Thixotropy of orange concentrate and quince puree

Orange juice with pulp and pectins is thixotropic at soluble solids concentrations of 55 and 60 degrees Brix in the range of temperatures from 0 to 20C and sheer rate from 72 to 57.6 s(-1). Quince puree is thixotropic at soluble solids concentrations of 12.3 to 28 degrees Brix in the range of temperatures between 0 to 20C and shear rate from 7.2 to 57.6 s(-1). The thixotropic behaviour of orange juice and quince puree increases with increasing concentration and decreasing temperature and they can be described by the kinetic model proposed by Figoni and Shoemaker (1983): sigma = sigma(e) + (sigma(0i) - sigma(e)) exp (- kt) The thixotropic structure of orange juice was destroyed by applying a shear rate of 57.6 s(-1) for 5 min, and for quince puree for 10 min. Quince puree shows a greater thixotropic character than orange juice, because it has a higher content of fiber, pulp and pectins and also because it shows a microscopic structure consisting of long particles and heterogeneous fibers.