Flow Properties of Low‐Pulp Concentrated Orange Juice: Serum Viscosity and Effect of Pulp Content

ABSTRACT 65° Brix serum samples from four concentrated orange juice (COJ) samples, between ‐19 and 30°C, were mildy shear‐thinning fluids with negligible yield stress. The power law model described well the flow data. For one sample, the Powell‐Eyring model also described the data. The activation energy of flow (E a ) for the samples was between 11.2–13.6 kcal/gmole. The power law parameters were determined for a 65°Brix sample as a function of pulp content (0–11%) between −19 and 30°C. At a fixed temperature, the apparent viscosity and the consistency index increased exponentially with pulp content. E a decreased with increase in pulp content and reached a constant value of about 10.2 kcal/gmole. Data on a high‐pulp (21.2%), 65° Brix, sample indicated the presence of yield stress, particularly at low temperatures. The Mizrahi‐Berk model predicted reliable values of the yield stress.