252 Chapter 13
(Dixon and Kell 1989 ). The absorption
capacity is related to biological factors (i.e.,
pH, water, and fat content) (Gill 1988 ;
Jakobsen and Bertelsen 2002 ), but also to
a large extent to packaging and storage con-
ditions, specifi cally CO 2 partial pressure,
headspace to meat volume ratio, and storage
temperature (Jakobsen and Bertelsen 2002 ;
Zhao et al. 1995 ). O ’ Sullivan et al. (2010)
used sensory panelists to assess the prefer-
ence of steaks packed under atmospheres
containing 50% O 2 (50 CO 2 ), 70% O 2 (30
CO 2 ), 80% O 2 (20 CO 2 ), or 100% CO 2. The
principal aim of this study was to explore
off - fl avors developed by CO 2 in commercial
MA packs as well as 100% CO 2. Samples
were tested by assessors after immediate
cooking, upon removal of the respective
packaging, and a second identical sample set
was served with samples left for 30 minutes
in ambient air to let any CO 2 dissipate prior
to cooking. From sensory analysis, panelists
had a preference for steaks packed under
atmospheres containing 50% O 2. The 50% O 2
packed treatments displayed a signifi cant
( P ≤ 0.05) and negative correlation with CO 2
fl avor, and this was even more pronounced
for samples where the CO 2 was allowed to
dissipate (Dis, P ≤ 0.001). There also
appeared to be a directional correlation of the
100% CO 2 samples to CO 2 fl avor, although
these results were not signifi cant (Fig. 13.3 ).
All other treatments proved to be nonsignifi -
cant. One explanation for this may be the
leanness of the meat used in this study, which
had a very low fat content. In addition, the
meat purchased was very stable in terms of
composition, with no signifi cant variation in
protein, fat, and moisture content. These cuts
are typical of those found in Irish
supermarkets.
In general, CAP is used for bulk product
or items of irregular shape, such as whole
lamb carcasses, or as master packs for retail -
ready product (Gill 2003 ). CAP is not suit-
able for individual trays of retail - ready
product because of the undesirable color ofControlled Atmosphere Packaging
of Meats
The storage life of chilled meat can be
extended by packaging the product under
controlled atmosphere packaging (CAP) with
N 2 or CO 2 (Gill and Molin 1991 ). The absence
of O 2 in an O 2 - free MAP or CAP system
results in a signifi cant shelf - life extension, as
these packaging formats offer hostile envi-
ronments to obligate aerobic spoilage micro-
organisms. CAP packaging has been used
commercially for the shipment of chilled
lamb to distant markets (Gill 1990 ).
However, these packaging systems initi-
ate the development of metmyoglobin in the
meat, which is unattractive to the consumer
(Hunt et al. 1999 ). The meat will bloom to
an attractive bright red color shortly (20 –
30 min) after opening the pack and exposing
the meat to air. Another negative attribute
associated with these packaging formats is
that the high usage of CO 2 may cause off -
fl avor or CO 2 taint in the meat, which can be
detected upon consumption (Nattress and
Jeremiah 2000 ). CO 2 is highly soluble in
water, most of which is contained in the
muscle, and also in fat tissue. This solubility
is increased with decreasing temperature.
When an atmosphere rich in CO 2 is used, the
high solubility of the gas in meat tissues must
be taken into account (Gill 2003 ). In an atmo-
sphere of 100% CO 2 , meat will absorb
approximately its own volume in gas. Thus,
the initial gas volume must exceed the
required fi nal volume by the volume of the
enclosed meat (Gill 2003 ). When high CO 2
levels are applied in a package headspace, the
concentration of CO 2 will decline due to
absorption of CO 2 in the meat. CO 2 dissolves
in meat until saturation or equilibrium is
reached. CO 2 is also suspected of affecting
the chemical quality of the meat (Jakobsen
and Bertelsen 2002 ). A lowering of meat pH
is a result of CO 2 absorption into the meat
and is a consequence of carbonic acid being
dissociated to bicarbonate and hydrogen ions