Lesson 5.docx

5.1 Introduction
Various terms for new packaging methods can be found in the
literature, such as active, smart, interactive, clever or intelligent
packaging.
The definitions of active and intelligent packaging are
 Active packaging changes the condition of the packed food
to extend shelflife or to improve safety or sensory
properties, while maintaining the quality of the packaged
food.
 Intelligent packaging systems monitor the condition of
packaged foods to give information about the quality of the
packaged food during transport and storage.
5.2 Active packaging
Active packaging refers to the incorporation of certain additives
into packaging film or within packaging containers with the aim
of maintaining and extending product shelf life. Packaging may
be termed active when it performs some desired role in food
preservation other than providing an inert barrier to external
conditions. Active packaging includes additives or ‘freshness
enhancers’ that are capable of scavenging oxygen, adsorbing
carbon dioxide, moisture, ethylene and/or flavor/odor taints,
releasing ethanol, sorbates, antioxidants and/or other
preservatives and/or maintaining temperature control.
Active packaging techniques for preservation and improving
quality and safety of foods can be divided into three categories;
absorbers (i.e. scavengers, releasing systems and other systems.
Absorbing (scavenging) systems remove undesired compounds
such as oxygen, carbon dioxide, ethylene, excessive water, taints

and other specific compounds. Releasing systems actively add
or emit compounds to the packaged food or into the head-space
of the package such as carbon dioxide, antioxidants and
preservatives. Other systems may have miscellaneous tasks,
such as self-heating, self-cooling and preservation. The main
active packaging systems are:
5.2.1 Oxygen scavenger:
The most common oxygen scavengers take the form of small
sachets containing various iron-based powders containing an
assortment of catalysts. These chemical systems often react with
water supplied by the food to produce a reactive hydrated
metallic reducing agent that scavenges oxygen within the food
package and irreversibly converts it to a stable oxide. The iron
powder is separated from the food by keeping it in a small,
highly oxygen permeable sachet.
5.2.2 Carbon Dioxide Scavengers/Emitters
There are many commercial sachet and label devices that can be
used to either scavenge or emit carbon dioxide. The use of
carbon dioxide scavengers is particularly applicable for fresh
roasted or ground coffees that produce significant volumes of
carbon dioxide. Fresh roasted or ground coffees cannot be left
unpackaged since they absorb moisture and oxygen and lose
desirable volatile aromas and flavors.
5.2.3 Ethylene Scavengers
Ethylene (C2H4) is a plant hormone that accelerates the
respiration rate and subsequent senescence of horticultural
products such as fruit, vegetables and flowers. Many of the

effects of ethylene are necessary, e.g. induction of flowering in
pineapples and colour development in citrus fruits, bananas and
tomatoes, but in most horticultural situations it is desirable to
remove ethylene or to suppress its effects. Effective systems
utilize potassium permanganate (KMnO4) immobilized on an
inert mineral substrate such as alumina or silica gel.
KMnO4 oxidizes
ethylene to acetate and ethanol and in the process a change
colour from purple to brown and hence indicates its remaining
ethylene-scavenging capacity. KMnO4-based ethylene
scavengers are available in sachets to be placed inside produce
packages or inside blankets or tubes that can be placed in
produce storage warehouses.
5.2.4 Ethanol Emitters
The use of ethanol as an antimicrobial agent is well documented.
It is particularly effective against mould but can also inhibit the
growth of yeasts and bacteria. Ethanol can be sprayed directly
onto food products just prior to packaging. The size and capacity
of the ethanol-emitting sachet used depends on the weight of
food, aw of the food and the shelf life required. When food is
packed with an ethanol-emitting sachet, moisture is absorbed by
the food and ethanol vapor is released and diffuses into the
package headspace.
5.2.5 Preservative Releasers
One most commonly used preservative releaser is a synthetic
silver zeolite that has been directly incorporated into food
contact packaging film. The purpose of the zeolite is apparently
to allow slow release of antimicrobial silver ions into the surface

of food products. Many other synthetic and naturally occurring
preservatives have been proposed and/or tested for antimicrobial
activity in plastic and edible films. These include organic acids,
e.g. propionate, benzoate and
sorbate, bacteriocins, e.g. nisin„ spice and herb extracts, e.g.
from rosemary, cloves, horseradish, mustard, cinnamon and
thyme, enzymes, e.g. peroxidase, lysozyme and glucose oxidase,
chelating agents, e.g. EDTA, inorganic acids, e.g. sulphur
dioxide and chlorine dioxide, and anti-fungal agents, e.g.
imazalil and benomyl. The major potential food applications for
antimicrobial films include meats, fish, bread, cheese, fruit and
vegetables.
5.2.6 Moisture Absorbers
Excess moisture is a major cause of food spoilage. Soaking up
moisture by using various absorbers or desiccants is very
effective at maintaining food quality and extending shelf life by
inhibiting microbial growth and moisture-related degradation of
texture and flavor. Moisture absorber sachets for humidity
control in packaged dried foods, several companies manufacture
moisture drip absorbent pads, sheets and blankets for liquid
water control in high aw foods such as meats, fish, poultry, fruit
and vegetables are available.
5.2.7 Flavour/Odor Adsorbers
The interaction of packaging with food flavors and aromas has
long been recognized, especially through the undesirable flavor
scalping of desirable food components. Two types of taints
amenable to removal by active packaging are amines, which are
formed from the breakdown of fish muscle proteins, and

Aldehydes that are formed from the autoxidation of fats and oils.
Volatile amines with an unpleasant smell, such as
trimethylamine, associated with fish protein breakdown are
alkaline and can be neutralized by various acidic compounds
[89]. The bags that are made from film containing a ferrous salt
and an organic acid such as citrate or ascorbate are claimed to
oxidize amines when they are absorbed by the polymer film.
Odor and Taste Control (OTC) technology removes or
neutralizes aldehydes.
5.3 Intelligent packaging
Intelligent packaging includes indicators to be used for quality
control of packed food. They can be so-called external
indicators, i.e., indicators which are attached outside the package
(time temperature indicators), and so-called internal indicators
which are placed inside the package, either to the head-space of
the package or attached into the lid.
5.3.1 Time temperature indicator (TTI)
A time temperature indicator (TTI) can be defined as a simple
device that can give the idea about easily measurable, time-
temperature dependent change which affects full or partial
temperature history of a food product to which it is connected.
The principles of TTI operation are based on mechanical,
chemical, electrochemical, enzymatic or microbiological
irreversible change.
5.3.2 Freshness indicators
Two types of the changes can take place in the fresh food
product i.e.

(i) Microbiological growth and metabolism resulting in pH
changes, formation of toxic compounds, off-odors, gas and
slime formation,
(ii) Oxidation of lipids and pigments resulting in undesirable
flavors, formation of compounds with adverse biological
reactions or discoloration.
A freshness indicator indicates directly the quality of the
product. The indication of microbiological quality is based on a
reaction between the indicator and the metabolites produced
during growth of microorganisms in the product. An indicator
that would show specifically the spoilage or the lack of
freshness of the product, in addition to temperature abuse or
package leaks, would be ideal for the quality control of packed
products.
5.3.3 Pathogen indicators
Commercially available Toxin GuardTM
is a system to build
polyethylene-based packaging material, which is able to detect
the presence of pathogenic bacteria with the aid of immobilized
antibodies. As the analyte (toxin, microorganism) is in contact
with the material it will be bound first to a specific, labelled
antibody and then to a capturing antibody printed as a certain
pattern. The method could also be applied for the detection of
pesticide residues or proteins resulting from genetic
modifications.

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