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`BLACKIE ACADEMIC 61 PROFESSIONAL
`An Imprint oi Chapman & Hall
`
`EA PArAoc'es” inring, Inc.
`Exhibit 1019
`
`p. E1
`
`

`
`Aseptic Processing and Packaging of Particulate Foods
`
`p. E2
`
`

`
`Aseptic Processing and Packaging
`of Particulate Foods
`
`Edited by
`
`EDWARD M.A. WILLHOFT
`Principal
`Epsom Technical Group Services
`Epsom
`Surrey
`
`m
`
`BLACKIE ACADEMIC & PROFESSIONAl
`
`An Imprint of Chapman & Hall
`London · Glasgow · New York · Tokyo · Melbourne · Madras
`
`p. E3
`
`

`
`Published by
`Blackie Academic & Professional, an imprint of Chapman & Hall,
`Wester Cleddens Road, Bishop briggs, Glasgow G64 2NZ
`
`Chapman & Hall, 2--<i Boundary Row, London SEl 8HN, UK
`
`Blackie Academic & Professional, Wester Cleddens Road, Bishop briggs,
`Glasgow G64 2NZ, UK
`
`Chapman& Hall Inc., 29 West 35th Street, NewYorkNY 10001, USA
`
`Chapman & Hall Japan, Thomson Publishing Japan, Hirakawacho Nemoto
`Building, 6F, 1-7-11 Hirakawa-cho, Chiyoda-ku, Tokyo 102, Japan
`
`DA Book (Aust.) Pty Ltd., 648 Whitehorse Road, Mitcham 3132, Victoria,
`Australia
`
`Chapman & Hall India, R. Seshadri, 32 Second Main Road, CIT East, Madras
`600 035, India
`
`First edition 1993
`
`©Chapman & Hall, 1993
`
`Typeset in 10/12 pt Times New Roman by DSC Corporatiqn, Cornwall, England
`Printed in Great Britain by Hartnolls Ltd, Bodrnin, Cornwall
`
`ISBN 0 7514 0010 6
`
`Apart from any fair dealing for the purposes of research or private study, or
`criticism or review, as permitted under the UK Copyright Designs and Patents
`Act, 1988, this publication may not be reprodnced, stored, or transmitted, in any
`fonn or by any means, without the prior permission in writing of the publishers,
`or in the case of reprographic reproduction only in accordance with the terms of
`the licences issued by the Copyright Licensing Agency in the UK, or in
`accordance with the terms oflicences issued by the appropriate Reproduction
`Rights Organization outside the UK. Enquiries concerning reproduction outside
`the terms stated here should be sent to the publishers at the Glasgow address
`printed on this page.
`The publisher makes no representation, express or implied, with regard to the
`accuracy of the information contained in this book and cannot accept any legal
`responsibility or liability for any errors or omissions that may be made.
`
`A catalogue record for this book is available from the British Library
`
`p. E4
`
`

`
`Preface
`
`Publications in food technology proliferate; however, noticeable by its absence
`of coverage is the subject of processing and packaging of particulates in foods.
`Recent years have seen significant advances which will almost certainly result
`in substitution of existing and conventional retorting. In addition, when com(cid:173)
`bined with high temperature/short time (HTST) processing, we can expect
`substantial further growth, reflecting quality and convenience advantages over
`products processed from yesterday's technologies. The anticipated growth in
`particulates is driven by both materials and packaging advances and only
`requires modest marketing of the organoleptic advantages to establish their place
`on menu options.
`The directions taken in packaging developments, especially those interfacing
`with the latest and established methods of processing, are increasingly influ(cid:173)
`enced by the need to design packaging on a cradle-to-grave basis. Time was when
`multi-laminated films on board satisfied the total needs of consumers of aseptic
`products. The problems of recycling combustible, i.e. energy generating mate(cid:173)
`rials laminated with aluminium foil, are becoming sensitive issues in a world
`preoccupied with recycling, and are creating openings for alternative and envi(cid:173)
`ronmentally friendly material combinations.
`This book brings together advanced technologies in the field, to provide
`information for professionals with interests in aseptic processing on how to go
`about selecting a system appropriate to their commercial needs and constraints.
`It covers markets for products, processing and materials in the USA, Europe and
`Japan. It avoids or minimizes duplication with works in similar fields and
`emphasizes the technologies behind processing plant, especially those for han(cid:173)
`dling particulates. Integration of processing with packaging is discussed, includ(cid:173)
`ing the latest proven technologies based on microwave cooking, resistive heating
`and neutral aseptic handling of packaging. The book also includes an apprecia(cid:173)
`tion of packaging requirements, microbiological aspects applied to aseptic pro(cid:173)
`cessing, and critical control point hazard analysis (HACCP). The efficacy of
`HTST is highlighted in terms of heightened sensory quality and improved
`sterility.
`The Dole process is included because it has stood the test of time and was an
`early adjunct to HTST. It is capable of being developed for particulates and,
`perhaps as importantly, with the emphasis on recycling tin-plate or its equivalent,
`is readily recyclable without unduly disturbing the environment.
`This book is recommended reading for food and packaging technologists,
`production and process engineers, quality control management, material conver-
`
`p. E5
`
`

`
`vi
`
`ASEPTIC PROCESSING AND PACKAGING OF PARTICULATE FOODS
`
`tors, microbiologists and, last but not least, market research and marketing
`persormel of food manufacturing companies and trading operations.
`Finally, I should like to thank each one of the authors for the time, patience and
`commitment that they put into presenting their contributions, and especially
`Margaret for her unstinting support throughout.
`
`E. M.A. W.
`
`p. E6
`
`

`
`Contents
`
`1 Aseptic processing and packaging of food particulates
`N.BUCHNER
`
`Introduction and basic principles
`1.1
`1.1.1 Advantages over in-container sterilized foods
`1.1.2 Advantages over pasteurized chilled foods
`1.1.3 Advantages over 'cleanfill'
`1.1.4 Advantages over frozen products
`1.1.5 Advantages over dried products
`1.2 Developments in aseptic processing and filling
`1.3 Aseptic processing-methodology
`1.3.1 Sterilization of products
`1.3.2 Sterilization of packaging materials and packages
`1.4 Maintaining sterility in aseptic machines
`1.4.1 Sterilization of aseptic installations
`1.5 Filling
`1.5.1 Filling principles for liquids
`1.5.2 Filling principles for particulate mixtures
`1.6 Closing packs
`1.6.1 Heat-sealing
`1.6.2 Types of packs
`1.7 Typical machines for aseptic packaging of particulate foods
`I. 7 .I Form/fill/seal machine for pouches
`I. 7.2 Thermoform!filllseal machine for cups and trays
`1.7.3 Filling and closing line for bottles and jars
`1.7.4 Fonn/fill/seal machine for cartons from sleeves
`1.7.5 Form/fill/seal machine for cartons from the reel
`1.8 Conclusion
`References
`
`2 The market for aseptic products, processing and packaging systems
`E. M.A. WILLHOFT
`
`Introduction
`2.1
`2:2 The west Europeao market
`2.3 The US market
`2.3.1 Alfa Laval
`2.3.2 APV Crepaco
`2.3.3 ASTEC
`2.3.4 Cheny Burrell
`2.3.5 DASI (TCI-Superior)
`2.3.6 FranRica
`2.3.7 Terlet
`2.4 Packaging systems
`2.5 Future requirements and trends
`References
`
`3 Packaging materials-their properties and criteria for selection
`B. I. TURTLE
`
`Introduction·
`3.1
`3.2 Pack selection
`
`1
`
`I
`I
`2
`2
`3
`3
`3
`4
`4
`9
`10
`II
`12
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`27
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`30
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`32
`33
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`35
`37
`38
`
`39
`
`39
`40
`
`p. E7
`
`

`
`vm
`
`ASEPTIC PROCESSING AND PACKAGING OF PARTICULATE FOODS
`
`3.'\ Pack criteria
`3.3.1 Product containment
`3.3.2 Physical protection
`3.3.3 Food safety
`3.3.4 Shelf-life
`3.3.5 Communication ofiuformation
`3.3.6 Sales appeal
`3.3.7 Cost-effectiveness
`3.4 Packaging materials compared
`3.4.1 Metal containers
`3.4.2 Rigid plastics containers
`3.4.3 High-barrier plastics containers
`3.4.4 The special needs of plastics aseptic packaging
`3.4.5 Glass containers
`3.4.6 Flexible packaging materials
`3.5 Heat-sealing
`3.5.1 Testing for leaking packs
`3.6 Shelf-life
`3. 7 Aseptic packs
`3.8 The cost of packaging
`3.8.1 Cost-effective packaging
`3.9 Food packaging legislation
`3.9.1 EC legislation
`3.10 Packaging and the environment
`3.10.1 Litter
`3.10.2 Disposal of waste
`3.10.3 Use of natural resources
`3.10.4 Recycling
`
`4 Ohmic heating
`P. J. SKUDDER
`
`Introduction
`4.1
`4.1.1 Consumer products
`4.1.2 Aseptic processing
`4.1.3 Ohmic heating
`4.2 Principles of aseptic processing
`4.2.1 Thermal sterilisation-the options
`4.2.2 Principles of thermal sterilisation
`4.3 Processing options
`4.3.1 Indirect plate heat exchangers
`4.3.2 Indirect tubular heat exchangers
`4.3.3 Direct steam injection and steam infusion
`4. 3.4 Scraped surface heat exchangers
`4.4 Ohmic heating
`4.2.1 Principles of ohmic heating
`4.2.2 Advantages of ohmic heating
`4.5 Design of the ohmic heater
`4.5.1 Mechanical design
`4.5.2 Temperature control
`4.6 Aseptic processing using the ohmic heater
`4.6.1 Processing system
`4.6.2 Plant sterilisation
`4.6.3 Product processing
`4.6.4 Alternative cooling
`4.6.5 Cleaning
`4.6.6 Throughputs
`4.7 Product quality
`
`40
`41
`41
`41
`41
`41
`42
`42
`42
`43
`47
`55
`57
`59
`61
`64
`66
`66
`67
`68
`68
`69
`69
`70
`70
`71
`71
`72
`
`74
`
`74
`74
`74
`74
`75
`75
`75
`76
`76
`76
`76
`77
`77
`77
`78
`78
`78
`78
`79
`79
`80
`·so
`81
`81
`82
`82
`
`p. E8
`
`

`
`CONTENTS
`
`4. 7.1 Microbial process validation
`4. 7.2 Cooking value
`4.8 Products
`4.9 Commercial installations
`4.9.1 Research systems
`4.10 Conclusions
`Acknowledgements
`Reference
`
`5 The ERCA neutral aseptic system
`C. J. ROBINSON
`
`5 .I
`Introduction
`5.1.1 Sterility without chemicals
`5.2 Basic construction of the ERCA machine
`5.2.1 Preparation of materials
`5.2.2 Machine operation
`5.3 Extension of basic machine to NAS® specification
`5.4 NAS® materials
`5.4.1 Plastic base web
`5.4.2 Lidding film
`5.4.3 Verification of sterility ofNAS® co-extruded materials
`5.5 NAS® machines
`5.5.1 General description
`5.5.2 Plastic fihn introduction
`5.5.3 Lidding film introduction
`5.5.4 Sterile tunnel
`5.5.5 Fom1ing
`5.5.6 Filler
`5.6 Productpreparation
`5.6.1 Production of superheated water
`5.6.2 Blending
`5.6.3 UHT process
`5.6.4 Cooling
`5.6.5 Cleaning (CIP)
`5.6.6 Process control
`5.7 Future developments
`
`6 Microwave processing and package integration
`R. E. COLES
`
`6.1 The technology revolution
`6.2 Consumer influence
`6.3 Packaging needs
`6.4 Packaging materials for microwaveable foods
`6.4.1 Microwave-passive materials
`6.4.2 Microwave-active and microwave-reflective materials
`6.4.3 Package geometry for even heating
`6.5 Microwave heating principles
`6.5.1 The significance of the wave
`6.5.2 Microwave interactions with materials
`6.5.3 Microwave heating factors
`6.6 Extending product shelf-life
`6.6.1 HTSTprocessing
`6.6.2 Microbial and sensory decay
`6.6.3 Pasteurization versus sterilization
`6.6.4 Temperature measurement
`6.6.5 Microwave sterilization
`
`ix
`
`82
`84
`87
`87
`87
`89
`89
`89
`
`90
`
`90
`90
`92
`92
`93
`. 97
`97
`98
`99
`99
`100
`100
`100
`103
`104
`105
`106
`108
`109
`109
`109
`110
`110
`110
`110
`
`112
`
`112
`113
`114
`115
`115
`118
`120
`124
`125
`125
`126
`131
`131
`134
`135
`137
`138
`
`p. E9
`
`

`
`X
`
`ASEPTIC PROCESSING AND PACKAGING OF PARTICULATE FOODS
`
`6.7 Types of microwave processing systems
`6. 7.1 The frequency debate
`6. 7.2 Penetration depths
`6. 7.3 Operating efficiencies
`6. 7.4 Relative operating costs for industrial microwave processing
`6.7.5 Batch versus continuous equipment
`6. 7.6 Continuous microwave pressure vessels
`6.7.7 Thermal stabilisation
`Acknowledgements
`References
`
`7 The Dole process
`F. S. WHITE
`
`Introduction
`7.1
`7.2 Technology overview
`7.3 The Dole system
`7.3.1 Can-sterilizing unit
`7.3.2 The filling section
`7.3.3 Instrumentation and controls
`7.3.4 System operations
`7.3.5 Superheated steam
`
`8 Micro biological aspects of aseptic processing and packaging
`D. A. JOYCE
`
`Introduction
`8.1
`8.2 Foodbome microorganisms
`8.2.1 Food poisoning
`8.3 Raw materials
`8.4 Processing
`8.5 Aseptic packaging
`8.5.1 Hydrogen peroxide and peracids
`8.5.2 Ultraviolet irradiation
`8.5.3 Ionising irradiation
`8.5.4 Thermal treatment
`8. 5.5 Integrity of packs
`8.6 Validation of aseptic processing and packaging
`8.6.1 Plant commissioning
`8.6.2 Sterility testing
`8. 7 Quality control
`8.7.1 End-product analysis
`8.7.2 The role of microbiological analysis
`8.8 Quality management
`8. 8.1 Hazard analysis: critical control point systems
`8.9 Further thoughts
`References
`
`9 Aseptic packaging of liquid foods
`S. WAKABAYASHI
`
`Introduction
`9.1
`9.2 Requirements for an aseptic packaging machine
`9.3 Perfmmance and features of an aseptic packaging machine ··
`9.3.1 Sterilization of packaging materials
`9.3.2 Filling and sealing
`9.3.3 Aseptic positive-pressure chamber
`
`Index
`
`140
`140
`142
`143
`143
`143
`143
`145
`146
`146
`
`148
`
`148
`148
`148
`149
`149
`150
`151
`153
`
`155
`
`155
`156
`157
`159
`160
`162
`162
`163
`164
`164
`165
`165
`166
`167
`169
`169
`171
`175
`176
`178
`179
`
`181
`
`181
`181
`183
`183
`185
`186
`
`189
`
`p. E10
`
`

`
`Contributors
`
`Professor Dr N. Buchner University of Stuttgart-Hohenheim, Postfach 70
`0562, Schloss I, 7000 Stuttgart 70 (Hohenheim),
`Gennany
`
`Mr R. E. Coles
`
`Mr D. A. Joyce
`
`Mr C. J. Robinson
`
`Dr P. J. Skudder
`
`Foodpack Information Centre, 16 Kenilworth
`Road, Cubbington, Leamington Spa, Warwick, UK
`
`David A. Joyce Associates, Manley Common,
`Cheshire W A6 9ES, UK
`
`Remy Gimpel Ltd, 103-109 Lavender Hill, London
`SWIISQI, UK
`
`APV Baker Ltd, Automated Processes Division, PO
`Box 4, Gatwick Road, Crawley, Sussex RH4 2QB,
`UK
`
`Mr B. I. Turtle
`
`45 Priory Orchard, Wantage, OX12 9EL, UK
`
`MrS. Wakabayashi
`
`Dr E. M. Willhoft
`
`Mr F. S. White
`
`Shikoku Kakoki Co Ltd, Toyo Bldg, No 20, 12-
`banchi, Jingu-mae 6-chome, Shibuya-ku, Tokyo
`!50, Japan
`
`Epsom Technical Group Services, 41 Higher Green,
`Epsom, Surrey KT17 3BB, UK
`
`Graham Engineering Corp, 1420 Sixth Avenue, PO
`Box 1140, York, Pennsylvania 17405, USA
`
`p. E11
`
`

`
`1 Aseptic processing and packaging of food
`particulates
`N.BUCHNER
`
`1.1
`
`Introduction and basic principles
`
`Aseptic processing and filling consists of presterilization of the product before
`filling the sterile product into a sterile----usually also presterilized-package in a
`sterile atmosphere with sterile mechanical means and subsequent closing of the
`package in a sterile manner. After the packaging process no further sterilizing
`influence is exerted from the packaged product, the packaging material, the interior
`atmosphere, or from outside the package. A so-called 'commercial sterility' has to
`be achieved with usually a maximum of one non-sterile package out of 10 000,
`allowing for conditions of storage and distribution.
`Aseptic processing and packaging has some advantages over competing meth(cid:173)
`ods of food preservation, but it has also some disadvantages. Aseptic processing
`and filling is associated with high capital expenditure on plant URed for presteriliz(cid:173)
`ing and filling of products and especially for automatic control of all conditions
`safeguarding product sterility; all steps controlling sterility should be controlled
`through automation. Limitations for aseptic processing and packaging still exist in
`the areas of presterilization and filling of difficult products; for example, liquids
`with large particles. Developments, however, are proceeding and these limitations
`are gradually disappearing.
`
`1.1.1 Advantages over in-container sterilized foods
`
`Quality of aseptically treated foods may be higher due to UHT (ultra high temper(cid:173)
`ature/short time) sterilization. This is especially valid with large packs, because
`heat penetration in retorting is time-consuming and consequently quality suffers
`from overheating. UHT treatment is usually performed with processes allowing
`fast heating and cooling; for example with thin layers of product in heat exchangers.
`High UHT temperatures make use of the fact that the sensitivity of microorganisms
`to high temperature is much higher than that of the food constituents. While the
`Q1o-value (factor for speeding up reactions when raising temperature by 1 oo C) for
`chemical reactions offood constituents is usually between 2 and 4, the equivalent
`value for killing bacteria is 10. If the temperature from the usual retorting value of
`121 oc is raised by 1 0°C, the time for the same killing rate for bacteria will be 10%,
`and with a 20°C rise only 1%. Iffor chemical reactions a Q1o of3 is assumed, they
`will be speeded up by only a factor of 3 x 3 = 9 when raising the temperature by
`20°C. As a result, a temperature 1ise from 121 octo 141 oc for sterilizing foods will
`
`p. E12
`
`

`
`2
`
`ASEPTIC PROCESSING AND PACKAGING OF PARTICULATE FOODS
`
`give theoretically only about 9% of the damage to quality, compared with retorting
`at 121 °C.
`Usually less energy is needed for UHT sterilization because at least part of the
`process heat may be recovered with heat exchangers. Recovery rates may be higher
`than 90%. Also, the aseptic process is a modern continuous flow process, needing
`fewer operators and space than retorting. At the discharge of the aseptic filler the
`packages are ready for storage. Packs do not require to be transferred into retorts
`where, depending on the nature of the retorts, certain expenditures are necessary
`for handling the packs. Packaging material and packs are sterilized under milder
`conditions than those existing in retorts and therefore a wider choice of packaging
`materials and packs is possible: packs may be cheaper, lighter, less space-consum(cid:173)
`ing and offer more convenience.
`Compared with retorted trays and cups of polypropylene/ethylene vinyl alco(cid:173)
`hol/polypropylene (PP!EVOH/PP) used for soups and other meals, aseptically
`filled packs from these materials do not suffer during subsequent storage from
`water vapour absorption by EVOH during retorting and raised oxygen transfer from
`the atmosphere. Even after drying the permeability of retorted EVOH may remain
`higher due to 'retort-shock'.
`
`1.1.2 Advantages over pasteurized chilled foods
`
`The nature of the products and processes determines whether the quality of
`aseptically filled products may be lower than that of pasteurized chilled foods.
`Aseptically filled products, however, have some advantages, if filled and sealed
`effectively. They are microbiologically safer, because they need no refrigera(cid:173)
`tion. No control is necessary for possible intenuptions of the chilling chain,
`which, in the case of the short shelf-life of pasteurized products, creates a cost
`penalty.
`As aseptic products do not need refrigeration, storage and distribution are
`cheaper and selling paths may be longer and permit more variation. Production
`batches may also be larger: so production becomes more economical. If a modified
`atmosphere is used for chilled products, often larger packs have to be used to
`contain sufficient C02 as a control medium for microorganisms.
`
`1.1.3 Advantages over 'cleanfill'
`
`Cleanfill is a process similar to aseptic filling. Total commercial sterility,
`however, is not the target of cleanfill, since a very low level of microorganisms
`remains after filling and sealing, allowing a shelf-life of 4-6 weeks when
`products are chilled. While the costs for cleanfill are somewhat lower than those
`for aseptic filling, and the quality image may be somewhat higher due to
`refrigeration, disadvantages are similar to those for pasteurized chilled products,
`with the exception that the microbiological risk is lower provided that only
`high-acid foods are cleanfilled.
`
`p. E13
`
`

`
`ASEPTIC PROCESSING AND PACKAGING OF FOOD PARTICULATES
`
`3
`
`1.1. 4 Advantages over frozen products
`
`Frozen foods have a long shelf-life, high quality and a low microbiological risk (if
`the cooling chain is not interrupted) similar to aseptically treated products. Freezing
`is suitable for a wide variety of products that cannot be aseptically filled, because
`of small production batches and difficulties of handling. Where, however, aseptic
`products are highly competitive, frozen foods demonstrate disadvantages: for
`example they require cooking whereas aseptic products are generally ready to eat
`or drink. Where products are heated for consumption little time is needed for aseptic
`products in contrast to frozen foods. In microwave ovens ice absorbs only about
`0.1% of the energy absorbed by water or water containing unfrozen food (Schubert,
`1990). This results in an extended heating time for frozen foods with very uoeven ·
`heating and overheating of melted zones.
`Aseptic products may also be distributed to couotries with a poor cold storage
`infrastructure. Maintaining quality of frozen foods during storage and distribution
`has an extremely high energy demand. More than 60% of the energy consumption
`in the food system, starting with agriculture or fishery and ending with the packaged
`product in the hands of the consumer, is needed for cooling during storage and
`distribution (Khaladadij-Nia and List, 1981).
`
`1.1. 5 Advantages over dried products
`
`Advantages of dried products are long shelf-life and absence of microbiological
`risk, weight reduction by drying and low-cost packs. Quality preservation by
`drying, however, is limited to foods suitable for drying. Quality and consistency of
`dried products may suffer by the drying process. In contrast to aseptic products,
`dried products need to be reconstituted for consumption and so their convenience
`is lower.
`
`1.2 Developments in aseptic processing and filling
`
`Aseptic methods have a history of nearly 80 years. In 1914, sterile filters for
`filtering wine were fully developed. In 1917, Dunkley in the USA received a patent
`for sterilizing cans and lids with saturated steam and subsequent aseptic filling. In
`Denmark and the USA processes and machines for aseptic filling were developed
`arouod 1920, but all these processes disappeared either from lack of reliability or
`flexibility. It could, however, be demonstrated that high-temperature/short-time
`treated milk had a superior quality compared with the retorted product (Emch,
`1978).
`In the early 1940s, the so-called Dole-Martin process was developed by Dr
`Martin, USA; indeed, machines for this process are still manufactured and supplied
`today. In 1962, the development of Alpura AG (Loliger) in Switzerland for the
`aseptic filling of milk in a modified Tetra Pak machine to produce the tetrahedron
`
`p. E14
`
`

`
`4
`
`ASEPTIC PROCESSING AND PACKAGING OF PARTICULATE FOODS
`
`packs from carton/polyethylene was completed, and the Swedish company, Tetra
`Pak, started marketing the process on a licence basis. This development was the
`beginning of the modem basis of aseptic filling, because it gave the impetus for
`expanding the method to different package types, such as bags, cups, different
`carton styles and, later, also bottles. This method usually applied sterilization with
`hydrogen peroxide as in the Alpura system but with many modifications. In 1969
`the Tetra Brick aseptic machine was introduced and, in the late 1970s, the aseptic
`Combibloc system using carton blanks instead of roll material was introduced.
`An important date for the expansion of aseptic methods was January 1981. After
`animal tests with high levels ofhydrogen peroxide this sterilizing medium had been
`attacked in Japan and, in January 1981, the US Food and Drug Administration
`(FDA) allowed sterilization of polyethylene surfaces (and later different plastics)
`as a safe method-after a thorough study of the Japanese findings. This gave a great
`impetus to aseptic methods, not only in the USA but throughout the world ..
`Packaging pastes with particles started gradually, when small particles of fruits or
`rice or tapioca were added to yogurt or pudding. In the mid-1970s, much develop(cid:173)
`ment work was performed for processing and filling fruit purees and particulates
`in drums (Loire, 1976) and later in bag-in-box packs. The scientific basis of those
`developments is described elsewhere (Kessler and Fiedler, 1985). In 1984-85 the
`first Combibloc packs containing aseptically processed soups entered the British
`and, later, other markets. New items such as tomato products followed
`(Mankowsld, 1987).
`Much development has been achieved in the last few years in filling soups and
`stews aseptically, for instance, into cups and trays suitable for microwave heating,
`. and this is on the verge of commercial application.
`
`1.3 Aseptic processing-methodology
`
`Aseptic processing comprises the following:
`
`1. Sterilization of the products before filling.
`2. Sterilization of packaging materials or containers and closures before
`filling.
`3. Sterilization of aseptic installations before operation (UHT unit, lines for
`products, sterile air and gases, filler and relevant machine zones).
`4. Maintaining sterility in this total system during operation; sterilization of
`all media entering the system, like air, ga~es, sterile water.
`5. Production of hennetic packages.
`
`1.3.1 Sterilization of products
`
`Presterilization of products consists usually of heating the product to the desired
`UHT temperature, maintaining this temperature for a given period in order to
`
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`ASEPTIC PROCESSING AND PACKAGING OF FOOD PARTICULATES
`
`5
`
`achieve the desired degree of sterility,' with subsequent cooling, usually to ambient
`temperature and sometimes to an elevated temperature to achieve the right viscosity
`for filling. Heating and cooling should be performed as rapidly as possible to
`achieve the best quality dependent upon the nature of the product. A fast heat
`exchange rate is desired for cost reasons.
`
`1.3.1.1 Methods for liquid products These are as follows.
`
`Sterile filtration. As mentioned already sterile filters were developed very
`early. They are used for clear liquids such as wine and fruit beverages (Haubs,
`1988) and also for pharmaceutical preparations, where heat may not be applied
`(Wallhauser, 1988), and for sterile water if needed in sterile installations. These
`sterile filters have to be protected from even small particles by prefilters. In the last
`15 years great progress has been made with filter materials, their construction and
`in-line testing for integrity, with the result that product sterility from filtration is
`now comparable with thermal sterilization methods.
`
`Plate-type heat exchanger. Plate heat exchangers have been used for steri(cid:173)
`lizing with subsequent hot filling of fruit juices for a long time. When applied
`to aseptic filling they serve both for heating (to higher temperatures) and cooling.
`The advantages of plate heat exchangers are a high heat-exchange rate due to
`the large exposed surfaces and the generation of turbulent flow at moderate costs;
`disadvantages are intolerance of gaskets to pressure and of the whole system to
`even small particles such as fibres. Therefore standard plate-type heat exchang(cid:173)
`ers with mechanical contacts with the plates may be recommended for clear
`liquids only.
`
`Steam injection in liquid. The most rapid method of heating liquid products is
`by injection of steam. Within fractions of a second the desired sterilization tem(cid:173)
`perature may be attained. Combined with the most rapid methods of cooling such
`as injection of the hot product into a vacuum chamber and evaporation of an
`equivalent amount of water, a very high quality level may be achieved. The method
`is suitable, however, for particle-free liquids only. When sterilizing particulate
`mixtures, it may be used for sterilizing the liquid separately as the particles have
`to be sterilized using a different method. A patent was applied for this process by
`Alpura AG, Switzerland, in 1949 (Emch, 1991 ). The method is combined usually
`with heating and cooling in heat exchangers to the lower temperature range, for
`instance below 80°C. A disadvantage of the system is the reduced heat recovery
`rate of about 50%.
`
`Liquid infusion into steam. A similar method is infusion of a thin fihn ofliquid
`into a steam atmosphere, which also gives rapid heating. One type infuses a thin
`flat film; with a newer method a thin circular film may be infused, avoiding thicker
`rims at the ends of the flat film requiring longer heating times. Cooling is also
`
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`
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`6
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`ASEPTIC PROCESSING AND PACKAGING OF PARTICULATE FOODS
`
`achieved by infusion of the liquid into a vacuum chamber and evaporation of water.
`Advantages in quality, range of application, preheating and heat recovery rates are
`similar to the method of steam injection.
`
`Friction heating. A method ofheating liquids by friction between rotating and
`static disks has been developed, which combines heating with some homogeniza(cid:173)
`tion. The method, suitable for liquids only, seems not to be applied commercially.
`
`1.3.1.2 Methods suitable for liquids with particulates. These are as follows.
`
`Plate-type heat exchangers with free-flowing plates. These heat exchangers
`with mechanically-stable, free-flowing and especially contoured plates without
`mechanical interconnections (except at the rims), have good heat-exchange rates
`due to large exposed surfaces and turbulent flow characteristics and, for this reason,
`they are applied to UHT treatment of liquids with smaller particulates up to 5-7
`mm, or about half of the distance between the plates (Buchwald, 1987).
`
`Tube-type heat exchangers. This type of heat exchanger has the widest field
`of application for UHT sterilization of liquids and pastes, also containing small
`particulates. The design of the apparatus is limited to a maximum size for particu(cid:173)
`lates to be handled. There are cylindrical tube-type heat exchangers and others with
`straight tubes. In the bows at the ends, turbulence is created, which mixes product
`and gives short heating and cooling times. Sizes of particulates are equivalent to
`cubes of 7-8 mm maximum, depending on the design. If one dimension of a
`particulate is smaller, others may be larger.
`
`Scrape-type heat exchangers. Scrape-type heat exchangers are similar to
`straight-tube heat exchangers, but they have a central rotating shaft carrying
`scraping devices for the heated surfaces to prevent burning and fouling of foods at
`the surfaces as well as providing a mixing action. These heat exchangers are
`suitable for liquids with high viscosity and also for liquids and pastes with
`particulates up to about 12 mm cube; although tests with specially designed and
`optimized versions have shown that particulates up to 3 7 mm could be processed.
`Scrape type heat exchangers have been used for a long time for heating and cooling,
`and also for UHT treatment prior to conventional filling, followed by retorting.
`Much basic work has been done to provide a better understanding of flow and
`heat-exchange characteristics (Ohlsson, 1988; Wernimont, 1988).
`
`Rotaholder. A system, being basically a tube sterilizer in which liquid and
`particles are flowing jointly, was developed with the addition of 'Rotaholders' in
`which the particulates are held back for a certain period by rotating holders with
`fork-devices through which the liquid may flow. This compensates for the longer
`time needed by particulates for heat penetration during heating and cooling. The
`heat load for particulates and liquid may thus be adjusted to achieve a good overall
`quality. Size limitation is 15-18 mm cubes with a maximum of 15% particulate
`
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`
`ASEPTIC PROCESSING AND PACKAGING OF FOOD PARTICULATES
`
`7
`
`content in the liquid. The viscosity of the liquid is limited by the necessity of a free
`:flow around the particulates in the holding device. This method is at an advanced
`development stage (Hermans, 1988).
`
`Sterilization of particulates in a fluidized steam bed. In Australia a system
`('Steriglen') was developed in which particulates, in the test meat and fish partic(cid:173)
`ulates were used, were separated from liquid, which was individually sterilized,
`and the particulates were introduced into a pressurized chamber through a pressure
`lock. In the chamber the particulates were heated in a fluidized bed by steam and
`then cooled with sterile nitrogen flowing through the layers of particulates. The
`cooled product was transpmted out of the system through a second pressure lock.
`The development was transferred to the USA and seems not to be commercially
`exploited.