646 Part VI: Fermented Foods
toxigenic molds might grow. So fungal starter cul-
tures are mainly used as a preventive measure against
the growth of other mycotoxin-producing molds and
give a typical white color on the surface as demand-
ed in certain Mediterranean areas.
CASINGS
Casings may be natural, semisynthetic, or synthetic,
but a common required characteristic is its perme-
ability to water and air. Natural casings are natural
portions of the gastrointestinal tract of pigs, sheep,
and cattle, and although irregular in shape, they have
good elasticity, tensile strength, and permeability.
Natural casings are typically used for traditional
sausages because they give a homemade aspect to
the product. Semisynthetic casings are based on col-
lagen that shrinks with the product and is permeable,
but cannot be overstuffed (Toldrá et al. 2004).
Synthetic cellulose-based casings are nonedible but
are preferred for industrial processes due to impor-
tant advantages such as controlled and regular pore
size, uniformity for standard products, and hygiene.
These casings are easily peeled off.
A wide range of sizes, between 2 and 15 cm, may
be used, depending on the type of product. Of course,
the diameter strongly affects fermentation and dry-
ing conditions. So pH drop is more important in
large diameter sausages, where drying is more diffi-
cult to achieve.
PROCESSING STAGE 1:
COMMINUTION
An example of a flow diagram for the processing of
fermented sausages is shown in Figure 28.1. Chilled
meats, pork alone or mixtures of pork and beef, and
porcine fats are submitted to comminution in a
grinder (Fig. 28.2). There are several plates with dif-
ferent hole sizes depending on the desired particle
size. Previous trimming for removal of connective
tissue is recommended, especially when processing
undry or semidry fermented sausages where no fur-
ther hydrolysis of collagen will occur. Salt, nitrate
and/or nitrite, carbohydrates, microbial starters, spi-
ces, sodium ascorbate, and optionally, other non-
meat proteins are added to the ground mass, and the
whole mix is homogenized under vacuum to avoid
bubbles and undesirable oxidations that affect color
and flavor (Fig. 28.3). Grinding and mixing take
several minutes, depending on the amount. In-
dustrial processes may use a cutter, as an alternative
to grinding and mixing, when the required particle
sizes are small. The cutter consists in a slowly mov-
ing bowl, containing the meats, fat, and additives,
which rotates against a set of knives operating with
rapid rotation. The fat and meat must be prefrozen
(6 to 7°C) to avoid smearing of fat particles dur-
ing chopping. This phenomenon consists in a fine
film of fat formed over the lean parts that may
reduce the release of water during drying (Roca and
Incze 1990). The cutter operates under vacuum to
avoid any damage by oxygen, although the opera-Figure 28.1.Flow diagram showing the most important
stages in the processing of fermented sausages.