Interaction of Haem Pigments With Sulphydryl Groups in Meat Curing.

Sodium nitrite added to meat provides flavour, preservative properties, and colour, given by the light unstable nitrosyl-myoglobin pigment. This research set out to reduce the use of sodium nitrite, thought carcinogenic at normal concentrations by earlier workers, and strongly suggests that its interaction with sulphydryl compounds present in meat tissue leads to the formation of nitrosylmyoglobin. A transmission spectrophotometric method developed to detect small colour changes in meat without prior extraction has shown pure sulphydryl compounds added both in model and meat systems dramatically improve the light stability and formation of the nitrosyl pigment at low sodium nitrite concentrations. S-nitrosocysteine, which may be an intermediate in the transfer of the NO group to myoglobin to form nitrosylmyoglobin, not only possesses all the desirable sodium nitrite properties but also dramatically reduces the chances of carcinogen formation, only very small amounts being needed to form the cured colour. S-nitrosocysteine also makes light stability dependent on the myoglobin/nitrosylmyoglobin conversion rate rather than on the residual sodium nitrite concentration. Thus S-nitrosocysteine is strongly favoured to replace sodium nitrite in meat curing