FOOD ANALYSIS

FOOD ANALYSIS

THEORY AND PRACTICE

THIRD EDITION

YESHAJAHU POMERANZ CLIFTON E. MELOAN

~ CHAPMAN & HALL

New York· London

This edition published in 1994 by Chapman & Hall One Penn Plaza New York, NY 10119

Published in Great Britain by Chapman & Hall 2-6 Boundary Row London SEI 8HN

© 1994 Chapman & Hall, Inc. Softcover reprint of the hardcover 1st edition 1994

All rights reserved. No part of this book may be reprinted or reproduced or utilized in any form or by any eIectronic, mechanical or other means, now known or hereafter invented, incIuding photocopying and recording, or by an information storage or retrieval system, without permission in writing from the publishers.

Library of Congress Cataloging-in-Publication Data

Pomeranz, Y. (Yeshajahu), 1922-Food analysis: theory and practice I Yeshajahu Pomeranz, Clifton

E. Meloan. - 3rd ed. p. cm.

IncIudes bibliographical references and index. ISBN 978-1-4615-7000-4 ISBN 978-1-4615-6998-5 (eBook) DOI 10.1007/978-1-4615-6998-5 1. Food-Analysis. I. Meloan, Clifton E. 11. Title.

TX54 1. P64 1994 664/ .07-dc20

British Library Cataloguing in Publication Data available

94-12419 CIP

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Contents

Preface xiii

PART I GENERAL

Chapter 1 Searching the Literature 3 Searching a New Field 4 Modem Information Retrieval Systems 7 Bibliography 10

Chapter 2 Sampling 16 Sampies 19 Statistical Concepts 20 Manual Sampling 21 Continuous Sampling 21 Sampling Errors 23 Bibliography 24

Chapter 3 Preparation of Sampies 26 Grinding Dry Materials 27 Grinding Moist Materials 29 Enzymatic and Chemical Treatment 31 Enzyme Inactivation 32 Minimizing Lipid Changes 34 Controlling Oxidative and Microbial Attack 35 Bibliography 36

Chapter 4 Reporting Resuits and Reliability of Analyses 37 Reporting Results 38

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vi Contents

Reliability of Analyses 41 Bibliography 51

PART 11 METHODS AND INSTRUMENTATION

Chapter 5 Theory of Spectroscopy 55 Absorption of Radiation 56 Rotations 61 Vibrations 62 Electronic Transitions 64 Molecular Energy States 65 Problems 67

Chapter 6 Visible and Ultraviolet Spectroscopy 68 Instrument Components 73 Quantitative Analysis 80 Some Recent Applications 84 Problems 85 Bibliography 86

Chapter 7 Measurement of Color 87 Optical Aspects 88 CIE Color System 89 Simplified Tristimulus Color Systems 92 Abridged Methods 94 Methods Based on Pigment Content 96 Bibliography 97

Chapter 8 Fluorimetry 99 Instrument Components 101 Experimental Precautions 102 Quantitative Analysis 103 Some Recent Applications 105 Problems 106 Bibliography 107

Chapter 9 Infrared Spectroscopy 108 Instrumentation 109 Qualitative Analysis 122 Quantitative Analysis 122 Fourier Transform Infrared (PT-IR) Spectroscopy 126 Infrared Reflectance· Spectroscopy 129 Recent Applications 133 Problems 135 Bibliography 135

Contents vii

Chapter 10 Flame Photometry, Atomic Absorption, and Inductively Coupled Plasmas 137 Flame Photometry 138 Atomic Absorption Spectroscopy 143 Electrothermal Process (Carbon Rod Fumace) 147 Inductively Coupled Plasma (ICP) Emission

Spectroscopy 148 Detection Limits 155 Some Recent Applications 156 Bibliography 156

Chapter 11 X-Ray Methods 158 Production and Detection of X-Rays 159 X-Ray Diffraction 161 X-Ray Fluorescence 162 Nondispersive X-Ray Spectroscopy 165 Quantitative Analysis 170 Some Recent Applications 170 Bibliography 170

Chapter 12 Potentiometry 172 Reference Electrodes l74 Indicator Electrodes 178 Some Recent Applications 186 Problems 186 Bibliography 186

Chapter 13 Coulometry 188 Constant -Current Coulometry 189 Controlled-Potential Coulometry 192 U se of Coulometry with Gas Chromatography 192 Some Recent Applications 196 Problems 197 Bibliography 198

Chapter 14 Conductivity 199 Acid-Base Titrations 201 Oxidation-Reduction Systems 203 Conductivity Detectors for Chromatography 203 Some Recent Applications 205 Bibliography 206

Chapter 15 Electrophoresis 208 Zone Electrophoresis 208 Paper Electrophoresis 211

viii Contents

CaIculation of Mobility 213 Disc Gel Electrophoresis 218 Isoelectric Focusing 220 Preparative Electrophoresis 222 Some Recent Applications 225 Problems 226 Bibliography 227

Chapter 16 Capillary Zone Electrophoresis 228 Electroosmosis 230 Electrophoresis 230 UV Spectroscopy 236 Fluorescence 236 Conductivity and Amperometry 237 Mass Spectrometry 237 Radioisotopes 237 Some Recent Applications 241 Bibliography 242

Chapter 17 Mass Spectroscopy 243 Components of a Mass Spectrometer 243 Low-Voltage Mass Spectrometry 250 Quantitative Analysis 251 Combined Mass Spectrometry with Gas

Chromatography 256 Some Recent Applications 259 Problems 259 Bibliography 260

Chapter 18 Nuclear Magnetic Resonance 262 Interpretation of NMR Spectra 264 Superconducting Magnets 269 Some Recent Applications 269 Bibliography 270

Chapter 19 Radioactivity, Counting Techniques, and Radioimmunoassay 271 Radioactive Decay 273 Counting Devices 273 Isotopic Dilution 279 Neutron Activation Analysis 282 Food Irradiation 286 Radioimmunoassay 287 Some Recent Applications 288 Problems 288

Contents ix

Bibliography 289

Chapter 20 Column Chromatography, Size Exclusion, and Ion Exchange 290 Displacement and Partition Chromatography 290 Size-Exclusion Chromatography 299 Affinity Chromatography (lncluding Immobilized

Enzymes) 303 Ion-Exchange Chromatography 313 Selecting a Chromatographic Technique 319 Some Recent Applications 322 Bibliography 323

Chapter 21 High-Performance Liquid Chromatography and Ion Chromatography 324 Basic HPLC Equipment and Operation 325 Major Types of HPLC 337 Definition of Terms 340 Ion Chromatography 346 Some Recent Applications 348 Bibliography 350

Chapter 22 Paper and Thin-Layer Chromatography 352 Paper Chromatography 352 Thin-Layer Chromatography 357 Some Recent Applications 364 Bibliography 364

Chapter 23 Gas-Liquid Chromatography 366 Instrument Components 366 Height Equivalent to a Theoretical Plate 381 Identification of Compounds 385 Some Recent Applications 386 Bibliography 387

Chapter 24 Extraction 389 Liquid-Liquid Batch Extraction 389 Continuous Extraction 391 Discontinuous Countercurrent Extraction 393 Extraction P Values 395 Supercritical Fluid Extraction 399 Some Recent Applications 405 Problems 407 Bibliography 407

Chapter 25 Centrifugation 409

x Contents

Basic Relationships 409 Equipment 411 Ultracentrifugation 412 Centrifugal Analysis 417 Bibliography 418

Chapter 26 Densimetry 419 Definitions and Basic Relationships 420 Measurement of the Density of Liquids 421 Measurement of the Density of Solids 427 Bibliography 429

Chapter 27 Refractometry and Polarimetry 430 Refractometry 430 Polarimetry 438 Some Recent Applications 446 Problems 447 Bibliography 448

Chapter 28 Rheology 449 Rheological Parameters 449 Rheological Methods and Instruments 455 Measuring the Components of Food Texture 460 Applications 466 Bibliography 483

Chapter 29 Serology, Immunochemistry, and Immunoelectrophoresis 488 Basic Considerations and Definitions 488 Immunochemical Methods 491 Applications 498 Bibliography 502

Chapter 30 Enzymatic Methods 506 General Considerations and Uses 506 Determination of Substrates 509 Determination of Enzymatic Activity 518 Other Applications of Enzymes 522 Automated Methods 528 Bibliography 529

Chapter 31 Analytical Microbiology 532 Principles of Microbiological Assays 533 Microbiological Methods 535 Determining Reliability of Microbial Assays 538

Contents xi

Assays of Vitamins, Amino Acids, and Nucleic Acids and Their Derivatives 539

Assessing the Nutritional Value of Proteins 542 Assay of Antibiotics, Heavy Metals, and

Miscellaneous 549 Automation of Microbiological Assays 550 Bibliography 551

Chapter 32 Thermal Analysis of Foods 555 Principles 555 DSC Investigations 557 Bibliography 562

PART III GENERAL APPLICATIONS AND CHEMICAL COMPOSITION

Chapter 33 General Remarks 567 Theoretical and Applied Investigations 567 Online Analyses 572 Bibliography 574

Chapter 34 Determination of Moisture 575 Moisture Contents of Foods 576 Basic Considerations 576 Drying Methods 578 Air-Oven Methods 581 Distillation Methods 584 Chemical Methods 588 Physical Methods 593 Bibliography 600

Chapter 35 Ash and Minerals 602 Ash and Mineral Contents 602 Determination of Ash 603 Ashing Procedures 605 Elemental Analysis 614 Bibliography 621

Chapter 36 Carbohydrates 625 Composition and Occurrence 625 Determination of Water-Soluble

and Water-Insoluble Solids 627 Qualitative Detection of Carbohydrates 630 Determination of Mono- and Oligosaccharides 633 Determination of Hexosamines 647

xii Contents

Determination of Nutrient Polysaccharides 649 Determination of Structural Polysaccharides 657 Bibliography 669

Chapter 37 Lipids 678 Nomenclature and Occurrence 678 Sources of Information 683 General Procedures for Extracting Lipids 684 Extraction of Lipids in Selected Foods 689 Indirect Methods of Lipid Determination 692 Fractionation of Extracted Lipids 695 Physical Assay Methods 699 Chemical Assay Methods 707 Automated Lipid Analyses 713 Fat Stability and Rancidity 715 Bibliography 724

Chapter 38 Nitrogenous Compounds 733 Proteins 733 Nonprotein Nitrogenous Substances 749 Bibliography 753

Chapter 39 Objective versus Sensory Evaluation of Foods 758 Color 759 Taste and Odor 759 Overall Evaluation 762 Bibliography 764

Index 766

Preface

The first edition of Food Analysis: Theory and Practice was published in 1971 and was revised in 1978. The second edition was published in 1987, and in 1993 we found it necessary to prepare a third edition to reflect and cover the most recent advances in the field of food analysis.

A complete revision of a book is an arduous and anguished task. The following are challenges that we wanted to address in this revision: to update the material without eliminating classic and time-preserved and honored methods used by the food analyst; to broaden and deepen the coverage and scope without increasing the size of the book; and to produce a textbook (for senior undergraduate and graduate students) with regard to objectives, scope, and outlay while providing a reference and resource for the worker and researcher in the field of food analysis. To meet those challenges we added much new material and took out practically the same amount of "rel-atively outdated" material. Every chapter has been extensively updated and revised; many of the pictures in the previous editions were deleted and, whenever available and appropriate, were replaced by diagrams or flow sheets. In Part I we have expanded the seetions on sampling, preparation of sam-pIes, reporting results, and reliability of analyses. We have deleted, in Part 11, the chapter on polarography and added chapters on capillary zone elec-trophoresis and thermal analysis, and expanded the chapter on extraction by adding supercritical fluid techniques. Finally, in Part III we have included discussions on rapid tests and online process monitoring.

Ovcr thc years we have reccivcd many constructivc criticisms and sug-

xiii

xiv Preface

gestions, for which we are most thankful. We believe the present edition is in every important aspect a new book and that it will be as useful to the student, teacher, and researeher as the previous ones.

Y. Pomeranz C. E. Meloan