Food Biochemistry and Food Processing (2 edition)

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18 Biochemistry of Fermented Meat 333

profile, which should be lower than 12%; and the level of oxida-

tion, measured as peroxide value, should be as low as possible

(Demeyer 1992). Some rancidity may develop after long-term

frozen storage since lipases present in adipose tissue are active

even at temperatures as low as− 18 ◦C and are responsible for

the continuous release of free fatty acids that are susceptible to

oxidation (Hern ́andez et al. 1999). So, extreme caution must be

taken with fats stored for several months as they may develop a

rancid flavor.

Other Ingredients and Additives

Salt is the oldest additive used in cured meat products since

ancient times. Salt, at about 2–4%, serves several functions,

including (1) an initial reduction inaw, (2) providing a charac-

teristic salty taste, and (3) contributing to increased solubility

of myofibrillar proteins. Nitrite is a typical curing agent used

as a preservative against pathogens, especiallyClostridium bo-

tulinum. Nitrite is also responsible for the development of the

typical cured meat color, prevention of oxidation, and contri-

bution to the cured meat flavor (Gray and Pearson 1984). The

reduction of nitrite to nitric oxide is favored by the presence

of ascorbic and erythorbic acids or their sodium salts. They

also exert antioxidative action and inhibit the formation of ni-

trosamines.

Carbohydrates like glucose and lactose are used quite often

as substrates for microbial growth and development. Disaccha-

rides, and especially polysaccharides, may delay the growth and

pH drop rate because they have to be hydrolyzed to monosac-

charides by microorganisms.

Sometimes, additional substances may be used for specific

purposes (Demeyer and Toldr ́a 2004). This is the case of

glucono-delta-lactone, added at 0.5%, which may simulate bac-

terial acidulation. In the presence of water, glucono-delta-lactone

is hydrolyzed to gluconic acid and produces a rapid decrease

in pH. The quality is rather poor because the rapid pH drop

drastically reduces the activity of flavor-related enzymes such

as exopeptidases and lipases. Phosphates may be added to im-

prove stability against oxidation; vegetable proteins, such as soy

isolates, to replace meat proteins; and manganese sulfate as a

cofactor for lactic acid bacteria.

Spices, either in natural form or as extracts, are added to give

a characteristic aroma or color to the fermented sausage. There

are a wide variety of spices (pepper, paprika, oregano, rose-

mary, garlic, onion, etc.), each one giving a particular aroma

to the product. Some spices also contain powerful antioxidants.

The most important aromatic volatile compounds may vary de-

pending on the geographical and/or plant origin. For instance,

garlic, which gives a pungent and penetrating smell, is typi-

cally used in chorizo, and pepper is used in salchichon and ́

salami. Paprika gives a characteristic flavor and color due to its

high content of carotenoids (Ordonez et al. 1999). The pres- ̃

ence of manganese in some spices, like red pepper and mus-

tard, is necessary for the activity of several enzymes involved

in glycolysis and thus enhances the generation of lactic acid

(L ̈ucke 1985).

Starters

Typical fermented products were initially based on the devel-

opment and growth of desirable indigenous flora, sometimes

reinforced with backslopping, which consists in the addition of

a previous ripened, fermented sausage with adequate sensory

properties. However, this practice usually gave a high hetero-

geneity in the product quality. The microbiota in spontaneously

fermented sausages have been identified in many different types

of sausages worldwide. The most frequent microorganisms

found wereL. curvatus, Lb. plantarum, Lb. sakei, St. carnosus,

St. xylosus, andSt. saprophyticus(Paramithitis et al. 2010).

The use of microbial starters, as a way to standardize pro-

cessing as well as quality and safety, is relatively new. In fact,

the first commercial use was in the United States in the 1950s,

followed by its use in Europe in the 1960s; since then, starters

have seen extensive use. Today, most of the fermented sausages

are produced with a combination of lactic acid bacteria, to get

an adequate acidulation, and two or more cultures to develop

flavor and facilitate other reactions, such as nitrate reduction.

In general, microorganisms used as starter cultures must sat-

isfy several requirements according to the purposes of their use:

nontoxicity for humans, good stability under the processing con-

ditions (resistance to acid pH, lowaw, tolerance to salt, resistance

to phage infections), intense growth at the fermentation temper-

ature (i.e., 18–25◦C in Europe or 35–40◦C in the United States),

generation of products with technological interest (i.e., lactic

acid for pH drop, volatile compounds for aroma, nitrate reduc-

tion, secretion of bacteriocins, etc.), and lack of undesirable en-

zymes (e.g., decarboxylases responsible for amine generation).

Thus, the most adequate strains must be carefully selected and

controlled as they will have a very important role in the process

and will be decisive for the final quality. The most important

microorganisms used as starters belong to one of the following

groups: lactic acid bacteria, coagulase-negative staphylococci,

Micrococcaceae, yeasts, or molds (Leistner 1992). These mi-

croorganisms provide a good number of enzymes involved in

relevant biochemical changes like the enzymatic breakdown of

carbohydrates, proteins, and lipids that affect color, flavor, and

texture (Flores and Toldra 2010). It must be taken into account ́

that these enzymes will be affected by the temperature of fer-

mentation and ripening,awand pH decrease during the process,

the length of ripening time, the content of salt, nitrate and ni-

trite, the type and content of carbohydrates, and the presence of

spices (Stahnke and Tjener 2007). The main roles and functions

for each group are shown in Table 18.3.

Lactic Acid Bacteria

The most important function of lactic acid bacteria consists in

the generation of lactic acid from glucose or other carbohy-

drates through either homo- or heterofermentative pathway. The

accumulation of lactic acid produces a pH drop in the sausage.

However, some undesirable secondary products, like acetic acid,

hydrogen peroxide, acetoin, etc., may be generated in case of

certain species having heterofermentative pathways.L. sakei

andL. curvatusgrow at mild temperatures and are usual in