Biomedical Engineering Reference
In-Depth Information
(i.e., the end of its shelf life). Such assessment is therefore on the overall flavor
quality of the prepared beverage. A separate assessment may be made on the head-
space aroma impact from the dry roasted and ground coffee using only the external
nostrils of the nose, i.e., by sniffing. In practice an early deterioration may not be
so readily marked in actual flavor quality of the beverage. Appearance changes in
the dry product are not generally evident, except moisture uptake during storage.
Shelf life data are of special relevance for trade purposes.
A number of investigations have also been performed to determine differences
in volatile compounds, as between robusta and arabica; such differences are clearly
evident in their respective beverage flavor characteristics. Grosch et al. (cited by
Reference 74) used the technique for assessing the important aroma impact com-
pounds by serial dilution techniques to obtain flavor dilution (FD) values in each of
arabica and robusta roasted coffee, both from brews and the dry product. Among
the differences, they found that 4-vinyl guiacol is especially characteristic in brewed
robusta coffee and furaneol in arabica; in the dry product, 3,5-dimethyl-2-ethyl
pyrazine appeared with the highest FD-factor in both coffee species. The use of
genetic engineering techniques may well be a useful tool to enhance volatile com-
pound production responsible for flavor; 3 another approach is the reduction of caf-
feine content because of consumer demand for decaffeinated coffee. 3
The functional role of vegetable and seed proteins in food processing is to provide
the required physical properties to the food material either during processing or in
the final product. The physical properties of both the starting materials (protein
extracts, isolates, concentrates, or flours) and products are determined by the level
of protein present, the proportions of different protein types, and the presence of
nonprotein components, and such properties are likely to manifest themselves in
different ways, depending on the processing procedures used. 63 The types of func-
tional properties sought in proteins are many and include those responsible for
emulsification, foam formation, and stabilization, and also for texturing. 63,65 Whereas
many functional properties rely on maintenance of the native configuration of the
proteins, several others arise through complete or partial denaturation of the proteins,
followed by rearrangements of the polypeptide chains and formation of new intra-
molecular and intermolecular bonds. In all cases, however, the behavior of a partic-
ular protein type depends ultimately on its intrinsic primary structure (amino acid
sequence) encoded by the genes. Thus, the proportions and functional properties of
certain seed proteins could be manipulated by genetic engineering to suit particular
applications in food processing. 63-65
Baking Quality
One example of the importance of protein functional properties is in baking quality.
Payne and Rhodes (cited by Reference 63) have described a number of different
baked products and the different qualities of wheat grain and wheat protein required
for each. An important part of the basis of baking quality lies in the composition of
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