606 Part VI: Fermented Foods
decarboxylases, transaminases, or deaminases con-
tribute to the formation of amines, acids, ammonia,
and thiols, which contribute to cheese flavor.
Lipases break down triglycerides into free fatty
acids and mono- and diglycerides. The short-chain
free fatty acids contribute to the sharp, pungent fla-
vor characteristics of the cheese. The degree of
lipolysis that is acceptable without producing soapy
and rancid flavors depends on the type of cheese.
Several Penicillium strains form methyl ketones,
lactones, and unsaturated alcohols through their en-
zymatic systems associated with -oxidation and
decarboxylation, -oxidation and lactonization, and
lipoxygenase activity. Aliphatic and aromatic esters
are synthesized by esterases present in a range of
microorganisms, including mesophilic and ther-
mophilic LAB (Choisy et al. 2000).
The texture of cheese is attributed to the three-
dimensional protein network that entraps fat and
whey. This structure is altered through proteolysis
during ripening to form a less firm and less elastic
cheese.
Carbon dioxide produced by the metabolism of
the bacteria and entrapped within the curd results in
the formation of eyes in several types of cheeses.
The small eyes characteristics of Edam, Gouda, and
related cheese varieties are formed by carbon diox-
ide produced from citrate by the Leuconostocssp. In
Swiss type cheeses, Propionibacterium freudenre-
ichiissp. shermaniimetabolize lactate to form the
carbon dioxide responsible for the eye formation.
These cheeses are ripened in hot rooms (20–22°C)
to optimize the growth of the propionibacteria and
allow eye formation.
Ripening of cheese is a time-intensive process,
thus, there is much interest in accelerating the ripen-
ing process without an adverse effect on cheese
quality. The addition of attenuated starters or a mix-
ture of enzymes has been explored as a possible
means to shorten the ripening processing. An impor-
tant consideration is that increased proteolysis or an
imbalance of enzyme activity can result in higher
contents of hydrophobic amino acids and peptides
that contribute to bitterness (Choisy et al. 2000).
Processed Cheese
Processed cheeses are produced by blending and
heating several natural cheeses with emulsifiers,
water, butterfat, whey powder, and/or caseinates to
form a homogeneous mixture. The proportion of
cheese used in the formulation ranges from 51% for
cheese spreads and cheese foods to 98% in pro-
cessed cheeses. Different types of natural cheeses
will produce processed cheeses with different flavor
and textural characteristics. The formulation of these
ingredients affects the consistency, texture, flavor,
and melting characteristics of the processed cheese.
The heating process inactivates the microorganisms
and denatures enzymes to produce a stable product.
The flavor of the processed cheese is generally
milder than the natural cheeses, due to the effects of
the heat. However, the melting properties of the
processed cheese are much improved due to the
addition of the emulsifiers. Processed cheeses range
in consistency from block cheese to sliced cheese
to cheese for spreading (Banks 1998, Fox et al.
2000).BUTTERFlavor and consistency are the most important qual-
ity attributes to consider during the processing of
butter. The characteristic flavor of butter is a result
of the formation of diacetyl by heterofermentative
LAB. Off-flavors due to lipolysis, oxidation, or other
contaminants should be avoided. The butter should
be firm enough to hold its shape, yet soft enough to
spread easily. Figure 26.2 outlines the process in-
volved for making butter and the by-product butter-
milk.
The first step in the processing of butter is skim-
ming the milk to obtain cream with a fat content of
at least 35%, in which the fat is dispersed as droplets
within the aqueous phase. This step increases the
efficiency of the process through increasing the
yield of butter, reducing the yield of buttermilk, and
reducing the size of machinery needed. The function
of the pasteurization step is to kill microorganisms,
inactivate enzymes, and make the butter less suscep-
tible to oxidative degradation. Following pasteuriza-
tion, the cream is inoculated with a starter culture
mixture (1–2%) of Lactococcusssp. and Leucon-
ostocssp., which contributes to the development of
the characteristic butter flavor. It is desirable that the
starter cultures grow rapidly at low temperatures.
During ripening, the cream begins to ferment and
the fat begins to crystallize. The formation of lactic
acid and diacetyl by the starter cultures contributes
to flavor development in the butter and buttermilk.