Handbook of Meat Processing

(Greg DeLong) #1
Freezing/Thawing 109

vidual pieces or cartons of smaller portions.
In commercial situations, freezing rates of
0.5 cm h^ −^1 in the deeper sections would be
considered “ fast, ” and there would be consid-
erable variation in freezing time within the
meat. The samples frozen by Sacks et al.
(1993) were much smaller (77.6 g in weight)
than most commercial products. Even with
such small samples, there was no signifi cant
difference in drip after 48 hours between
cryogenic freezing at − 90 ° C and a walk - in
freezer operating at − 21 ° C.
Even partial freezing will increase drip.
Hence tempering of meat to aid cutting,
dicing, slicing, etc. will increase drip loss,
though not to the same extent as full freezing.
Irie and Swatland (1993) found that drip loss
from 3 mm thick slices of pork that had been
“ lightly frozen ” before slicing average
8.0 ± 4.2% over a 4 - day period. Drip losses
from samples that had been kept in a freezer
at − 10 ° C for 6 days had a higher drip loss of
14.0 ± 4.3%.
Excessive drip may have a small effect on
the eating quality of meat. Perceived juici-
ness is one of the important sensory attributes
of meat. Dryness is associated with a decrease
in the other palatability attributes, especially
with lack of fl avor and increased toughness
(Pearson 1994 ). However, moisture losses
during cooking are typically an order of mag-
nitude higher than most drip losses during
refrigeration. Consequently, small differ-
ences in drip loss will have little effect on
eating quality.

Odor and Flavor

There is no evidence that freezing and
thawing has any effect on meat fl avor.
However, meat fl avor can alter during frozen
storage. This is principally caused by lipid
(fat) oxidation, also referred to as oxidative
rancidity, which results in unacceptable “ off ”
or “ rancid ” fl avors. The importance of lipid
oxidation in frozen meat may be illustrated
by a short quotation from a paper published

portionately more drip than pork and lamb.
The potential for drip loss is inherent in fresh
meat and related to the development of rigor
mortis in the muscle after slaughter and its
effect on pH. In pigs, especially, there are
large differences in drip loss from meat from
different breeds. Taylor (1972) showed that
there was a substantial difference, up to 2.5 -
fold, in drip loss between four different
breeds of pig.
There can be large differences in drip loss
between different muscles. Taylor (1972)
showed that there was a 1.7 - to 2.8 - fold dif-
ference in drip between muscle types in pigs.
Since most of the exudate comes from the cut
ends of muscle fi bers, small pieces of meat
also drip more than large intact carcasses,
and the way that different muscles are cut
will also have an infl uence on drip.
A number of scientifi c investigations,
which can be compared to commercial prac-
tice, have defi ned the effect of freezing rate
on drip production. Petrovic et al. (1993)
stated that the optimal conditions for freezing
portioned meat are those that achieve freez-
ing rates between 2 and 5 cm h^ −^1 to − 7 ° C.
Grujic et al. (1993) suggest even tighter
limits: 3.33 to 3.95 cm h^ −^1. They found that
“ slow freezing ” up to 0.39 cm h^ −^1 resulted in
decreased solubility of myofi brillar proteins;
increase in weight loss during freezing,
thawing, and cooking; lower water - binding
capacity; and tougher cooked meat. “ Very
quickly frozen ” meat ( > 4.9 cm h^ −^1 ) had a
somewhat lower solubility of myofi brillar
proteins, lower water - binding capacity, and
somewhat tougher and drier meat. The
samples were thawed after storage times of 2
to 3 days at − 20 ° C so the relationship between
freezing rates and storage life was not inves-
tigated. Sacks et al. (1993) found that after
2.5 months, drip loss from mutton samples
frozen using cryogenics was > 2% less than
in those using air freezing.
These results are scientifi cally very inter-
esting; however, in industrial practice most
meat is air frozen in the form of large indi-

Free download pdf