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

Authors


  • Presented at the 43rd Annual Meeting of the Institute of Food Technologists, New Orleans, LA, June 20–22, 1983.

  • The Conselho National de Desenvolvimento Cientifico e Tecnologico, Brazil, supported the senior author (AAV). Flavio C.P. Viegas, FRUTESP, Brazil and Dr. C.S. Chen, Dept. of Citrus, Florida, provided concentrated orange juice samples. Denise C.P. Jardim provided valuable technical help. A Fulbright Research Grant (to MAR) made planning of this work possible.

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 (Ea) 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. Ea 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.

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