HEAT AND MASS TRANSFER, vol.56, no.8, pp.2503-2513, 2020 (SCI-Expanded)
Drying characteristics, color, pH, degrees Brix, energy, thermal image and micrograph parameters of the whole, half cut and puree black chokeberry samples were analyzed. Experiments were carried out with a freeze dryer at a temperature of -50 degrees C. The results indicated that drying time was being highest with whole samples, whereas the lowest with puree samples. According to the nine different thin-layer drying models, the Midilli et al. model was the best model to explain the thin-layer freeze drying of black chokeberry. The slope of the puree samples was found steeper in the drying rate. In terms of colorimetric parameters of chroma (C) and total color difference ( increment E) has similarly affected by drying methods (P < 0.05). By comparison of pH values, no significant differences found between freeze dried samples (P < 0.05). However, the maximum change of the degrees Brix value was determined by puree dried samples. In addition, higher energy efficiency was calculated by puree drying. Although the micrographs of half cut and puree dried samples were not distinguishable, the temperature distribution of whole samples was more uniform. As a conclusion, alternative drying methods could be useful in commercial uses such as puree with many advantages.