ISOLATION AND IDENTIFICATION OF NITROSOPROLINE IN UNCOOKED BACON

CONTRARY to sporadic reports of nitrosamines in other foods, N-nitrosopyrrolidine (NO-Pyr) has been found in approximately 80% of bacon samples tested after frying (Crosby et al., 1972; Fazio et al., 1973; Sen et al., 1973). Although concentrations of NO-Pyr as high as 108 pg/kg (ppb) (Fazio et al., 1973) have been noted, the quantities usually found are in the range of lo-20 pg/kg. This, however, is a matter of concern since NO-Pyr has been found to be carcinogenic to some test animals (Druckrey et al., 1967; Greenblatt and Lijinsky, 1972a, b; Greenblatt et al., 1973). Nitrosopyrrolidine could be formed by the nitrosation of pyrrolidine, which may arise from the cyclization of putrescine ( 1,4-tetramethylenediamine) or from the decarboxylation of proline. Another possible pathway involves prior nitrosation of proline followed by decarboxylation to yield NO-Pyr. The decarboxylation of nitrosoproline (NO-Pro) has been reported recently (Bills et al., 1974; Fiddler et al., 1973; Pensabene et al., 1974) in bacon model systems under conditions similar to those for frying bacon. Nitrosopyrrolidine is found only in cooked bacon (Fazio et al., 1973; Sen et al., 1973; Pensabene et al., 1974). The concentration formed appears to be dependent on the amount of nitrite added during bacon curing (Sen et al., 1974), the bacon adipose tissue (Fiddler et al., 1974) and the temperature of cooking (Fiddler et al., 1973; Pensabene et al., 1974). In this paper we are reporting the isolation and identification of NO-Pro in uncooked bacon and its possible role as the precursor for NO-Pyr.