degree per hectolitre are the legal parameters upon which beer is
taxed (Directive 92/84/EEC, 1992). For this motive, an unavoidable
parameter to be controlled during the first fermentation of beer is
specific gravity (SG), correlated with sugar concentration in the
wort and, therefore, alcohol content in the final product. The industrial
trend is to monitor the fulfilment of SG to the defined specification
through the use of Quality Control Charts, which allow a fast
visual check of the trend of the system being controlled through
mean and control limits statistically defined. However, with this
univariate quality assurance strategy is difficult to date back to
the source of the no standard behaviour leading to the abnormality
in the batch (Kourti, 2005). The main problem is that a failure in a
parameter evaluated might be originated from several correlated
variables, often non-measured, governing such a complex bioprocess
as it is beer first fermentation (Kourti, 2006).