Validation of experimental results
To validate the experimental results a mass balance of each
cryoconcentration cycle was made, which was compared with theory
(Eq. (4)).
The ice mass ratio (W) has a downward trend with the cryoconcentration
cycle from blueberry (Fig. 6a) and pineapple juice
(Fig. 6b), respectively. This behavior is attributed to the increased of
percentage of concentrate over the cryoconcentration cycles (Table 1).
A good agreement was observed between the experimental (We) and
predicted (Wp) ice mass ratios over the cryoconcentration cycles and
for both juices (Fig. 5a–b). The RMS values over the cryoconcentration
cycles and for both juices fluctuated between 4.4% and 6.5%. These
values of RSM were lower than 25%, which is what Lewicki (2000)
considered as an acceptable fit, and these valueswere close to the values
7.3%, 5.2% and 4.9% reported by Hernández et al. (2010), Sánchez et al.
(2010) and Petzold et al. (2013), respectively.
Separate solutes from the cryoconcentration phase of frozen juices
with block freeze concentration assisted by centrifugation is a consequence
of using an external driving force (centrifugation), and under
these conditions the ice block acts a porous solid through which the
concentrated solution percolates through drainage channels among
ice crystals in a similar fashion as reported for vacuum-assisted freeze
concentration (Petzold et al., 2013) and centrifugal freeze concentration
of sucrose solutions (Petzold & Aguilera, 2013).