The sulphuric acid hydrolysis was performed in an autoclave capable to control the temperature (`1 C). In order to allow all the mater to be wetted, and to obtain a good supernatant recovery, the liquid/solid ratio was selected in a range (Table 1) where the potato powder was well submerged in the reaction mixture. The experiments were performed in 250 mL bottles. The set of experiments followed a Box- Benkhen experimental design using four factors (indepen- dent variables) and three levels (see below the statistical section). The operational conditions were set as shown in Table 1.