Brix sucrose and trehalose stayed more stable just after drying. Lowest change in puncture force was found in 50 Brix trehalose-treated samples even after 12 months. Samples pretreated using 20 Brix trehalose had the higher preference by the panelists. Practical ApplicationsApple drying is rather important because of large production capacity in the world. For reducing quality losses and the cost, osmotic pretreatments and then using cabin or tunnel dryers, which are based on hot air circulating, have been widely used. Usually sucrose, dextrin, glucose have been used for osmotic dehydration implementations to fruits like apple, kiwi and mango, until now. Sucrose implementation is the most successful for fruits and therefore it has widest usage in fruit processing. But there are many disadvantages of using sucrose like caramelization and changes in flavor and viscosity. Our previous research showed that trehalose has rather good effects to improve the quality of dried vegetables such as carrot and potato. The results of this research can also serve as a valuable resource to further researches for utilization of alternative osmotic materials such as trehalose similar to our research to decrease negative effects of drying process.
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    Changing of Viscosity and Thermal Properties of Olive Oil with Different Harvesting Methods and Waiting Period
    (Univ North, 2018) Sağlam, Cihangir; Tan, Fulya; Aktaş, Türkan
    The aim of this paper is to determine how different harvesting methods of olives and the waiting period before the extraction of the extra virgin olive oil affect the viscosity and some thermal properties, namely thermal conductivity and thermal resistivity. Olive trees in the Aegean region of the western part of Turkey were harvested by using six different harvesting methods: by hand, harvesting by a beating pole on a synthetic fabric, harvesting by a beating pole on a platform, harvesting by machine on a synthetic fabric, harvesting by machine on a platform and direct collecting of dropped olives by hand. Olive oil samples were obtained in certain intervals between the harvesting and processing that was made by using a laboratory type system. The viscosity values of oil samples were measured by using a vibro-viscometer. The thermal conductivity and thermal resistivity of oil samples were measured simultaneously by using the KD2 Thermal properties analyzer. As a result, viscosity, thermal conductivity and thermal resistivity values changed related to the harvesting method and the waiting period after harvesting to obtain olive oil. While viscosity (dynamic) and thermal conductivity values increased with the increase of the waiting time, thermal resistivity values decreased. The lowest viscosity and thermal conductivity values and the highest resistivity values were found for oils that were obtained from olives harvested by hand.
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    Characterization of almond processing residues from the Central Valley of California for thermal conversion
    (Elsevier, 2015) Aktaş, Türkan; Thy, Peter; Williams, R. B.; McCaffrey, Zach; Khatami, R.; Jenkins, B. M.
    Characterization of biomass relevant to thermochemical conversion processes and other applications is critical to the design and proper operation of energy conversion, biorefining, and other facilities, especially in regard to estimating critical problems related to fouling and slagging from ash constituents. Residue feedstock from almond production was obtained from seven huller and sheller facilities located throughout the Central Valley of California. Results of proximate (moisture, ash, volatile and fixed carbon content), ultimate (C, H, N, S, O composition), heating value, major and trace elements, and melting behavior analyses (all reported on a wt.% dry basis) reveal many similarities and also differences that potentially affect their utilization. The moisture content of air-dried feedstock is an average of 9.7% with only the separated hull material having a higher value (12.2%) and the fine component (<2 mm) a lower value (8.2%) on an as received basis. The volatile matter is relatively constant (72-76%). The ash content reflects a variable soil component in most fractions with a low average in hell of 3.5% and increasing to 22% in the fine fraction. The elemental C/O ratio is constant at about 1.15 and only appears slightly higher in the woody fraction (1.21). Nitrogen (0.4-0.8%) and sulfur (0.2-0.3%) are elevated compared to many other types of biomass, with the large variation in N probably related to irrigation water source and fertilization practices. Chlorine is generally low (<0.05) and varies without KCl control in both the crude feedstock and the ash. The ash of the almond biomass is very high in K, varying between 18-36% and only S, Ca, and Preaching substantial amounts. The trace element concentrations are mostly well below local soil compositions with only Ga, Sr, and Cu well above and thus suggest few, if any, regulatory utilization challenges. The elevated feedstock concentrations of S and N may be sufficient to cause some environmental concern for certain types of thermal conversion processes, mostly in relation to NOx and SOx emissions. The high ash content together with the very high K content can cause adverse bed behavior, corrosion, and fouling in boilers, despite the relatively high ash melting temperatures (>1100 degrees C) suggested by pellet fusibility test. (C) 2015 Elsevier B.V. All rights reserved.
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    Comparison of mechanical properties of some selected almond cultivars with hard and soft shell under compression loading
    (Wiley, 2007) Aktaş, Türkan; Polat, Refik; Atay, Ümran
    The mechanical properties of Nonpareil versus Gulcan 101-23 almond cultivars that have different shell properties were loaded between two parallel plates to determine the rupture force, rupture energy, rupture power requirement, toughness and firmness. The tests were carried out with three moisture contents, namely, 7.2, 22.9 and 33.6% wet basis and three loading axes (x, y, z). Physical characteristics of the almond cultivars such as length, width, thickness, geometric mean diameter, sphericity, volume, surface area and weight were determined. Physical properties of both cultivars increased as a numerical by increasing moisture content. The highest rupture force in all moisture content levels was obtained for almond pit loaded along the y-axis. In addition to rupture force, values of absorbed energy, toughness, power requirement and firmness were calculated as mechanical properties. The maximum force required to initiate pit rupture was found as maximum 554.3 N at y-axis for 7.2% moisture content and minimum 126.9 N at x-axis for 33.6% moisture content for Gulcan 101-23 cultivar. These values were determined as 53.3 and 11.2 N, respectively, for Nonpareil cultivar. Rupture force, absorbed energy, toughness, power requirement and firmness decreased with an increase of moisture content. The difference between mechanical properties of Nonpareil versus Gulcan 101-23 almond cultivars was found to be highly significant (P < 0.001).
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    Determination of Calorific Value of Briquettes Obtained Using Inner and Outer Shells of Pistachio Nuts
    (Agronomski Fakultet Sveucilista U Zagrebu, 2015) Polat, Refik; Oğuz, Hidayet; Aktaş, Türkan; Erdogdu, Ahmet Emrah
    In this research, moisture content, ash ratio and calorific values of briquettes were determined for briquetted inner and outer shells of pistachio nuts after the processing of pistachio nuts that were dried and separated from shell parts during processing. Inner and outer shells of pistachio nuts were grinded and formed into briquette form. Briquettes were prepared using olive prina as additive with % 20, % 30 and % 40 ratio and were compressed using briquetting machine. At the end of the briquetting process, briquettes of 100 mm in diameter and the length of 10-30 cm were obtained. Moisture and ash content with calorific values of samples which were formed into briquette were determined. As a result of these evaluations, improvements of physical features were observed in addition to the increase of briquette's olive prina ratios obtained in consequence of briquetting of pistachio shells by being mixed olive prina. It was determined that increasing of olive prina rate decreased calorific value.
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    Determination of Optimum Shaking Frequency and Amplitude of Prototype Body Shaker Used for Mechanical Harvesting of Pistachio
    (Agronomski Fakultet Sveucilista U Zagrebu, 2017) Polat, Refik; Güner, Metin; Erdoğan, Doğan; Gezer, İbrahim; Atay, Ümran; Aktaş, Türkan
    Important problems have been seen during harvesting of different fruit trees in Turkey. The highest cost in fruit growing constitutes harvesting process as 43.99% of total cost. In this research, a body shaker which was mounted to tractor three-point linkage system and driven by power take off system was designed and manufactured to decrease the cost of harvesting of tree fruits. A tractor with 70 BG power is enough to transport and operate this body shaker. This prototype was functioned with a system including a hydraulic pump taking movement from power take-off and hydraulic motor. Body shaker could be controlled by only one person. Harvesting tests using different frequencies and amplitudes were carried out with body shaker. Two pistachio tree cultivars namely Siirt and Kirmizi were used during the harvesting tests. Pistachio fruits which remained on the branch and leaved from branch were weighed separately to determine of harvesting efficiency. For this aim, performance of body shaker was determined. As a result, the best performance result was determined using 40 Hz frequency and 20 mm amplitude. The harvesting efficiency values in harvesting tests carried out using 40 Hz frequency and 20 mm were calculated 93.27% for pistachio cultivar of Siirt and 87. 06% for pistachio cultivar of Kirmizi.
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    Determination of Quality Characteristics and Compliance with Standards of Wood Pellet Samples Produced in Turkey
    (Tarım Makinaları Derneği, 2022) Aktaş, Türkan
    In this research, the quality properties of wood pellets produced and sold as fuel in our country were determined and the compliance of solid biofuels with different standards (DIN51731, DIN Plus, ÖNORM 7135, ISO 17225-2) related to fuel properties investigated. In addition, flue gas analyzes were carried out for these samples. The emission results obtained were compared with the emission limits determined by the European Union regulations of 2015/1185 and 2015/1189, TS EN 303-5 standard, regulations on "Control of Industrial Air Pollution" (SKHKKY) and “Regulation on Control of Air Pollution Resulting from Heating" (IKHKKY)”. For this purpose, samples were collected from 10 different companies that manufacture and sell wood pellets from 5 different cities in Turkey, and the length (mm), diameter (mm), density (kg/m3), mechanical strength (%) , moisture content (%), ash content (%), calorific value (MJ/kg) and flue gas emission values were determined. According to the measurement results, It was determined that the length value is between 15.69-30.82 mm, the diameter value is between 6.06-10.39 mm, the density value is between 0.51-1.15 kg/m3, the mechanical strength value is 95.11-99.22%, moisture contents between 4.32-5.72%, ash contents between 1.03-2.03%, and heating values between 18.08-18.49 MJ/kg. Among the flue gas emission values, the O2 content was measured between 12.7%-71.7%, the amount of CO was measured between 1443-2127 ppm, and the amount of NOx was measured between 83.7-213 ppm. In terms of the limit values for the quality characteristics specified in the ISO 17225-2 standard, which is also valid in our country, 100% of the samples are suitable in terms of length, moisture content and heating value; In terms of diameter and bulk density, 80% of the samples were determined to comply with the standards.On the other hand, when the ash content results were examined, it was determined that the samples were not suitable for ENplusA1 class, 40% of the samples were in ENplusA2 class and 80% were in ENplusB class, 20% of the samples were non-standard. The CO emission values in the flue gas samples resulting from the burning of the pellet samples exceeded the emission limit value determined in the EU regulations, so it was determined that the pellet samples examined within the scope of this study were not suitable for any heating system specified in the EU Ecodesign-directive. Likewise, when the emission limits determined in IKHKKY and SKHKKY are examined, it has been determined that the pellet samples are not suitable in terms of CO emission in the combustion systems specified in these regulations. According to the CO emission values specified in the TS EN 303-5 standard, all the pellet samples we examined can only be used in all heating systems up to "Class 3" up to 50 kW thermal power, 80% of the pellets can be used in systems with 50kW-150 kW thermal power but it has been determined that none of them is suitable for systems with higher thermal power.
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    Drying behavior of prina (crude olive cake) using different types of dryers
    (Taylor & Francis Inc, 2016) Çelen, Soner; Aktaş, Türkan; Karabeyoğlu, Sencer Süreyya; Akyıldız, Aylin
    The purpose of this research is to investigate the drying kinetics and determine the suitable drying method of prina, which is obtained after pressing of olives in olive oil factories, and which cannot be used efficiently in certain sectors. Drying experiments were performed at drying temperatures of 60 degrees C, 70 degrees C, and 80 degrees C at a fixed air velocity of 2m/s using a hot air dryer and with microwave powers of 90W, 360W, and 600W using a microwave dryer. The prina layer thicknesses were selected as 7, 9, and 11mm for both drying methods. The minimum energy consumption values were measured as 42.0Wh for 600W power level and 7mm layer thickness, and 10260Wh for 7mm layer thickness and 80 degrees C temperatures. It was found that energy consumption during hot air drying was more than that of microwave drying. As a result, the suitable dryer and thickness of layer were selected as microwave dryer and 7mm, respectively. The results of statistical analyses showed that the most suitable model to define the drying behavior of prina samples were found to be the Page model for the microwave dryer and Wang & Singh model for the hot air dryer. Also, penetration depth, the loss tangent value (tan), dielectric constant of material (E), and dielectric loss factor (E) of dried prina were calculated as 34.51cm, 0.1059, 75.65, and 8.01, at 2450MHz, respectively.
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    Drying of sliced vegetables pretreated with sugar solutions
    (2011) Fujii, Sachie; Yoshımoto, Noriko; Aktaş, Türkan; Yamamoto, Shuichi
    Steam blanching (3-4 minutes) followed by soaking into trehalose-maltosyltrehalose mixture solutions for 10 minutes was found to be a very effective pretreatment method for drying of sliced vegetables (potatoes and carrots). Peroxydase measurements showed that the enzyme activity was completely inactivated by a 3-minute steam blanching. Blanched samples were soaked in a 20 wt% (weight percent) sugar solution for 10 minutes at room temperature, and then dried by hot-air drying at 303K. The dried product with sugar solution treatment resulted in good product properties such as less shrinkage or deformation and better colorness retention. Especially, a solution composed of 18wt% trehalose and 2wt% maltosyltrehalose was quite effective in terms of the product quality and the drying efficiency.
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    Drying of Yeasts-Factors Affecting Inactivation During Drying
    (Taylor & Francis Inc, 2011) Fujii, Sachie; Sakamoto, Yuichi; Aso, Tamami; Aktaş, Türkan; Yoshimoto, Noriko; Yamamoto, Shuichi
    The inactivation behavior of baker's yeasts during low-temperature hot air drying and freeze drying was investigated. The activity was determined by measuring the fermentative abilities. Inactivation was observed during the falling drying rate period even at low temperature (30 degrees C). As their fermentation activities in suspensions at 30 degrees C are maintained up to a few hours, this decrease was found to be due to dehydration inactivation. Similar dehydration inactivation was also observed during freeze drying. The dehydration inactivation became more significant when the drying rate was increased. The stability of dried yeasts increased with decreasing water content. The addition of sorbitol before drying further improved the stability of dried yeasts.
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    Effects of Different Drying Methods on Drying Kinetics and Color Parameters of Strawberry Tree (Arbutus unedo L.) Fruit
    (Namık Kemal Üniversitesi, Ziraat Fakültesi, 2013) Aktaş, Türkan; Orak, Hakime Hülya; Şahin, Füsun Hastürk; Ekinci, Neslihan
    Changing of drying kinetics and color parameters of strawberry tree fruits that were notreated (NPT), ethyl oleate pretreated (EO) and water blanched at 80 ºC (WB) for one minute were evaluated during hot air drying at 50 °C, 60 °C and 70 °C and vacuum drying at 60 °C, 70 °C and 80 °C for halved and whole fruits. In addition to drying behaviors of strawberry tree fruits at different drying methods, triLstimulus color parameters such as Hunter L*, a* and b* values were measured. HMF (formation of 5Lhydroxymethylfurfural) occurring was also determined due to drying process. EO pretreatment was found highly effective on decreasing of drying time both for hot air drying and vacuum drying processes while WB pretreatment found to be more effective to keep color properties of strawberry tree fruits. Color properties were found to be better in half samples compared to whole dried fruits. HMF values verified this result. Hot air drying process caused to shorter drying time. High drying air temperatures (70 ºC for hot air drying and 80 ºC for vacuum drying) for all samples caused to occur HMF while HMF occurred in only whole dried NPT and WB treated fruits for hot air drying process at 60 ºC. All these data show that hot air drying method at 60 ºC drying temperature and, halving of fruits before drying can be proposed for drying of strawberry tree fruits in respect of drying kinetics, color and HMF values.
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    Effects of different drying techniques on drying characteristics and some quality attributes of sorrel (Rumex Acetosa L.)
    (Scibulcom Ltd., 2017) Hastürk Şahin, F.; Aktaş, Türkan; Altan, Deniz Damla; Eryılmaz Açıkgöz, Funda
    This research aimed to determine the effect of different drying methods on changes of drying behaviours and some quality parameters (dry matter, colour, water activity) of sorrel (Rumex acetosa L.) leaves. For this purpose, three drying methods were applied for sorrel namely, convective hot air drying using tunnel type dryer, open sun drying and shadow drying. Hot air drying experiments of plants were performed at three drying temperatures that were 40, 50, 60°C and at two air velocities that were adjusted as 1 and 2 m/s. Drying process took 3-17 h in hot air dryer depend on air temperature and air velocity, 50 h in open sun drying and 80 h in shadow drying. The colour parameters for the colour change of the sorrel leaves were quantified using the CIE L?, a?, b? system. The brightness (L?) values of dried sorrels were determined lower than those values of the fresh samples. Redness (a?) values of all dried samples were found higher than those values determined for fresh samples. Yellowness (b?) values decreased for all drying applications. This result shows that the yellow colour tone decreased in the all dried sorrel samples. Water activity (aw) value decreased for all dried samples.