28 Biochemistry of Fermented Meat 651This could be used to produce cured meats free of
nitrate and nitrite (Moller et al. 2003).
PROCESSING STAGE 5: SMOKING
Smoking is mostly applied in northern countries
with cold and/or humid climates. Initially, it was
used for preservation purposes, but today its contri-
bution to flavor and color is more important (Ellis
2001). In some cases, smoking can be applied just
after fermentation or even at the start of the fermen-
tation. Smoking can be accompanied by heating at
60°C and has a strong impact on the final sensory
properties. It has a strong antioxidative effect and
gives a characteristic color and flavor to the product,
which is the primary role of smoking. The bacterio-
static effect of smoking compounds inhibits the
growth of yeasts, molds, and certain bacteria.
SAFETY
The stability of the sausage against pathogen and/or
spoilage microorganisms is the result of successive
hurdles (Leistner 1992). Initially, the added nitrite
curing salt is very important for the microbial stabil-
ity of the mix. During mixing under vacuum, oxy-
gen is gradually removed, and redox potential is
reduced. This effect is enhanced when ascorbic acid
or ascorbate is added. Low redox potential values
inhibit aerobic bacteria and make nitrite more effec-
tive as bactericide. During the fermentation, lactic
acid bacteria can inhibit other bacteria, not only by
the generation of lactic acid (and the subsequent pH
drop), but also by generation of other metabolic
products such as acetic acid and hydrogen peroxide
and, especially, bacteriocins (low molecular mass
peptides synthetized in bacteriocin-positive strains;
Lücke 1992). The drying of the sausage continues
the reduction in water activity to low values (aw
below 0.92) that inhibit growth of spoilage and/or
pathogenic microorganisms. Thus, the correct inter-
action of all these factors assures the stability of the
product.
Some foodborne pathogens that might be found in
fermented meats are briefly described. Salmonellais
more usual in fresh, spreadable sausages (Lücke
1985) but can be inhibited by acidification to pH 5.0
and/or drying to aw0.95 (Talon et al. 2002).
Lactic acid bacteria exert an antagonistic effect
against Salmonella(Roca and Incze 1990). Sta-
phylococcus aureusmay grow under aerobic or
anaerobic conditions and requires aw0.91 for in-
hibition, but is sensitive to acid pH. So, it is impor-
tant to control the elapsed time before reaching the
pH drop in order to avoid toxin production. Further-
more, this toxin is produced only in aerobic condi-
tions (Roca and Incze 1990). Clostridium botulinum
and its toxin production capability are affected by a
rapid pH drop and low aweven more than by the
addition of lactic acid bacteria and nitrite (Lücke
1985). Listeria monocytogenesis limited in growth
at aw0.90 combined with low pH values and spe-
cific starter cultures (Hugas et al. 2002). Escherichia
coliis rather resistant to low pH and awbut is
reduced when exposed to aw0.91 (Nissen and
Holck 1998). Adequate prevention measures consist
in correct cooling and a hazard analysis critical con-
trol point (HACCP) plan with application of good
manufacturing practices (GMP), sanitation, and strict
hygiene control of personnel and raw materials.
In recent years, most attention has been paid to
biopreservation as a way to enhance preservation
against spoilage bacteria and foodborne pathogens.
The bioprotective culture consists in a competitive
bacterial strain that grows very fast or produces an-
tagonistic substances like bacteriocins. Another pre-
cise way consists in the direct addition of purified
bacteriocins. Those bacteriocins belonging to group
IIa (also called pediocin-like) that display inhibition
against Listeriahave been reported to be the most
interesting for the meat industry (Hugas et al. 2002).
Parasites like Trichinella spiralisare almost elim-
inated through modern breeding systems. Pork meat
free of trichinae must be used as raw material for
fermented sausages; otherwise, heat treatments of
the sausage to reach internal temperatures above
62.2°C are required to inactivate them (Sebranek
2004).
The generation of undesirable compounds, listed
in Table 28.4, depends on several factors. The most
important factor is the hygienic quality of the raw
materials. For instance, the presence of cadaverine
and/or putrescine may be indicative of the presence
of contaminating meat flora. Another factor is pro-
cessing conditions, which may favor the generation
of biogenic amines; however, the type of natural flo-
ra or microbial starters used for the process is the
most important issue, because the presence of mi-
croorganisms with decarboxylase activity can in-
duce the generation of biogenic amines. In general,