Handbook of Meat Processing

126 Chapter 6

ions. NaCl is soluble to 35.7 g/100 ml in cold

water and 39.1 g/100 ml in hot water. Its

molecular weight is 58.45 Dalton. A solution

of 1% NaCl is equivalent to a concentration

of 0.17 mol/litre (M); in sausage batters, the

common 2% NaCl is equivalent to 0.34 M,

while the fi nal concentration of NaCl in a dry

cured ham is around 5%  0.85 M.

Microbial Inhibition

The ions go into solution by becoming sur-

rounded by water molecules (Fig. 6.3 ). The

polar water (H 2 O) molecules, which are mol-

ecules with a 105 ° angle between the two

hydrogen atoms and the oxygen atom, exhibit

a partially negative load around the oxygen

atom and a partially positive charge at the H

atoms. Due to this polarity, the water mole-

cules are immobilized (no free movement)

around the ions in several layers and are no

longer available for chemical/enzymatic

reactions, neither in food nor in microorgan-

isms. We call this immobilization: the water

activity (a w ) is reduced. In pure water, the

a w = 1.00. In a totally dry product, a w = 0. By

freezing, the water molecules are also bound

in the presence of oxygen, does not take
place in nitrite - cured meat, since nitrite has
sequestered the oxygen. Commonly, this
change in fl avor is called curing fl avor.
Furthermore, nitrite or its derivatives bind
to myoglobin (forming NO - myoglobin,
responsible for the heat - stable red color of
meat products), or they react with ascorbate,
amino acids, and other compounds (Honikel
2008 ).
Additionally, NO 2 − and NO 3 − anions bind
cations like Fe 2+ /Fe 3+ , which exist in cells in
the form of free ions. There are microorgan-
isms in which the binding to Fe ions by nitrite
inhibits the growth of the microorganisms
such as Clostridium botulinum (Grever and
Ruiter 2001 ; L ü cke 2008 ).
So we now understand more about the
action of salt and nitrate/nitrite in curing. But
due to the different modes of action, the
curing with salt and salt plus nitrite or nitrate
is discussed separately in this chapter.

Action of Salt in Meat Products

Chemically, salt is sodium chloride (NaCl),
which dissociates in water into Na + and Cl^ −^

Figure 6.1. Scheme of the proposal of Hoagland (1910, 1914) for the action of nitrate in cured meat
products.

Figure 6.2. Oxidation of nitrous acid to nitric acid.

H 2 O Na+ OH 2

O

H 2

H 2

O

Cl–

H 2

O

OH 2 H 2 O

O

H 2

Figure 6.3. Action of water molecules on salt ions

leading to solution of salt and immobilization of

water molecules; the orientation of the H 2 O mole-

cules indicates their polarity.