Oil location and surface morphology are important targets
in microstructural studies of the fried potato tissue.
CLSM was used to observe some important microstructural
aspects of the frying such as the oil location and surface
morphology. Figs. 7 and 8 show potato chips fried in
oil containing the thermoresistant fluorescent probe Nile
Red which were directly observed by CLSM, thus avoiding
artifacts associated with sample preparation for light
microscopy. This, together with the fact that CLSM makes
optical sections in the samples at different depths (rather
than physical sectioning for classical microscopy) allowed
observation of oil distribution in the crust as close to the
real situation as possible (Pedreschi et al., 1999). Fig. 7A
and B show different patterns of oil distribution in control
and blanched samples, respectively. Fig. 7A shows that oil
in the surface layers of control potato chips is located preferentially
around the cells in their walls. Pedreschi et al.
(1999) using CLSM demonstrated that oil location in the
crust of potato chips was like an ‘‘egg-box” surrounding
intact dehydrated potato cells but did not penetrate into
them, which was later confirmed by Bouchon and Aguilera
(2001). On the other hand, in blanched potato chips fried at
150 C, oil in the surface layers is mostly covering concave
irregular surfaces corresponding probably to cells whose
walls were disrupted during cutting of the raw slices, before
frying and blanching (Fig. 7B). Three-dimensional reconstructions
of the CLSM image galleries of Fig. 7A and B
are shown in Fig. 7A1 and A2, respectively. Fig. 7A1
shows that oil location follows the cell shapes locating preferentially
inside the intercellular spaces or in the cell walls.
Fig. 7A2 shows that surface oil in blanched chips is mostly
accumulated over the entire surface scanned, covering uniformly
the cells and the intercellular spaces.