Biomedical Engineering Reference
In-Depth Information
consumption based on sensory, nutritional, microbiological, or other quality criteria.
Changing the composition and form of the food product, the environment to which
it is exposed, or the packaging system can lead to alterations in shelf life.
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Functionally, packaging is designed to contain and protect foods, while providing
added value to consumers. In today's retail market, products must often sell them-
selves, and packaging is therefore an important vehicle for point-of-purchase com-
munication with consumers. New developments in packaging materials and process-
ing technologies have created the potential for new food products that have more
limited shelf life expectations than their traditional shelf stable or frozen counter-
parts, but still meet consumer needs. Other new products can provide an extended
shelf life over traditional fresh foods.
2
The appeal of minimally processed, refriger-
ated foods such as modified atmosphere packaged fresh pasta is attributed to the
“fresh-like” quality of the product, yet with the convenience of an extended shelf life.
With few exceptions, food quality decreases with time of storage, irrespective
of the preservation methods used and the control of storage conditions, even for
foods held in a frozen state.
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Undesirable quality changes that take place during
storage may affect texture, flavor, color, overall appearance, and the nutritive value
and safety of food products. However, the rate and magnitude of many of these
quality changes can be minimized with suitable packaging systems designed to aid
control of the major influencing extrinsic deteriorative factors, namely, moisture,
oxygen, light, temperature, and aroma transfer.
To ensure that consumers will find food product quality acceptable at the time of
purchase, and also to ensure safety, food processors and manufacturers routinely deter-
mine a shelf life for each product they produce. Procedures for shelf life testing of foods
are fairly well established and have been well described by Speigel,
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and in relation to
specific food products by Man and Jones.
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Shelf life studies have been based historically
on an assessment of either physical, chemical, and/or sensory changes in product quality,
often accelerated by storage at elevated temperatures. An important packaging consid-
eration in shelf life studies is the changes that occur in the barrier properties of plastic
packaging materials due to elevated temperatures and relative humidities. Changes in
barrier characteristics, such as an increased permeability to oxygen, could have a
substantial influence on the shelf life of some packaged products.
This chapter will discuss briefly the basic categories of packaging materials, the
major environmental factors that impact on food quality changes and how they affect
package properties. Finally, various approaches to shelf life testing and prediction
will be addressed in relation to packaging.
PACKAGING AND SHELF LIFE STABILITY
Successful food packaging applications are highly dependent on the nature of food
materials and their preservation requirements, and on understanding how the package
and the food behave during and after manufacturing processes. Early studies on the
influence of packaging materials and food product properties on shelf life identified
moisture sorption behavior of foods to be a key factor that determined whether
degradation took place by microbial, oxidative, enzymic, or non-enzymic processes.
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