Biomedical Engineering Reference
In-Depth Information
5.4 Improving Shelf Life and Quality
Assurance of Food Products
Because food predominantly is made of biological materials, it is extremely
perishable and the quality of the products rapidly deteriorates without proper
actions to protect it from outside influences and internal processes. Man has
learned to employ a variety of techniques to slow down the deterioration
process, of which packaging, cooling, and chemical protection through salt,
sugar, or alcohol are the most commonly used. Unfortunately, these strate-
gies are less and less popular since they reduce the freshness of the food.
Consumers have a strong tendency to prefer fresh or mildly preserved prod-
ucts. The result is that, at the moment, in the industrialized societies of the
Western world, about 30% to 40% of all the foods that are being produced
end up as waste, without being eaten by the consumers for whom they were
intended. In view of the ever-growing world population and the food scar-
city in large parts of the world, this is a highly undesirable situation.
5.4.1 Barrier Properties
Many of the quality deterioration processes are driven by oxygen, either
through direct oxidation of the product or components of the product, or
because the organisms responsible for spoilage, such as bacteria or fungi,
need oxygen to function and propagate. Therefore, reducing the amount
of oxygen in the atmosphere of the product is an effective way of slowing
down the spoilage processes. Maintaining the oxygen-deprived atmosphere
obviously requires packaging that is tight for oxygen. Glass or metals are
effective barriers against oxygen and have been used extensively in the
past. Unfortunately, they have specific disadvantages and consumers more
and more prefer other packaging materials, which are, however, invariably
less effective as a barrier against oxygen. Together with the demand for
low-weight, which means thin, and often transparent packaging—because
consumers want to be able to inspect the product inside the package—this
makes it virtually impossible to fulfill the oxygen barrier requirements.
Here, nanotechnologies can come to the rescue.
In nanocomposite materials, nanosized clay platelets are incorporated into
the matrix of the polymer packaging material (Rhim and Ng 2007). These
platelets increase the diffusion path length of oxygen, effectively improving
the barrier properties of the material (Sorrentino et al. 2007). Because the
particles are nanosized, they do not scatter visible light and therefore do
not interfere with the transparency of the original material. Other strategies
make use of very specific nanosized layers on top of the packaging material
to reduce the oxygen permeability. In some applications, oxygen scavenger
molecules are included in the packaging concept to catch oxygen getting into
