106 Chapter 5
sub - zero temperatures but does not undergo
a phase change and freeze until the pressure
is released. Rapid nucleation results in small
even ice crystals. However, studies on pork
and beef (Fernandez - Martin et al. 2000 ) and
on pork (Zhu et al. 2004 ) failed to show any
real commercial quality advantages, and an
increase in toughness was found in the later
study.
There are few published data relating
thawing processes to the palatability of meat,
and eating quality is generally independent
of thawing method. However, two reports
indicated that cooking directly from the
frozen state produced less juicy lamb rib -
loins (Woodhams and Smith 1965 ) and less
tender beef rolled rib joints (James and
Rhodes 1978 ) when compared with meat that
had been thawed before cooking.Tenderness and Texture
To quote an Australia CSIRO report (1988) ,
“ Toughness (in meat) is caused by three
major factors — advancing age of the animal,
‘ cold shortening ’ (the muscle fi ber contrac-
tion that can occur during chilling), and unfa-
vorable meat acidity (pH). ” There is general
agreement on the importance of these factors,
with many experts adding cooking as a fourth
equally important infl uence.
The texture of frozen meat will have been
generally fi xed by what happened to the meat
during the primary chilling of the carcass.
Chilling can have serious effects on the
texture of meat if it is carried out too rapidly
when the meat is still in the pre - rigor condi-
tion, that is, before the meat pH has fallen
below about 6.2 (Bendall 1972 ). In this state,
the muscles contain suffi cient amounts of the
contractile fuel adenosine triphosphate (ATP)
for forcible shortening to set in as the tem-
perature falls below 11 ° C, the most severe
effect occurring at about 3 ° C. This is the so -
called “ cold shortening ” phenomenon, fi rst
observed by Locker and Hagyard (1963) and
its mechanism described by Jeacocke (1986).quarters, or boned - out primals in 25 - kg
cartons. It is not unusual for meat to be frozen
twice before it reaches the consumer. During
industrial processing, frozen raw material is
often thawed or tempered before being turned
into meat - based products (i.e., pies, conve-
nience meals, burgers, etc., or consumer por-
tions, fi llets, steaks, and so on). These
consumer - sized portions are often refrozen
before storage, distribution, and sale.
The Effect of Freezing and
Thawing on Meat Quality
There is a general view that fast freezing
offers some quality advantage, with “ quick
frozen ” appearing on many meat products
with the expectation that consumers will pay
more for a quick - frozen product. Studies
have shown that freezing rate infl uences ice
crystal size, location (intra - or extra - cellular),
and morphology (Grujic et al. 1993 ).
However, there are little data in the literature
to suggest that, in general, the method of
freezing or the rate of freezing has any sub-
stantial infl uence on the quality characteris-
tics or fi nal eating quality of meat. Slightly
superior chemical and sensory attributes have
been found in meat cryogenically frozen in a
few trials (Dobrzycki et al. 1977 ; Sebranek
et al. 1978 ; Sebranek 1980 ), but other trials
have not shown any appreciable advantage
(Lampitt and Moran 1933 ), especially during
short - term storage (Hill and Glew 1973 ). As
an example, in a study comparing frozen beef
burgers, no signifi cant difference could be
seen in cooking losses or eating quality
between samples frozen using either spiral,
impingement, or cryogenic methods, even
after 2 months storage (Sundsten et al. 2001 ).
In terms of increased throughput, however,
the study did reveal some slight commercial
advantages of fast freezing.
High - pressure freezing and in particular
“ pressure shift ” freezing is attracting consid-
erable scientifi c interest (LeBail et al. 2002 ).
The meat is cooled under high pressure to