EXAMINATION OF DRYING KINETICS FOR RED GRAPE POMACE

Abstract

In this study, the drying kinetics of red grape pomace processed as a by product during grape juice production of the Black Dimrit grape species was investigated as a function of different drying conditions. Drying process was carried out at temperatures of 40, 50, 60 ve 70 ⁰C and air velocities of 1.0, 1.4 and 1.8 m/s with an initial sample thickness  of  0.75 cm  on average until constant weight was attained. The kinetic behaviour of red grape pomace was considered as thin layer drying process. In order to evaluate the effective diffusivity, eleven models of diffusion including Newton, Page, Modified Page, Henderson & Pabis, Logaritmic, Two term, Exponential two term, Diffusion, Modified Henderson & Pabis, Verma and Midilli were then performed. The assessment of the performance was made by the comparison of the coefficients of determination, root of mean square error and reduced chi-square between the observed and predicted moisture ratios. Statistical analysis resulted in the compatibility of Midilli, Two term, Modified Henderson & Pabis and Verma models for the experimental conditions. The effective mositure diffusivity varied from 2.85x10-10 to 1.67x10-9 m2/s over the temperature and air velocity range. Temperature dependence of diffusivity was well reported for the air velocity of 1 m/s by an Arrhenius type relationship. The activation energy of red grape pomace was calculated as 26,26 kJ/mol.

Keywords

• Moisture diffusivity,moisture ratio,grape pomace,drying kinetics,thin layer

SİYAH ÜZÜM POSASININ KURUTMA KİNETİĞİNİN İNCELENMESİ

Abstract

Bu çalışmada siyah Dimrit cinsi üzümün üzüm suyuna işlendikten sonra arta kalan üzüm posasının farklı sıcaklık ve farklı hava akım hızlarında kurutma kinetiği araştırılmıştır. Kurutma işlemi, 40, 50, 60 ve 70 ⁰C sıcaklıklarda; 1.0,1.4 ve 1.8 m/s hava akım hızlarında, ortalama kalınlığı 0.75  cm olan, aynı ağırlıktaki üzüm posası örneklerinin tepsili kurutucuya yerleştirilmesiyle yapılmıştır.  Üzüm posasının kinetik davranışı ince tabaka kurutma şeklinde değerlendirilmiş ve bu davranışın Newton, Page, Modifiye Page, Henderson ve Pabis, Logaritmik, Çift terimli, Üstelçift, Difüzyon, Modifiye Henderson ve Pabis, Verma ve Midilli olmak üzere onbir farklı modele uyumluluğu incelenmiştir. Bu modellerin uyumluluk derecesi, her deneme için gözlenen ve tahmin edilen nem oranlarının hesaplanmasından sonra regresyon katsayıları, ortalama hata kareler toplamı ve kikare katsayıları karşılaştırılarak saptanmış ve istatistiksel analizler sonucunda Midilli, Çift terimli, Modifiye Henderson ve Pabis, ve Verma modellerinin üzüm posasının kinetik davranışına uyduğu gözlemlenmiştir. İncelenen kurutma sıcaklığı aralığında etkin difüzyon katsayısı (D_eff) 2.85x10^-10 ve 1.67x10^-9 m²/s aralığında değişmekte olup, Difüzyon katsayısının 1.0 m/s hava akış hızı için kurutma sıcaklığı ile ilişkisi  Arrhenius teorisi ile doğrulanmıştır. Üzüm posasının aktifleşme enerjisi 26,26 kJ olarak hesaplanmıştır.

Keywords

• Siyah üzüm posası,nem oranı,etkin difüzyon katsayısı,kurutma kinetiği,ince tabaka

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