FLEISCHWIRTSCHAFT international_04_2018

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Fleischwirtschaft international 4_2018
Storage
Packaging assures quality
Fig. 2: The composition of the gas mixture has to be adapted to the meat to be
packaged. O. Fischer / pixelio.de
gas has a very high penetration
capacity and penetrates the bacterial
membrane causing changes in
the intra-cellular pH which cannot
be buffered by the microorganisms
(NARASIMHA and SACHINDRA,
2002).
Absorption of CO2 by the meats
leads to a decrease in the volume of
the package which provides a similar
look like vacuum packages. It is
known as pack collapse. Dissolved
CO2 in meats leads to the formation
of carbonic acid due to the reaction
between CO2 and H2O. This drop in
the pH of meats leads to lowering
the water retention ability, resulting
in an accumulation of liquid in the
package (LUND et al., 2007). However,
the absorption of CO2 depends
on various factors, such as pH,
moisture, fat content, packaging
and storage condition, partial pressure
of CO2 etc. High levels of CO2
are desirable for the preservation of
meats because it inhibits superficial
microbial growth and enhances the
shelf-life. Among various gas uses
in the MAP, only CO2 has antimicrobial
effects. Microbial properties
of CO2 is hampered in presence of
some other gas, especially oxygen.
The growth of microorganisms in
MAP is inhibited by CO2 due to its
bacteriostatic effect. The bacteriostatic
effect of carbon dioxide is
influenced by the various factors
like concentration of CO2, level of
initial contamination, age of microbes,
storage condition i.e. temperature,
humidity, type of products
etc.
However, some disadvantages
are also documented at high concentrations
of CO2 in MAP, such as
a dark color of meat especially due
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to formation of metmyoglobin at
low O2 concentrations (VIANA et al.,
2005). The gas mixture for the
packaging of beef in MAP varies
from 75–80% O2 and 20–25% CO2.
The increase of the O2 concentration
above 55% may not provide
additional benefits to maintain the
color attributes as higher levels of
the O2 content may promote lipid
oxidation, leading to the production
of off-flavor compounds.
The selection of the combinations
of gas mixtures depends on
the product sensitivity to O2 and
CO2, consumer’s product color
demands in the market and the type
of microbial growing on the meats.
For the storage of the fresh meat O2
is very important because it helps in
the formation of oxymyoglobin
which is responsible for the formation
of a bright red color; but it is
not required in the gas combination
for the preservation of pork.
Oxygen (O2)
Oxygen is an important gas for the
survivability of aerobic microorganisms.
It plays a major role in the
determination of storage life of
meats. However, oxygen plays an
important role in the maintenance
of the meat color, which is an important
parameter for the marketing
of fresh products. So various
researchers focused on finding the
correct gas combination for the use
in MAP for maintaining the color,
storage stability, reduced microbial
growth and reduced fat oxidation.
However, oxygen plays a major
role in MAP to maintain the color
stability of meat by formation of
oxmyoglobin, which is responsible
for the bright red color of meat.
Oxygen is essential for the
growth of the spoilage microbes
and it also enhances the oxidative
rancidity in meats leading to reduced
shelf-life. Thus the proper
gas combinations for the maintenance
of the red meat color, oxidative
detrition and control of the
oxidative process in meats are still
desirable. The ultra-low level of
oxygen used for pork is less than
1% and for beef 0.05%, respectively.
The benefits of the ultra-low oxygen
over the high oxygen gas combination
are reduced lipid oxidation as
well a reduced aerobic microbe’s
growth.
Nitrogen (N2)
It is very well documented that the
composition of the gas mixture in
MAP systems (O2, CO2 and N2) can
effectively control/ stop the growth
of aerobic micro-organisms of
perishable food items such as meat,
fish and their products, as well as
maintain the visual quality of red
meat. The objective of MAP is the
exclusion of oxygen from the
sounding of packaged meat and
meats with the help of a combination
of gases which have unique
properties of inhibiting oxidative
changes and microbial growth.
Nitrogen is an inert gas and it has
unique properties like low solubility
in polar as well in nonpolar solvents.
Its main function in MAP is to
replace O2, indirectly reducing the
oxidation of fat enriched products
and the growth of aerobic microorganism.
It helps in the extension
of the shelf-life of the meats in MAP.
Nitrogen plays another important
role in MAP in combination with
CO2, by preventing pack collapsing.
Carbon monoxide
Carbon monoxide gas combines
with myoglobin and forms a complex
compound known as carboxymyoglobin,
which is responsible for
the maintaining cherry red color in
fresh meat. However, due to its
toxic nature most of the regulatory
bodies do not approve its use except
Norway. The level of CO use in the
MAP is 0.4%; at this level it improves
the color.
Effect on the
quality attributes
Color and appearance, sensorial
attributes, microbial and oxidative
changes are the important parameters
that limit the shelf-life and
marketability of meats (Tab. 2).
Therefor researchers want to minimize
these changes in meats by
using various techniques and
preservatives. Out of all techniques
available at present, MAP offers a
novel approach for maintaining the
quality attributes and extending
storage life. The overall effect of
MAP can be grouped into following
three categories as:
r Effect on sensory attributes
r Effect on microbial quality
r Effect on lipid oxidation.
Effect on sensory attributes
Color is the prime attribute that
affects the marketing and purchasing
of meats. Consumers judge the
quality of meat products with the
help of color. However, color of