Principles of Food Sanitation

surroundings improve morale, produc-

tivity, and product turnover.

●The established trend toward increased

centralized processing and packaging

dictates a need for increased emphasis

on sanitation. Increased processing and

handling necessitate a more intensive

sanitation program.

●Sanitation is good business.

Effect on Product Discoloration

Biochemical discoloration is related to the
amounts of oxygen and carbon dioxide pres-
ent. Figure 17–1 illustrates how the partial
pressure of oxygen affects the myoglobin
chemical state, which ultimately influences
muscle color. High carbon dioxide partial
pressure can cause a gray or brownish dis-
coloration by association of carbon dioxide
with myoglobin at the free binding site, and
the rate of metmyoglobin formation
increases with decreasing oxygen pressure.
A major cause of discoloration is related
to microorganisms. Microbes consume avail-
able oxygen at the product surface, which
reduces available oxygen needed to maintain

the muscle pigment myoglobin in the

oxymyoglobin state. Oxidation can cause an

abnormal brown, gray, or green discol-

oration of meat by oxidation of the ferrous

iron of the heme compound to the ferric

state and direct attack by oxygen on the por-

phyrin ring. The color of fresh meats

becomes unacceptable when metmyoglobin

reaches approximately 70% of the surface

pigment. Formation of metmyoglobin is

accelerated by decreased oxygen pressure as

a result of oxygen consumption through

growth of aerobic microorganisms. The crit-

ical partial pressure for oxygen has been

found to be 4 mm. Rapid oxidation to met-

myoglobin occurs below this level.

Research has suggested that the primary

role of bacteria in meat discoloration is the

reduction of the oxygen tension in the sur-

face tissue. This conclusion has been based

on the following observations:

1. Rate of oxygen uptake on the muscle
   tissue surface is related to microbial
   activity and color change.


2. Oxidation to metmyoglobin occurs at
   intermediate levels of oxygen demand

Meat and Poultry Plant Sanitation 299

Purple Brown Red

0 20 40 60 80 100 120 140 160

Metmyoglobin

Oxymyoglobin

100 Reduced myoglobin

0

Total Pigment (%)

Oxygen Partial Pressure

(Millimeters of Mercury)

Partial pressure of O

2

in air at a pressureof one atmosphere

Figure 17–1Relationship of partial oxygen pressure to myoglobin chemical state.