Since at the maximum both derivatives must be zero, it is possible
to calculate the optimum temperature and ethanol concentration
for a maximum antioxidant extraction; Tm = 0.690 and
Em = 0.467 in codified values, equivalent to 65.3 C and 73.1% ethanol
in real values (see Table 1 for codification/decodification). At
this point the predicted maximum total phenolic concentration
was 56.2 mg GAE/g db.