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Handbook of Seal Integrity in the Food Industry

Handbook of Seal Integrity in the Food Industry

Michael Dudbridge

ISBN: 978-1-118-90459-6

Feb 2016, Wiley-Blackwell

232 pages

$96.99

Description

Seal integrity is vital in food supply chains with modern methods of food retailing and a requirement for very high levels of consumer satisfaction. Robust packages are an important factor in food preservation, consumer confidence in the product as well as waste minimisation and cost control throughout the system.

The Handbook of Seal Integrity in the Food Industry is aimed at people working in food supply chains and associated industries from packing machine operators to quality managers and from retail technical staff to packaging machine designers and maintenance engineers. This well illustrated and comprehensively indexed handbook paints a complete picture of all of the factors that operate together in the creation of food packages with high performing seals.

A comprehensive review of the reasons for poor seal integrity is included along with suggestions for improvements in maintenance, machine set up and operation. Seal testing systems are featured along with management techniques to ensure a high level of performance and consistency in your business and a “right first time” approach within packaging systems. The design and operation of the main types of sealing system is reviewed for rigid, semi rigid and flexible packaging systems along with an overview of packing materials such as thermoplastics.

Finally the handbook looks at innovations in the packaging of food products with a view of developments in packaging materials, sealing systems and on-line seal integrity measurement and monitoring systems.

Introduction, xiv

About the author, xv

CHAPTER 1 Overview of sealing technologies, formats and systems, 1

1.1 Introduction, 1

1.2 The importance of packaging and seal integrity, 1

1.3 The sealing of rigid containers, 3

1.4 Hermetic seals, 3

1.5 Developments in the canning process, 4

1.5.1 Thinner materials, 5

1.5.2 New materials, 5

1.5.3 Additional protection of the container from secondary packaging, 6

1.6 Heat sealed packages, 6

1.7 What is a good seal?, 8

1.8 So … what is a good seal?, 10

1.9 Seal management in a packing operation, 12

1.9.1 Setting the required standards, 12

1.9.2 Second step – set up a testing system for seals in your business, 12

1.10 Testing systems, 13

1.10.1 Mechanical squeeze test, 13

1.10.2 Sniffer systems, 13

1.10.3 Vision systems, 14

1.10.4 Ultrasound systems, 14

1.11 How is a good seal made?, 14

1.12 Heat sealing, 15

1.12.1 Heated tooling, 15

1.12.2 Induction sealing, 15

1.12.3 Ultrasonic sealing, 16

1.12.4 Spin welding, 17

1.12.5 Hot gas/radiant heat sealing, 17

1.13 Non]heat sealing methods, 17

1.13.1 Cold sealing, 17

1.13.2 Adhesive sealing, 17

1.13.3 Solvent sealing systems, 17

1.14 Packaging materials, 18

1.15 Sealing parameters, 18

1.15.1 Sealing temperature, 18

1.15.2 Flow characteristics, 19

1.15.3 Surface printing, 19

1.15.4 Material strength, 20

1.15.5 Material structures, 20

1.16 Packaging systems, 21

1.16.1 Bag]making systems, 21

1.16.2 Pouch sealing systems, 21

1.16.3 Tray sealers, 22

1.16.4 Horizontal form fill seal (HFFS) systems, 22

1.16.5 Flow wrapping system, 23

1.17 The requirements of industry for seal integrity in its packaging systems – an overview, 24

1.17.1 Safety, 24

1.17.2 Containment, 24

1.17.3 Shelf]life extension, 24

1.17.4 Seal strength, 25

1.17.5 Accessibility, 25

1.17.6 Display attractiveness, 26

1.17.7 Portion control and multi]compartment trays, 27

1.17.8 Consumer confidence, 27

1.18 Industry sectors – some recent increases in seal performance requirements, 28

1.19 Making changes to packaging materials or systems, 29

CHAPTER 2 The operation and design of tray sealing machines, 30

2.1 Introduction, 30

2.2 The principles of sealing preformed trays, 30

2.3 Types of tray sealing machines, 31

2.3.1 Small hand]operated machines, 31

2.3.2 Larger, more automated machines, 31

2.3.3 Very large tray sealing systems, 32

2.4 The components of a tray sealing system, 33

2.4.1 The tray handling system, 33

2.4.2 The top film handling system, 34

2.4.3 The sealing tools, 34

2.4.4 The grabber arms, 35

2.5 Tray sealing machine set]up, 37

2.5.1 The top tool, 37

2.5.2 The bottom tool, 37

2.5.3 The grabber arms for in]line machines, 39

2.5.4 Temperature settings, 39

2.5.5 Dwell times, 39

2.5.6 Top film feed, 40

2.5.7 Top film tension, 41

2.5.8 The in]feed stopper positions for in]line machines, 42

2.6 Maintenance of tray sealing machines, 42

2.6.1 Maintenance of the top tool, 43

2.6.2 The maintenance of the bottom tool, 45

2.6.3 Maintenance of the in]feed, grabber and out]feed systems, 47

2.6.4 Maintenance of the film handling system including the scrap take]up system, 49

2.7 Machine services, 49

2.8 The special case of modified atmosphere tray sealing, 49

2.9 The special case of controlled atmosphere tray sealing, 50

2.10 The trays used in tray sealing operations, 51

2.11 Top film used in tray sealing operations, 51

CHAPTER 3 The design and operation of bag]making machines, 53

3.1 Introduction, 53

3.2 System overview, 53

3.2.1 The film handling system, 53

3.2.2 Back sealing system, 53

3.2.3 The filling process, 54

3.2.4 The top seal, 54

3.3 Types of VFFS machine, 57

3.3.1 Top and bottom sealing jaw design variations, 57

3.3.2 Back seal design variations, 58

3.3.3 The implications of the back seal for the overall seal integrity of the pack, 60

3.4 Components of a VFFS machine, 61

3.4.1 Film handling and forming system, 61

3.4.2 Multiple functions of the forming system, 62

3.4.3 The sealing jaws, 63

3.4.4 Support arms, 67

3.4.5 Exit conveyor systems, 68

3.4.6 Controls of a VFFS system, 68

3.5 VFFS machine set]up, 69

3.6 Maintenance of VFFS systems, 70

3.7 The feed of product into the VFFS, 70

3.8 Sealing jaw maintenance, 71

3.9 Jaw and back sealer heating systems, 73

3.10 Film forming system, 73

3.11 Calibration, 75

3.12 The special case of modified atmosphere packing with VFFS, 76

3.13 Packaging materials for VFFS systems, 77

3.13.1 Sealing surfaces, 78

3.13.2 Printed materials, 79

CHAPTER 4 The design and operation of horizontal form fill seal systems, 80

4.1 Introduction, 80

4.2 The sequencing of an HFFS system, 80

4.2.1 Thermoplastic material introduced and heated, 80

4.2.2 Moulding of softened film, 81

4.2.3 Cooling and filling, 82

4.2.4 Sealing, 82

4.2.5 Cutting, 83

4.3 Types of HFFS machines, 84

4.3.1 Machines with two heating stations, 84

4.3.2 Machines with two moulding stations and two sealing stations, 85

4.4 Components and subsystems of HFFS machines, 85

4.4.1 The bottom film handling systems, 85

4.4.2 The moulding system, 86

4.4.3 The filling station, 88

4.4.4 The lidding section, 89

4.4.5 Labelling of the packs, 90

4.4.6 The cutting section, 91

4.4.7 The vacuum system, 92

4.5 Setting up an HFFS machine, 93

4.5.1 Temperature control of the heaters in the moulding section, 93

4.5.2 Positioning of the sealing heads, 94

4.5.3 Positioning of the star stamps, guillotine and rotary cutting knives, 95

4.6 Maintenance, 96

4.6.1 The gripper chains, 96

4.6.2 The sealing heads, 97

4.6.3 Seal area contamination, 97

4.7 Special case of modified atmosphere packing, 98

4.8 Films used, 100

CHAPTER 5 The causes of seal integrity issues, 101

5.1 Introduction, 101

5.2 Background, 101

5.3 Objective, 102

5.4 Study methods, 102

5.4.1 The interview, 102

5.4.2 Shop floor study, 102

5.4.3 Vacuum testing, 103

5.4.4 Dye penetration testing, 103

5.5 Companies studied, 103

5.5.1 Category of food product, 103

5.5.2 Product constituents, 104

5.5.3 Size of factory, 104

5.5.4 Intensity of production, 105

5.6 Key results, 105

5.7 Rate of seal failure, 105

5.8 Discussion of the impact of poor seal integrity, 107

5.9 Disposal and repacking of food, 108

5.10 Disposal of packaging, 108

5.11 Managing the sealing activity, 108

5.11.1 Methods for monitoring the integrity of seals, 108

5.11.2 Management of the standard operating procedures, 110

5.11.3 Maintenance procedures, 111

5.12 Conclusions, 112

5.12.1 Robust filling methods, 112

5.12.2 Standard operating procedures, 112

5.12.3 Planned preventative maintenance, 113

5.12.4 Seal testing, 113

5.12.5 Rework of packs, 113

5.12.6 Packaging materials, 114

5.13 Moving forward, 114

5.14 Lessons for packaging managers and supervisors, 114

CHAPTER 6 Seal testing techniques, 116

6.1 Introduction, 116

6.2 Seal strength, 116

6.3 Leaking seals, 117

6.4 Seal appearance, 117

6.5 Testing seal strength, 119

6.5.1 Burst tests, 119

6.6 ASTM International seal testing standards, 120

6.6.1 Seal strength – ASTM F88 and F2824, 120

6.6.2 Seal strength – ASTM F2824, 122

6.6.3 Burst test – ASTM F1140, 122

6.6.4 Creep test – ASTM F2054, 122

6.6.5 Vacuum dye or dye penetration test – ASTM D3078, 122

6.7 Pouch integrity testing, 123

6.8 Seal strength by inflation and seal integrity testing (destructive tests), 125

6.8.1 Burst testing, 125

6.8.2 Creep and creep]to]failure testing, 125

6.9 Leak detection, 126

6.9.1 Pressure decay method, 126

6.9.2 Vacuum decay method, 127

6.10 Non]destructive tests, 128

6.11 Shop floor detection of leaking packs, 128

6.11.1 The mechanical squeeze test, 129

6.11.2 The trace gas detection methods, 129

6.11.3 Computer vision systems, 130

6.11.4 Vacuum decay systems, 131

6.11.5 Vibration and deceleration analysis, 131

6.11.6 Ultrasonic systems, 131

CHAPTER 7 Packaging materials and their impact on seal integrity, 133

7.1 Introduction, 133

7.2 What is a thermoplastic?, 134

7.2.1 Molecular structure of thermoplastics, 134

7.3 Commonly used sealable thermoplastics, 137

7.3.1 High]density polyethylene (HDPE), 137

7.3.2 Low]density polyethylene (LDPE), 137

7.3.3 Linear low]density polyethylene (LLDPE), 139

7.3.4 Polypropylene (PP), 139

7.3.5 Polyvinyl chloride (PVC), 139

7.3.6 Polyethylene terephthalate (PET), 139

7.4 Co]polymers, 140

7.4.1 Acid co]polymers, 140

7.4.2 Ethylene vinyl acetate, 140

7.4.3 Ionomers, 140

7.5 Eco polymers, 140

7.5.1 Polylactic acid (PLA), 140

7.5.2 Polyhydroxyalkanoates (PHA), 141

7.6 Adhesive and cohesive sealing, 141

7.6.1 Intertwining of the molecules, 141

7.6.2 Intermolecular forces, 141

7.6.3 Adhesive sealing, 141

7.7 Laminated packing materials, 142

CHAPTER 8 Seal strength, 143

8.1 Introduction, 143

8.2 Seal strength – a definition, 143

8.3 The implications of distribution, retail and domestic situations, 144

8.3.1 Transit trials and simulations, 144

8.3.2 The impact of temperature changes, 145

8.3.3 The impact of pressure changes, 146

8.3.4 Returnable transit containers (RTCs), 147

8.3.5 Logistics route, 147

8.3.6 Retail pressure, 148

8.3.7 Transport home, 148

8.4 Measurement of seal strength, 149

8.4.1 Hot tack seal strength, 149

8.4.2 Burst testing, 152

8.4.3 The pull test, 153

CHAPTER 9 Peelability and openability, 154

9.1 Introduction, 154

9.2 Peelable films, 155

9.2.1 Delamination, 155

9.2.2 Adhesive peel, 156

9.2.3 Cohesive peel, 157

9.3 Sealing machine set]up for peelable films, 158

9.4 The age of the film, 160

9.5 The design of the seal area, 161

9.6 The selection of a peelable film, 161

9.7 Product condition when sealing, 161

9.8 Openability, 161

9.8.1 Why consider openability?, 162

9.8.2 The tear notch, 162

9.8.3 The peel tab, 163

9.8.4 Perforations and lines of weakness, 163

9.8.5 Rip strip, 165

9.8.6 Easy]open lids, 165

CHAPTER 10 Resealing a pack, 167

10.1 Introduction, 167

10.2 Is it resealed?, 167

10.3 Types of resealable packs, 168

10.3.1 The clip]on lid, 168

10.3.2 The dead fold system, 169

10.3.3 The sticker system, 170

10.3.4 The zip system, 171

10.3.5 The velcro type system, 171

10.3.6 The screw cap, 171

10.3.7 The flip lid, 172

10.3.8 Sports cap, 174

10.3.9 Resealing using adhesives, 174

10.3.10 Injection moulding, 176

10.4 Single portion packs, 176

CHAPTER 11 Seals for non]flexible packs, 177

11.1 Introduction, 177

11.2 Sealing systems for heat]processed cans, 177

11.3 Glass jar sealing systems, 179

11.4 Bottle sealing systems, 180

11.5 Sealing methods for rigid containers, 181

11.5.1 Preformed container and preformed lid, 181

11.5.2 Preformed container and lid moulded into position, 182

11.5.3 Preformed container and a clip]on lid, 183

CHAPTER 12 Oxygen and moisture migration, 184

12.1 Introduction, 184

12.2 How does oxygen migrate through materials and how do we measure OTR?, 185

12.3 Packaging specifications, 185

12.4 The theory of diffusion, 186

12.5 Measurement of OTR, 187

12.6 MTR, 188

12.7 Impact on MAP systems, 189

12.8 Controlled atmosphere packaging, 190

12.9 Impact of down]gauging of material thicknesses, 191

12.9.1 Increased MTR and OTR, 191

12.9.2 Packing machine operation, 191

12.10 Barrier layers to improve OTR and MTR, 191

CHAPTER 13 Tamper evidence technology, 192

13.1 Introduction, 192

13.2 Neck sleeves and paper bands, 192

13.2.1 Tamper bands, 193

13.2.2 Tamper evident screw caps, 193

13.3 Induction sealed tamper evidence systems, 193

13.4 Injection moulded parts, 195

13.5 The screw cap with band, 196

13.6 Test buttons on jars, 196

13.7 Film overwrap for cartons, 197

13.8 Stickers and paper labels, 197

CHAPTER 14 Innovations in packaging to improve seal integrity and the detection of sealing issues, 200

14.1 Introduction, 200

14.2 Packaging materials, 200

14.2.1 The LINPAC Rfresh Elite® system, 201

14.2.2 Packaging shape and usability, 201

14.3 Sealing systems, 201

14.3.1 Laser sealing, 201

14.3.2 The integrity seal, 202

14.4 Detection systems, 202

14.4.1 Seal scope, 202

14.4.2 Modified atmosphere packaging, 203

14.4.3 Carbon dioxide]sensitive labels, 203

14.4.4 Multispectral imaging, 203

14.4.5 Laser scatter, 204

14.4.6 Polarised light, 204

14.4.7 Multiple image analysis, 206

14.4.8 Active and intelligent inks, 206

14.4.9 Bump Mark, 206

14.4.10 Smart labels, 206

Index, 207