RHEOLOGICAL BEHAVIOR AND PHYSICOCHEMICAL CHARACTERISTICS OF GOLDENBERRY (PHYSALIS PERUVIANA) JUICE AS AFFECTED BY ENZYMATIC TREATMENT ASHRAF M. SHAROBA 1 and MOHAMED FAWZY RAMADAN 2,3 1 Food Science Department Moshtohor Faculty of Agriculture Benha University Banha, Al Qalyubiyah, Egypt 2 Agricultural Chemistry Department Faculty of Agriculture Zagazig University 44511 Zagazig, Egypt Accepted for Publication November 3, 2009 ABSTRACT Goldenberry (Physalis peruviana) juice was prepared and enzymatically treated with two dosages (300 and 600 ppm) of Pectinex Ultra SP-L, then, the juice was concentrated to 30 and 40°Brix. Rheological properties of juices were studied at a wide range of temperatures (5 to 100C) and shear rate range from 0.3 to 100/s using Brookfield Digital Viscometer. The Herschel–Bulkley, Casson and Bingham rheological models were applied to describe the rheo- logical properties of different juices. These properties are key parameters required to solve food industry problems in numerous areas such as quality control, evaluation of consumer acceptance and texture. The results indicated that juice concentrates behave as non-Newtonian fluids (pseudoplastic) and have a definite yield stress. The Bingham and Casson, plastic viscosity, yield stress, consistency index and flow index decreased with increasing enzyme dosage and temperature. The effect of temperature on the viscosity described by means of an Arrhenius-type equation. The activation energy for viscous flow depends on the total soluble solids. Moreover, sensory evaluation for juices was carried out. In consideration of industrial utilization, detailed knowledge on the rheological and physicochemical characteristics of cape gooseberry juice is of major importance. 3 Corresponding author: M.F. Ramadan, Biochemistry Department, Faculty of Agriculture, Zagazig University, 44511 Zagazig, Egypt. TEL: 002-012-97824248 or 002-055-2320282; FAX: 002-055- 2287567 or 002-055-2345452; EMAIL: hassanienmohamed@yahoo.com Journal of Food Processing and Preservation 35 (2011) 201–219. DOI: 10.1111/j.1745-4549.2009.00471.x 201 © 2010 Wiley Periodicals, Inc.