Trend in flexible packaging application

1. BARRIER PROPERTIES of FILMS
current technology &
applications
Henky Wibawa
AMCOR FLEXIBLES INDONESIA
Technical Director
March 2012

2. Introduction

3. Introduction
The primary functions of packaging are containment, protection,
information and convenience.
Probably the most basic function of a packaging is to contain its filling
good. Milk, loose peas or potato chips would have a hard time finding
its way to the consumer without retail packaging.
Protection is often considered as the most important functionality of
the package. Shielding the food from the attack of animals (mice,
insects etc.), micro-organisms, impede its contamination with dust,
dirt or chemicals, resist the impact of shocks, vibrations or
compressive forces and guarding the filling good from the adverse
effects of too much or too little moisture, light or oxygen is the ‘raison
d’être ‘ of the package.

4. Introduction Packaging at the POS/POP

5. Packaging Materials

6. Aluminium Foils
Aluminium foil is essentially impermeable to gasses and water vapour
above a thickness of approx. 20 microns. For thinner gauges one can
detect a small but non-zero permeability due to pinholes (e.g. a 7mm
foil has a water vapour transmissions rate (WVTR) of approx. 0.2 g
/m² *day at 38°C and 90 % rel, humidity and a O2 transmission rate
of 0.1-0.2 ml /m2*day*bar).
Aluminium foil exhibits desirable deadfold characteristics ; i.e. when
wrapped around an object, it will assume its profile with no springback
(e.g. butter wrapper).
Typical applications are in coffee packaging (PET/Al/LDPE), medical
and consumer health care packaging (hard annealed Al foil for blisters,
sachets), dry soups (BOPP/Al/LDPE) or lidding material for ready
meals (PET/Al/PP) and dairy products (heat seal lacquered foil).

7. Biaxially Oriented Polypropylene
With 0.9 g/m³, BOPP has the lowest density of the common packaging materials.
Its melting point lies with 169 °C high enough to allow for sterilisation
applications.
BOPP prominent qualities are: excellent moisture barrier, toughness, clarity and
low cost. Low tear resistance make it suitable for easy-open applications. Some
of the disadvantages (low gas and aroma barrier, poor sealabilty, printability and
maschinability) are surmounted by co-extrusion or coatings:
Co-extrusion with PP-PE co-polymer sealability
Acrylate coating increased gloss, printability and
machinability
PVDC coating increased gas and aroma barrier,
sealability
PVOH oxygen barrier, printability
Metallisation oxygen, aroma, moisture and light
barrier
BOPP can also be produces in an opaque variety either by filling with white
particles or by cavitation. This latter method leads to pearlised, light weight
material with low light transmission and high gloss. The combination of the above
mentioned variables leads to a broad spectrum of possible applications in food
packaging. Main applications are chocolate bars, biscuits, snacks, ice cream,
sweets etc.

8. Biaxially Oriented Polyester
Polyethyleneterephthalate has density of 1.40 g/m3 and a melting
point of 260°C. PET films are almost exclusively used in the bi-
oriented, heat stabilised form.
PET posses outstanding tear resistance, high transparency and gloss as
well as remarkable resistance to scratching and abrasion. In addition
its excellent printability combined with an advantageous machinability
and dimensional stability makes it one of the converters preferred
materials. PET can be used a temperature range of –50 °C to +150°C.
It exhibits good barrier properties with respect to water vapour, gases
and fats. Typical examples where PET is used are PET/AL/LDPE (coffee
pouches, medical sachets), PET met./LDPE (snacks, coffee, biscuits) or
PET/Al/PP as peelable, sterilisable lidding material for ready meals.
PET is furthermore the prevailing substrate for special barrier layers.
The most common one is certainly the metallisation. Others include
clay platelets, SiOx and PVDC. They will be discussed further on.

9. Biaxially Oriented Polyamide
The denomination polyamide refers to whole family of polymer. Nylon
(PA-6) is produced by a ring opening reaction of e-caprolactam, a
molecule that already contains the amid group in its initial structure.
The most widespread polyamides in flexible packaging are PA 6 and
PA 6-6 with a density of 1.13 and a melting point of 220 °C, allowing
for 140°C sterilisation procedures. Nylon films are characterised by
high impact resistance and high tensile strength. They exhibit good
stiffness and are resistant to fats, oils, dilute bases and acids. Their
barrier with respect to gases is very good in dry conditions, but
deteriorates rapidly with increasing humidity. Water vapour
transmission rate is quite high and increases with rising moisture
content of the material. BOPA are produced showing up to threefold
improved tear resistance, increased impact strength, improved optical
properties and higher barrier values.
The main applications of polyamides are to be found in the field of
MAP/ vacuum packaging of cured meat and cheese products
(OPA/PE).

10. EVOH
Ethylene-vinyl alcohol resins are hydrolysed co-polymers of ethylene
and vinylacetate. The resulting structure combines the excellent gas
barrier properties of vinyl alcohol and the chemical resistance and
processability of polyethylene. EVOH exhibits under dry conditions an
exceptional gas barrier. Under the influence of humidity, these barrier
properties deteriorate however dramatically. This is due to the fact
that EVOH contains large amounts of hydrophilic hydroxy groups,
which readily interact with water.
EVOH films are usually embedded in polyolefin layers with a good water
barrier.
EVOH resins are highly crystalline, thermally stable, have high
mechanical strength, elasticity and surface hardness, very high gloss,
low haze, good abrasion resistance, very high resistance to oils and
organic solvents, and provide an excellent barrier to odours. EVOH
multi-layer materials are often employed in modified atmosphere
packaging of ready meals, cured meat, bakery products or fresh pasta.
(PE/EVOH/PE or PA/EVOH/PE for lidding PS/EVOH/PE for tray material).

11. PVdC
Vinylidene chloride is usually co-polymerised with vinyl chloride
(typically 20%) to yield a soft, tough and relatively impermeable film.
It is an especially heavy polymer (density 1.68 – 1.75 g/m3). Pure
PVdC results in a stiff, brittle film hardly suitable for packaging
purposes. Co-polymers of PVdC show a unique combination of low
water vapour transmission rate and oxygen permeability (SARAN® 25
m: WVTR 2.4 g/m2*day (38°C/90%RH), O2 -TR: 16
ml/m2*day*bar (23°C/50%RH)).
PVdC lattices are very often applied as aqueous dispersion to paper
and plastics films to provide barrier to gases and moisture and odours.
It provides furthermore a reasonable sealability to any substrate.
Typical applications are medical blister (PVC 250 m / 40 g/m2 PVDC)
or biscuit wrapping (PAP 60 g/m2 / PVDC 20 g/m2).

12. BAREX
BAREX is a tradename for rubber-modified co-polymers of acrylonitrile and
methyl acrylate. They were originally developed for beverage bottle usage
because of their excellent barrier properties, clarity, high impact strength and
insolubility in many organic solvents. In flexible packaging its outstanding
resistance to oils, fats and aggressive products are appreciated. It replaces
polyethylene as a sealant in cases where the product is too aggressive to be in
direct contact with polyolefins. In laminates with paper/aluminium foil/BAREX it
is frequently used in form of sachets for packaging soups, spices, aromas,
perfumes or lemon juice.

13. Coated materials: metallising
Metallised film is developed by vapourising molten metal, and
depositing it onto a cold polymer web. Aluminium is most commonly
used because of its cost-effectiveness. The process takes place in a
vacuum chamber; the amount of metal applied is carefully controlled by
instrumentation, and the vacuum temperature of the metal and speed
of the web feed must also be closely monitored. The thickness of the
deposited layer is approximately 30 nm. Metallisation improves the
moisture- and gas-barrier properties of the film and prevents light from
reaching the product. It also confers the material a glossy metal
appearance. It is therefore also used for decorative purposes e.g. in the
confectionery market segment. The two most common substrates are
PET and OPP. HDPE and OPA are less frequently metallised. Applications
are very wide spread in packaging of water- and oxygen sensitive filling
goods

14. Raw materials - Barrier films
Vacuum coated films
Metallization process
THE KEY PARAMETERS OF THE METALLIZING PROCESS ARE:
•stable vacuum for even and consistent coating;
•temperature control to avoid deformation and damage to the material;
•accurate winding control especially on the low tension range.

15. Coated materials: SiOx, AlOx
As an alternative to Al-metallisation transparent barrier layers can
be employed. The so-called glassy barrier layers consist of
amorphous metal oxides of approx. 30 nm thickness. In practise only
two play a significant role, namely silicon oxide (SiOx) and aluminium
oxide (Al2O3) layers. Three different methods of deposition exist:
Thermal evaporation of SiO, electron beam induced evaporation of
SiO/SiO2 and Plasma enhanced chemical vapour deposition.
Main applications are packaging of oxygen/ moisture sensitive foods
in areas where it is desirable to see the product (transparent barrier).
Substrates are mainly PET but also to some extend OPP. Both are
microwaveable. When the fragile and rather brittle glassy layer is
protected by an additional layer, the structure becomes retortable.
Another target market is the replacement of triple structures such as
PET/Al/PE by duplex structures such as PET-SiOx/PE.
Yet another method to create a thin transparent layer is to apply an
organic lacquer with dispersed clay platelets, creating a tortuous path
for gases, organic solvents, aromas and UV light. This trick leads to a
high barrier material with a WVTR of about 25g/m²*day and an
oxygen permeability of < 1cm3/m²*day (23°C/85%RH).

16. Low density polyethylene and derivatives
PE is the largest volume single polymer used in food packaging. The
way in which the gaseous monomer ethylene is polymerised determines
to large extend the density and the properties of the final product.
The crystallinity of low density polyethylene LDPE usually varies
between 50 – 70 % and its density between 0.915 – 0.935 g/cm3. The
softening point of LDPE is just below 100°C thus precluding its
utilisation in sterilisation applications. LDPE is tough, with good tensile
strength, impact and tear resistance and posses an exceptional barrier
to water. The permeability for oxygen and other gases is however very
high. It has very good chemical resistance to acids, alkalis but is
sensitive to hydrocarbons, oils and greases. Oils and many other
organic compounds including many aromas are absorbed by LDPE
leading to swelling of the polymer. The most outstanding property of
LDPE is its ability to be fusion welded to itself to yield good, tough,
liquid tight seals.
LLDPEs can be produced in wide range of densities ranging from 0.90 to
0.935 g/cm3. A mayor feature of LLDPE is that its molecular weight
distribution is narrower than that of LDPE leading to a an improved
chemical resistance, tear resistance and impact strength, higher surface
gloss, and higher melting point.

17. Ionomers
With density 0.94g/cm3 are co-polymers of ethylene and a small
amount of an unsaturated short chain carboxylic acid (e.g. methacrylic
acid). The resulting polymer is than neutralised to varying degrees with
metal derivatives (e.g. zinc acetate) leading to an ionisation of the
carboxylic acid groups. As a consequence ionic cross-linking occurs
between different branches of the polymer leading to enhanced
stiffness and toughness. In comparison with LDPE ionomers have an
improved oil and grease resistance, which particularly appreciated when
sealing packages with oily or greasy contents, as it allows for correct
sealing even through fat contaminated sealing areas. Ionomers also
exhibit increased clarity and abrasion resistance with respect to LDPEs.
The moisture barrier is however reduced due to a lower degree of
crystallinity. The most prevalent trade name for ionomers is Surlyn® by
DuPont. The two captions currently used are sodium and zinc. The
former has a better hot tack and better fat resistance while the latter
results in a better adherence to aluminium and metallised surfaces. A
typical application is in combination with polyamide for MAP/vacuum
packaging of meat and poultry and cheese products.

18. More polymers

19. Packaging Industries Can Take Advantage of Innovative Technology.
New Microwave Packaging Concepts
Active Packaging Concepts
Reactive coatings (micro contact inks,
polymer electronics etc.)
Digital print technologies/ Ink jet
Barrier packaging
Variable labels & labeling
Package security features
Nanotechnology

20. Transport Properties

21. WVTR
The water vapour transmission (WVTR) rate of a packaging material
depends on two mayor factors: the permeation rate through the
material and the difference in water vapour pressure in- and outside
the package (the chemical potential gradient, Dm). To give an example
, the water vapour pressure at 23°C, 85% rel. humidity is 23,5 mbar is
only about a third of that at 38°C and 90% rel. humidity (72,6 mbar).
The permeation rate is again a function of two mayor factors: the
solubility of water in the polymer and its diffusion coefficient (P = D x
S. The solubility of water depends on the interaction between the polar
water molecule and the polymer molecular structure. The more polar
groups the polymer contains, the higher the enthalpy of solution and
the higher the solubility. The diffusion depends on the degree of
crystallinity and on the moisture content of the polymer. The higher the
crystallinity, the lower the diffusion speed is. The moisture content has
two opposing effects on the diffusion process. On the other hand does
interaction with the polymer bind the water reducing its mobility.
The temperature dependence is thus expressed in the form. WVTR also
depends on the thickness of the relevant material. It is often assumed
to be a linear relationship.

22. Gas permeability
For ambient gases other than water vapour the same is true as for the
above mentioned WVTR except that the solubility is to a much lesser
degree dependent on the nature of the polymer. It turns out that the
permeability ratio of a pair of gases will be relatively constant over a
series of polymers. The ratios of the permeabilities of CO2 to N2 vary
only by a factor of approx. 2 whereas the individual film permeabilities
exhibit a factor of up to 500. It can also be seen that independent of
the film material oxygen permeates about six times as fast as nitrogen
and CO2 about four times as fast as oxygen and about 24 times as fast
as nitrogen. There is no pattern for the ratios of water vapour to any of
the three gases. It might seem strange that CO2, the largest of the
three gas molecules, has the highest permeability coefficient.
Some of the factors influencing the permeability of polymers are :
the chemical nature of the polymer (polymer – permeant interaction)
microstructure of the polymer – crystallinity, thickness of the film,
temperature, relative humidity (swelling, plasticising), and other
volatile compounds (such as solvents) which lead to swelling
additional layers such as metallisation, SiOx, Ormoceres®, CHx,
diamond-like layers, clay platelets, PVdC or others.

23. Raw materials - Plastics
Barrier films
Material Characteristic O.D. µm O2 TR WV TR
2
cc/m *24h g/m2*24h
PET Standard PET / 12 110 50
23°C 0% RH 38°C 90% RH
PET PVDC coated / 12 8 8
23°C 85% RH 38°C 90% RH
PET SiOx coated / 12 3.5 39
23°C 85% RH 38°C 90% RH
PET Al2O3 coated / 12 2 2
23°C 0% RH 38°C 90% RH
PET metallised 2.0 12 1.5 1.5
23°C 75% RH 38°C 90% RH
PET white and metallised 2.2 12 1.5 1.5
23°C 75% RH 38°C 90% RH
PET with inorganic coating / 12 1 25
23°C 60% RH 38°C 90% RH
PET metallised very high barrier 2.6 12 0.08 0.04
25°C 85% RH 38°C 90% RH
PEN Polyethylen naphtalate / 19 <1 3.8
38°C 90% RH
PAN Polyacrilonitrile / 0.8 5
23°C 75% RH 38°C 90% RH

24. Raw materials - Plastics
Barrier films
M aterial Characteristic O.D. µm O 2 TR W V TR
cc/m 2 *24h g/m2*24h
BOPP Standard bioriented PP / 20 2000 7.5
23°C 0% RH 38 °C 90% RH
BOPP Acrylic coated / 26 750 5
23°C 0% RH 38°C 90% RH
BOPP PVdC coated / 26 25 4.2
23°C 0% RH 38°C 90% RH
BOPP metallized 2.3 20 100 0.7
23°C 0% RH 38°C 90% RH
BOPP cavitated and metallized 2.4 40 130 2
23°C 0% RH 38°C 90% RH
BOPP metallised high barrier 2.2 16 30 1.5
23°C 0% RH 38°C 90% RH
BOPP PVOH coated / 25 3 5
23°C 0% RH 38°C 90% RH
BOPP metallized very high barrier ? 18 0.5 0.3
23°C 0% RH 38°C 90% RH
BOPP cavitated - metallized very high barrier 3.6 35 0.2 0.4
23°C 0% RH 38 °C 90% RH
OPA Standard oriented polyamide / 15 30 180
23°C 0% RH 38 °C 90% RH
PA PA - EVOH - PA / 10 evoh 0.5 180
23°C 0% RH 38°C 90% RH
PP PP - EVOH - PP / 15 evoh 0.3 100
23°C 0% RH 38°C 90% RH
PE PE - EVOH - PE / 15 evoh / 130
38°C 90% RH

25. Seal
Sealing has a decisive influence on the whole package permeability, the
factor that in the end determines the total amount of oxygen or gas
that enters or leaves the package. Whatever you again with a high
barrier layer you might loose by improper sealing. Replacing a laminate
PET/Al/PE-LD with a structure OPP (high barrier) / OPP coex. without
adjusting the packaging machine might lead to a flawed seal. The
second problem with the seal is the drainage effect; if the barrier layer
is not close enough to the filling good. In this case oxygen and /or
water might diffuse via the cutting edge of the seal along the more
permeable layer towards the filling good without having to pass the
barrier. An example of such a packaging material was the structure
(from outside to inside) : OPP 20mm / Al 12 mm / Paper 40 g /m²/wax
which was used for packaging Ritter Sport Chocolate for a long time.

26. Converting of packaging materials

27. Converting Procedure
Photos Scanning for
Colour Separation Cylinder
Customer Design & Engraving
Concept Artwork
Flexo
Text Composing Sleeves
(Text + Images)
C o n v e r t i n g
Metallising Waxing /Coating (Co) Extrusion Lamination Printing
-adhesives - inks / - primers
-lacquers
- aluminium - resins - primers film/ foil/ paper
- paraffins
- film/ foil/ paper - solvents
Slitting
Die Cutting Bag-Making

28. Extrusion
Extruders consist of barrel, screw, drive mechanisms and control. The
solid polymer is fed into the extruder as powder, flakes or pellets and
then melted and mixed by being passed through an Archimedean
screw. The shear friction of the pellets between each other and to the
machine causes heating of the polymer, which finally leads to melting.
The extruder is heated additionally in various zones to be able to
control the temperature distribution, but this heating itself does not
effect the melting of the solid polymer. The polymer melt temperature
depends mainly on the rotation speed of the screw, the demanded
output and the pressure of the polymer melt at the outlet filter.
Extrusion can also be used for coating with polymer blends, the
extruder then requires different feeder stations. Because food
packaging can require a wide range of properties, two or more
polymers are often coextruded through a single die to form a multi-
layer film structure. Coextrusion is recommended for producing multi-
layer films because of its lower cost; it can be used instead of
lamination, avoiding the problem of double handling that occurs when
a film lamination is being produced. Coextrusion is sometimes
preferred because laminations require a separate manufacturing
process for each film used in the final laminate.

29. Lamination
A lamination is created when two or more individual films are bonded
together with special adhesives and run through rolling, heated
cylinders to produce a composite film structure.
One talks about wet bond laminating when the adhesive is wet in the
moment of joining of the two webs, whereas dry bonding lamination is
effected when the adhesive is dried before bonding. In the case of wet
bond laminating one of the webs has to be permeable to the solvent
(e.g. water based casein glue used to laminate paper and aluminium
foil). Solvent-based adhesives are very often two component
polyurethane – isocyanate systems with ethylacetate as the principal
solvent. Curing occurs after lamination during the following few days.
Solvent-free adhesive systems are usually based on short chain
precursor polymers e.g. oligourethanes which serve as their own
solvent and a curing agent.
Lamination is preferred when a specific film composition cannot be
effectively run on coextrusion systems due to equipment limitations,
and also when the high temperatures required in coextrusion would be
harmful to films. Lamination is also recommended when it is desirable
to produce a composite film with properties superior to those afforded
by a single film layer of the same gauge.

30. Lamination Arrangements
n roller arrangements for different types of lamination
1. Wax
lamination
2. Wet lamination
3. Solvent-free
lamination
4. Dry lamination
5. Dry lamination
uncoated web
coated web
laminate

31. Coating
The coating process involves the application of various materials to the
film-web substrate to special features, improve properties, or change
the handling characteristics (sticking, slipping, etc.) of a film. Two
main families of coating exist: protective coatings (overlacquer) and
coatings with a sealing function. The former have to be hard, scratch
resistant and thermally stable (e.g. NC-, epoxy- or PET-based
systems), the latter have to be flexible, tight, chemically resistant and
sealable (eg.g EVA-, PVA-, PVC- or PVDC-based systems). In practise a
hole panoply of different resins, additives and solvents exists from
which the converter can choose to find the right combination for each
individual application. Coating equipment consists of a coating head,
often an engraved rotogravure cylinder, a drying unit, and the film-
handling system.

32. Printing
Printing is one important step in producing a package material. The
choice of the printing technique and inks will to a large extend
influence on the visual and sensory (off-flavours, rest solvents) quality
of the final material. Two different methods are commonly employed in
flexible packaging :
Rotogravure printing technique commonly used in packaging. Printing
can be performed on foil, film and paper/carton. Rotogravure machines
usually range between 6 to 12 colours. Printing speed is 100-
300m/min. In rotogravure an engraved cylinder is rotating partially
within the printing ink, where its indentions are filled with the
respective ink. Excess ink is removed by a doctor blade. The ink from
the indentions is then transferred onto the substrate, which is pressed
to the rotogravure cylinder by a second press cylinder. The quality of
the print is very high, but set-up of the printing machine takes
approximately 10min per colour.
Flexo printing is the second standard printing method in packaging.
Printing plates are mounted to a cylinder, which then transfers the ink
from a cylinder dipping into the ink reservoir to the substrate with
nearly no pressure applied. Set-up times are somewhat shorter than
for rotogravure. Also available with UV curing inks as UV Flexo.

33. Snacks example ... what are on the market?

34. Packaging machines and gas flushing

35. Application and control
Packaging line and material performances

36. Pillow packs
The HFFS is employed for the making of pillow packs.
A tube is formed from hot or cold sealable wrapping
film by means of an unwinder and corresponding
turning system. The product slugs, in an exactly
defined interval, are then inserted into this tube
means of an in-feed chain (Fig. 3a). The tube is then
sealed along its length. In order to firmly seal the
package ends, it is passed through a cross-sealing
station (Fig. 3b). Thanks to our unique cross sealing
technology, a tight seam is created between the
portioned slugs. Cutting occurs simultaneously. The
result: A pillow pack characterised by the typical
“end fins".

37. Flat bottom pouches
Vertical bag formation: The bags are manufactured
by forming a pack around a vertical moulded tube.
The passage over the form-giving shoulder is the
critical step in the making of the pouch as it imposes
considerable mechanical strain on the packaging
material. The so-formed tubular pack is then sealed
lengthways. At the end of the moulded tube, the
pack is sealed along the bottom and the individuals
are separated. This yields an open-top bag is then
conveyed to the cup filler of the packaging system.
There are also variations where filling occurs directly
from the moulded tube.

38. Coffee vacuum packaging
Manufacturing a bag on the mandrel wheel is a
unique procedure. Firstly, for each paper or film
section fed from the reel stack is precisely positioned
and placed around one of the metal mandrels the
mandrel wheel. The intermittently mandrel wheel
now conveys the so formed package cases to further
stations at which the bottom and side seams are
created sealed to yield neatly formed bags left open
at the top. These are then transferred to the cup
filler of the packaging system. After they have been
filled, the bags closed and sealed at the top.
Depending on the product and the customer
requirements, various seals are possible. Evacuation
vacuum wheel with up to 30 chambers gas flushing
also number among the possible designs.

39. Product sensitivity-food deteroriation mechanism
Factors that influence shelf-life are basically to be
classified into three areas: Food properties, package
properties and climatic storage condition. The former
have been treated previously, the latter clearly affect
the kinetics of the shelf-life determining process of
food degradation in multiple ways.
Foods are complex blends of often hundreds of
different compounds. Their chemical and physical
properties determine they sensitivity with respect to
inevitable degradation. Here it gives an overview of
the principal factors influencing the degradation of
foods.

40. Physical
Bruising and mechanical deterioration of products is of principal
concern to food producers and packaging engineers. Examples are
physical abuse of fruits or vegetables during packaging or distribution
or crushing of biscuits or chips.
Temperature induced texture changes are usually the result of
phase changes. Examples are sugar and fat bloom as a case of re-
crystallisation and phase segregation respectively. Freezer burn
constitutes an example of water sublimation and temperature
fluctuations around the dew point may lead to unwanted condensation
of water in the package.
Flavour scalping The absorption of flavour and aroma
compounds by the packing materials inner liner is on of the most
important problems of compatibility in flexible packaging]. The most
prominent example is certainly the case of fruit juice in contact with
polyolefin sealing layers.

41. Physical
Moisture gain or loss can alter considerably the texture of foods.
Intermediate moisture foods such as pet food or cakes may harden
due to an excessive loss of humidity. Pasta turns brittle when it
changes from the rubbery to the glassy state and inversely snacks
such as potato chips or curls turn soggy when they move in the
inverse direction. Caking is yet another example where the increase of
moisture and temperature induce a glass – rubbery transition leading
to the agglomeration in powdery products.
The sorption behaviour of foods is quantified with the aid of so-called
water absorption isotherms. They put into relation the amount of
absorbed water (moisture in g/g dry solid) with the relative ambient
humidity. This is true for a specific temperature, hence the term
isotherm and after an equilibrium state has been reached. A typical
water absorption isotherm of a biscuit is shown in aw stands for water
activity which relates to the relative humidity RH like RH = 100*aw.

42. Chemical
During processing and storage of food stuffs a great variety of
chemical reactions can alter the food chemical composition and lead to
degradation in terms of nutritive value or organoleptic properties. The
mayor modes are mentioned below:
Enzymatic During processing of foods, tissue damage occurs
which causes the release of various chemical constituents into the
cellular fluid. These chemicals can then react with each other or with
compounds from the environment. For example lipoxidase enzymes
released from certain cell constituents (mitochondria) can attack fats
and cause rancidity. Similarly, the polyphenol oxidase can react with
some parts of the cell and oxygen to form the well known brown colour
of bruised or cut fruit (e.g. apples or bananas).
Lipid oxidation Many foods contain unsaturated fats, which are
important for human nutrition. Unfortunately, these fats are subject to
direct attack by oxygen through an auto-catalytic free radical
mechanism. This results in rancid off-flavours which render the food
undesirable to consume. Very little fat has to oxidise for the consumer
to detect rancidity and reject the food. Light and trace metals can
under certain circumstances catalyse the reaction rate by orders of
magnitude.

43. Chemical
Nonenzymatic Browning (NEB) NEB stands for another mayor family of
chemical reactions leading to a loss of nutritional and organoleptic
value of the affected food. NEB is the result of reactions between
reducing sugars such as glucose, fructose or lactose and amino group
containing compounds such as proteins. Browning can also occur by
heating sugars to high temperatures (or very long reaction times) or
through the oxidation of vitamin C. Undesirable aspects of NEB are the
production of bitter flavours, darkening of light-coloured dry products
such as infant formulae or juices and the staling of coffee. Factors
which influence the rate of NEB are temperature, water activity and
acidity (pH).
Moisture Moisture changes may induce food deterioration by physical
means (see above) or chemical means. All the above mentioned modes
of deterioration enzymatic, lipid oxidation, NEB and also microbial
growth are strongly affected by water. The rates at which these
reactions take place depend markedly on the water activity of the food.
One also has to take into consideration that water activity rather than
total moisture content is the relevant parameter determining undesired
chemical changes in foods.

44. Microbial
Micro-organisms constitute an important mechanism by which many
foods, especially fresh ones , lose their quality. This is because
microbes are ubiquitous in the environment and grow very fast.
Knowledge of the rate of growth of microbes as a function of the
environmental conditions is very essential in the prediction of shelf-life
of foods such as fresh meat, poultry and fish as well as dairy products
such as milk, cheese and yoghurt. Also affected are brad, cured meat,
fruit juices and fruits and vegetables.
The basic methods for the control of micro-organisms are the
following:
- Lower temperature to slow growth
Raise temperature to kill them
Remove or bind water to slow or prevent growth
Lower pH
Control O2 or CO2 level to control population
Manipulate food composition to remove nutrients needed by the
microbes
Add preservatives (e.g. sodium benzoate)

45. MAP, CAP and Active Packaging

46. Active packaging
Active packaging does more than simply provide a barrier to outside
influences. It can control, and even react to, events taking place inside
the package.
Fresh foods just after harvest or slaughter are still active biological
systems. The atmosphere inside a package constantly changes as
gases and moisture is produced during metabolic processes. The type
of packaging used will also influence the atmosphere around the food
because some plastics have poor barrier properties to gases and
moisture. The metabolism of fresh food continues to use up oxygen in
the headspace of a package and increases the carbon dioxide
concentration. At the same time water is produced and the humidity in
the headspace of the package builds up. This encourages the growth of
spoilage micro-organisms and damages the fruit and vegetable tissue.
Many food plants produce ethylene as part of their normal metabolic
cycle. This simple organic compound triggers ripening and ageing. This
explains why fruit such as bananas and avocados ripen quickly when
kept in the presence of ripe or damaged fruits in a container and
broccoli turns yellow even when kept in the refrigerator.

47. Ethylene scavenging
A chemical reagent, incorporated into the packaging film, traps the
ethylene produced by ripening fruit or vegetables. The reaction is
irreversible and only small quantities of the scavenger are required to
remove ethylene at the concentrations at which it is produced.
Systems developed are already commercially available. These usually
involve the inclusion in the package of a small sachet, which contains
an appropriate scavenger. The sachet material itself is highly
permeable to ethylene and diffusion through the sachet is not a serious
limitation. The reacting chemical for ethylene is usually potassium
permanganate, which oxidises and inactivates it. However many other
possibilities are conceivable: activated charcoal impregnated with an
oxidising agent such as KBRO3; electron deficient aromatic compounds
(e.g. dicarboxyoctyl ester substituted benzene); or simply ethylene
absorbing compounds such as activated charcoal, molecular sieves or
clay materials.

48. Carbon dioxide release
High carbon dioxide levels are desirable in some food packages
because they inhibit surface growth of micro-organisms. Fresh meat,
poultry, fish, cheeses and strawberries are foods, which can benefit
from packaging in a high carbon dioxide atmosphere.
However with the introduction of modified atmosphere packaging there
is a need to generate varying concentrations of carbon dioxide to suit
specific food requirements. Since carbon dioxide is more permeable
through plastic films than is oxygen, carbon dioxide will need to be
actively produced in some applications to maintain the desired
atmosphere in the package.
So far the problems associated with diffusion of gases, especially
carbon dioxide, through the package, have not been resolved and this
remains an important research topic.

49. Other developments
Other systems of active packaging which are either
already available or could soon be seen in the market
place include:
- sachets containing iron powder and calcium
hydroxide which scavenge both oxygen and carbon
dioxide. These sachets are used to extend the shelf
life of ground coffee.
- film containing microbial inhibitors other than
those noted above. Other inhibitors being
investigated include metal ions and salts of propionic
acid.
- specially fabricated films to absorb flavours and
odours or, conversely, to release them into the
package.

50. Innovations and Trends
Looking ahead
Innovation is an essential Factor
?
Product Material Machine Packaging Trends:
- Differentiation - Existing function - New Technologies ....types of packaging
- User Obser- to create new ap- - Fast speed and serving size
vation plication - Greater flexibility trends.
- Socioeconomic - Reduce cost-in- - Mass customi-
use sation
- Health and Safety
Market Trends and Drivers: Competitive Trends:
- Kids and Teenagers - Competing on Convenience
- Ready-to-use Products on Hand - Importance of being smaller
- Cooking Trends - Meals and Side Dishes
- Parameters for Convenience - Dairy Products
- Expanding Distribution - Beverages
- Package Sizes - Snacks and Confectioneries
- Vending Machine Trends - Health & Personal Care
- Natural Food Store Trends - etc.
- Warehouse Club Trends
- Convenience Store Trends

51. Thank You
henkie.wibawa@amcor.com
YOUR FUTURE PRODUCT
DEVELOPMENT DETERMINE
OURS !