Awareness of the problem has led to changes in production practices
for cured meats such as the use of low levels of nitrite in preference to
nitrate and the increased use of ascorbic acid which inhibits the nitro-
sation reaction. These measures have produced significant reductions in
nitrosamine levels.
Mention should also be made here of the other contributions made by
nitrite to the quality of cured meats. Reduction of nitrite to nitric oxide
produces the characteristic red colour of cured meats. The nitric oxide
co-ordinates to the haem ferrous ion in the muscle pigment myoglobin
converting it to nitrosomyoglobin (Figure 4.13). When raw cured meats
such as bacon are cooked this pigment decomposes to produce nit-
rosylhaemochrome which has the pink colour also seen in cooked cured
hams. Only small quantities of nitrite are required to produce the cured
meat colour: theoretically 3 mg kg^1 is sufficient to convert half the
myoglobin present in fresh meat, but because of competing reactions,
25 mg kg^1 are required to give a stable colour.
Nitrite also contributes to the typical cured meat flavour. Taste panels
can distinguish cured meats where nitrite has not been used but the
Figure 4.13 Reactions of nitrite with meat myoglobin
Chapter 4 105