Biomedical Engineering Reference
In-Depth Information
5.2.2 Process Innovation and Optimization
The ability to create very well-defined structures in silicon and silicon-like
or silicon-based materials—that are developed on the basis of the processes
from microelectronics in microtechnology—has enabled new concepts in the
processing of food materials. Since the possibilities in this field are virtu-
ally limitless, there are many opportunities for the food industry to improve
on important processes. Here, three examples will be given: separation and
fractionation, emulsification, and low-volume/high-value microproduction
of specific chemical components.
Cees van Rijn (2004) has made an extensive description of the possibilities of
microtechnology devices in separation technology. With the lithography pro-
cesses developed for the microelectronics industry, it is possible to make very
well-defined structures with high precision. It has been demonstrated that it is
possible to make a very thin SiN membrane with holes having the same size
and shape, which can be used to sieve out certain components from fluid food
substances. In this way, yeast cells can be cleared from beer, but also bacteria
from milk, resulting in pasteurized milk without heating treatment. There are
obvious advantages to this process with respect to product quality, cost, and
sustainability. Having full control over the shape of the holes, uniformity in the
size of the holes, and thinness of the membrane are prerequisites for this pro-
cess. On the basis of the same principle, it is also in theory possible to separate
a complex mixture into its individual components. If applied to milk, it would
be feasible to fractionate milk into proteins, casein micelles, fat, and bacteria.
Although no new products are created, just by fractionating milk, a lot of value
is added to the components that are now available to different processes.
Derived from the same technology as the microsieves, it is also possible to
innovate the emulsion process (Joscelyne and Trägårdh 2000). Traditionally,
an emulsion, for example, oil in water (mayonnaise), is created by applying
high shear forces (stirring) on a mixture of two components and some surface-
active additives. The result are droplets from one component in the continu-
ous phase of the other component. A large variety of droplet sizes are created
in this way. With membrane emulsification, the discontinuous phase (in may-
onnaise, the oil) is pressed through the same well-defined holes as described
above. They then form droplets in the continuous phase, which flows over it.
Since all the holes are of the same size, all droplets are also equally sized, form-
ing a monodisperse emulsion. The advantage of a monodisperse emulsion is
that the stability is higher. However, now that micro- and nanotechnologies
allow control over these kinds of processes at the nanolevel, it is also possible
to devise new products such as double emulsions. In a double emulsion, the
inside of the discontinuous phase in its turn also contains a discontinuous
component. In the example of mayonnaise, the oil droplets could have a core
of water again. Since this would replace a lot of the oil in mayonnaise with
water, it would result in a real low-calorie mayonnaise but with full fat taste
and mouth feel, thus not diminishing consumer satisfaction.
