Handbook of Meat Processing

Emulsifi cation 159

through sensory, chemical, and physical

measurements. They can be performed on

batter or on the fi nal product. Most of them

are off - line measurements performed in a

laboratory. Rapid measurements can be per-

formed at - line (e.g., water and fat content),

but few on - line measurements are available.

Off - Line Measurements

In the following, only measurements directly

related to the emulsifi cation process (i.e.,

water and fat binding and microstructure)

will be discussed.

Microstructure Characterization

Microscopical techniques are useful to char-

acterize the structure of comminuted meat

products. Light microscopy achieved the

observation of fat globules ’ distribution and

protein gel in emulsion - type buffalo meat

sausages (Krishnan and Sharma 1990 ). It

revealed that caseinate and modifi ed whey

form distinct dairy protein gel regions within

meat batters, and this could explain their

ability to enhance the textural properties of

the meat batters compared with the other

dairy proteins (Barbut 2006 ). In minced

ostrich meat batter, confocal microscopy

suggested that the size of the fat droplets

varied with gum type (Chattong et al. 2007 ).

In chicken meat gels, it showed that low - fat

protein gels obtained by pressure and con-

taining microbial transglutaminase had a

more compact and homogeneous micro-

structure compared with controls that were

pressurized but contained no MTGase

(Trespalacios et al. 2007 ). Scanning electron

microscopy was useful to show structure dif-

ferences in low - fat sausages (Morin et al.

2004 ; C á ceres et al. 2008 ).

Differential scanning calorimetry (DSC)

showed that sausages with a higher gum -

to - protein ratio required additional energy

for protein denaturation to occur (Morin et al.

2004 ). It was used to study structural changes

et al. 1984 ; Fern á ndez - Mart í n et al. 2002 ;
Hong 2008 ), (3) during heating (Fernandez -
Martin et al. 1997 ; Yuste et al. 1999a ;
Chattong 2007 ; Supavititpatana and
Apichartsrangkoon 2007 ), or (4) after heating
to increase shelf life (Yuste et al. 1999b ;
Ruiz - Capillas et al. 2007 ).
The effects of high pressure on commi-
nuted meat are diffi cult to compare, due to
the diversity of meat matrixes and the various
ways high pressure is applied. Moreover,
high - pressure conditions are not precisely
enough described (Jim é nez - Colmenero
2002 ).
High - pressure treatment applied to beef
muscles for manufacturing frankfurters suc-
cessfully reduced salt level to 1.5% without
any noticeable change in cook loss, and
emulsion stability of the frankfurters could
be improved with salt reduction, indepen-
dently of the applied pressure level (Crehan
et al. 2000 ). Main limitations are due to
texture modifi cations (MacFarlane et al.
1984, 1986 ; Crehan et al. 2000 ). Pressure -
induced protein gels differ from those induced
by heat, being glossier, smoother, and softer,
and having greater elasticity (Supavititpatana
and Apichartsrangkoon 2007 ). Heat - induced
gels and pressure - induced gels show differ-
ent properties. Heating ( > 40 ° C) under high -
pressure conditions limits the gelling process
of meat systems (Jimenez - Colmenero 2002 ).
When pressure was applied to frankfurters
after cooking, pressurized sausages showed
different texture attributes (less hard) than
heat - treated sausages (Mor - Mur and Yuste
2003 ; Ruiz - Capillas et al. 2007 ). High -
pressure treatment was combined with micro-
bial transglutaminase to enhance the binding
properties, textural parameters, microstruc-
ture, and color in low - fat and low - salt chicken
gels (Trespalacios et al. 2007 ).

Control

Like every food product, the quality of fi nely
comminuted meat products is assessed