Wild medlar fruit (Mespilus germanica) is rich in sugars and organic acids. In this study, wild medlar concentrates in four concentrations of 14, 28, 42 and 56 %(°Brix), preparation and physicochemical properties including pH, acidity, density and color, and rheological properties (at 20, 30, 40, 50, 60 and 70 ° C) were studied. The pH was in the range from 3.37 to 3.62 and acidity according to citric acid was in the range of 1.05 to 3.90 %. Density of concentrated sample (56 %) was 1277 kg/m³. Color of samples was analyzed using image processing technique and image parameters including L*, a* and b* for the sample with a concentration of 56% was 20.54, 1.69 and 1.36, respectively. With increasing in concentration, the sample was darker and L* index decreased. Concentrate used in all concentrations showed Newtonian behavior and viscosity increases with increasing concentration. With increasing in temperature from 20 to 70 ° C, the viscosity of the concentrate (56 %), decreased from 2517 to 223 mPa.s. The magnitude of activation energy was found in the range of 9.59–43.39 kJ/mol K.

Keywords: Activation energy, Density, Medlar, Rheology, Viscosity

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