Packaging Innovation Fund: Integrity Seal Final Report March 2007
Development of “Integrity Seal”
Sealing Technology
Development of “Integrity Seal” Hermetic Sealing technology for flexible packaging
and application into the Food Industry.
WRAP works in partnership to
encourage and enable businesses
and consumers to be more efficient
in their use of materials and
recycle more things more often.
This helps to minimise landfill,
reduce carbon emissions and
improve our environment.
Contents
1 Introduction
5
2 Integrity Seal
9
3 Fresh Produce Trials
11
4 Snack Product Trials
15
5 Film Trials
17
6 Benefits Analysis
19
7 Industry Potential
24
8 Overall Conclusions
25
Appendix 1
Integrity Seal technology
26
Appendix 2
Packaging savings from using
Integrity Seal technology
28
Appendix 3
Seal quality data
30
Appendix 4
Leafy salad shelf-life data
32
Appendix 5
Fresh vegetable shelf-life data
34
Appendix 6
Productivity data
35
Table of Figures
37
While steps have been taken to ensure its accuracy, WRAP cannot accept responsibility or be held liable to any
person for any loss or damage arising out of or in connection with this information being inaccurate, incomplete or
misleading. For more detail, please refer to our Terms & Conditions on our website - www.wrap.org.uk
Executive summary
International Food Partners Ltd were awarded funding from WRAP’s Packaging Innovation Fund in October 2005
to develop a superior sealing technology for flexible packaging, which would reduce the amount of packaging
material required to form the seal and make the seals hermetic. Current (crimp) sealing technology used for
flexible packaging often results in a poor, non-hermetic seal. This can reduce food product shelf-life due to
changes in headspace gases or moisture content. When seals leak it makes it impossible for the packaging
material to control the level of barrier or permeability required for the product. This means that the product may
well not achieve its desired shelf-life and either has to be disposed of in store or, more likely, by the consumer.
Traditional crimp sealing which has been used since automatic packaging machines were invented cannot
produce hermetic sealing with thin-gauge monolayer polymers such as Oriented Polypropylene (OPP). Crimp
sealing relies on the thin layer of sealant on the face of the film, usually just a few microns thick, to make the
heat seal. Such a thin layer is insufficient to melt and flow to make the seal hermetic. Furthermore, the traditional
rigid sealing jaws do not apply uniform pressure across the seal width because the thickness of the film varies at
the back seal and gussets. This results in the seal area either being over-pressured or under-pressured, causing
thermal distortion of the seal.
Laminated films are sometimes used in an attempt to produce hermetic seals. While they can be successful, they
cost more to manufacture and use more polymer. Typically the sealant layer on a laminate is 12–20 micron with
a substrate layer of 15–20 micron, resulting in a total thickness of 35–40 micron.
A standard crimp seal is typically 15mm long, so a significant amount of film is used in an attempt to form a
hermetic seal. In reality, the width does not contribute to making a hermetic seal and so is an unnecessary use of
film. Such a long seal can take up 10–20% of the amount of film used for the total pack, depending on pack size.
The objective of this project was to make a hermetic seal using an impulse heating system which would cut and
melt the film to make a welded seal only 1mm wide. The cut and weld principle would also allow hermetic seals
to be made irrespective of the number of layers of film.
Traditional impulse sealing technology has been around for many years but has not been used widely because of
its limited speeds and poor reliability. The Integrity Seal technology is a new generation of impulse technology
combined with innovative seal jaw design and water cooling.
The system works by rapidly heating the low mass impulse element on the sealing jaw to beyond the polymer
melt temperature. Only one jaw of the sealing machine is heated. The other jaw comprises a moulded rubber
anvil which presses the film against the impulse element. The ‘V’ shape of the anvil helps sever the film as it
melts, so producing a fully welded seal. Before the jaws separate they are cooled by chilled water circulating
behind the element. The seal created is hermetic and at only 1mm wide is very much neater than traditional
crimp seals.
The project was sponsored by Marks & Spencer and involved some of their suppliers for Fresh Produce and Snack
Products as follows:
Fresh Leafy Salads: Tilmanstone Salads, Vitacress Salads
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Fresh Vegetables: Exotic Farm Produce
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Snacks: United Biscuits (KP)
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Trials successfully demonstrated that the Integrity Seal produced hermetic seals under production conditions on
different types of vertical bagging machines, with additional significant benefits, including:
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Faster machine speeds (leafy salads)
Reduced rework (leafy salads)
Better product quality and longer shelf-life (leafy salads and vegetables)
Film saving of 10% from reduced seal area
Potential film saving of 10–15% from using thinner gauge film
Reduced store shrinkage due to better quality product
Development of ‘Integrity Seal’ sealing technology
3
Contents
1.0
Introduction .......................................................................................................................... 5
1.1
Background ............................................................................................................................. 5
1.2
Project Methodology ................................................................................................................ 6
1.2.1
Staged trials ............................................................................................................... 6
1.2.2
PIRA independent assessment..................................................................................... 7
1.3
Project success criteria............................................................................................................. 7
1.3.1
The sealing jaw performance ...................................................................................... 7
1.3.2
Pack performance ....................................................................................................... 8
2.0
Integrity Seal......................................................................................................................... 9
2.1
Limitations with current technology .......................................................................................... 9
2.2
The Integrity Seal technology................................................................................................. 10
3.0
Fresh Produce Trials ............................................................................................................ 11
3.1
Leafy salads .......................................................................................................................... 11
3.2
Tilmanstone Salads ................................................................................................................ 11
3.3
Vitacress Salads ..................................................................................................................... 12
3.4
Fresh Vegetable Trials: Exotic Farm Produce .......................................................................... 13
4.0
Snack product trials............................................................................................................. 15
4.1
United Biscuits (KP) ............................................................................................................... 15
4.1.1
Ashby trials............................................................................................................... 15
4.1.2
Rotherham trials ....................................................................................................... 16
5.0
Film Trials ............................................................................................................................ 17
5.1.1
Summary of results ................................................................................................... 17
6.0
Benefits Analysis ................................................................................................................. 19
6.1
Packaging material weight saving........................................................................................... 19
6.2
Product shelf-life benefits and reduced wastage ..................................................................... 19
6.3
Technical benefits .................................................................................................................. 19
6.3.1
Seal integrity ............................................................................................................ 19
6.3.2
Product quality benefits............................................................................................. 20
6.3.3
Machine performance benefits................................................................................... 20
6.3.4
Elimination of seal contamination on delivered packs ................................................. 21
6.3.5
Health and safety benefits......................................................................................... 21
6.4
Commercial benefits .............................................................................................................. 21
6.4.1
Packaging material saving ......................................................................................... 21
6.4.2
Longer shelf-life ........................................................................................................ 22
6.4.3
Reduced production costs ......................................................................................... 22
6.4.4
Marketing benefits .................................................................................................... 22
6.5
Other productivity and financial benefits................................................................................. 22
6.6
Consumer research findings ................................................................................................... 23
7.0
Industry Potential ............................................................................................................... 24
8.0
Overall Conclusions ............................................................................................................. 25
Appendix 1 Integrity Seal technology.............................................................................................. 26
Appendix 2 Packaging savings from using Integrity Seal technology .............................................. 28
Appendix 3 Seal quality data ........................................................................................................... 30
Appendix 4 Leafy salad shelf-life data ............................................................................................. 32
Appendix 5 Fresh vegetable shelf-life data...................................................................................... 34
Appendix 6 – Productivity Data ....................................................................................................... 35
Table of Figures ............................................................................................................................... 37
Development of ‘Integrity Seal’ sealing technology
4
1.0
1.1
Introduction
Background
WRAP’s Innovation Fund supported International Food Partners Ltd (IFP) in developing Integrity Seal because of
its potential to reduce packaging usage by at least 10% on all food products wrapped in flexible film bags and
pouches on automatic packaging machines. The seal’s potential to eliminate leaks would also have a significant
impact on levels of food waste, because less fresh food would be thrown away on account of premature spoilage
and loss of shelf-life.
Crimp-sealed bags as made on automatic vertical form-fill-seal bagging machines and horizontal flow wrapping
are a common packaging format for a wide range of food products. Traditionally the bag is sealed by profiled
rigid metal crimp jaws which apply heat and pressure to activate the sealant layer of the packaging material. This
technique has been used for many years and relies on the width of the seal to produce a degree of air tightness.
However, rigid metal jaws are incapable of applying optimum pressure across the full width of the seal because of
the differences in film thickness across the bag width. At the back seal, for example, the film has either two or
four layers depending on whether the seal is an overlap style or fin style.
Similarly, if the pack has gussets the film is four layers thick in the gusset area. Additional random creases tend
to form where the film tension has been lost. Wherever there is a change in the film thickness the rigid jaw only
applies optimum pressure at the thickest point, hence when the film thickness changes from two to four layers a
pipe leak occurs. It may be possible to seal the pipe leaks using laminates with a thick sealant layer, but this is an
expensive solution and uses more packaging material than is necessary. Films commonly used in the fresh
produce industry, such as Oriented Polypropylene (OPP), have a thin sealant layer of 2–3 microns.
The traditional resistance-heated crimp jaws activate the sealant layer by transmitting heat through the film. The
pack is sealed through the combination of pressure and a controlled dwell time. The difficulty with this method is
how to get the heat through the film to inner sealing layers without distorting the film core. It is very common to
see packs on supermarket shelves with excessively heated, shrivelled film.
In addition, machine operators often believe that more heat produces a better seal, and so frequently increase
the sealing temperature. In reality higher temperatures reduce seal integrity. The polymer will try to escape from
the heat source, and with uneven jaw pressure the polymer will thin down in the areas of higher pressure.
IFP started the project in 2000, developing prototype concepts with their own resources and finances. Through
this project WRAP provided the resources to enable the laboratory system to be developed to a fully operational
system for fitting to existing production bagging machines.
IFP approached Ceetak Ltd, a UK company specialising in sealing systems and rubber products, and asked them
to help develop a sealing technology which would guarantee hermetic seals.
IFP chose Ceetak as the engineering partner primarily because of its depth of experience with many types of
sealing systems, combining rubber technology with heated jaw tooling. An exclusive partnership was therefore
formed, with Ceetak providing the engineering design and development, and installation services to concept
briefs from IFP, while IFP provided the marketing and on-site technology transfer to customers.
The outcome of the collaboration was Integrity Seal, which uses the Ceetak Quick Pulse Heating technology
(QPH) as the basis and combines it with water chilling and innovative rubber anvil technology to produce a
unique sealing system. The special heating element has low mass and high conductivity to generate sealing
temperatures well above the polymer melt temperature. Conventional crimp jaws operate around 135 ºC but for
Integrity Seal the operating range is usually above 280 ºC. In addition the system uses water chilling to lower the
temperature on every seal cycle to cool the film so it sets before the jaws open.
The WRAP funding allowed Ceetak to install a laboratory workshop for the initial prototype construction and
testing before the systems were taken to customer sites. This included equipment for testing the seal quality both
for strength (tensile tester) and for integrity, a gas analyser and vacuum immersion tank. Two full systems were
also constructed specifically for factory trials on Sandiacre and Ilapak machines – common types in the fresh
produce industry.
Development of ‘Integrity Seal’ sealing technology
5
Marks & Spencer, after seeing the Integrity Seal concept, agreed to support the WRAP application and also
became a project partner.
The full list of partners is given below:
Partner
International Food Partners Ltd
Ceetak Ltd
Marks & Spencer plc
Tilmanstone Salads
Vitacress Salads
Exotic Farm Produce
United Biscuits (KP)
1.2
Role
Project Management
System manufacture
Retail evaluation
Leafy salad producer
Leafy salad producer
Fresh vegetable manufacturer
Snack producer
Key Contacts
Graham Clough – Director
Mark Franklin – Sales Manager
Helene Roberts – Head of Packaging
Chris Taylor – Technical Manager
Mike Rushworth – Operations Director
Hilary Gamon – NPD Manager
Barry Pamplin – Packaging Technology
Manager
Project Methodology
1.2.1 Staged trials
The first stage of the project involved setting up laboratory trials at Ceetak using a bench top sealer to test the
prototype system and establish its operating parameters. Film samples were obtained from all the manufacturing
partners for the trials and retail packs were purchased to enable the testing of filled bags. The seal quality and
strength was measured by a combination of vacuum immersion tank tests, penetrative dye tests and tensile tests.
Optimum settings were found for each film type which produced hermetic seals.
The second stage of the project involved repeating the trials at the partners’ sites using product straight from the
production lines. The tests were again conducted using the bench top sealing rig. This was the first time that the
system had been used under chilled conditions and so the aim of these trials was primarily to confirm that
hermetic seals could still be made under low ambient conditions. The trials were successful.
The third stage involved setting up Integrity Seal on production machines at each of the partner companies to
run trials under genuine production conditions. Fresh leaf salad was run at Tilmanstone Salads and Vitacress on
Sandiacre and Ilapak machines respectively, fresh vegetables were run at Exotic Farm on a continuous motion
Sandiacre and peanuts and snacks at KP on intermittent motion Sandiacre machines. At all the locations it was
demonstrated that hermetic seals are possible with the 1mm-wide weld seal. Full details of the technical and
commercial benefits are listed in Section 6 of this report, ‘Benefits analysis’.
The fourth stage of the programme was a one month production / commercial trial at Tilmanstone Salads,
supplying Marks & Spencer with Iceberg Lettuce and Spinach. The aim of this trial was primarily to run significant
pack volumes on a production machine to assess the seal’s reliability. The system was run with the standard
printed wrap so the bags were the same overall cut length but actually had a larger internal volume due to the
narrow seal. Over 175,000 bags were run during this trial.
The fifth stage of the programme was to fit the sealing system to a production machine at Tilmanstone Salads
and run for three months, with new film printed to the shorter bag length. The main objective of stage five was
to prove the daily performance characteristics of the system and to compare its performance against standard
crimp jaws. The system was run on three product types, daily, seven days a week for three months with product
selling nationally in Marks & Spencer stores. Iceberg Lettuce and Summer Salad varieties were selected as they
are particularly oxygen-sensitive and have the shortest shelf-life. Spinach was also packed, being a good example
of a low respiring leaf. It is also a difficult variety to pack due to its variable leaf size so would challenge the seal.
Over 600,000 bags were run during this trial, producing a film saving of 315kg.
During the trial the following data were collected:
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Machine speed
Net Machine Efficiency (NME)
Rework levels due to entrapped product in the seal
Development of ‘Integrity Seal’ sealing technology
6
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Tightness of the seal – headspace gas levels
Strength of the seal – vacuum immersion tank test
Micro leak level – penetrative dye test
Life of the jaw components
Machine Operator interface
Engineering maintenance issues
Product shelf-life – sensory
Product shelf-life – microbiological
1.2.2 PIRA independent assessment
Marks & Spencer requested that unbiased data be obtained from an independent laboratory to confirm the seal
quality. PIRA therefore compared the seal quality of Integrity Seal samples to control samples with crimp seals.
The seal quality was measured in three ways:

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Dye test to look for micro leaks
Vacuum immersion tank to look for micro leaks and failure mode
Tensile test to measure the seal strength and mode of failure
The data from the PIRA tests correlated well with the data recorded by IFP and the manufacturing partners
during the production trials. The independent tests conducted by PIRA confirmed that the performance
characteristics in all the product applications matched the data recorded by IFP during the various factory trials.
Full details of the PIRA tests are available on request.
1.3
Project success criteria
Project success criteria were agreed with WRAP and the project partners.
1.3.1
The sealing jaw performance
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Jaws should fit easily to existing machines
The system must work on servo and pneumatic machine types
The life of the system must be comparable to existing technology
The jaws must be designed for IP 65 rating
The jaws must be easily cleaned
Any components subject to wear must be easily replaced
All parts should be corrosion resistant
The system control should easily work with the machine functions
The system must be capable of making pillow packs and block-bottom gusseted bags
Figure 1 A block-bottom seal on a gusseted bag
Development of ‘Integrity Seal’ sealing technology
7
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The system must be easy to operate
Sealing must cut through trapped leaves
Figure 2 A pillow pack showing seal
1.3.2 Pack performance
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Better product quality potential
Longer shelf-life – sensory and microbiological
Uses less material than conventional crimp seals
Hermetic seals
No packs in store with product in seal
Good pack appearance – no heat distortion
High strength seals do not burst but easy to open
Works on all current packaging materials
Works on new-generation compostable materials
Development of ‘Integrity Seal’ sealing technology
8
2.0
2.1
Integrity Seal
Limitations with current technology
Crimp sealing has been used for sealing flexible packaging on automatic packaging machines since they were first
invented. The principle involves using a wide-profiled seal jaw typically 15mm wide to apply heat and pressure for
a controlled dwell time to activate the surface layer of the packaging material.
Crimp sealing jaws cannot make hermetic seals on thin polymer films because the metal jaws are rigid and so do
not apply uniform pressure across the width of the seal. This means that where the film thickness varies at the
back seal or gussets, the film is not compressed evenly. This is particularly so when there are random, unwanted
creases in the seal area. All the pressure is taken at the thickest points, i.e. where there are three layers at the
back seal overlap and where there are four layers in the case of a gusseted pack. The rest of the seal area with
only two layers receives very little pressure, allowing the polymer to flow away from the heat source. Because the
film is not held under pressure at these points it suffers thermal distortion and develops pinhole leaks.
The ribbed profile of standard crimp jaws, shown in Figure 3, is designed to compress the film in a controlled
manner but it also creates problems. Polymer slowly builds up on the jaws and if not cleaned regularly causes the
film to stick to the jaw. This causes rippling of the film in the crimped area and spoils the appearance of the pack,
as well as impairing its integrity. Any product or packaging material touching the constantly heated jaws gets
burnt on, and has to be removed by wire brushing. The centre knife is always a problem, requiring frequent
cleaning for optimum performance. Product commonly gets trapped in the knife slot and builds up over time,
eventually impeding the knife movement.
Figure 3 The ribbed profile of standard crimp jaws
Dye tests show that all crimp seals have pinhole leaks at the bag edges, the back seal overlap point and at the
point of any creases. Figure 4 shows dye penetrating at the back seal overlap (left) and at a random crease in a
conventional crimp seal
Figure 4 Typical cross-seal failures
Monolayer packaging films commonly used for fresh produce are particularly prone to seal leaks because the
active surface layer which makes the seal is only 2–3 micron thick. Hence there is little polymer present to make
the seal hermetic.
Development of ‘Integrity Seal’ sealing technology
9
Where hermetic sealing is paramount it is common to use laminated films with a thicker sealant layer of 15–20
micron. Such films are more expensive and use more polymer simply to make a seal.
The width of a crimp seal is typically 10% of the total film area used for the finished bag and can be as much as
20% for smaller bags typical in the snack market. As there is no guarantee that a wider seal produces hermetic
seals and rigid jaw designs will always apply uneven pressure there is a need for a new approach to making
hermetic seals.
2.2
The Integrity Seal technology
Integrity Seal is a new-generation impulse heating technology which uses a novel means of applying heat to the
film, combined with a unique non-heated front rubber cutting anvil.
With Integrity Seal only the rear jaw is heated. A narrow laminated impulse element heats when triggered by the
jaw closing signal. The low mass design allows the element to heat very rapidly to the polymer melt temperature,
typically 280 ºC. Because the element is also very narrow only a small area of film is heated. The rear jaw also
has a chamber behind the element filled with chilled water. The function of the chilled water is to cool the seal in
order to harden the polymer so it is strong enough to support the falling product. To assist cleaning and extend
the life of the element a self-adhesive Teflon tape covers the face of the element. When worn it is simply pulled
away and replaced.
Figure 5 The front and rear jaw of the Integrity Seal
The front jaw uses a unique design of moulded silicone rubber as a cutting device. A V-shaped protrusion in the
centre of the anvil acts as a cutting blade to press the polymer against the heated rear jaw so that the high
temperature produces a weld seal. The heat transmission is partially through the cut edge of the film so the
resulting seal is made from the full thickness of the polymer, typically 70 micron. A further design feature of the
rubber anvil is the inclusion of embossed shoulders either side of the ‘V’ which help clamp the polymer during the
heating process and produce a neat embossed seal area just 1mm wide.
The ‘V’ blade is simply pressed into the housing, so allowing rapid and easy change, without tools, when it
becomes worn. For additional information see Appendix 1: ‘Integrity Seal technology’.
Figure 6 The temperature controller has a visual display showing details of the process
Development of ‘Integrity Seal’ sealing technology
10
3.0
3.1
Fresh Produce Trials
Leafy salads
The fresh produce market was the first choice for testing and commercialisation of the Integrity Seal because of
the short shelf-life of the product and sensitivities to pack atmosphere. Traditional crimp seal technology does not
produce a hermetic seal, and this limits the shelf-life of produce sealed by this method. There would be
significant advantages if a hermetic seal could be formed. Fresh produce respires from the moment it is harvested
to the end of its shelf-life. There are different levels of respiration rate sensitivity. Some leaf varieties such as
iceberg and cos lettuce are highly sensitive to oxygen, whereas many baby leaf varieties such as young spinach,
rocket and lamb’s lettuce are not. It is therefore necessary to use a variety of breathable films to control the
oxygen and carbon dioxide levels in the headspace. When crimp seals leak this control of pack atmosphere is lost
or severely compromised, so the film is no longer controlling shelf-life.
Leaking seals allow in oxygen from the atmosphere. This promotes further respiration, producing more carbon
dioxide and shortening the life of the product. Hermetic seals prevent oxygen getting through the packaging
material. The objective is to reduce the oxygen in the headspace to near zero and maintain a carbon dioxide level
of between 5 and 10%.
Marks & Spencer nominated two of their suppliers for the leaf salad trials: Tilmanstone Salads and Vitacress
Salads. They packed a range of salad varieties from heavy-leaf sensitive varieties such as iceberg lettuce and
baby leaf non-sensitive varieties such as young spinach, on two different types of packing machine: Sandiacre
intermittent motion machines and Ilapak continuous motion bagging machines.
3.2
Tilmanstone Salads
Marks & Spencer initially requested a depot trial involving supplying two salad types: iceberg lettuce in blockbottom bags and spinach in a pillow pack style. The trial ran for one month in April 2006. The aim was to
evaluate the integrity seal technology under production conditions and to see how the packs performed in the
market. Sandiacre machines were used for the trial: one a servo type and the other pneumatic. There was no
difference in performance between the two types.
Figure 7 M&S Spinach packs showing the old seal (front) and the new (back)
Each machine performed well and line speeds were around 10% faster than normal. Packs retained for shelf-life
verification showed that the Iceberg Integrity Seal packs lasted 8 days – 3 days longer than the standard.
Spinach packs also lasted 9 days – 2 days longer than normal. During the trial the jaws were taken off the
machine daily and replaced with standard crimp jaws, which confirmed the ease of changeover and gave the
machine operators experience in carrying out the change.
Following the successful trial it was agreed to run a more extensive study over 3 months with a larger product
range and with bags printed to the shorter length (to take account of the new, narrower seal).
Development of ‘Integrity Seal’ sealing technology
11
The trial was conducted between October and December 2006 and was extremely successful, confirming the
system reliability, consistency and performance / pack benefits. As a consequence Marks & Spencer decided to
introduce Integrity Seal during 2007 for their fresh salad range.
Figure 8 Integrity Seal packs alongside standard packs on M&S shelves
3.3
Vitacress Salads
Vitacress Salads predominantly use continuous-motion Ilapak bagging machines; therefore the challenge was to
verify that the new technology would work satisfactorily on this type of machine. In addition there was a need to
confirm that both monolayer OPP films and laminated co-extruded OPP film could be handled successfully for
straight seals and gusseted block-bottom seals respectively.
Vitacress packs mainly baby leaf salads, which flow differently to the heavier leaf varieties packed at Tilmanstone
Salads.
Figure 9 M&S Young spinach (packed at Vitacress)
The trials were conducted over a three-week period on the same machine, meaning that that daily changes
between Integrity Seal and standard crimp seal jaws had to be made in order for normal production to continue.
The key points learned from these trials are as follows:
Development of ‘Integrity Seal’ sealing technology
12
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The Integrity Seal jaws need to be symmetrical on the top surface to make it easier to form a neat
gusset. When this modification was incorporated and tested in a repeat trial the results were comparable
to the findings from the Tilmanstone Salads trials.
The jaws need to be accurately aligned.
The importance of jaw pressure – it needs to be high, but not high enough to over-stress the machine
mechanism.
The quality of the seals was comparable to the seal quality produced at Tilmanstone Salads on the
Sandiacre machine.
Seal quality was measured by vacuum testing bags containing product, and dye testing for micro leaks. Packs
were also subjected to headspace gas, organoleptic and microbiological shelf-life tests. The results showed that
there was no difference in shelf-life between Integrity and standard sealed packs.
The ability of the seal system to seal through product contamination was tested and in many cases good seals
were produced. The leaf is completely severed and pushed away from the seal area, allowing the film to still
make a weld seal. Very thick and bulky stalks were partially crushed and severed but not completely pushed out
of the seal area. In some of these cases the bag still passed the vacuum and dye tests.
Figure 10 A perfect seal – leaf has been severed
3.4
Fresh Vegetable Trials: Exotic Farm Produce
Integrity Seal technology was run at Exotic Farm Produce in Boston on a continuous-motion Sandiacre machine to
pack a range of fresh vegetables. This trial showed that Integrity Seal is capable of handling heavy products at
high speeds. The weight range was from 250 to 750g and speeds were between 60 and 85 packs per minute.
All fresh vegetables are packed in perforated films so do not require a hermetic seal; nevertheless there is still a
need to produce high-integrity seals so the perforated film can control the headspace gases.
Exotic Farm use only one type of packaging film – Amcor P-Plus – and only produce pillow pack style bags.
The trials were conducted over a two-week period on the same machine. During the trial period the jaws were
removed to allow the machine to run normal production with standard crimp jaws.
The key points learned from these trials are as follows:
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Changing between crimp seal and Integrity Seal jaws is a simple exercise once the correct alignment has
been established.
Sealing pressure needs to be high without over-stressing the machine mechanism.
The optimum sealing conditions established in the laboratory trials were repeated on the product
machine.
Exotic Farm run their machines between 50 and 120 packs per minute in normal production so trials were
conducted to establish the maximum speed possible with Integrity Seal. 85 packs per minute was found to be the
maximum possible with the current controller, which had a maximum limit of 300 ºC. To achieve faster speeds it
will be necessary to increase the sealing temperature to compensate for the shorter seal time.
Development of ‘Integrity Seal’ sealing technology
13
Packs were retained for headspace gas, and organoleptic shelf-life tests. The results confirmed that there was no
difference in sensory shelf-life, although lower carbon dioxide levels were found with broccoli. Broccoli has a very
high respiration rate so can produce very high levels of carbon dioxide which can cause packs to blow
prematurely. Hence the lower levels encountered with Integrity Seal could be beneficial.
The ability of the Integrity Seal technology to seal through product contamination was tested and found to be no
worse than the current crimp seal when the contamination is a large piece of vegetable. However, small pieces
were cut through and sealed, so reducing rework levels. As much as 20% rework is sometimes evident due to
product trapped in the crimp seals; with Integrity Seal this was below 10% and where large pieces of vegetable
were caught in the seal the packs were completely open. So, as with leafy salads, there will be no packs leaving
the factory with product trapped in the seal.
The only issues still to be resolved are:
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Operating life of the system running at higher temperatures – good performance so far but need more
production hours.
Maximum operating speed.
Since the initial trials Integrity Seal has been upgraded with a higher seal temperature capability and initial
laboratory trials show that this higher range capability will produce the higher speeds. Further trials are to be
conducted at Exotic Farm on behalf of Marks & Spencer.
Development of ‘Integrity Seal’ sealing technology
14
4.0
4.1
Snack product trials
United Biscuits (KP)
United Biscuits (KP) trialled Integrity Seal on their leading snack products – Hula Hoops and Skips – as well as on
peanuts and Marks & Spencer Prawn Cocktail shells and Potato Rings.
The Integrity Seal technology was fitted to intermittent-motion Sandiacre machines in two factories: Ashby,
running Hula Hoops and Marks & Spencer Prawn Cocktail shells and Potato Rings, and Rotherham, running dry
roast and salted peanuts.
4.1.1 Ashby trials
The machine at Ashby ran for over 4½ hours non-stop at 56 bags per minute with high levels of seal integrity
producing around 15,000 packs. KP Skips and Marks & Spencer Prawn Cocktail shells were also packed during
this extended trial.
Figure 11 Marks & Spencer Prawn Cocktail shells showing Integrity seal
KP operate their machines at between 50 and 100 packs per minute in normal production so trials were
conducted to establish the maximum speed possible with the Integrity Seal technology. 56 packs per minute was
found to be the maximum possible with the current equipment. To achieve faster speeds it will be necessary to
increase the sealing temperature to compensate for the shorter seal time. The control unit used for the trials had
a maximum of 300 °C.
Other key points learned from the trials are as follows:
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The trials showed that high-integrity seals can be made running snack products.
The jaw pressure needs to be high without over-stressing the machine mechanism. KP staff requested
that IFP consult Sandiacre to verify that the pressure required for Integrity Seal to work was not
detrimental to the structure or engineering components of the machine. IFP will follow up as requested.
Seal quality was measured by dye testing for micro leaks, vacuum tank for pressure leaks and tensile
strength with comparisons against controls. The crimp seal controls tested were consistent and to the
normal standard. Micro leaks – which are inevitable with crimp seal technology – were found as
expected, at the bag corners and occasionally at the back seal overlap. Integrity Seal bags showed a
high level of consistency and seal integrity.
The ability of the seal system to seal through product contamination was tested and found to be no
worse than the current crimp seal.
Tensile tests showed seal strengths of between 0.12N and 1.4N for the standard crimp seals and 0.76N
to 2.2N for Integrity Seals. Integrity Seal’s do not peal open because the seal is only 1 mm wide but fail
by snapping across the edge of the weld. All Integrity Seal samples tested snapped at these high
strengths confirming that the seal is both strong but will open easily when pulled sufficiently. Hence the
consumer can open the bag easily.
The shelf-life achieved on Hula Hoops matched the current 12 weeks of the existing packs. In the snack
industry seal integrity is generally much better than with fresh produce so the level of leakage is much
Development of ‘Integrity Seal’ sealing technology
15
less, although not perfect. Integrity Seal will hopefully eliminate the small proportion of packs that do
still leak, but it is unlikely that shelf-life will be extended.
Once it has been demonstrated that Integrity Seal can be operated at higher speeds under production conditions,
it will be possible to investigate the potential for employing thinner gauge materials.
A short trial packing Hula Hoops with the higher temperature controller was successful and 105 bags per minute
was achieved. However, at the faster speed it was found that bags were not moving away from the jaw
sufficiently quickly and were sticking together. Hula Hoop packs weigh only 25–34g, which means that there is
little weight to help the pack fall away from the sealing jaws. For such applications it will be necessary to fit an air
pulse as the jaws open to help the pack fall – a common technique in the salad industry.
Following successful initial trials KP are proceeding with a market trial using Integrity Seal technology to seal
snack multi-bags. In addition to savings made on packaging material, multi-bags will benefit from a hermetic seal
remaining inflated during transit and on shelf.
4.1.2 Rotherham trials
The objective was to test the performance of Integrity Seal technology under production conditions packing both
roasted salted and dry roasted peanuts. The Integrity Seal technology was set up on an intermittent motion
Sandiacre bagging machine, at the KP Rotherham plant.
The trials were run at 36 bags per minute which was the maximum possible with the temperature limit on the
prototype control system. KP normally operate within the range 45–70 bags per minute and so speeds will need
to be increased before the system can be adopted commercially. The developments already in hand will provide a
system with a higher speed capability.
Figure 12 KP Dry Roasted Peanuts pack with the new seal
The ability of the seal system to seal through product contamination was tested and found to be no worse than
the current crimp seal. The Rotherham factory uses larger bore air cylinders on its Sandiacre machines so there is
more than adequate pressure for sealing. Out of 100 packs tested only 2 were found to have product
contamination in the seal area causing leaks. These two packs were of the dry roast variety, which is particularly
difficult to pack because of the dusty seasoning coating the nuts.
The shelf-life achieved on all the peanut packs matched the current 12 weeks with the existing packs.
There is potential to reduce the film specification for peanuts as Integrity Seal technology may not require such a
heavy PE layer to make the seal.
Development of ‘Integrity Seal’ sealing technology
16
5.0
Film Trials
The objective of these trials was to test Integrity Seal technology running thinner gauge and compostable films,
and to assess the impact on shelf-life of gassed and non-gassed bags. These trials were run at Tilmanstone
Salads with products selected from the 3-month commercial trial, using packs in the current standard film as
controls. The sealing properties were assessed, together with the general machinability of the films.
Tilmanstone provided the following films from Amcor:



25 micron OPP unprinted
30 micron OPP unprinted
40 micron PLA unprinted
International Food Partners Ltd obtained the following films from Octopus Packaging:


25 micron PLA unprinted
30 micron PLA unprinted
The following standard current film was run as a control:

20 micron CPP/15 micron OPP
Products run during the trials were Iceberg Lettuce and Summer Salad with the block-bottom style of bag.
5.1.1 Summary of results
Integrity Seal technology gave excellent results on the 25 and 30 micron OPP films, with integrity and shelf-life
comparable to the 35 micron standard film. There was no extension to shelf-life due to the quality of the raw
material being received at that time. At 5 days, shelf-life was comparable to the control samples. The level of
failures, identified by dye testing, were comparable to the 35 micron film packs sealed with the Integrity Seal,
and occurred when additional creases were present in the gusset area.
Figure 13 The block-bottom style seal in the 30 micron OPP film held with no dye leaks
Trials with the 25 micron film were also successful but showed a slightly higher number of failures due to
additional creases in the gussets. Again, these were no worse than for crimp seals. It was noticed that the seal
width, which is normally 1mm in 35 micron films, was actually wider with the 25 micron OPP film, at 1.5mm. This
was probably because the thinner film gave less resistance during the sealing process and so squeezed out
further, making a wider seal.
Development of ‘Integrity Seal’ sealing technology
17
Figure 14 25 Micron OPP with wider 1.5 mm seal
Producing well-formed block-bottom bags is always more difficult than producing pillow packs – whether with a
crimp seal or Integrity Seal – so the level of leakage is always higher. Integrity Seal technology can make
hermetic seals when there are up to 4 layers of film, but it does not always make a hermetic seal when there are
6 layers. It is therefore recommended that thinner films are used for the pillow packs as this will ensure a higher
level of integrity and control of shelf-life.
Block-bottom bags normally require a laminate to produce inside-to-inside and outside-to-outside seals, but with
Integrity Seal it was possible to make both seals with just monolayer film. Being able to use monolayer film rather
than a laminate will generate further material and financial savings.
The trials with the PLA films were unsuccessful. Only the 40 micron film could actually be run through the
machine; the 25 and 30 micron films were so brittle they could not be fed past the forming shoulder of the
vertical form-fill-seal machine without cracking and splitting. On a vertical form-fill-seal machine the film has to
fold through approximately 270 degrees in a three-dimensional movement to form the bag shape and this places
a severe strain on the film. Unless the film has a high level of tensile strength it breaks at this point. The 40
micron film was strong enough to feed through the machine and could actually be sealed, but the brittleness of
the film caused stress cracking of the seal edges during subsequent handling. In particular, the cracking was
observed at the interface between the different layers. Most cracks appeared at the point of the gusset end
where the film changes from 4 layers to 2 layers.
Figure 15 40 micron PLA film produced stress cracks at the bag edge away from the seal area, showing the
inherent brittleness of the film
It is possible that 40 micron film could be used in a pillow pack format but the problem of the overall brittleness
of the film must be overcome. Alternative biopolymer materials with different mechanical properties were not
tested.
Overall the trials with thinner OPP films were very successful with no issues in running the films in terms of
handling characteristics or final seal quality. If anything the seal quality was better as wider seals were produced.
Development of ‘Integrity Seal’ sealing technology
18
6.0
Benefits Analysis
Integrity Seal technology offers several advantages:
6.1
Packaging material weight saving
A reduction in film area of between 10 and 15% (20% on snack packs) as a result of using shorter bags will save
around £15,000 per year per bagging machine, based on a two-shift, six day a week operation using a 35 micron
OPP type film.
A gauge reduction from 35 to 30 micron will save a further 14% in terms of weight of film. Whether this gives a
14% price reduction will depend on the policy of the film manufacturers, but certainly a further substantial saving
can be forecast.
Successful trials were run with 25 micron OPP film at Tilmanstone’s, although further commercial testing will be
needed to confirm market and consumer acceptance of such thin films.
These benefits could produce a total 20% saving in overall material costs. Reduced rework also means less waste
material to be disposed of, adding another saving.
For more detailed calculations and estimated material savings see Appendix 2.
6.2
Product shelf-life benefits and reduced wastage
Extended shelf-life is possible with fresh produce because the hermetic seal now possible with Integrity Seal
stops oxygen getting in and carbon dioxide leaking out of the pack. Hence the packaging material can lower the
product respiration rate. Gas flushing of packs is commonly used to help extend product life but this is ineffective
when seals leak and the gas mix is lost. The typical gas mix of 5% oxygen and 5% carbon dioxide is designed to
lower respiration and inhibit microbiological decay. Data recording during the trials showed greater consistency in
the headspace gases where the Integrity Sealing technology had been applied.
Improving the product quality and extending the shelf-life can deliver several benefits. With product lasting
longer in the pack there is a greater likelihood that the consumer will not have to throw any of the product away.
Currently most fresh salads have matching display and use-by dates so technically the product should be
consumed on the day of purchase. In many cases this will not happen and the average consumer will use their
senses to decide whether the product is still usable.
It may also be possible to extend the use-by date so the product does not have to be consumed on day of
purchase, helping the consumer plan ahead for meals. The improvement in the shelf-life of fresh salad and
reduction of in-store waste will also reduce costs. Marks & Spencer stated that store shrinkage can be as high as
8% at certain times of year when the leaf is delicate.
The main financial benefit of extended shelf-life may be the opportunity to optimise production scheduling and
distribution. Although stores now have daily deliveries, any potential to reduce delivery costs and impact on the
environment should be looked at seriously. The extra shelf-life of 2–3 days with no loss of quality could allow for
less frequent deliveries to store and/or optimised production schedules.
6.3
Technical benefits
The technical benefits of Integrity Seal include:
6.3.1 Seal integrity
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Seal tightness is superior to crimp seals – no micro leaks, so headspace gas is controlled by the film
permeability, not leaking seals.
Random creases, which always occur in a bag made on a vertical form-fill-seal machine and are a major
contributor to leakage, will now be sealed hermetically due to the welding action of this technology.
Controlling seal tightness now means the packaging material can do a better job of controlling
headspace gases via permeability of the film. With such improved control it will be possible to reduce
film gauge and better control permeability rates.
Development of ‘Integrity Seal’ sealing technology
19

Seal strength is superior – crimp seals leak at 0.25 bar in an immersion vacuum tank test. Integrity Seals
fail by bursting at 0.5 bar.
Figure 16 M&S Iceberg Lettuce holding 0.5 bar pressure with no leaks
Figure 17 Vacuum tank test at Rotherham confirmed hermetic seal on KP peanut pack
For additional information on the test results and photographs see Appendix 3, ‘Seal quality data’.
6.3.2 Product quality benefits


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
Better product quality and longer shelf-life proven on fresh product applications due to airtight seals,
both pillow and block-bottom styles.
Improved product quality due to lower production respiration and rate of decay rate – no oxidation or
enzymatic browning.
Fresh vegetables – better quality due to improved CO2 control.
Lower respiration rate increases tolerance to higher temperatures.
Better control of the headspace gases and film permeability reduces the risk of the product undergoing
anaerobic decay.
For additional information and photographs see Appendices 3 and 4.
6.3.3 Machine performance benefits
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
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For most applications the sealing time is faster than with crimp sealing because the heat is applied at
very high temperature to the cut edge of the film. Hence machine speeds are typically 10% faster.
Only one impulse element is required; the other jaw is non-heated.
Wear components – Teflon tape and rubber anvil are easily and quickly replaced, ensuring the seal
quality is easy to maintain.
The system is immediately ready to run when switched on – no jaw heating time.
Development of ‘Integrity Seal’ sealing technology
20
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
Changes in sealing temperature and time are instantaneous both up and down, no time needed for
stabilisation.
The system can be retrofitted to existing machines or built into new machines. In the case of pneumatic
machines it may be necessary to fit a larger air cylinder to increase the cutting force.
The jaws are simply screwed to the existing cross-frames of the machine.
Jaw closure is sensed independently of the machine control and could be fitted with sensors to open the
jaws in the event of foreign body inclusions.
The temperature profile of the heated jaw on each cycle is monitored with a visual display.
The seal temperature range is not critical – only it must be above the polymer melt temperature.
The chilled water system can be centralised to feed multiple machines and positioned away from the
high-care area.
The chilled water system is a closed loop system so does not use copious amounts of water.
6.3.4 Elimination of seal contamination on delivered packs




The cutting action of the ‘V’ notch on the surface of the rubber anvil severs the majority of leaf types
and still makes an hermetic seal.
Seals are not completed when large contamination is present, i.e. large leaves, thick stalks, foreign
matter, so bags drop unsealed and are easily identified and removed from the line.
Integrity seal still makes a hermetic seal in the presence of moisture and free water.
Bags therefore do not get to store with product trapped in the seal, as commonly happens with crimp
seals.
Figure 18 A perfect seal
6.3.5 Health and safety benefits
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Both jaws are safe to touch after every cycle.
Both jaws can be wiped clean at any time.
Product does not get burnt onto the sealing jaws when an open bag comes through the machine and
product spills out.
There is no sharp metal knife.
Jaws’ electrics are IP65-rated.
No tools are needed to change either the Teflon tape or the rubber anvil.
The chilled water has an antimicrobial additive to prevent legionella and other bacteria.
6.4
Commercial benefits
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Integrity Seal not only offers many production advantages; it dramatically improves the pack performance and
brings several commercial benefits. The industry is looking for ways to reduce packaging, reduce costs and
improve product quality. Integrity Seal delivers all of these.
6.4.1 Packaging material saving
Film area/ weight reduction of 8% to 20%:
Multi-bags 8.75%

Development of ‘Integrity Seal’ sealing technology
21
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Single portion packs (salads, vegetables or snacks) 10%
Snack size packs (fruit slices, nuts and savoury snacks) 13 to 20%
Gauge / weight reduction potential of 12–14%: Examples:

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OPP film used for salads and vegetables – down to 30 micron from 35 micron, 14.28% (confirmed by
trials)
OPP Laminates used for snack products – down from 40 micron to 35 micron, 12.5% (projected)
Only uses 1mm of bag length at each end to make a hermetic seal.
6.4.2 Longer shelf-life




Oxygen-sensitive, fresh leafy salads shelf-life increased from 5 days to 8 days
Non sensitive leaf varieties, e.g. Spinach, shelf-life increased from 7 to 9 days
Snack products – comparable shelf-life at 12 weeks on single bag applications.
Potential where any product is packed in flexible packaging material and requires a hermetic seal to
control quality whether it is reliant on permeability or barrier to gases, moisture vapour and odours.
6.4.3 Reduced production costs
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Reduced rework reduces disposal costs for waste packaging material.
Higher line efficiency reduces total manufacturing costs.
Integrity Seal technology seals all types of polymers and eliminates the need for laminated or extruded
sealant layers.
Potential for layers in snack products to be reduced.
6.4.4 Marketing benefits
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6.5
Potential to differentiate with the neater and narrower Integrity Seal.
Integrity Seal can be used for both pillow packs and block-bottom gusseted bags
Pillow packs tear open easily because the film fractures along the edge of the weld and propagates
across the top of the bag.
Hermetic seals on multi-bag applications prevent the bag deflating over time so it looks better on the
shelf.
The seal never looks overheated and blistered, as can happen with crimp sealing.
The bags stand better because there is no folded crimp seal.
Integrity Seal also presents a marketing opportunity – new sealing method offers improved freshness
and saves on packaging.
There is no crimp to fold back and get stuck to the film side – a common occurrence on fresh produce
applications.
Consumer preference for the neater looking seal when tested with fresh produce.
Some initial caution on snack products because of the unfamiliar appearance but liked when shown the
seal strength and easy opening.
Integrity Seal is being offered to the market on a lease basis and is sold as a profitable system. The
savings in film usage and the increased productivity more than pay for the investment so the system will
save money for the user.
Other productivity and financial benefits
Line speeds are 10–12% faster, giving the opportunity for significant cost reductions because of reduced
production times. This translates to 6–7 minutes per hour.
Combined with the improved efficiency due to less rework, the actual production time for a given batch will be
further reduced by at least another 10%.
A major problem when filling product on vertical bagging machines is the product contamination between the
jaws. Where line operators see the contamination they remove the packs from the line but they do not see every
pack, particularly when printed film is used in the seal area. Consequently many packs go unnoticed and get to
store with impaired product quality and shelf-life. As Integrity Seal cuts through many of the leaves and still
makes a seal it eliminates the seal contamination problem. Only when the contamination is particularly large or
bulky does the seal suffer and then the seal is completely open and easily seen by the line checker and removed.
Development of ‘Integrity Seal’ sealing technology
22
Rework levels vary considerably depending on the nature of the raw material but can be very high, even as much
as 20%. Integrity Seal reduces the level to well below 5%. Although product can be reworked the bag obviously
cannot, so has to be disposed of. Taking an average film loss from 10% reworked product for a typical factory
running 20 million bags per year the weight of film thrown away is around 9 tonnes but if the rework can be
lowered to 1–2% the figure drops to around 1 tonne.
6.6
Consumer research findings
At the request of Marks & Spencer an independent market research agency was engaged to conduct focus group
research to gauge the reaction of typical M&S customers to the new seal format. Category Consulting Ltd was
used for the research, which was conducted in the London Colney M&S store. Three group sessions were
conducted – each involving 12 female respondents recruited in store whilst purchasing appropriate products.
More detailed research would obviously be needed to establish consumer opinions on the appearance and
usability of any specific product having the Integrity Seal.




Overall findings: The new bag seal would be accepted by shoppers and is unlikely to have any
detrimental effect upon sales, although it is unlikely to affect sales positively either. The exception is in
crisps and snacks, where the respondents prefer the current pack to the new one. The new nut pack,
however, is preferred over the existing one as it is easier to open. Overall, respondents do not express
strong preferences for one style or the other. Although they appreciate the environmental benefits, they
do not really care enough to be excited by the new concept. Ease of opening is seen as the main benefit
to consumers and bags splitting being the main frustration.
Salad Bags: This category scored best in terms of preference for the new concept and there was no
doubt that the new concept in pillow pack format (no gusset) was preferred. Most comments on
frustrations with existing salad bags were unprompted and respondents’ feelings were strongest in this
category.
Vegetable Bags: This category received a more tempered response although, overall, the new concept
was preferred, except for concerns where microwave cooking is used. The bag format did, however, rate
much better than any existing vegetable tray formats and highlighted a key opportunity area for
package and waste reduction.
Crisps, nuts & snack bags: Crisps and snack bags where not preferred, because the respondents
were not used to the appearance of the new ‘plumper’ bags and had concerns about packs popping
open. This could present an opportunity for pack differentiation. Nuts were more readily accepted in the
new format, due to the difficulties already being experienced when trying to open the existing bags.
Development of ‘Integrity Seal’ sealing technology
23
7.0
Industry Potential
This WRAP-funded project has enabled the fresh produce and snack product applications to be evaluated and
optimised (fully for fresh produce, partially for snacks). However Integrity Seal technology can be applied to any
other product that is heat sealed in flexible packaging material on automatic and even hand-sealing machines.
The same system which works on vertical form-fill-seal machines will work on horizontal linear motion flowwrapping machines. It is also possible to develop the system for use on rotary flow wrapping machines by the
simple addition of rotating manifolds to feed the chilled water.
The potential for other products is considerable:








Cereals
Bakery
Confectionery
Biscuits
Dairy products such as cheese
Fresh meat and cured meats
Soups
Sachet packed products – condiments
In addition there are also many potential non-food applications:




DIY products
Toiletries and soaps
Cosmetics
Detergents and household products
In essence any product that goes in a flexible pack that is heat sealed could be suitable for this method.
Development of ‘Integrity Seal’ sealing technology
24
8.0
Overall Conclusions
The project overall has been very successful in that Integrity Seal has been taken from a prototype concept to a
fully commercial technology. Part-way through the trials it was decided to incorporate further design
improvements to improve the performance and include IP rating for safety in wet food environments. A further
development was the introduction of a higher temperature controller to increase the speed capability for fresh
vegetables and snack products.
The 4 months of running fresh salads for Marks & Spencer under normal production conditions was the key test
of the technology and showed that with Integrity Seal technology it is possible to run shorter bags, make
hermetic seals and improve product quality. The system also ran more efficiently and with improved productivity,
running 10–15% faster and with significantly less rework.
Packs made with Integrity Seal technology were challenged with the penetrative dye test and vacuum immersion
tank and all in applications it was confirmed that hermetic seals are possible.
In the majority of fresh produce trials an increase in shelf-life was achieved due to the elimination of uncontrolled
leaks, hence the packaging material was able to actually control the headspace gases more effectively. This was
the case for both low- and high-respiring varieties, even when perforated P+Plus OPP film was used. With highsensitivity varieties an additional 2–3 days was possible and with low-respiring varieties 2 days. In isolated cases
where shelf-life was comparable to that obtained with standard crimp seal technology, this was thought to be due
to sub-optimal raw material being packed.
Shelf-life on snack products was unchanged at 12 weeks. Leakage levels on snack products are much less severe
than with fresh products although product contamination can cause both crimp and integrity seals to fail. The
main interest for snack products is the reduction in film area and the potential to reduce the gauge of the film
without sacrificing barrier properties.
Although commercial trials were not conducted on the vegetable and snack products there is still keen interest
with the partners. For vegetable and single snack bags the key issue is being able to run at 100 bags per minute
or faster, which the higher-rated system should be capable of. Further trials are planned in these areas.
The final indicator of the successful outcome of the project is the fact that Marks & Spencer have decided to
introduce Integrity Seal technology during 2007 for their fresh leafy salads.
Initial reaction from presentations to some of the other major retailers has also been extremely positive.
Development of ‘Integrity Seal’ sealing technology
25
Appendix 1 Integrity Seal technology
Integrity Seal is a new-generation impulse heating technology combined with innovative rubber technology. It is
unique as a sealing technology that applies heat to the cut edge of the film, not through the body of the film. In
so doing, it produces a weld bead seal which is hermetic. Only one of the pair of jaws is heated and each jaw is
of totally different construction.
The rear sealing jaw
The rear jaw, pictured in Figure 19, comprises a low-mass heating element which is both narrow and thin,
mounted on a stainless block which is also a chamber for chilled water. The current feed is through IP65-rated
terminal blocks at each end of the jaw. Similarly, the chilled water is fed in at the ends and circulates constantly
back to the chiller unit.
Figure 19 Integrity Seal rear jaw
The system is triggered by a proximity probe that senses when the jaws have come together. A current is passed
through the element, raising its temperature very quickly to above the polymer melt temperature (typically
between 270 and 300 ºC). The next stage of the sealing cycle involves cooling the jaw to a low enough
temperature, typically 80 ºC, to set the bead seal hard enough to support the falling product. This is
accomplished by the chilled water circulating behind the element. The constant flow of chilled water at around 10
ºC reduces the high sealing temperature within milliseconds. At each stage of the heating and cooling cycle a
visual display is provided on the controller to verify that the stage has been completed.
There are a number of benefits from the cooling action. First, the jaw can be safely touched after every cycle so
when film or product has to be removed from between the jaws there is no risk of burns from the jaw. Second,
any product remaining on the jaw does not get burnt onto the surface so can be wiped away. The heating
element is protected by a self-adhesive Teflon tape which also acts as a wipe-clean surface and extends the life
of the element. The jaw is designed to suit the application and may have additional side shoulders to assist in
forming the gussets on block-bottom bags. The jaw can also have additional rubber pads mounted either side of
the element. The rubber strips are used for clamping the film against the front jaw during the seal contact time to
eliminate the tendency for the bag to fall prematurely, which can produce some polymer stringing. The rubber
also distributes the pressure as the jaws come together, so reducing the risk of solid foreign bodies damaging the
element.
The front sealing jaw
The front jaw (Figure 20), is of totally different construction to the back jaw, with no heating element. A moulded
rubber anvil strip is mounted in a channel in the centre of the jaw. The rubber moulding is designed with a raised
‘V’ notch in the centre of the top face and with embossed shoulders either side of the ‘V’. The rubber anvil
replaces the conventional metal knife, and works by pressing the film against the high-temperature element. As
the ‘V’ notch compresses, the embossed shoulders then further complete the seal and produce a 1mm-wide
Development of ‘Integrity Seal’ sealing technology
26
patterned welded seal. The heat is therefore applied primarily into the cut edge of the film, producing a very
strong weld seal.
Figure 20 The front jaw picture and diagram
The controller
Integrity Seal comes with its own temperature controller which has a visual display showing the key functions of
seal temperature, sealing time, cooling temperature, actual element temperature and a dynamic display of the
heat application on every cycle.
The unit is of flexible design and can either be attached to the existing machine panel or placed in a remote
location. The sealing cycle starts when a signal is received from a proximity probe sensing the jaws have closed.
The water chiller
Chilled water is supplied to each machine from a centralised unit remote from the bagging machines. The units
can either be within the high-care room or located in adjacent areas such as mezzanine floors or roof space.
Figure 21 shows a small single unit used for the factory trials.
Figure 21 The water chiller used for the trials
Development of ‘Integrity Seal’ sealing technology
27
Appendix 2 Packaging savings from using
Integrity Seal technology
Illustrative packaging savings using Integrity Seal technology for fresh produce
Calculations based on a typical Fresh Salad / Vegetable Bag
Saving from using shorter bag (10–15% area saving):
Based on a typical bag size as follows:
Original wrap size
New wrap size
Saving
One original wrap @
One new wrap @
460mm * 272mm = 0.1251m2
460mm * 240mm = 0.1104m2
0.0147m2 or 11.75%
0.1251m2 weighs 4.53g
0.1104m2 weighs 4.00g
Saving per wrap is therefore 0.53g
Saving per million bags is therefore 53kg or 0.53 tonnes
Estimated number of fresh produce bags made per year:
10.5 million bags per machine per year
Assuming a minimum of 112 machines in the fresh produce industry in the UK this makes 1,176 million packs
annually.
Based on 1,176 million bags the saving is 627 tonnes of film per year
Additional weight saving from using thinner gauge film (14.3%):
Calculations based on reducing the film gauge from 35 micron to 30 micron
One original wrap in 35 micron film @ 0.1251m2 weighs 4.53g.
Therefore with a weight reduction of 14.3% the new weight will be 3.88g giving a saving of 0.65g per pack.
Weight saving per million bags is therefore 650kg or 0.65 tonnes
Based on 1,176 million bags the saving is 762 tonnes of film per year
TOTAL COMBINED SAVING IS THEREFORE 1,389 tonnes
Development of ‘Integrity Seal’ sealing technology
28
Illustrative packaging savings using Integrity Seal technology for snack products
1) United Biscuits (KP) multi-pack application:
Calculations based on the film specification:
20 micron OPP (white) / 20 micron OPP (clear)
Based on a typical bag size as follows:
Original wrap size
Integrity Seal wrap size
Area saving using a shorter bag
One Original wrap @
Integrity Seal wrap @
515mm * 367mm = 0.1890m2
515mm * 335mm = 0.1725m2
0.0165m2 or 8.73%
0.1251m2 weighs 7.07g
0.1104m2 weighs 6.45g
Weight saving per wrap is therefore 0.62g
Weight saving per million bags is therefore 617kg or 0.617 tonnes
Approximate number of multi-bags produced by KP is 48 million per annum generating a saving of approximately
30 tonnes
Assuming KP have a 25% share of the multi-bag market, the total number of bags is in the region of 200 million
Based on 200 million multi-packs the saving is 120 tonnes of film per year
2) Single pack application: snack products – 25g pack (used in multi-packs)
Calculations based on the film specification:
20 micron OPP (clear) / 15 micron (metallised) OPP
Based on a typical bag size as follows:
Original wrap size
Integrity Seal size
Area saving using a shorter bag
One Original wrap @
Integrity Seal wrap @
247mm * 138mm = 0.034086m2
247mm * 120mm = 0.029640m2
0.004446m2 or 13.04%
0.034086m2 weighs 1.088g
0.029649m2 weighs 0.946g
Weight saving per wrap is therefore 0.1419g
Weight saving per million bags is therefore 142kg or 0.142 tonnes
If Integrity Seal is also applied to the 25g single bags in the multi-pack the number of single bags would be 336
million so the additional weight saving would be 47 tonnes.
3) Single snack pack application: snack products – 34g pack
Calculations based on the film specification :
20 micron OPP (clear) / 15 micron (metallised) OPP
Based on a typical bag size as follows:
Original wrap size
Integrity Seal wrap size
Area saving using a shorter bag
One Original wrap @
Integrity Seal wrap @
241mm * 172mm = 0.04145m2
241mm * 154mm = 0.03711m2
0.00434m2 or 10.47%
0.04145m2 weighs 1.3228g
0.03781m2 weighs 1.1843g
Weight saving per wrap is therefore 0.1385g
Weight saving per million bags is therefore 139kg or 0.139 tonnes
Development of ‘Integrity Seal’ sealing technology
29
Appendix 3 Seal quality data
During the trials Integrity Seals were subject to dye testing and pressure testing in vacuum immersion tank tests.
In all cases samples were superior to current crimp seals.
Pressure tests
In a typical crimp seal, there are usually multiple air leaks at between 0.2–0.3 bar pressure. In the Integrity Seal
the mode of failure is for the seal to burst; there are rarely any micro leaks.
Figure 22 Iceberg lettuce in a vacuum immersion tank being tested for pressure
The degree of vacuum that a pack will withstand depends on the size of the pack, the volume of the contents and
the headspace volume, so direct comparisons between products are not possible. In general, however, Integrity
Seal packs will withstand more than double the vacuum of a crimp seal.
Figure 23 Marks & Spencer Prawn Cocktail shells withstanding 0.3 bar pressure
Dye tests
The penetrative dye test is used to search for micro leaks. It is a non stressing method and very sensitive. It can
detect leaks as small as a few micron and in some cases so small that they will not affect the shelf-life of the
product. Hence accurate interpretation of the results is important. The results of the dye test must always be
verified by headspace gas readings and sensory analysis.
Dye tests on fresh vegetable packs: crimp seals vs Integrity Seal
Development of ‘Integrity Seal’ sealing technology
30
Figure 24 Integrity Seal: No dye leaks
Figure 25 Typical crimp seal leaks
Figure 26 Typical crimp seal blisters
Figure 27 Typical edge crimp edge leakage
Development of ‘Integrity Seal’ sealing technology
31
Appendix 4 Leafy salad shelf-life data
% Gas and Sensory Score
Iceberg Shelf Life Performance
12
10
8
Headspace O2
6
Headspace CO2
4
Sensory Score
2
0
1
2
3
4
5
6
7
8
9
Days Shelf Life
Figure 28 Iceberg shelf-life performance
% Gas and Sensory Score
Summer Salad Shelf Life Performance
18
16
14
12
10
8
6
4
2
0
Headspace O2
Headspace CO2
Sensory Score
1
2
3
4
5
6
Days Shelf Life
Figure 29 Summer salad shelf-life performance
% Gas and Sensory Score
Spinach Shelf Life Performance
25
20
Headspace O2
15
Headspace CO2
10
Sensory Score
5
0
1
2
3
4
5
6
7
8
9
Days Shelf Life
Figure 30 Spinach shelf-life performance
Development of ‘Integrity Seal’ sealing technology
32
Iceberg Lettuce Shelf life Comparison
Headspace gas %
12
10
IS Headspace O2
8
IS Headspace CO2
6
Crimp seal Headspace O2
4
Crimp seal Headspace CO2
2
0
P+0 P+1 P+2 P+3 P+4 P+5 P+6 P+7 P+8 P+9
Days shelf life
Figure 31 Iceberg lettuce – comparison between Integrity Seal (IS) and standard crimp seal
Headspace Gas %
Summer Salad Shelf Life Comparison
18
16
14
12
10
8
6
4
2
0
IS Headspace O2
IS Headspace CO2
Crimp seal Headspace O2
Crimp seal Headspace
CO2
P+0 P+1 P+2 P+3 P+4 P+5 P+6 P+7 P+8 P+9
Days Shelf Life
Figure 32 Summer salad – comparison between Integrity Seal (IS) and standard crimp seal
Baby Spinach Shelf Life Comparison
25
Headspace Gas %
IS Headspace O2
20
IS Headspace CO2
15
Crimp seal Headspace O2
10
Crimp seal Headspace
CO2
5
0
P+0 P+1 P+2 P+3 P+4 P+5 P+6 P+7 P+8 P+9
Days Shelf Life
Figure 33 Spinach – comparison between Integrity Seal (IS) and standard crimp seal
Development of ‘Integrity Seal’ sealing technology
33
Appendix 5 Fresh vegetable shelf-life data
Broccoli florets
Headspac e
20
IS O2
15
IS CO2
10
Crimp O2
5
Crimp CO2
0
1
2
3
4
5
6
7
Days shelf life
Figure 34 Broccoli florets – comparison between Integrity Seal (IS) and standard crimp seal
Headspace gases
Carrot batons
18
16
14
12
10
8
6
4
2
0
IS O2
IS CO2
Crimp O2
Crimp CO2
1
2
3
4
5
6
7
Days shelf life
Figure 35 Carrot batons – Comparison between Integrity Seal (IS) and standard crimp seal
Headsapce gas
Carrot/Cauliflower. Broccoli
18
16
14
12
10
8
6
4
2
0
IS O2
IS CO2
Crimp O2
Crimp CO2
1
2
3
4
5
6
7
Days shelf life
Figure 36 Carrot, Cauliflower, Broccoli – Comparison between Integrity Seal (IS) and standard crimp seal
Development of ‘Integrity Seal’ sealing technology
34
Appendix 6 – Productivity Data
Machine speed comparisons
Location
Tilmanstone
Tilmanstone
Tilmanstone
Machine Type
Intermittent Sandiacre
Intermittent Sandiacre
Intermittent Sandiacre
Product
Iceberg Lettuce
Summer Salad
Spinach
Standard speed
45–50 per min
45–50 per min
30 per min
Integrity Seal speed
55 per min
55 per min
40 per min
Vitacress
Exotic Farm
Exotic Farm
Exotic Farm
KP Ashby
KP
Rotherham
Continuous Ilapak
Continuous Sandiacre
Continuous Sandiacre
Continuous Sandiacre
Intermittent Sandiacre
Spinach
250g Carrots
750g Casserole
350g Broccoli
Hula Hoops
45 per min
100 per min
70 per min
70 per min
105 per min
45 per min
80 per min
70 per min
70 per min
105 per min
Intermittent Sandiacre
Peanuts
45 per min
36 per min
Note: Where Integrity Seal failed to match or exceed the current speed this was due to the limit of
sealing temperature of the unit. This has been resolved with a higher temperature range.
The table above shows machine speeds achieved and comparisons with current production
A comparison was made at Tilmanstone Salads between Line 1 running Integrity Seal technology and the
adjacent identical machine on line 2 running crimp seals, over the three-month trial period.
Figure 38 clearly shows that most production days the line operating the Integrity Seal technology ran at higher
Net Machine Efficiency (NME) levels. NME is calculated from the number of bags run over the entire run time so
includes all stoppages. The gap in the data at the end of October was when the Integrity Seal jaws were removed
for a design modification, and the dip in the graph on 9 December was when production halted due to factory
maintenance.
Net Machine Efficiency Comparisons
Line 1 - Iceberg - Summer Salad - Spinach
Line 2 - All other baggeds salads
90
80
70
60
50
40
30
20
10
Line 1 Integrity Seal
13
7
10
4
1
28
25
22
19
16
13
7
10
12
9
0
Line 2 Crimp Seal
Figure 37 Graph of net machine efficiency comparisons
The data in Figure 39 were gathered by an independent auditor on one specific day at random during the trial.
The audit was not planned so the product selection comprised whatever was running at the time. It again shows
a high level of efficiency for Integrity Seal.
Development of ‘Integrity Seal’ sealing technology
35
Summary
Product
Bags
Bags
Bags
Bags
Bags
Iceberg with Integrity
Summer Salad with
Salad Bowl 100g
Large Salad Bowl
Cal
Seal
Integrity Seal
Bag
Bag
Spinach
85%
63%
82%
57%
99%
89%
99%
94%
100%
92%
100%
100%
84%
51%
81%
53%
Performance
83%
Quality
93%
Availability
100%
NME @ Max Rate
77%
Figure 38 Summary table of bag performances
Development of ‘Integrity Seal’ sealing technology
36
Table of Figures
FIGURE 1 A BLOCK-BOTTOM SEAL ON A GUSSETED BAG................................................................................................... 7
FIGURE 2 A PILLOW PACK SHOWING SEAL ................................................................................................................... 8
FIGURE 3 THE RIBBED PROFILE OF STANDARD CRIMP JAWS .............................................................................................. 9
FIGURE 4 TYPICAL CROSS-SEAL FAILURES ................................................................................................................... 9
FIGURE 5 THE FRONT AND REAR JAW OF THE INTEGRITY SEAL........................................................................................ 10
FIGURE 6 THE TEMPERATURE CONTROLLER HAS A VISUAL DISPLAY SHOWING DETAILS OF THE PROCESS ..................................... 10
FIGURE 7 M&S SPINACH PACKS SHOWING THE OLD SEAL (FRONT) AND THE NEW (BACK) ...................................................... 11
FIGURE 8 INTEGRITY SEAL PACKS ALONGSIDE STANDARD PACKS ON M&S SHELVES .............................................................. 12
FIGURE 9 M&S YOUNG SPINACH (PACKED AT VITACRESS) ............................................................................................ 12
FIGURE 10 A PERFECT SEAL – LEAF HAS BEEN SEVERED ............................................................................................... 13
FIGURE 11 MARKS & SPENCER PRAWN COCKTAIL SHELLS SHOWING INTEGRITY SEAL........................................................... 15
FIGURE 12 KP DRY ROASTED PEANUTS PACK WITH THE NEW SEAL ................................................................................. 16
FIGURE 13 THE BLOCK-BOTTOM STYLE SEAL IN THE 30 MICRON OPP FILM HELD WITH NO DYE LEAKS ...................................... 17
FIGURE 14 25 MICRON OPP WITH WIDER 1.5 MM SEAL ............................................................................................. 18
FIGURE 15 40 MICRON PLA FILM PRODUCED STRESS CRACKS AT THE BAG EDGE AWAY FROM THE SEAL AREA, SHOWING THE INHERENT
BRITTLENESS OF THE FILM ............................................................................................................................... 18
FIGURE 16 M&S ICEBERG LETTUCE HOLDING 0.5 BAR PRESSURE WITH NO LEAKS .............................................................. 20
FIGURE 17 VACUUM TANK TEST AT ROTHERHAM CONFIRMED HERMETIC SEAL ON KP PEANUT PACK .......................................... 20
FIGURE 18 A PERFECT SEAL .................................................................................................................................. 21
FIGURE 19 INTEGRITY SEAL REAR JAW .................................................................................................................... 26
FIGURE 20 THE FRONT JAW PICTURE AND DIAGRAM .................................................................................................... 27
FIGURE 21 THE WATER CHILLER USED FOR THE TRIALS ................................................................................................ 27
FIGURE 22 ICEBERG LETTUCE IN A VACUUM IMMERSION TANK BEING TESTED FOR PRESSURE .................................................. 30
FIGURE 23 MARKS & SPENCER PRAWN COCKTAIL SHELLS WITHSTANDING 0.3 BAR PRESSURE................................................ 30
FIGURE 24 INTEGRITY SEAL: NO DYE LEAKS ............................................................................................................. 31
FIGURE 25 TYPICAL CRIMP SEAL LEAKS .................................................................................................................... 31
FIGURE 26 TYPICAL CRIMP SEAL BLISTERS ................................................................................................................ 31
FIGURE 27 TYPICAL EDGE CRIMP EDGE LEAKAGE ......................................................................................................... 31
FIGURE 28 ICEBERG SHELF-LIFE PERFORMANCE .......................................................................................................... 32
FIGURE 29 SUMMER SALAD SHELF-LIFE PERFORMANCE ................................................................................................. 32
FIGURE 30 SPINACH SHELF-LIFE PERFORMANCE ......................................................................................................... 32
FIGURE 31 ICEBERG LETTUCE – COMPARISON BETWEEN INTEGRITY SEAL (IS) AND STANDARD CRIMP SEAL ............................... 33
FIGURE 32 SUMMER SALAD – COMPARISON BETWEEN INTEGRITY SEAL (IS) AND STANDARD CRIMP SEAL .................................. 33
FIGURE 33 SPINACH – COMPARISON BETWEEN INTEGRITY SEAL (IS) AND STANDARD CRIMP SEAL ........................................... 33
FIGURE 34 BROCCOLI FLORETS – COMPARISON BETWEEN INTEGRITY SEAL (IS) AND STANDARD CRIMP SEAL ............................. 34
FIGURE 35 CARROT BATONS – COMPARISON BETWEEN INTEGRITY SEAL (IS) AND STANDARD CRIMP SEAL ................................ 34
FIGURE 36 CARROT, CAULIFLOWER, BROCCOLI – COMPARISON BETWEEN INTEGRITY SEAL (IS) AND STANDARD CRIMP SEAL ........ 34
FIGURE 37 GRAPH OF NET MACHINE EFFICIENCY COMPARISONS ...................................................................................... 35
FIGURE 38 SUMMARY TABLE OF BAG PERFORMANCES ................................................................................................... 36
Development of ‘Integrity Seal’ sealing technology
37
Written by: Graham Clough, International Food Partners Ltd
Waste & Resources
Action Programme
The Old Academy,
21 Horse Fair,
Banbury, Oxon
OX16 0AH
Tel: 01295 819 900
Fax: 01295 819 911
E-mail: info@wrap.org.uk
Helpline freephone
0808 100 2040
www.wrap.org.uk/retail
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