152 Chapter 7
The swelling depends both on pH and
NaCl content (Hamm 1972 ; Offer and Knight
1988 ). Without salt, there is a maximum at
pH 3.0, a minimum (the average isoelectric
point of meat proteins) at pH 5.0, and from
there a constant increase within the physio-
logical pH range (Rusunen and Puolonne
2005 ). Due to the selective binding of ions,
salts move the isoelectric point. In cooked
pork and beef sausages, approximately the
same water holding as with 2.5% NaCl in pH
5.7 can be reached with 1.5% NaCl in pH 6.1
and above (Puolanne et al. 2001 ).
Since sodium intake generally exceeds
nutritional recommendations in industrial-
ized countries and approximately 20% – 30%
of common salt intake comes from meat
products, there is increasing interest among
consumers and processors in reducing the use
of NaCl content in meat processing (Jimenez -
Colmenero et al. 2005 ). In cooked sausages,
it can be concluded that without phosphate,
the NaCl content can be lowered to 1.5% –
1.7%, and with phosphate, to 1.4% without
jeopardizing the technological quality and
yield approaches (Ruusunen and Puolanne
2005 ). However, lowering salt content raises
several problems. In low - salt meat products,
the increased meat protein content (i.e., lean
meat content) reduces perceived saltiness and
the intensity of the characteristic fl avor
decreases (Ruusunen and Puolanne 2005 ).
The functionality of the traditional myosin
heat - set matrix may be limited due to low
ionic strength (Pietrasik and Li - Chan 2002 ).
This can lead to a decrease in textural char-
acteristics: low - salt batters produce gels that
are less hard and chewy, and they have poorer
binding properties than gels produced with
higher salt (Pietrasik and Li - Chan 2002 ).
Excessive loss of water can lead to a mushy
texture. Depending on their origin (beef,
pork, or poultry), meat proteins show differ-
ent gelation patterns and different responses
to salt (Barbut and Mittal 1989 ).
The simultaneous reduction of both salt
content and fat content is not easily achieved.Sodium Chloride
Sodium chloride (NaCl) is involved in water
holding, fi rmness, taste, and fl avor, as well as
the microbiological safety of meat products
(Puolanne et al. 2001 ). NaCl usually ranges
from 0% in salt - free products to 4% in steril-
ized products. In meat processing, typically
2% – 3% salt is incorporated in the product
formulation (Claus et al. 1994 ). Sodium
chloride increases water binding in meat lin-
early from 0 to 0.8 – 1.0 ionic strengths in
the water phase (Hamm 1972 ; Offer and
Knight 1988 ). This corresponds to less than
5% NaCl in lean meat, provided that the
water content is about 75% (Ruusunen and
Puolanne 2005 ). Salt induces important
changes in myofi brils. Negative protein
charges are increased because chloride ions
are more strongly bound to the proteins than
sodium ions. According to Hamm (1972) ,
this causes repulsion between the myofi bril-
lar proteins (myofi laments), which results in
a swelling of myofi brils or even a partial
solubilization of fi laments. Offer and Knight
(1988) indicate that the selective binding of
chloride ions to the myofi brillar proteins
causes a loosening of the myofi brillar lattice,
due to a repulsion between the molecules of
myosin fi laments breaking down the shaft of
the fi lament. Moreover, sodium ions are
pulled very close to the fi lament surfaces by
the proteins ’ electrical forces. This increases
osmotic pressure within the myofi brils,
causing the fi lament lattice to swell. The
factors inhibiting the unlimited swelling are
the actomyosin cross - bridges between the
fi laments and Z - lines. In sausage meat, the
sarcomere alteration depends on the interac-
tion of the ionic strength with the processing
conditions, particularly of the mincing and
mixing conditions (Ripoche et al. 2001 ).
Comminution alone enhances the meat -
setting properties, in that the thermal stabili-
ties of myosin and actin are modifi ed and
protein salt - solubility is increased (Fern á ndez -
Mart í n et al. 2002 ).