2.1. Susceptibility of the ‘Primura’ variety to enzymatic
browning
Potato (Solarium tuberosum L.) tubers of the cultivar
‘Primura’ (from Montagnana, Italy) were purchased from a
local supplier and kept at 20 ◦C in darkness prior to processing. Slices of about 6–7 cm diameter were cut and laid down
in closed vessels (1 l volume) that were kept at 20 ◦C and
at two constant oxygen partial pressures (20.9 and 100 kPa,
respectively) in the presence of a source of humidity (about
100% RH). In this experiment no chemical inhibitors of
enzymatic browning were used. Oxygen levels were established
by a flow-through system connected to the lid of the
vessels. In order to verify the real gas composition, samples
of the vessel headspace were periodically extracted through
a sampling port in the lid and analysed using a gas chromatograph
(Hewlett Packard HP 5890 series II) equipped
with a thermoconducibility detector and a steel column
(2 m × 6 mm; CTR I Alltech, Milan). Tristimulus colorimetry
was performed on the surface of the same slice after short
time intervals (5–10–30–60–90–120–150–180 min) using
a colorimeter MINOLTA Chroma-Meter mod. CR210. The
instrument was standardized against a white tile (L* = 97.63;
a* = −0.68; b* = 2.77) before each measurement. The
CIE parameters were expressed as L*, a* and b*
with regard to time zero. All values were the average
of ten measurements, each carried out on three different
slices.