4. Conclusions
Tens of vacuum cooling experiments with selected
pre-cooked solid food semiproducts have been carried
out. Experimental evaporated water–pressure dependencies
and the product of mass transfer coefficient and
mass transfer surface, kS, were evaluated. The volume
of samples was measured and then linearly correlated to
kS. The last parameter was found to be volume-dependent
for beef and chicken meat only, while it was volume-independent
for carrots, potatoes and pork meat.
For parsley, a very slight dependence on the volume was
found.
For most of the samples studied the volume dependence
of kS was negligible. Hence the mean values of
kS were determined. For engineering calculations of the
temperature history during vacuum cooling mean kS values can be recommended as shown in Table 2. For
beef and chicken meat the correlations given in Table 1
should be used to estimate kS as a function of the
sample volume in the fixed validity ranges.
The theoretical assumption expressed by Eq. (3) was
not confirmed to be generally valid. The mass transfer
rate during vacuum cooling, related to the product kS, is
food material-dependent, which can be explained by the
specific structure and water bounding capacities of every
food product investigated.