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

334 Part 3: Meat, Poultry and Seafoods

Table 18.3.Main Roles and Effects of Microorganisms in Fermented Meats

Group Microorganisms Primary Role Secondary Role Chemical Contribution Effects

Lactic acid

bacteria

L. sakei, L. curvatus,

L. plantarum,

L. pentosus,

P. acidilactici,

P. pentosaceus

Glycolysis Proteolysis (endo

and exo)

Lactic acid generation

Generation of free amino acids

pH drop

Safety

Firmness

Taste

Micrococcaceae K. varians, S. Xylosus,

S. carnosus

Nitrate reductase,

lipolysis,

Catalase

Proteolysis (exo) Reduction of nitrate to nitrite

Generation of free fatty acids,

ready to oxidation

Generation of free amino acids

Degradation of hydrogen

peroxide

Safety

Aroma

Taste

Yeasts Debaryomyces

hansenii

Lipolysis Deamination/

deamidation

Transamination

Generation of free fatty acids

Transformation of amino acids

Lactic acid consumption and

generation of ammonia

Aroma

Taste

pH rise

Molds Penicillium

nalgiovense,

P. chrysogenum

Lipolysis,

proteolysis

(exo)

Deamination/

deamidation

Transamination

Generation of free fatty acids,

ready to oxidation

Generation of free amino acids

and its transformation

Generation of ammonia

Aroma

Taste

pH rise

external

aspect

the processing of European sausages whileL. plantarumandP.

acidilacticigrow well at higher temperatures (30–35◦C) closer

to the fermentation conditions in the sausages produced in the

United States. Lactic acid bacteria also have a proteolytic sys-

tem, consisting in endo- and exopeptidases, that contributes to

the generation of free amino acids during processing and most

of them are also able to generate different types of bacteriocins

with antimicrobial properties. Recently, an absence of effect of

certain lactic acid bacteria likeL. curvatus,L. sakei,Str. Griseu,

andP. pentosaceuswas reported in American dry sausages

ripened for a short time and finally heat processed (Candogan

et al. 2009).

Micrococcaceae

This group consists ofStaphylococcusandKocuria(formerly

Micrococcus), which are major contributors to flavor due to

their proteolytic and lipolytic activities (Casaburi et al. 2006).

However,L. curvatusandS. xylosuswerereportedtohavenosig-

nificant effect on proteolysis and lipolysis (Casaburi et al. 2007),

although the sensory characteristics were observed to improve

in long-ripened sausages (Casaburi et al. 2008). Another impor-

tant function consists of the nitrate reductase activity, necessary

to reduce nitrate to nitrite and contribute to color formation and

safety. However, these microorganisms must be added in high

amounts because they grow little or even die just at the onset of

fermentation, when low pH conditions prevail. Preferably, low

pH-tolerant strains should be carefully selected. The species

from this family also have an important catalase activity that

contributes to color stability and, somehow, prevention of lipid

oxidation.

Yeasts

Debaryomyces hanseniiis the predominant yeast in fermented

meats, mainly growing in the outer area of the sausage due to

its aerobic metabolism.D. hanseniihas a good lipolytic activity

and is able to degrade lactic acid. In addition, it also exhibits an

important deaminase/deamidase activity, using free amino acids

as substrates and producing ammonia as a subproduct that raises

the pH in the sausage (Dur ́a et al. 2002).D. hanseniihas also

some proteases of interest like proteases A, B, and D, as well as

prolyl and arginyl aminopeptidases (Bolumar et al. 2005, 2006a,

2008).

Molds

Some typical Mediterranean dry fermented sausages have molds

on the surface. The most usual arePenicillium nalgiovenseand

P. chrysogenum. They contribute to flavor through their prote-

olytic and lipolytic activity, and to appearance in the form of a

white coating on the surface (Sunesen and Stahnke 2003). They

also generate ammonia through their deaminase and deamidase

activities and contribute to pH rise. Inoculation of sausages with

natural molds present in the fermentation room is dangerous

because toxigenic molds might grow. So, fungal starter cultures

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 demanded in certain Mediterranean areas.

Casings

Casings may be natural, semisynthetic, or synthetic, but a com-

mon required characteristic is its permeability to water and air.