(food chem lab steps later....pdf)
Permeability is an
important aspect to be considered in designing packaging materials for
foods. This is because the environment in which the food is packaged or kept
determines the shelf life of food. Other than protective and containment
purposes, packaging is also considered as a preservation method for food. This
can be achieved by creating appropriate conditions in the food packaging such
as keeping low amount of moisture and gases. Low moisture and gases content in
the packaging inhibits the growth of microorganism hence risk of food spoilage
can be reduced hence extending the shelf life of food. In order to control the
moisture and gases level in the packaging, it is important to design the
packaging material with adequate permeability. Permeability affects the rate of
transmission of water and gases into and out of the packaging material. In this
experiment, the permeability of three different packaging materials were
investigated by determining the water vapour transmission rate (WVTR) and water
vapour permeability (WVP) of these packaging materials, and were also compared.
By
definition, water vapour transmission rate (WVTR) is the amount of water vapour
that flow through the surface of a film per unit time under steady conditions.
The water vapors flow in a perpendicular direction to the film surfaces (Koles
& Kirwan, 2011). The WVTR is determined by measuring the amount of moisture
contained in the food by determining the weight increase. According to Huynh-Ba
(2009), the diffusion of moisture in and out of a packaging material depends on
several factors including the thickness of the packaging, surface area of the
packaging and the difference between the internal relative humidity of the
packaging material and the relative humidity of the outside which is the
storage room. The difference between the relative humidity reflects the
moisture transfer rate. The smaller the difference in the relative humidity
inside and outside, the slower the moisture transfer rate or the WVTR and vice
versa.
The determination of the
barrier properties of a polymer is crucial to estimate and predict the
product-package shelf-life. The specific barrier requirement of a package
system depends upon the food characteristics and the intended end-use
applications. Generally plastics are relatively permeable to small molecules
such as gases, water vapour, organic vapours, and liquids, and they provide a
broad range of mass transfer characteristics, ranging from excellent to low
barrier values, which are important in the case of food products. Water vapour
and oxygen are two of the main permeants studied in packaging applications,
because they may move from the internal or external environment through the
polymer package wall, resulting in possible negative changes in product quality
and shelf-life [18]. For example, the improving of the oxygen barrier
performances of a film is of great importance because oxygen promotes a lot of
degradation mechanisms of a food, such as corrosive phenomena, oxidations, and
great modification of organoleptic properties .
To avoid food degradation,
carbon dioxide becomes more and more important for MAP technology because it
can potentially reduce the degradation phenomena associated with processed
fresh vegetable products, leading to a significantly longer shelf-life. For
example, for fresh products like fresh cut fruits, potatoes, and vegetable
(ready to eat), respiration rate is of a great importance in the MAP design, in
which the identification of the best packaging solution technology is a crucial
factor.
Aim- In practical, silica gel was used to
investigate the water permeability of the packaging materials. Silica gel has
high affinity of water hence it will absorb the water from the surrounding.
Therefore, weight increase of the silica gel indicates the amount of water that
permeates the packaging film. Hence, from the amount of water absorbed by the
silica gel was plotted against storage time to determine the WVTR. The WVTR
value was then used to determine the water vapour permeability (WVP) of the
packaging material.
For More:ttp://www.burchamintl.com/papers/petpapers/62.pdf
For More:ttp://www.burchamintl.com/papers/petpapers/62.pdf
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