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FLOW BEHAVIOR OF CLARIFIED PEAR AND APPLE JUICES AT SUBZERO TEMPERATURES
Author(s) -
FALGUERA VÍCTOR,
VICENTE MANEL,
GARVÍN ALFONSO,
IBARZ ALBERT
Publication year - 2013
Publication title -
journal of food processing and preservation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.511
H-Index - 48
eISSN - 1745-4549
pISSN - 0145-8892
DOI - 10.1111/j.1745-4549.2011.00630.x
Subject(s) - rheometer , rheology , chemistry , viscosity , thermodynamics , food science , physics
The flow behavior of clarified pear and apple juices has been studied at subzero temperatures (between −1 and −18C), using a concentric cylinder rheometer. The results indicated that these clarified and depectinated juices behave as Newtonian fluids. As the soluble solids content increases, rheological measurements could be performed at lower temperatures because of the freezing point falling. The variation of viscosity with temperature could be quantified using an Arrhenius‐type equation, and its change with soluble solids content was described by an empirical exponential expression. Flow activation energy was evaluated in a range of 41–91 kJ/mol for pear juice and of 39–88 kJ/mol for apple juice, for concentrations between 50 and 70 Brix. PRACTICAL APPLICATIONS The manufacturing of fluid products includes numerous processing operations from the raw material to the final product. It is necessary to know how viscosity changes with temperature and soluble solids content. These parameters will have essential importance in the handling, calculation and design of all the unit operations involved in processing, especially those based on heat transfer and momentum transfer. In order to avoid the loss of organoleptic and nutritional properties caused by thermal concentration, alternative technologies such as cryoconcentration are being developed. In this way, rheological properties of food fluids just above their freezing point must be investigated to ensure an optimum design of the new cryoconcentration equipment.