Rheological properties of cloudy and clarified juice of Malus floribunda as a function of concentration and temperature

The rheological behaviour of cloudy and clarified juice of Malus floribunda was studied as a function of solid concentration, in a range of 45-70 Brix , at nine temperatures (5-50C). Cloudy and clarified juices are slightly th ixotropic at 65-70 Brix and .5-10C. At lower concentrations and higher temp eratures the thixotropy is low and can easily be eliminated by shearing. Th e power law model was applied to fit the pseudoplastic behaviour depending on the concentration level. Cloudy juice has pseudoplastic behaviour for co ncentrations higher than 45 Brix. Clarified juice is pseudoplastic at 65 Br ix for temperatures lower than 25C and Newtonian at higher temperatures and for solid concentrations lower than 60 Brix. The activation energy for flo w evaluated with the Arrhenius-Guzman equation, increases with solid concen tration and ranged from 10.8 to 3.45 kcal gmol(-1) for cloudy juice and 15. 3 to 7.9 kcal gmol(-1) for clarified juice. A nonlinear correlation account ing for temperature and concentration effects on the consistency coefficien t was identified.