Cereals processing technology

64 Cereals processing technology
Fig. 4.3 Traditional beer brewing (Henry 1996).
barley to reduce haze and improve the shelf life of beer in cold storage has been
achieved using mutants and may be more precisely controlled using genetic
transformation to block specific steps in the pathways leading to proanthocyanidin
formation. One complication of this change may be that the absence of
proanthocyanidins in the wort may result in reduced protein precipitation during
boiling. The overall result can be a decline in product stability due to increased
levels of protein in the beer. This illustrates the need to understand all the
interactions during processing before implementing changes to novel cereal raw
grains.
Molecular markers have been developed for many malting quality attributes
and these may accelerate the development of new malting quality barley
varieties for use in beer production (Han et al. 1997).
Genetic engineering of barley to improve cell wall breakdown during malting
and brewing (Fincher 1994) and lipids contributing to beer flavour (Hoekstra et
al. 1994) have been the subject of active research. Modifications of starch
properties and metabolism and protein composition may also be important
(Edney 1996). A fundamental limitation is that extract levels are limited by the
need to preserve a minimum amount of husk to act as a filter bed in many
traditional brewing processes. Grains with extremely high proportions of
endosperm necessary for extreme extract levels will have insufficient husk. New
filtration technologies could overcome this limitation allowing the development
of very high extract barleys. Reliance on enzymes in the malt for starch
breakdown during mashing and the issue of yeast nutrition also requires that a