Curing 133action of salt, and improve appearance and
fl avor.
Nitrogen exists in seven different states of
oxidation, starting from ammonia (NH 3 ) with
a formal electron load of − 3, through nitro-
gen gas with a formal load of 0, to NO (load
+2), nitrite ( NO 2 −, formal load +3), NO 2 gas
(load +4), to nitrate ( NO 3 −, formal load +5).
In the case of curing salts, the states of NO
(load +2) to nitrate (load +5) mainly occur.
Figures 6.1 and 6.2 show the changes in
nitrous acid occurring in meat systems. After
nitrous acid is formed from nitrite in an
acidic environment, it can form its anhydride
(N 2 O 3 ), which is in equilibrium with the
oxides NO and NO 2. NO reacts with myoglo-
bin or amino acids like cystein, or with glu-
tathione, whereas NO 2 reacts with water,
forming again one molecule of nitrous acid
and one molecule of nitric acid. In this reac-
tion sequence, nitrite or nitrous acid (oxida-
tion state N 3+ ) is oxidized to nitric acid
(nitrate), with oxidation state N 5+. When NO
is the other reaction partner, it has a N 2+ oxi-
dation state and has been reduced.
In the past few decades, ascorbic acid or
its salt, ascorbate resp. isoascorbate (erythor-
bate), has been used in cured meat batters. A
reaction of ascorbate with oxygen forms
dehydroascorbate, and thus prevents the oxi-
dation of nitrite to nitrate (Andersen and
Skibsted 1992 ; Skibsted 1992 ; Skibsted et al.
1994 ). On the other hand, ascorbate may
react with nitrite (nitrous acid or NO) as Dahl
et al. (1960) , Fox and Ackerman (1968) , and
Izumi et al. (1989) have shown. Ascorbate
reacts with “ nitrite ” by binding NO. The
bound NO seems to be able to react as NO
with other meat ingredients. Ascorbate is also
added to reduce the formation of nitrosa-
mines. The sequence of reactions of ascor-
bate preventing nitrosamine formation has
not been fully elucidated. It may be due to the
reduction by ascorbate of residual free nitrite
in meat products (EFSA 2003 ) or the binding
of NO to ascorbate and its retarded release.during a drying process, reaches concentra-
tions of 4 to 6% NaCl in the fi nished product.
The salt lets the structures swell and become
more tender. Salt enhances stability and shelf
life.
Raw Sausages
Raw sausages like salami are manufactured
by adding salt (ca. 3%) to a minced or com-
minuted meat plus fat batter without adding
water. The fermentation (which lowers
pH) and drying process (which enhances
the salt concentration to 3.5 – 5%) make the
product shelf stable, often without refrigera-
tion. The swollen protein structures also
“ glue ” the particles together at cool room or
ambient temperatures and keep the products
sliceable.
Liver Pat é , Liver Sausages,
and Blood Sausages
Meat products like these use either meat that
is cooked without salt, or raw liver or blood,
which contains no myofi brillar proteins. As
discussed above, salt cannot swell heat -
denatured myofi bers, and liver and blood
proteins do not form heat - stable networks
above chill room temperatures. In some
products, the sliceability at higher tempera-
tures is obtained by the addition of gelatin.
Action of Nitrite and Nitrate
Together with Salt in
Meat Products
Nitrite and nitrate are not used as sole curing
agents. Each is always applied with salt.
The concentrations of nitrite and nitrate are
in the range of 100 to 200 mg/kg, while the
salt in meat products is 2000 mg/kg and
more. As already mentioned, salt lowers
the water activity and enhances food safety.
Salt also changes the protein structures of
meat. Nitrite and nitrate support the safety