Curing 135

Many countries have similar regulations.
For example, the regulations of the United
States should be mentioned here. The
U.S. Code of Federal Regulations (U.S.
Government 2005 ) states that the food addi-
tive sodium nitrite may be safely used in or
on specifi ed foods in accordance with the
following prescribed conditions:

As a preservative and color fi xative,
with sodium nitrate, in meat curing
preparations for the home curing of
meat and meat products (including
poultry and wild game), with directions
for use which limit the amount of
sodium nitrite to not more than 200
parts per million in the fi nished meat
product, and the amount of sodium
nitrate to not more than 500 parts per
million in the fi nished meat product.
All regulations, directives, and laws take
into account that nitrite is a toxic substance,
and that unlike other additives, nitrite does
not remain unchanged in the product during
processing. The discoveries of the early 20th
century are also taken into consideration.
Nitrate is only effective after being reduced
to nitrite. This is caused by microorganisms
only in products that are not heat treated early
after manufacturing, such as raw hams and
raw sausages.

Chemical Changes of Nitrite and

Nitrate in Meat

Sodium or potassium salts of nitrite (Table

6.3 ) are added to meat products. Both salts

are very soluble (Honikel 2007 ) and dissoci-

ate into their ions. The mother compound,

nitrous acid, is the actual reactive compound

(Hoagland 1914 ). It, however, exists at

meat ’ s pH values mainly in its undissociated

form. If 150 mg/kg nitrite are added at pH

5.7, nitrous acid is formed as shown in Table

6.4 in minute amounts of about 0.45 mg/kg

HNO 2. This means that only 1/336 of the

nitrite added is converted to nitrous acid.

This small amount is in equilibrium with its

anhydride N 2 O 3 (Fig. 6.1 ), which again dis-

sociates into NO + NO 2. The NO can react

with myoglobin, or with oxygen, forming

NO 2 ; the NO 2 reacts with water and nitrous

and nitric acid (Fig. 6.2 ).

This means that only very small concen-

trations of NO are available in a batter to

react with different compounds. If the pH of

the batter is higher than 5.7, then even less

nitrous acid is formed. At lower pH values,

the concentration of nitrous acid increases.

Thus, the nitrite concentration in a batter

depends on its pH.

Table 6.5 shows that increasing batter pH

from 5.3 to 6.3 increases the remaining nitrite

Table 6.4. Nitrous acid concentration in unheated meat batters

Assumption: pH 5.7 of batter = 2 · 10^ −^6 M H +

Assumption: addition of 150 mg NaNO 2 /kg = 2.17 · 10^ −^3 M NaNO 2

Facts: p k a of HNO 2 = 3.35; k a = 4.47 · 10^ −^4 M

NaNO 2 (MW = 69 D)

Na+−+++NO^2 H HNO + Na 2 +

(MW = 46 D) HNO 2  HNO+−+ 2

Calculation:

(^) 4.47 · 10 − (^4) M

CC−+⋅
C
NO H
HNO
2
2
CHNO M^2 () =
⋅⋅⋅
⋅
( )
−−
−
21710 210
44710
36
4
.
.
M
= 0.446 mg/kg ∼ 0.5 mg/kg (ppm)
0 446
150
2
2

. ppm HNO present
ppm NaNO added

=^1

(^336)