DEHYDRATION OF FOODS DEHYDRATION OF FOODS SERIES EDITOR GUSTAVO V BARBOSA-CÂNOVAS, WASHINGTON STATE UNIVERSITY EDITORIAL BOARD JOSE M AGUILERA UNIVERSIDAD CATOLICA RICHARD W HAR TEL UNIVERSITY OF WISCONSIN JOZEF L KOKINI RUTGERS UNIVERSITY MICHAEL J McCARTHY UNIVERSITY OF CALIFORNIA MARTIN R OKOS PURDUE UNIVERSITY MICHA PELEG UNIVERSITY OF MASSACHUSETTS M ANANDHA RAO CORNELL UNIVERSITY JORGE WELTI-CHANES UNIVERSIDAD DE LAS AMERICAS DEHYDRATION OF FOODS GUST A VO V BARBOSA-CĂNOV AS WASHINGTON STATE UNIVERSITY HUMBERTO VEGA-MERCADO MERCK SHARP & DOHME OUIMICA DE PUERTO RICO SPRINGER-SCIENCE+BUSINESS MEDIA, B.V I(!)F International Thomson Publishing Cover design: Trudi Gershenov Copyright © 1996 by Springer Science+Business Media Oordrecht Originally published by Chapman & Hali in 1996 AII righls reserved No part of this book covered by the copyright hereon may be reproduced or used in any fann or by any means ·graphic, electronic, Of mechanical, including photocopying, recording, taping, Of information storage and retrieval systems-without the written permission of the publisher 23456789 10 XXX 01 00999897 Library of Congress Catalogil1g-in-Publication Data Gustavo V Dehydration of foods / Guslavo V Barbosa-Canovas and Humberto Vega-Mercado p cm Includes bibl:ographical references and index Barbosa-Cănovas, L Food··Drymg Vega·Mercado, Humberio TI Title TP371.5.B365 1996 95-44230 668' 0284 dc20 CIP ISBN 978-1-4419-4723-9 ISBN 978-1-4757-2456-1 (eBook) DOI 10.1007/978-1-4757-2456-1 WWW: http://www.thomson.com EMAIL: findit@kiosk.thomson.com thomson.com is the on-line portal for ihe products, services and resources available Iram International Thomson Publishing (ITPl.This Internet kiosk gives users immediate access to more than 34 ITP publishers and over 20,000 products Through thomson.com Internet users can search catalogs, examine subject-specific resource centers and subscribe la electronic discussion fists.You can purchase ITP producls from your local bookse!!er, or directly through thomson.com Ta aur families CONTENTS CHAPTER INTRODUCTION TO DEHYDRATION OF FOOD 1.0 Introduction 1.1 Theoretical Aspects 1.2 Dryers 1.3 Final Remarks 1.4 References CHAPTER FUNDAMENTALS OF AIR-WATER MIXTURES AND IDEAL DRYERS 2.0 Introduction 2.1 Fundamentals of Air-Water Mixtures 2.1.1 Ideal Gas Relationships 2.1.2 Moisture Content of Air 2.1.3 Psychrometric Chart 2.1.3.1 Dry Bulb Temperature 2.1.3.2 Relative Saturation or Relative Humidity 2.1.3.3 Percentage Saturation ar Percentage Absolute Humidity 2.1.3.4 Humid Volume ar Specific Volume 2.1.3.5 Humid Heat 2.1.3.6 Enthalpy of a Vapor-Gas Mixture 1 7 9 10 12 13 13 15 15 15 16 16 vii viii Con ten ts 2.2 2.3 2.4 2.5 2.1.3.7 Dew Point 2.1.4 The Saturated Condition 2.1.5 Adiabatic Saturation Temperature 2.1.6 Wet Bulb Temperature Mixing Two Streams of Air Reat and Mass Balances in Ideal Dryers 2.3.1 Continuous Dryer Without Recirculation 2.3.2 Continuous Dryer With Recirculation Concluding Remarks References CHAPTER PHYSICAL, CHEMICAL, AND MICROBIOLOGICAL CHARACTERISTICS OF DEHYDRATED FOODS 3.0 Introduction 3.1 Water Content of Foods 3.2 Determination of Water Content 3.3 Water Activity 3.3.1 Thermodynamic's of Water Activity 3.3.1.1 Raoult's Law 3.3.2 Theoretical and Empirical Models to Predict aw and Applications 3.3.2.1 Nonelectrolytic Solutions 3.3.2.2 Electrolytic Solutions 3.3.2.3 MulticOIuponent Mixtures 3.3.3 Measurement ofWater Activity 3.3.3.1 Vapor Pressure 3.3.3.2 Freezing Point Depression and Boiling Point Elevation 3.3.3.3 Osmotic Pressure 3.3.3.4 Dew Point Rygrometer 3.3.3.5 Thermocouple Psychrometer 3.3.3.6 Isopiestic Methods and Graphic Interpolation 3.3.3.7 Electric and Rair Rygrometers 3.3.3.8 Water Potential 3.4 Sorption Phenomena and Sorption Isotherms 3.4.1 Rysteresis Phenomenon 16 17 18 18 22 24 24 26 27 27 29 29 30 31 32 33 35 36 37 40 44 53 54 54 55 56 56 57 58 59 59 60 Con ten ts 3.4.2 Temperature Effect on Sorption 3.4.3 Brunauer-Emmett-Teller (BET) Equation 3.4.4 Heat of Sorption and Free Energy Change 3.4.5 Empirical and Theoretical Models of Sorption Isotherms 3.4.5.1 Henderson Model 3.4.5.2 Iglesias-Chirife Model 3.4.5.3 Guggenheim-Anderson-de Boer (GAB) Model 3.4.5.4 Smith Model 3.4.6 Sorption Isotherm and Water Activity Standards 3.5 Food Stability 3.5.1 Microbial Spoilage 3.5.2 Enzymatic Reactions 3.5.3 Nonenzymatic Reactions 3.5.4 Lipid Oxidation 3.5.5 Physical and Structural Phenomena 3.5.5.1 Glass Trasition Temperature 3.5.5.2 Techniques to Study Food Structure 3.5.6 Destruction of Nutrients, Aroma, and Flavor 3.6 Concluding Remarks 3.7 References ix 62 63 65 66 66 67 67 68 68 70 70 72 75 78 78 80 89 90 94 95 CHAPTER DEHYDRATION MECHANISMS 101 4.0 Introduction 4.1 The Drying Process 4.1.1 Constant Rate Period 4.1.2 Falling Rate Period 4.1.2.1 Diffusion Theory 4.1.2.2 Capillary Theory 4.1.2.3 Evaporation-Condensation Theory 4.1.2.4 The Luikov Theory 4.1.2.5 The Philip and De Vries Theory 4.1.2.6 The Berger and Pei Theory 4.1.2.7 The Whitaker Theory 4.1.2.8 Strongin-Borde Model 4.1.2.9 Regular Regime Theory 101 103 107 111 111 118 118 120 124 127 130 141 143 x Contents 4.2 4.3 4.4 4.5 The Drying Process and Water Activity Concluding Remarks Nomenclature References 148 150 151 153 CHAPTER CABINET AND BED DRYERS 157 5.0 lntroduction 5.1 Fundamentals 5.1.1 Components of a Dryer 5.2 Mass and Heat Balances 5.2.1 Batch Dryers 5.2.2 Through Circulation Batch Dryer 5.2.3 Continuous Dryers 5.3 Description of Dryers 5.3.1 Batch Dryers 5.3.1.1 Kiln Dryer 5.3.1.2 Cabinet or Tray Dryer 5.3.1.3 Rotary Dryer 5.3.2 Continuous Dryers 5.3.2.1 Tunnel Dryers 5.3.2.2 Belt ar Conveyar Dryers 5.3.3 Steam Dryers 5.3.4 Heat Pumps 5.4 Concluding Remarks 5.5 Nomenclature 5.6 References 157 158 159 160 160 163 168 170 170 170 171 172 173 175 176 181 182 183 183 184 CHAPTER SPRAY DRYING 185 6.0 lntroduction 6.1 Fundamentals 6.1.1 Pressure Nozzles 6.1.2 Rotary Atomizers 6.1.3 Pneumatic Atomizers-Two Fluids 6.2 lnteraction Between Droplets and Drying Air 6.3 Heat and Mass Balances 6.4 Drying of Droplets 6.4.1 Pure Liquid Droplets 185 187 187 191 195 197 199 200 201 316 Other Methods of Dehydration of Foods and Packaging Aspects considerations must be taken into account when selecting a packaging material Microbiological and Biological Considerations The prevention or reduction in microbial contamination is one of the functions of packages, as shown in Figure 9.20 The nature of packaging materials determines the protection offered by a package Glass containers possessing the appropriate type of dosure can be used in most packaging applications Metal containers made from aluminum and tin-free steel are used mostly for liquid products Paper and plastic materials are used as flexible packaging materials This application indudes the use of paper and plastics for the manufacture of wrapping, bags, envelopes, liners, and overwraps Table 9.3 summarizes the general properties of films used for dried food packaging The packaging requirements for aH dehydrated foods take into consideration two main causes of spoilage: moisture and oxygen Dried foods are fragile, sensitive to light, and subject to cross contamination and insect aUack (Sacharow and Griffin, 1970; Paine and Paine, 1992) Dried meat requires protection against moisture, mechanProcessing Quality Good Packaging Poor Protection Time Figure 9.20 Quality loss during processing and storage (Adapted from Karel, 1975.) 9.8 Packaging of Dehydrated Foods Table 9.3 317 Properties and applications of films on dried foods Permeability Name Heat Water Gases Volatiles Oils HighT LowT Seal Shrinkable Regenerated cellulose Waxed coated Copolymer coated Polyethylene (PE) Low density High density Irradiated Polypropylene Cast Oriented Rubber hydrochloride Pliofilm Fluoroethylene P P P P P P P P P P G G + + P P M G M M M M M M M M P M M G G G + + + + P P P P P P P P G G P G + + +/- V P V P G P M P P G V G + + + P = poor; M = moderate; V = variable; G =good, + = feasible; - not feasible Brennan et al., 1990; Paine and Paine, 1992 ical damage and oxygen Tin plate cans or heat-sealable laminates with aluminum foil are used in the packaging of dried meat products Some examples of laminates are polyester-polyethylene-aluminum foil-polyethylene and cellophane-polyethylene-aluminum foil-polyethylene Poultry products should be either vacuum packaged or inert gas flushed and hermetically sealed in cans or pouches Laminates for poultry products include cellophane-polyethylene- aluminum foil-polyethylene, cellophan- aluminum foil-polyamide, cellophan- aluminum foil-polyvinil chloride and rubber hydrochloride Dried egg whites are mainly protected from moisture absorption whereas whole eggs or yolks must also be protected from oxygen This type of product is mainly sold in bulk packages Vacuum or gas packed cans, canisters, sealed liners in carton boxes, or metal drums are used to package egg products 318 Other Methods of Dehydration of Foods and Packaging Aspects Dried milk is packaged in aluminum foillaminates Paper-polyethylene-foil-polyethylene is used in most dried milk applications Large units are packaged in cans, jars, ar in lined paperboard cartons Smoked or cured fish can be packaged in polyamide-polyethylene-polyester-polyethylene laminated films or high density polyethylene The major problem in the handling and storage of fruits and vegetables is insect attack Packaging should be made from a material that insects will not penetrate Wooden boxes, corrugated cartons, spiral-bound paper containers, and large tins are used for bulk packaging of fruits Retail packaging includes paperboard folded cartons laminated with a liner ar overwraps, coated cellophane bags, polyethylene, and polypropylene bags Fruit flakes or powders are packaged in glass bottles, foillaminated flexible pouches, or in friction lidded tins Dried legumes (i e., beans, peas, lentils) are packaged in simple plastic bags of cellophane or low-density polyethylene films The usual gas for flushing dehydrated foods is nitrogen, which is inert with a low fat and moisture solubility Carbon dioxide has also been used ta modify packaging atmospheres (Fierheller, 1991) 9.9 CONCLUDING REMARKS The main concepts for drying were used ta develop additi anal techniques that reduce energy consumption, such as solar solar dryers, ar improve product properties such as fluidized bed drying Nevertheless, the best drying technique will be determined based an the type of product, its composition, and its physical properties Packaging of dried products is the next most important step afier a drying operation The selection of an appropriate packaging material plays an important role in 9.10 References 319 the storage stability of the product Again, the type of product, its composition, and physical properties have to be considered when selecting a packaging component 9.10 REFERENCES Arsem, H B and Ma, Y H 1990 Simulation of combined microwave and radiant freeze dryer Drying Technol 8(5):993-1016 Bansal, N K and Garg, H P 1987 Solar crop drying In Advances in Drying, VoI 4, edited by A S Mujumdar Hemisphere Publishing, New York Brennan, J G., BuUers, J R, Cowell, N D., and Lilley, A E U 1990 Food Engineering Operations, Third edition Eisevier Applied Science, New York Charm, S E 1978 Dehydration In The Fundamentals of Food Engineering, Third edition AVI Publishing, Westport, CT De Leiris, J D 1986 Water activity and permeability In Food Packaging and Preservation Theory and practices, edited by M Mathlouthi Eisevier Applied Science, New York Eichner, K 1986 The influence of water content and water activity on chemical changes in foods of low moisture content under packaging aspects In Food Packaging and Preservation Theory and practices, edited by M Mathlouthi Eisevier Applied Science, New York Fierheller, M G 1991 Modified atmosphers packaging of micellaneous products In Modified Atmosphere Packaging of Food, edited by B Ooraikul and M E Stiles Ellis Harwood Limited, Chichester, UK Garg, H P 1987 Solar food drying In Advances in Solar Energy Technology Heating, Agricultural and Photovoltaic Applications of Solar Energy, VoI D Reidel Publishing, Dordrecht, Holland Geankoplis, C J 1983 Drying of Process Materials In Transport Processes and Unit Operations, Second edition Allyn and Bacon, Boston, MA Goswami, D Y., Lavania, A., Shahbazi, S and Masood, M 1991 Analysis of a geodesic dome solar fruit dryer Drying Technol 9(3):677-691 Harper, J M 1989 Food Extruders and Their Applications In Extrusion Cooking, edited by C Mercier, P Linko and J M Harper American Association of CereaI Chemists, Inc St Paul, MN Heldman, D R and Singh, R P 1981 Food dehydration In Food Process Engineering Second edition AVI Publishing, New York Imre, 1., Fâbri, 1., Gemes, 1., and Hecker, G 1990 Solar assisted dryer for seeds Drying Technol 8(2):343-349 Karel, M 1975 Protective packaging of foods In Principles of Food Science Port II Physical Principles of Food Preservation, edited by M Karel, O R Fennema, and D B Lund Marcel Dekker, New York Koszinowski, J and Piringer, O 1986 Influence of the packaging material and the nature of the packed goods on the 10ss of volatile organic compounds Permeation of aroma components In Food Packaging and Preservation 320 Other Methods of Dehydration of Foods and Packaging Aspects Theory and Practices, edited by M Mathlouthi Elsevier Applied Science, New York Masters, K 1993 Importance of proper design of the air distributor plate in a fluidized bed system AIChE Symp Series 297.89:118-126 Norton, B 1991 Solar Energy Thermal Technology Springer-Verlag, London, UK Paine, F A and Paine, H Y 1992 A Handbook of Food Packaging, Second edition Chapman & HaU, London, UK Rosse1l6, C., Berna, A., and Mulet, A 1990 Solar drying of fruits in a mediterranean climate Drying Technol 8(2):305-321 Sacharow, S and Griffin, R C 1970 Food Packaging AVI Publishing, Westport, CT Sochanski, J S., Goyette, J., Bose, T K., Akyel, C., and Bosisio, R 1990 Freeze dehydration of foamed milk by microwaves Drying Technol 8(5): 1017-1037 Spotts, M R and Waltrich, P F 1977 Vacuum dryers Chem Eng 84(2): 120-123 Stehli, D and Escher, F 1990 Design and continuous operation of a solar convection dryer with an auxiliary heating system Drying Technol 8(2): 241-260 Tsamparlis, M 1990 Solar drying for real applications Drying Technol 8(2): 261-285 Williams-Gardner, A 1971 Industrial Drying Leonard Hill Books, London, UK ApPENDICES This section provides general information about physical properties of water and air 321 322 Appendixes Appendix Properties of superheated steam Absolute Pressure (kPa) -Sat Temp (OC) 10-45.81 50-81.33 75-91.78 100-99.63 150-111.37 400-143.63 700-164.97 1000-179.91 1500-198.32 v h v h v h v h v h v h v h s v h v h Temperature (OC) ~ - 100 150 200 250 2500-223.99 v h v h 3000-233.90 v h 360 420 500 35.679 17.196 19.512 21.825 24.136 26.445 29.216 31.986 2687.5 2783.0 2879.5 2977.3 3076.5 3197.6 3320.9 3489.1 8.4479 8.6882 8.9038 9.1002 9.2813 9.4821 9.6682 9.8978 3.418 3.889 4.356 4.820 5.284 5.839 6.394 7.134 2682.5 2780.1 2877.7 2976.0 3075.5 3196.8 3320.4 3488.7 7.6947 7.9401 8.1580 8.3556 8.5373 8.7385 8.9249 9.1546 2.270 2.587 2.900 3.211 3.520 3.891 4.262 4.755 2679.4 2778.2 2876.5 2975.2 3074.9 3196.4 3320.0 3488.4 7.5009 7.7496 7.9690 8.1673 8.3493 8.5508 8.7374 8.9672 3.565 1.6958 1.9364 2.172 2.406 2.639 2.917 3.195 2676.2 2776.4 2875.3 2974.3 3074.3 3195.9 3319.6 3488.1 7.3614 7.6134 7.8343 8.0333 8.2158 8.4175 8.6042 8.8342 1.28 1.4443 1.6012 1.7570 1.9432 2.129 2.376 2772.6 2872.9 2972.7 3073.1 3195.0 3318.9 3487.6 7.4193 7.6433 7.8438 8.0720 8.2293 8.4163 8.6466 0.4708 0.5342 0.5951 0.6458 0.7257 0.7960 0.8893 2752.8 2860.5 2964.2 3066.8 3190.3 3315.3 3484.9 6.9299 7.1706 7.3789 7.5662 7.7712 7.9598 8.1913 0.2999 0.3363 0.3714 0.4126 0.4533 0.5070 2844.8 2953.6 3059.1 3184.7 3310.9 3481.7 6.8865 7.1053 7.2979 7.5063 7.6968 7.9299 0.2060 0.2327 0.2579 0.2873 0.3162 0.3541 3478.5 2827.9 2942.6 3051.2 3178.9 3306.5 6.6940 6.9247 7.1229 7.3349 7.5275 7.7622 0.1325 0.1519 0.1697 0.1899 0.2095 0.2352 2796.8 2923.3 6.7090 3037.6 3.1692 3299.1 3473.1 6.9179 7.1363 7.3323 7.5698 0.1114 0.1255 0.1411 0.1562 0.1757 3467.6 6.4546 2000-212.42 300 2902.5 3023.5 3159.3 3291.6 6.5453 6.7664 6.9917 7.1915 7.4317 0.0870 0.0989 0.1119 0.1241 0.1399 3462.1 2880.1 3008.8 3149.1 3284.0 6.4085 6.6438 6.8767 7.0803 7.3234 0.0706 0.0811 0.0923 0.1028 0.1162 2855.8 2993.5 3138.7 3276.3 3456.5 6.2872 6.5390 6.7801 6.9878 7.2338 vis the specific volume (m /kg), h is the enthalpy (kJ/kg), and s is the entropy (kJ/kg K) Appendixes Appendix Vapor Temp pressure 0.01 12 15 18 21 24 27 30 33 36 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 323 Properties of saturated steam Spec Volume (m /kg) (kPa) Liq Sat Vap 0.611 0.758 0.935 1.148 1.402 1.705 2.064 2.487 2.985 3.567 4.246 5.034 5.947 7.384 9.593 12.349 15.758 19.940 25.03 31.19 38.58 47.39 57.83 70.14 84.55 101.35 120.82 143.27 169.06 198.53 232.1 270.1 313.0 316.3 415.4 0.0010002 0.0010001 0.0010001 0.0010003 0.0010005 0.0010009 0.0010014 0.0010020 0.0010027 0.0010035 0.0010043 0.0010053 0.0010063 0.0010078 0.0010099 0.0010121 0.0010146 0.0010172 0.0010199 0.0010228 0.0010259 0.0010291 0.0010325 0.0010360 0.0010397 0.0010435 0.0010475 0.0010516 0.0010559 0.0010603 0.0010649 0.0010697 0.0010746 0.0010797 0.0010850 206.14 168.132 137.734 113.386 93.784 77.926 65.038 54.514 45.883 38.774 32.894 28.011 23.940 19.523 15.258 12.032 9.568 7.671 6.197 5.042 4.131 3.407 2.828 2.361 1.982 1.673 1.419 1.210 1.037 0.892 0.771 0.669 0.582 0.509 0.446 Enthalpy Entropy (kJ/kg) (kJ/kg K) 0.00 12.57 25.20 37.80 50.41 62.99 75.58 88.14 100.70 113.25 125.79 138.33 150.86 167.57 188.45 209.33 230.23 251.13 272.06 292.98 313.93 334.91 355.90 376.92 397.96 419.04 440.15 461.30 482.48 503.71 524.99 546.31 567.69 589.13 610.63 2501.4 2506.9 2512.4 2517.9 2523.4 2528.9 2534.4 2539.9 2545.4 2550.8 2556.3 2561.7 2567.1 2574.3 2583.2 2592.1 2600.9 2609.6 2618.3 2626.8 2635.3 2643.7 2651.9 2660.1 2668.1 2676.1 2683.8 2691.5 2699.0 2706.3 2713.5 2720.5 2727.3 2733.9 2740.3 Liq Sat Vap 0.0000 0.0457 0.0912 0.1362 0.1806 0.2245 0.2679 0.3109 0.3534 0.3954 0.4369 0.4781 0.5188 0.5725 0.6387 0.7038 0.7679 0.8312 0.8935 0.9549 1.0155 1.0753 1.1343 1.1925 1.2500 1.3069 1.3630 1.4185 1.4734 1.5276 1.5813 1.6344 1.6870 1.7391 1.7907 9.1562 9.0773 9.0003 8.9253 8.8524 8.7814 8.7123 8.6450 8.5794 8.5156 8.4533 8.3927 8.3336 8.2570 8.1648 8.0763 7.9913 7.9096 7.8310 7.7553 7.6824 7.6122 7.5445 7.4791 7.4159 7.3549 7.2958 7.2387 7.1833 7.1296 7.0775 7.0269 6.9777 6.9299 6.8833 324 Appendixes Vapor Temp pressure (OC) 150 155 160 165 170 175 180 190 200 225 250 275 300 (kPa) 475.8 543.1 617.8 700.5 791.7 892.0 1002.1 1254.4 1553.8 2548 3973 5942 8581 Spec Volume (m /kg) Liq 0.0010905 0.0010961 0.0011020 0.0011080 0.0011143 0.0011207 0.0011274 0.0011414 0.0011565 0.0011992 0.0012512 0.0013168 0.0010436 Sat Vap Enthalpy (kJ/kg) H, 0.393 632.20 0.347 653.84 0.307 675.55 697.34 0.273 719.21 0.243 0.217 741.17 763.22 0.194 0.157 807.62 0.127 852.45 0.078 966.78 0.050 1085.36 0.033 1210.07 0.022 1344.0 Entropy (kJ/kg K) Hv Liq Sat Vap 2746.5 2752.4 2758.1 2763.5 2768.7 2773.6 2778.2 2786.4 2793.2 2803.3 2801.5 2785.0 2749.0 1.8418 1.8925 1.9427 1.9925 2.0419 2.0909 2.1396 2.2359 2.3309 2.5639 2.7927 3.0208 3.2534 6.8379 6.7935 6.7502 6.7078 6.6663 6.6256 6.5857 6.5079 6.4323 6.2503 6.0730 5.8938 5.7045 Appendixes Appendix Physical properties of water at the saturation pressure Temp Density i3 Cp k Ci (0C) (kg/m3 ) (x 10-4 K-l) (kJlkg K) (W/m K) (x 10.6 m /s) o 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 999.9 1000.0 999.7 999.1 998.2 997.1 995.7 994.1 992.2 990.2 988.1 985.7 983.2 980.6 977.8 974.9 971.8 968.7 965.3 961.9 958.4 951.0 943.5 934.8 926.3 916.9 907.6 897.3 886.6 876.0 862.8 852.8 837.0 827.3 809.0 799.2 325 -0.7 0.95 2.1 3.0 3.9 4.6 5.3 5.8 6.3 7.0 7.5 8.0 8.5 9.1 9.7 10.3 10.8 11.5 12.1 12.8 13.5 14.3 15.2 16.2 17.2 18.6 4.226 4.206 4.195 4.187 4.182 4.178 4.176 4.175 4.175 4.176 4.178 4.179 4.181 4.184 4.187 4.190 4.194 4.198 4.202 4.206 4.211 4.224 4.232 4.250 4.257 4.270 4.285 4.396 4.396 4.480 4.501 4.560 4.605 4.690 4.731 4.857 0.558 0.568 0.577 0.587 0.597 0.606 0.615 0.624 0.633 0.640 0.647 0.652 0.658 0.663 0.668 0.671 0.673 0.676 0.678 0.680 0.682 0.684 0.685 0.686 0.684 0.684 0.680 0.679 0.673 0.670 0.665 0.655 0.652 0.637 0.634 0.618 0.131 0.135 0.137 0.141 0.143 0.146 0.149 0.150 0.151 0.155 0.157 0.158 0.159 0.161 0.163 0.164 0.165 0.166 0.167 0.168 0.169 0.170 0.171 0.172 0.172 0.173 0.173 0.172 0.172 0.171 0.170 0.168 0.167 0.164 0.162 0.160 ~ (X V 10-6 Pa s) (x 10-6 m /s) 1793.64 1534.74 1296.44 1135.61 993.41 880.64 792.38 719.81 658.03 605.07 555.06 509.95 471.65 435.42 404.03 376.58 352.06 328.52 308.91 292.24 277.53 254.97 235.36 211.82 201.04 185.35 171.62 162.29 152.00 145.14 139.25 131.41 124.54 119.64 113.76 109.83 1.79 1.54 1.30 1.15 1.01 0.88 0.81 0.73 0.66 0.61 0.56 0.52 0.48 0.44 0.42 0.37 0.36 0.34 0.33 0.31 0.29 0.27 0.24 0.23 0.21 0.20 0.19 0.18 0.17 0.17 0.16 0.15 0.15 0.15 0.14 0.14 i3 is the coefficient of volumetric thermal expansion, cp is the specific heat, k is the thermal conductivity, Ci is the thermal diffusivity, fL is the absolute viscosity, and v is the kinematic viscosity Appendixes 326 Appendix4 Physical properties of dry air at atmospheric pressure Temp Density Cp k 13 (0C) (kglm3 ) (x 10-3 K-l) (kJ/kg K) (W/m K) -20 O 10 20 30 40 50 60 70 80 90 100 120 140 160 180 200 250 1.365 1.252 1.206 1.164 1.127 1.092 1.057 1.025 0.996 0.968 0.942 0.916 0.870 0.827 0.789 0.755 0.723 0.653 3.97 3.65 3.53 3.41 3.30 3.20 3.10 3.00 2.91 2.83 2.76 2.69 2.55 2.43 2.31 2.20 2.11 1.89 1.005 1.011 1.010 1.012 1.013 1.014 1.016 1.017 1.018 1.019 1.021 1.022 1.025 1.027 1.030 1.032 1.035 1.043 0.0226 0.0237 0.0244 0.0251 0.0258 0.0265 0.0272 0.0279 0.0286 0.0293 0.0300 0.0307 0.0320 0.0333 0.0344 0.0357 0.0370 0.0400 (ỵ (X 10-6 m 2/s) 16.8 19.2 20.7 22.0 23.4 24.8 26.2 27.6 29.2 30.6 32.2 33.6 37.0 40.0 43.3 47.0 49.7 60.0 (X v IL 10-6 Pa s) (x 10-6 m 2/s) 16.279 17.456 17.848 18.240 18.682 19.123 19.515 19.907 20.398 20.790 21.231 21.673 22.555 23.340 24.124 24.909 25.693 27.557 12.0 13.9 14.7 15.7 16.6 17.6 18.6 19.4 20.7 21.5 22.8 23.6 25.9 28.2 30.6 33.0 35.5 42.2 13 is the coefficient of volumetric thermal expansion, cp is the specific heat, k is the thermal conductivity, (ỵ is the thermal diffusivity, IL is the absolute viscosity, and v is the kinematic viscosity Appendix Properties of ice Temperature (OC) -101 -73 -45.5 -23 -18 -12 -7 O Thermal conductivity (W/mK) Specific heat (kJlkg K) Density (kg/m3 ) 3.50 3.08 2.72 2.41 2.37 2.32 2.27 2.22 1.382 1.587 1.783 1.922 1.955 1.989 2.022 2.050 925.8 924.2 922.6 919.4 919.4 919.4 917.8 916.2 INDEX acids, 275 agglomeration, 211 air properties, 326 aroma, 3, 29 atomization, 186 belt dryers, 173, 176 Biot number, 143 boiling point elevation, 54 browning enzymatic, 71-74 non enzymatic (see Maillard) cabinet dryers, 171 heat balance, 24, 161, 163 mass balance 24, 163 caramelization, 75 chemi cal potential, 33 Clausius-Clapeyron, 62 collapse temperature, 246 Dalton's law, 13 dew point, 16 hygrometer, 56 dispersability, 211 diffusion coefficients, 112-116, 122-126,132, 136, 139, 142, 270 droplets air, 197 drying of, 200 pure liquid, 201 dissolved solids, 207 insoluble solids, 208 microstructure, 209 drum dryers, 299 drying rate, 299 vacuum, 300 dryers batch,5 bed,5 co-current, 169-170 components159 continuous, 4,168,173 direct, 4, 159, 293 ideal continuous, 24 ideal with recirculation, 26 indirect, 4, 159, 295 kiln, 170 steam, 181 327 328 Index drying, 101 data, 103 experiments, 105 rate, 104, 299 rate curve, 105 times, 162-165, 169, 240, 298 drying theories Berger and Pei, 127 capillary, 118 constant rate, 105, 107-111 diffusion, 111 evaporation-condensation, 118 falling rate, 105, 111 Fick's Law, 112-113 Knudsen diffusion, 114 Luikov's, 120 Philip and De Vries, 124 Regular Regime, 143 Strongin-Borde Model, 141 Whitaker, 130 effective diffusivity (see diffusion coefficients) electrolytes, 40 enthalpy, 16 enzymatic reactions, 3, 72, 230 equations BET,63 Bromley,42 Ferro-Chirife-Boquet, 47 Ferro-F ontan -Benmergui-Chirife, 45 Grover,37 GAB,67 Henderson, 66 Iglesias-Chirife, 67 Langmuir, 63 Lang-Steinberg, 48 Money and Born, 37 Norrish,38 Pitzer,40 Pitzer-Kim, 49 Raoult,35 Ross,44 Salwin-Slawson, 50 Smith,68 UNIFAC, 52 UNIQUAC, 52 extruders configuration, 304 energy input, 303 shear rate, 303 single screw, 302, 303 twin screw, 304 extrusion cooking, 302 fat, 31 food stability, 70 structure, 89, 245 flavors, 3, 29 fluidized bed batch drying, 307 continuous drying, 308 industrial equipment, 308-310 freeze dehydration, 6, 229, 231, 276 heat balance, 235, 243 mass balance, 237, 244-245 primary drying, 232-235 secondary drying, 232-235 variables, 232 freeze dryers atmospheric, 260 condensation, 247, 250 continuous, 253 defrosting, 247, 252 freezing step, 231, 233 industrial, 255 microwave heating, 256-258 pre-concentration, 247, 250 pre-freezing, 247 freezing point depression, 54 Froude number, 307 Gibb's free energy, 33 glass dynamic,85 trasition, 80 heat balances, 24, Index conduction, convection, pumps,182 radiation, transfer coefficient, 166, 298 humid heat,16 volume, 15 humidification, humidity molal,12 absolute, 12 percentage, 15 relative, 15 hurdle technology, 271 antimicrobials,274 fish,281 fruits,279 IMF,282 meat,281 osmotic dehydration (see osmotic) pH,273 vegetables, 280 hysteresis, 60 hygroscopicity, 102 hygrometers, 56, 58 ice properties, 326 ideal gas law, 10 insolation, 290, 292 isopiestic,57 Karl Fisher, 32 lipid oxidation, 78, 230 Lewis number, 120 Maillard reaction, 75, 230 microbial spoilage, 29, 70 microcrystalline cellulose, 57 microregions, 90, 247 microwaves, 256, 301 mixtures air streams, 22 electrolytes, 45, 49 nonelectrolytes, 47, 48 moisture (see water content) non-enzymatic reactions, 3, 75 nutrients, 3, 93 osmosis, 265 osmotic agents,272 dehydration, 6, 265 mass balance, 268 pressure, 55 solutions, 266, 271 equipment, 277 packaging dried egg, 317 dried fruits, 318 dried meat, 317 dried milk, 318 films,317 light, 314 mechanical damages, 313 microbial considerations, 316 permeability, 313 poultry,317 smoke fish, 318 partial pressure, 10, 36, 54 penetretion period permeability food plastics films physical properties, 29, 78 pneumatic atomizer,195-197 dryers,310-312 polyphenoloxidase, 74 pressure nozzles, 187-191 proteins, 31, 101 psychrometers wet bulb-dry bulb, 21 thermocouple, 56 psychrometric chart, 13 quality loss, 230 329 330 Index radiation, 290 Raoult's law, 35 reconstitution osmodried foods, 283 spray dried foods, 210 freeze dried foods, 231 retention aromas,90 microregions,90 nutrients, 93 volatiles, 246 rotary atomizers, 191-195 dryers,l72 co-current, 198 counter current, 198 heat balance, 200 mixed mode, 198 mass balance, 199 open loop, 185 temperature profiles, 198 state diagram, 86,87 steam superheated, 322 saturated, 323 sugar gain, 269 sulfites,274 sun drying, 276, 289 saturated air, 17 salt solutions, 58, 70 saturation adiabatic, 18 percentage (see humidity) shelf life, 229 shrinkage, 245 sinkability,211 solar dryers natural convection, 293, 295 forced convection, 296 wind ventilated, 296 solubility, 211 sorption equations (see equations) free energy change, 33 heat of, 65 isotherms, 3, 57, 59 standards, 57, 68 spray dried coffee,218 eggs, 219 enzymes,221 foam spray, 212-216 microorganisms, 221 milk,216 tea, 218 whey protein, 223 spray dryers close loop, 186 temperature dry bulb, 13 wet bulb, 18 log mean difference, 162 thermal conductivity, 133 thermal diffusivity, 122, 126, 134 through circulation dryers, 163 transition first order, 81-82 second order, 81-82 temperature,81 tray dryers, 161 tunnel dryers, 175 vacuum dryers, 297 drying time, 298 viscocity, 81 water activity, 3, 31, 32, 53, 148, 267 bound,30 content, 30, 103 determination, 31, 103 dynamics, 84 loss, 269, 302 phase diagram, 232 physical properties, 325 potential, 59 salt solutions, 57, 68 wettability, 211 ... implementation Gustavo V Barbosa-Canovas and Humberto Vega-Mercado -CHAPTER INTRODUCTION TO DEHYDRATION OF FOOD 1.0 INTRODUCTION It is not known when the preservation of foods by dehydration. . .DEHYDRATION OF FOODS DEHYDRATION OF FOODS SERIES EDITOR GUSTAVO V BARBOSA-CÂNOVAS, WASHINGTON STATE UNIVERSITY EDITORIAL BOARD... et al., Dehydration of Foods © Springer Science+Business Media Dordrecht 1996 Introduction ta Dehydration of Foods celery, potatoes, spinach, sweet corn, turnips, and soup mixtures Fruit dehydration