noncoliform bacteria. The sanitary significance of this lies in the fact that the presence
of coliform bacteria usually points to unsanitary handling after the completion of the
pasteurization process (assuming that the phosphatase test gave evidence of effective
pasteurization). In raw milk, the coliform test indicates the degree of contamination,
either from careless handling or unsanitary equipment.
Section II. MICROBIOLOGY OF MEATS
GREEN RING DISCOLORATION
a. Undesirable Color Changes. Green ring discoloration and other
undesirable color changes are caused by the formation of hydrogen peroxide by certain
groups of bacteria. These bacteria will multiply after the meat product has been stuffed
into its casing and will cause the discoloration. Meat will normally contain enough of the
enzyme catalase to inactivate the hydrogen peroxide produced by bacteria. There are
also certain bacteria that produce catalase that will aid in inactivating the hydrogen
peroxide. Hydrogen peroxide is produced during the overnight holding period and
during the warming period after the meat is removed from the cooler. Killing bacteria in
the cooking process does not completely ensure that some sort of discoloration will not
occur. The hydrogen peroxide formed before the cooking process is not inactivated by
cooking and will continue to exert its action until the product is eventually discolored.
b. Preventive Measures. Green ring discoloration may be prevented by one or
more of the following measures:
(1) Care in production of trimmings. This would include the length of time
the trimmings are held, temperature at which they are held, and the prevention of
Reducing the length of the curing period.
Proper sanitation of stuffers and casings.
Proper tempering procedures.
Control of cooking time and temperature.
(6) Proper control of beef trimmings. Old beef trimmings are a very
common source of hydrogen peroxide-producing bacteria and must be inspected very
closely if they are to be used in the production of sausage products.
c. Other Factors. Green rings may develop in sausage products that have very
low bacterial counts and may not develop in those products that have very high counts.
This is explained by the fact that bacteria capable of producing hydrogen peroxide must
be present, and all groups of bacteria are not capable of producing hydrogen peroxide.