Rheological measurements were taken in a concentric
cylinder viscometer, Mettler RM 180 (Mettler-Toledo,
Greinfesee, Switzerland) with attached computer (Met-
tler SWR27 software). A measure system DIN 53019
was used (Re
=Ri
1:084). The temperature was main-
tained at 20°C by a thermostatic bath and controlled by
a thermocouple submerged in the sample. The maxi-
mum dierence between the selected temperature and
those in the sample during shear rate variation was
0.3°C.
Thixotropy was determined at a constant shear rate
of 10 sÿ1
for 600 s after a 4 h equilibration time after
loading the sensor system. In the beginning, during the
®rst minutes, the stress decreased very little with
the shear time, indicating a very slight thixotropy. Then
the sample was left at rest for 6 h and with a new
measurement it was con®rmed that the structure was not
recovered. So for practical purposes associated with
high shear rates, it could be considered that the puree is
not thixotropic. Therefore, before the rheological mea-
surements, thixotropy was eliminated shearing the
sample for 5 min at a shear rate of 200 sÿ1
. Rheograms
for ¯ow studies were done at shear rates from 15 to
700 sÿ1
.