Material and methods
2.1. Samples
The supernatant water sample used for the validation of the
method was derived from the natural fermentation of cassava
starch at room temperature (ranging from 21.5 to 31.0C) for
32 days, when it reached the plateau acidity of 2.0 mL of NaOH
0.1 mol/L for each aliquot of 10 mL (Marcon et al., 2006). The
sample was kept frozen until the time of analysis. Due to the
impossibility of obtaining samples of free organic acids and the
high concentration of acetic and butyric acids in the sample, a
50-fold dilution of the sample was obtained with ultrapure water
for the evaluation of the precision and accuracy validation
parameters, while for lactic and propionic acids the dilution was
2-fold.