Nrisinha P. Sen

Absence of volatile N-nitrosamines in cooked nitrite-free cured muscle foods

Nitrite-free cured pork systems were prepared using the preformed cooked cured-meat pigment (CCMP) and sodium ascorbate. Absence of volatile N-nitrosamines in cooked nitrite-free systems was confirmed using a gas chromatography-thermal energy analyzer (GC-TEA) methodology. Similar results were obtained when cod, cod surimi or mixtures containing pork with 15 or 50% cod or cod surimi were used. However, counterpart samples cured with sodium nitrite (156 ppm) and sodium ascorbate (550 ppm) produced N-nitrosodimethylamine at 1·0 ppb levels or less. Results demonstrate that nitrite-free curing of meat and meat/fish systems containing the preformed CCMP is successful in yielding products devoid of volatile N-nitrosamines.

A method for the determination of methyl carbamate and ethyl carbamate in wines

A method is described for the simultaneous determination of methyl carbamate (MC) and ethyl carbamate (EC) in wines that is based on: (a) extraction of the sample with dichloromethane using an extraction tube or an alumina-Celite column, (b) concentration of the extract to a small volume, and (c) determination by gas-liquid chromatography-thermal energy analyser (N-mode). The method is highly sensitive (1-2 ng/ml), accurate (recoveries greater than 80%), and precise (CV, 5-10%). Nineteen of 27 samples of wines analysed contained traces (up to 2.7 ng/ml) of MC, and most contained EC (up to 70 ng/ml). Wines treated in the laboratory with 200 ppm dimethyl pyrocarbonate (DMPC)-a cold sterilant recently approved for use in wines-indicated that such a treatment may increase the MC contents of the wines to 10 ng/ml. Additional studies suggested that formation of MC in DMPC-treated wines is dependent on both pH and ammonia content of the wines. The identity of MC in a few selected samples was confirmed by gas-liquid chromatography-high resolution (10 K) mass spectrometry. The natural low levels of MC found in these wines are not considered to pose a risk to human health.

Nitrosamines in cured pork products packaged in elastic rubber nettings: An update

Previous research has shown that traces to fairly high levels of certain N-nitrosamines can form in cured pork products packaged in elastic rubber nettings. The N-nitrosamines are formed due to the interaction of nitrite additive in the meat and amine additives in the rubber that are used as accelerators in the curing of rubber. This paper briefly reviews earlier findings and presents some recent results. Of twenty samples of such pork products analyzed, one was negative, six contained 12–32 μg/kg levels of N-nitrosodibenzylamine (NDBZA) but no N-nitrosodi-n-butylamine (NDBA), and the remaining samples contained appreciable levels of both the compounds (NDBA up to 48 μg/kg and NDBZA up to 520 μg/kg). These results suggest that the problem of N-nitrosamine formation in these products is yet to be resolved.

Analytical methods for the determination and mass spectrometric confirmation of 1‐methyl‐2‐nitroso‐1,2,3,4‐tetrahydro‐β‐carboline‐3‐carboxylic acid and 2‐nitroso‐1,2,3,4‐tetrahydro‐β‐carboline‐3‐carboxylic acid in foods

A method is described for the determination of the two title compounds that is based on: (a) extraction of the acidified sample with methanol, (b) removal of fats and lipids by partitioning of the extract with n-hexane, (c) clean-up on acidic alumina extraction cartridge, and (d) determination by a post-HPLC column chemical denitrosation-thermal energy analyser (TEA) technique or by conventional HPLC-TEA analysis after derivatization of the compounds with diazomethane. Confirmation was carried out by HPLC-mass spectrometry of the free acids and also by gas chromatography-mass spectrometry of the methyl esters. The formation of both 1-methyl-2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid and 2-nitroso-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in nitrosated samples of several Japanese and Chinese pickled vegetables, one soy sauce, and two cheeses was demonstrated.

The analysis and significance of bound N‐nitrosoproline in nitrite‐cured meat products

An alkaline hydrolysis method is described for the release of bound N-nitrosoproline (NPRO) from cured meats that is more efficient than an enzymic method reported previously. The bound NPRO contents of 17 cured meats analysed ranged between non-detectable and 578 micrograms/kg (mean 143 micrograms/kg). Administration of defatted meat powder, prepared from such meats, to rats led to increased excretion of free NPRO in the urine that could not be inhibited by concurrent administration of ascorbic acid. The significance of these findings with regard to the use of such cured meats in in vivo N-nitrosation studies is discussed.

Prevention of artifactual formation of nitrosamines during the analysis of baby bottle rubber nipples

It has been found that considerable amounts of nitrosamines may be formed as artifacts during the analysis of rubber nipples by a method that involves Soxhlet extraction of the samples with dichloromethane. The extent of such formation was monitored by incorporating morpholine as a marker amine and studying the formation of nitrosomorpholine, which varied between 9 and 80 ng per analysis depending on the type of sample analysed and the brand of dichloromethane used. The problem could be minimised by pre-testing dichloromethane for its N-nitrosation potential and by incorporating propyl gallate, an N-nitrosation inhibitor, in the method.