MATHEMATICAL MODELLING OF VACUUM DRYING CHARACTERISTICS FOR MAHLAB PUREE

Öz

Mahlab has bitter taste, strong aroma and high anthocyanin content and it might be used for producing different fruit snack bars which the drying step is very important for the manufacture. In this article, mathematical modelling of the drying of mahlab puree in vacuum dryer at different temperatures is investigated. Thin-layer drying processes were performed using a temperature controlled vacuum drying oven at 50, 60 and 70°C under 50 mbar absolute pressure and the weight data were collected at certain time intervals. The drying curves were fitted to eight different drying models. In this curve fitting, nonlinear regression analysis was used to evaluate the parameters of the selected models. Additionally, effective diffusion coefficient was obtained from diffusion model of Fick and the activation energy was determined using Arrhenius equation. According to statistical analysis results for three drying temperatures, Midilli et al. drying model has shown a better fit to the experimental drying data of mahlab puree. The effective diffusion coefficients were found as 1.71x10-10, 6.21x10-10 and 8.64x10-10 m2/s at 50, 60, and 70oC, respectively. The activation energy that expresses the temperature dependency of the diffusion coefficients was calculated as 75.2 kJ/mol.

Anahtar Kelimeler

• Mathematical modelling,mahlab,vacuum drying,activation energy,mass ratio

MAHLEP PÜRESİNİN VAKUM KURUTMA KARAKTERİSTİKLERİNİN MATEMATİKSEL MODELLENMESİ

Öz

Mahlep, acımsı tada, güçlü aromaya ve yüksek antosiyanin içeriğine sahiptir ve bu özellikleriyle, üretim aşamasında kurutmanın önem kazandığı aperatif tüketime yönelik meyve barlarının üretimi için kullanılabilmektedir. Bu çalışmada, farklı sıcaklıklarda gerçekleştirilen mahlep püresinin vakumlu kurutucudaki kurutma işleminin matematiksel modellenmesi incelenmiştir. İnce tabaka kurutma işlemi, sıcaklık kontrollü vakumlu kurutma fırını kullanılarak 50 mbar basınç altında, 50, 60 ve 70°C farklı kurutma sıcaklıklarında gerçekleştirilmiş olup, kütle kaybı belirli aralıklarla ölçülmüştür. Kurutma eğrileri sekiz farklı kurutma modeline göre elde edilmiştir. Matematiksel modellemede, seçilen modellerin parametrelerini değerlendirmek için doğrusal olmayan regresyon analizi kullanılmıştır. Ayrıca Fick'in difüzyon modelinden etkin difüzyon katsayısı elde edilmiş ve aktivasyon enerjisi Arrhenius denklemi kullanılarak belirlenmiştir. Üç farklı kurutma sıcaklığı için istatistiksel analiz sonuçlarına göre Midilli ve ark. kurutma modeli, mahlab püresinin deneysel kurutma verilerine en iyi uyum gösteren model olmuştur. Kurutma sıcaklıkları olan 50, 60 ve 70oC için etkin difüzyon katsayısı sırasıyla 1.71x10-10, 6.21x10-10 ve 8.64x10-10 m2/s olarak bulunmuştur. Difüzyon katsayılarının sıcaklığa olan bağlılığını ifade eden aktivasyon enerjisi ise 75.2 kJ/mol olarak hesaplanmıştır.

Anahtar Kelimeler

• Matematiksel modelleme,mahlep,vakum kurutma,aktivasyon enerjisi,kütle oranı

Kaynakça

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