Types of Active Principles
Active packaging describes mainly food packaging that interacts chemically or biologically
with its contents or head space to extend shelf-life or. Since oxygen scavenging sachets
were introduced to the Japanese market in 1978 the packaging industry has extended the
traditional packaging tasks such as transport, protection or communication by active
features. Packaging may be termed active when it affects one or more attributes of the
packaging in a lasting and desired way. Oxygen scavengers are not the only applications
used in active packaging. Besides the oxygen scavengers, antimicrobial agents, moisture
absorbers, ethylene absorbers, ethanol and carbon dioxide emitters can be used as active
features in order to address the weak points in the shelf life of packed goods.
Oxygen scavengers are the best known and most widely used active packaging
technologies today. They had been designed to remove residual oxygen from the
headspace of the package and/or to achieve zero-permeation. To achieve this goal
a chemical absorbent is incorporated into the packaging material or added inside
the package by means of sachets or labels. Also, the use of entrapped
oxygen-consuming micro-organisms has been proposed as an alternative.
Common food applications for oxygen scavenger packaging include oxygen sensitive
beverages, fresh products, e.g. fresh pastas, snack food, ready-to-prepare and
PDF: Oxygen scavenger Overview
Antimicrobial agents incorporated into packaging materials are used more and more
during the last years for food packaging. The objective of these agents is to
control or to inhibit the growth of non-desirable micro-organisms on the food
surface. These particles are often transported (migration) from the package to the
food surface and are already used as coatings on different polymeric materials or
in the mass of the polymer. The activity of these antimicrobial agents is carried
out either by contact of micro-organisms onto the internal face of the packaging
material, either directly in the food by emission or slow diffusion of the
antimicrobial agent from the packaging material to the food. The packaging material
containing the active substance should be sufficiently permeable to allow diffusion
and controlled release during storage.
Types of Intelligent and Smart Principles
Intelligent or smart packaging is a special form of active packaging. One of the main
purposes is to indicate whether the quality of the product has decreased before the product
deteriorates. Time-temperature indicators (TTIs) are the most used applications in the field
of intelligent packaging. Further Applications with growth prospect are freshness indicators
and tracking services via intelligent expiry date label.
A time-temperature indicator (TTI) is a small measuring device attached to the package
surface that exploits a change in a physical or physiochemical property to produce irreversible
evidence of exceeding a predetermined temperature threshold or record the cumulative
time-temperature history. TTIs are working by physical, enzymatic or chemical reactions and are
increasingly used to track both chilled and frozen foods. A TTI should be easy to activate and
the observable colour change or colour development should correlate with the negative influence
of the microbiological process. TTIs are provided in different versions, with different activation
temperatures and flow times. Depending on their type, they should be appropriate for specific
product categories with defined temperature sensitivity.
Freshness indicators are attached inside the packaging and since they are
dependent on any inference from temperature history, they signal directly product
quality of the packed food. They detect volatile or non-volatile compounds or
changes in the product itself. Used methods are visible indicator tags in contact
with package headspace, labels and optical detectors. Freshness indicators detect
the presence of microbiological metabolites. The indicator systems for metabolites
include colour change of a dye or liquid crystals, formation of colour compounds,
changes in optical properties or a miniaturised electronic nose.
The sole use of freshness indicators can be enhanced, and most important of all,
brought to a universally interpretable level by extending the indicator with
interpretation instructions which are accepted and understood by all parties
involved in the handling chain of the perishable goods in question.
Tracking services: If the quality of goods is limited by expiry, it becomes
important to meet correct decisions upon their disposal during transportation,
storage and sale, otherwise, losses may occur due to premature expiry before
reaching the point of sale, or food safety rules could be violated. The key
decisions preventing premature spoilage can be made in following operational
areas: i) food processing ii) packing process iii) logistic and shelf management
at the point of sale. It is evident that such decisions can only be met properly
if information about the status of goods is provided, i.e., the packed good can be
tracked over the delivery and storage processes.