FOOD PROCESS ENGINEERING AND TECHNOLOGY Food Science and Technology International Series Series Editor Steve L. Taylor University of Nebraska – Lincoln, USA Advisory Board Ken Buckle The University of New South Wales, Australia Mary Ellen Camire University of Maine, USA Roger Clemens University of Southern California, USA Hildegarde Heymann University of California – Davis, USA Robert Hutkins University of Nebraska – Lincoln, USA Ron S. Jackson Quebec, Canada Huub Lelieveld Bilthoven, The Netherlands Daryl B. Lund University of Wisconsin, USA Connie Weaver Purdue University, USA Ron Wrolstad Oregon State University, USA A complete list of books in this series appears at the end of this volume Food Process Engineering and Technology Zeki Berk Professor (Emeritus) Department of Biotechnology and Food Engineering TECHNION Israel Institute of Technology Israel AMSTERDAM • BOSTON • HEIDELBERG • LONDON • NEW YORK • OXFORD PARIS • SAN DIEGO • SAN FRANCISCO • SINGAPORE • SYDNEY • TOKYO Academic Press is an imprint of Elsevier To my students Academic Press is an imprint of Elsevier 30 Corporate Drive, Suite 400, Burlington, MA 01803, USA 32 Jamestown Road, London NW1 7BY, UK 525 B Street, Suite 1900, San Diego, CA 92101-4495, USA 360 Park Avenue South, New York, NY 10010-1710, USA First edition 2009 Copyright © 2009 Elsevier Inc. 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(www.macmillansolutions.com) Printed and bound in the United States of America 09 10 11 12 13 10 9 8 7 6 5 4 3 2 1 Contents Introduction – Food is Life ..................................................................................... 1 1 Physical properties of food materials ............................................................. 7 1.1 Introduction ........................................................................................... 7 1.2 Mechanical properties ............................................................................ 8 1 . 2 . 1 D e fi nitions .................................................................................. 8 1.2.2 Rheological models ..................................................................... 9 1.3 Thermal properties ............................................................................... 10 1.4 Electrical properties .............................................................................. 11 1.5 Structure .............................................................................................. 11 1.6 Water activity ....................................................................................... 13 1.6.1 The importance of water in foods ............................................... 13 1.6.2 Water activity, defi nition and determination ............................... 14 1.6.3 Water activity: prediction ........................................................... 14 1.6.4 Water vapor sorption isotherms ................................................. 16 1.6.5 Water activity: effect on food quality and stability .......................19 1.7 Phase transition phenomena in foods .................................................... 19 1.7.1 The glassy state in foods ............................................................ 19 1.7.2 Glass transition temperature ...................................................... 20 2 Fluid fl ow ..................................................................................................... 27 2.1 Introduction ......................................................................................... 27 2.2 Elements of fl uid dynamics .................................................................... 27 2.2.1 Viscosity .................................................................................... 27 2.2.2 Fluid fl ow regimes ...................................................................... 28 2.2.3 Typical applications of Newtonian laminar fl ow .......................... 30 2.2.3a Laminar fl ow in a cylindrical channel (pipe or tube) ........ 30 2.2.3b Laminar fl uid fl ow on fl at surfaces and channels ............. 33 2.2.3c Laminar fl uid fl ow around immersed particles .................34 2.2.3d Fluid fl ow through porous media ....................................36 2.2.4 Turbulent fl uid fl ow ................................................................... 36 2.2.4a Turbulent Newtonian fl uid fl ow in a cylindrical channel (tube or pipe) ............................................................................ 37 2.2.4b Turbulent fl uid fl ow around immersed particles .............. 39 2.3 Flow properties of fl uids ........................................................................ 40 2.3.1 Types of fl uid fl ow behavior ........................................................ 40 2.3.2 Non-Newtonian fl uid fl ow in pipes ............................................. 41 vi Contents 2.4 Transportation of fl uids ........................................................................ 43 2.4.1 Energy relations, the Bernoulli Equation ..................................... 43 2.4.2 Pumps: Types and operation ...................................................... 46 2.4.3 Pump selection .......................................................................... 52 2.4.4 Ejectors ..................................................................................... 55 2.4.5 Piping ....................................................................................... 56 2.5 Flow of particulate solids (powder fl ow) ................................................56 2.5.1 Introduction .............................................................................. 56 2.5.2 Flow properties of particulate solids ........................................... 57 2.5.3 Fluidization ............................................................................... 62 2.5.4 Pneumatic transport .................................................................. 65 3 Heat and mass transfer, basic principles....................................................... 69 3.1 Introduction ......................................................................................... 69 3.2 Basic relations in transport phenomena ................................................. 69 3.2.1 Basic laws of transport .............................................................. 69 3.2.2 Mechanisms of heat and mass transfer ....................................... 70 3.3 Conductive heat and mass transfer ........................................................ 70 3.3.1 The Fourier and Fick laws ........................................................... 70 3.3.2 Integration of Fourier’s and Fick’s laws for steady-state conductive transport ............................................ 71 3.3.3 Thermal conductivity, thermal diffusivity and molecular diffusivity ............................................................ 73 3.3.4 Examples of steady-state conductive heat and mass transfer processes .............................................................. 76 3.4 Convective heat and mass transfer ......................................................... 81 3.4.1 Film (or surface) heat and mass transfer coeffi cients ................... 81 3.4.2 Empirical correlations for convection heat and mass transfer ..................................................................................... 84 3.4.3 Steady-state interphase mass transfer ......................................... 87 3.5 Unsteady state heat and mass transfer ................................................... 89 3.5.1 The 2 nd Fourier and Fick laws .................................................... 89 3.5.2 Solution of Fourier’s second law equation for an infi nite slab ............................................................................... 90 3.5.3 Transient conduction transfer in fi nite solids ............................... 92 3.5.4 Transient convective transfer in a semi-infi nite body .................... 94 3.5.5 Unsteady state convective transfer .............................................. 95 3.6 Heat transfer by radiation ..................................................................... 96 3.6.1 Interaction between matter and thermal radiation 96 3.6.2 Radiation heat exchange