Figs. 1 and 2 showthe main results of FA and p-CA solubilisation
obtained in these experiments. An increased catalyst concentration
accelerated the solubilisation of ferulic acid, whose maximum
concentration (about 1100–1200mg/L) required no less than 6 h
at 0.5N and only 1–2 h at 2.0N (Fig. 1). A clear decrease in ferulic
acid concentration took place after the achievement of this
maximum threshold, as the likely result of oxidative degradation
whose rate increased from 5.3 to 18.3mgL−1 h−1 when Ca was
raised from 0.5 to 2.0N. No significant degradation was detected
at the lowest catalyst level (0.2N). Among the identified phenolic
compounds, p-CA was released at the highest concentration. It
exhibited a time behaviour (Fig. 2) similar to that of ferulic acid and
reached amaximum threshold concentration of 2783 mg/L after 6 h
ofhydrolysis with 2.0NNaOH.Onthe contrary, using themost dilute
catalyst solution ensured only 62% of this level, thus confirming
the low effectiveness of alkaline treatments under too mild conditions.
Also this productwas subject to time-dependent degradation
that occurred at a rate even higher than that of FA and increasing
with the catalyst level (27.5 and 35.2mgL−1 h−1 at Ca = 1.0 and 2.0N,
respectively).