BLBS102-c18 BLBS102-Simpson March 21, 2012 13:30 Trim: 276mm X 219mm Printer Name: Yet to Come
338 Part 3: Meat, Poultry and SeafoodsMyofibrillar
proteinsCarbohydrates Triacylglycerols
phospholipidsNitrate CatalasePyruvate Peptides fatty acidsFree Nitrite Peroxides
destructionFree
Lactic acid amino acidsVolatile
compoundsNitric oxidepH Taste Aroma Color
Figure 18.7.Scheme showing the most important reactions by muscle and microbial enzymes involved in chemical and biochemical changes
affecting sensory quality of fermented meats.deamination and/or deamidation reactions by deaminases and
deamidases, respectively, present in yeasts and molds; or amines
by microbial decarboxylases.
Another important group of enzymatic reactions, affecting
muscle and adipose tissue lipids, is known as lipolysis (Toldra ́
1998). Thus, a large amount of free fatty acids (between 0.5%
and 7%) is generated through the enzymatic hydrolysis of tria-
cylglycerols and phospholipids. Most of the observed lipolysis
is attributed, after extensive studies on model sterile systems and
sausages with added antibiotics, to endogenous lipases present
in muscle and adipose tissue (e.g., lysosomal acid lipase, present
in the lysosomes and very active at acid pH; Toldra 1992, Hierro ́
et al. 1997, Molly et al. 1997).
Catalases are mainly present in microorganisms such asKocu-
riaandStaphylococcus;they are responsible for peroxide reduc-
tion and thus contribute to color and flavor stabilization. Nitrate
reductase, also present in these microorganisms, is also impor-
tant for reducing nitrate to nitrite in slow-ripened sausages with
an initial addition of nitrate. Recently, two strains ofLactobacil-
lus fermentumhave proved to be able to generate nitric oxide
and give an acceptable color in sausages without nitrate/nitrite.
This 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 contribution 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 fermentation.
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 antimi-
crobial effect of some smoking compounds, especially phenols,carboxylic acids, and formaldehyde inhibit the growth of certain
bacteria even though some yeasts and molds may be resistant
(Sikorski and Kolakowski 2010).SAFETY
The stability of the sausage against pathogen and/or spoilage mi-
croorganisms is the result of successive hurdles (Leistner 1992).
Initially, the added nitrite curing salt is very important for the mi-
crobial stability 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 effective 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; Lucke ̈
1992). The drying of the sausage continues the reduction inawto
low values (awbelow 0.92) that inhibit growth of spoilage and/or
pathogenic microorganisms. Thus, the correct interaction 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 (Lucke 1985), but can be inhibited by acid- ̈
ification to pH 5.0 and/or drying toaw<0.95 (Talon et al.
2002). Lactic acid bacteria exert an antagonistic effect against
Salmonella(Roca and Incze 1990).Staphylococcus aureusmay
grow under aerobic or anaerobic conditions and requiresaw<
0.91 for inhibition, but is sensitive to acid pH. So, it is important
to control the elapsed time before reaching the pH drop in order
to avoid toxin production. Furthermore, this toxin is produced
only in aerobic conditions (Roca and Incze 1990).Clostridium
botulinumand its toxin-producing capability are affected by a
rapid pH drop and lowaweven more than by the addition of