146 Chapter 7
typical sensory properties such as appear-
ance, texture, fl avor, or noise. Finely com-
minuted products are defi ned by their smooth
surface. The “ knackwurst, ” which contains
pork, beef, spices, and some garlic, is named
for the familiar popping noise when bitten
( “ Knack! ” ). Generally, “ cold emulsions ”
give sliceable products, whereas “ hot emul-
sions ” give spreadable products. Third, it is
a means to create “ value - added ” meat: rela-
tively low - value meat offcuts can be used,
including trimmings or parts of the animal
that are less acceptable in their whole state
due to a high content of connective tissue
or fat (Sebranek 2003 ; Wilson 1981 ).
Emulsifi cation operation also has side effects:
it improves keepability and safety by the use
of ingredients such as salt and by thermal
treatment. It is also a means to improve nutri-
tional properties through low - fat and low - salt
products or through products enriched with
fi bers and micronutrients. Relevant proper-
ties are obtained by a proper combination of
ingredients and processing procedures.Formulation
Basic meat batter ingredients are lean meat,
fat, water, and sodium chloride, but various
nonmeat ingredients are often used.Meat Muscles and Meat Derivatives
Structure of Muscles
High - quality lean meat shows very good
functional properties. It is well recognized
that solubilized muscle proteins are a natural
emulsifying agent due to the nature of the
amino - acid side - chains situated along their
lengths, some of which are lyophilic and
others hydrophilic (Wilson 1981 ). Meat pro-
teins have very different properties, depend-
ing on their functional role in the muscle.
They can be divided into three groups, based
on their solubility characteristics (Nakai and
Li - Chan 1988 ; Zayas 1997 ). Proteins that areular and colloidal interactions, which govern
whether emulsion droplets aggregate or
remain as separate entities (McClements
1999 ). These interactions affect protein func-
tionality attributes such as emulsifi cation,
gelation, and water binding (Gordon and
Barbut 1997 ). Main molecular forces are
repulsive electrostatic forces, attractive van
der Waals forces, and steric overlap.
Hydrogen bonding and hydrophobic interac-
tion are higher - order interactions that occur
between specifi c chemical groups commonly
found in food molecules (McClements
1999 ). Hydrogen bonds and electrostatic
attractions appear to have some importance
and seem to participate in the binding of the
interfacial protein fi lm (IPF) to the protein
matrix (Mandigo 2004 ). Hydrophobic inter-
actions are strong attractive forces that act
between nonpolar groups separated by water
(McClements 1999 ). They happen when sur-
faces are nonpolar, either because they are
not completely covered by emulsifi er (during
homogenization or at low emulsifi er concen-
tration) or because the emulsifi er has some
hydrophobic regions exposed to aqueous
phase (e.g., adsorbed proteins) (McClements
1999 ). Protein hydrophobicity is important
for effective formation of the IPF and
stabilization of the protein matrix (Mandigo
2004 ). During heating, myofi brillar proteins
start to denature, leaving several hydropho-
bic domains exposed. Hydrophobic interac-
tions are then more likely, as is enhanced
protein aggregation that immobilizes the fat
globules by physical entrapment (Mandigo
2004 ).
Aims of Emulsifi cation
The emulsifi cation unit operation has three
specifi c aims. First, it has to ensure the
physicochemical stability of the product.
Emulsifi cation determines the characteristic
structure of the batter, which greatly infl u-
ences fat and moisture separation from the
product during cooking. Second, it creates