Handbook of Meat Processing

Technological Quality of Meat for Processing 29

been used as indicators of meat quality.

Highly marbled meat has traditionally been

thought to be the ideal because of the effects

of fat on fl avor and tenderness. However,

Rincker et al. (2008) reported that intramus-

cular fat (0.8 – 8.0%) explained less than

15% of the variance in pork fl avor scores.

Consumers could tell no difference in pork

fl avor scores until the fat content reached

4.5%. In addition, visible fat content in pork

is a major determinant of purchase intent

with consumers preferring leaner products

(Brewer et al. 2001 ; Rincker et al. 2008 ).

Fernandez et al. (1999) reported that pork

texture and taste are enhanced at intramuscu-

lar fat levels up to 3.25%, but inconsistent

effects occurred with respect to tenderness/

toughness.

Ellis et al. (1996) reported that longissi-

mus muscle from pig genotypes selected for

the propensity to increase marbling are more

tender and juicy, and have lower shear values.

The Duroc breed produces pork that is highly

marbled with good eating quality (Ellis et al.

1996 ). Brewer et al. (2002) reported that

chops from Duroc and Pietrain pigs had the

most visible marbling, while those from

Duroc/Landrace and Large White had the

least. Chops from Duroc, Duroc/Hampshire,

and Pietrain pigs had the highest fat content.

Meat from these breeds, however, differs

from other breeds with regard to muscle fi ber

type and the incidence of PSE (Chang et al.

2003 ).

Cattle breeds with different growth

rates but the same degree of marbling differ

substantially in tenderness and Warner

Bratzler shear value (Chambaz et al. 2003 ).

Historically, selection of beef breeds has

been based on marbling, irrespective of

growth rate and simultaneous selection pres-

sure for reduced overall fat deposition.

Postmortem p H Decline

Postmortem biochemical changes dramati-

cally affect tenderness and fl avor. The loss of

supplemented into swine diets has been
shown to stabilize meat color and decrease
fl uid loss when fed at > 200 mg/kd of diet
during fi nishing (Asghar et al. 1980 ).
Shifting carcass bone/muscle/fat ratio can
also be accomplished with steroid - like drugs.
Feeding beta - agonists can have signifi cant
effects on feedlot performance and/or carcass
characteristics. Quinn et al. (2008) reported
that feeding ractopamine - hydrochloride to
fi nishing heifers generally improved the
effi ciency of carcass gain with minimal effect
on marbling score, yield grade, loin muscle
area, or percentages of carcasses grading
USDA Choice. Avendano - Reyes et al.
(2006) reported that feeding either zilpaterol -
or ractopamine - hydrochloride considerably
improved gain - to - feed ratio, hot carcass
weight, and carcass yield. Zilpaterol increased
loin muscle area. Both beta - agonists
decreased meat tenderness compared with
controls. Smith et al. (2007b) reported that
implanting anabolic steroids increased hot
carcass weight and loin muscle area for both
heifers and steers. However, implants had no
effect on dressing percent, fat thickness,
yield grade, marbling score, intramuscular
lipid content, or concentrations of major fatty
acids.
Montgomery et al. (2004) reported that
supplementation of three biological types of
cattle (Bos indicus, Bos Taurus - Continental,
Bos Taurus - English) with vitamin D3 (0.5
million IU/d) for 8 days prior to slaughter
improved tenderness by affecting muscle
Ca ++ concentrations, calpain activities, and
muscle proteolysis.

Marbling Effects on

Meat Quality

A high plane of nutrition, especially during
the fi nishing phase, can increase intramuscu-
lar fat to a greater or lesser degree depending
on species, breed, animal age, and a variety
of other factors. The fatness and marbling
associated with a high plane of nutrition have