Experiments
in
the
center
of
the
design were performed to estimate possible pure error. Due
to
systematic
errors,
all
the
experiments
were
carried
out
at
random
to
minimize
the
effect
of
unexplained
variability
on
the responses observed. The dependent variable (response)
was total polyphenol content (TPC). The optimized conditiondetermined
by
the
experimental
design
was
used
to
prepare
the extract, denominated optimized extract, and then subject
it
to
nanofiltration.