c. Other Sources. The inspector may find other deteriorative conditions such
as dehydration or microbial spoilage in determining discoloration in meat and meat
d. Surface Discolorations. The following surface discolorations may be
observed in meat and meat products.
(1) Browning. A brownish discoloration on the cut or outside surface of ham
or sausage is often associated with dehydration. The cured meat pigment is chemically
altered to metmyoglobin under storage conditions. Low humidity, especially at storage
temperatures considered to be too high for the product, may result in a rather rapid
browning of cured meat products. A packaging film which is less permeable to water
and oxygen will retard the onset of this type of discoloration. Browning of the lean areas
of bacon is commonly observed. In addition to dehydration, the discoloration is
sometimes traced to the presence of excessive nitrite. A high nitrite content will tend to
oxidize the pigment in the cut lean surfaces to metmyoglobin.
(2) Fading due to undercure. Fading may be an indication of insufficient
nitrite in the cure. Consequently, a low residual nitrite level will result in a weak cured
color. This type of discoloration is often observed on the cut surfaces of hams or in
such products as frankfurters. Under such conditions, the interior color is pale pink,
which tends to fade rapidly upon exposure to oxygen.
(3) Greening due to overcure. Nitrite burn, which is due to an excess of
nitrite in the cure, is often observed in acid-cured meat products such as the fermented
sausages and pickled pigs' feet. In fermented sausages, it may arise from excessive
nitrite reduction by bacteria during the fermentation process. Nitrite burn in pickled pigs'
feet usually produces a browning of the muscle tissues and an undesirable greening of
the skin and other collagenous tissues. Even the vinegar pickle may acquire a greenish
(4) Fading from rancid fats. Fats with a high organic peroxide content are
sometimes incorporated into sausages. This may result in instability of the surface
color. Such fats may also impair the flavor of the product. Attempts to store
frankfurters for prolonged periods of time in the frozen state often result in rancidity
development and surface fading.
(5) Chemical fading. Although the cured meat pigment is heat stable, it is
very susceptible to oxidation. Any oxidizing chemical applied to the cured meat surface
may result in a discoloration. For example, very dilute solutions of hydrogen peroxide
will cause a fading or greening of the cured meat surface. Overzealous use of
hypochlorites as sanitizing agents can result in difficulties if any of the chemical reaches
the surface of cured meats.