Food Biochemistry and Food Processing (2 edition)

BLBS102-c18 BLBS102-Simpson March 21, 2012 13:30 Trim: 276mm X 219mm Printer Name: Yet to Come

18 Biochemistry of Fermented Meat 335

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. Natu-

ral casings are typically used for traditional sausages because

they give a homemade aspect to the product. Semisynthetic cas-

ings are based on collagen that shrinks with the product and is

permeable, but cannot be overstuffed (Toldra et al. 2002). Syn- ́

thetic cellulose-based casings are nonedible but are preferred for

industrial processes due to important advantages such as con-

trolled 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, de-

pending on the type of product. Of course, the diameter strongly

affects fermentation and drying conditions. So, pH drop is more

important in large-diameter sausages, where drying is more dif-

ficult to achieve.

PROCESSING STAGE 1: COMMINUTION

An example of a flow diagram for the processing of fermented

sausages is shown in Figure 18.1. Chilled meats, pork alone

or mixtures of pork and beef, and porcine fats are submit-

ted to comminution in a grinder (Fig. 18.2). There are several

plates with different hole sizes depending on the desired parti-

cle size. Previous trimming for removal of connective tissue is

recommended, especially when processing undry or semidry fer-

mented sausages where no further hydrolysis of collagen will oc-

Raw materials

Comminution

Storage

Additives

Stuffing

starters

Casings

Fermentation

Smoking

(optional)

Ripening/drying

Packaging

shipping

Figure 18.1.Flow diagram showing the most important stages in

the processing of fermented sausages.

Figure 18.2.Grinding of meats and fats. There are many sizes of

grinder plates in accordance to the required particle size.

cur. Salt, nitrate and/or nitrite, carbohydrates, microbial starters,

spices, sodium ascorbate, and optionally, other nonmeat 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. 18.3). Grinding and mixing take sev-

eral minutes, depending on the amount. Industrial processes may

use a cutter, as an alternative to grinding and mixing, when the

required particles sizes are small. The cutter consists in a slowly

moving 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 ◦Cto− 7 ◦C) to avoid smear-

ing of fat particles during 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,

Figure 18.3.Detail of the batter after mixing in a vacuum mixer

massager.