Richard A. Scanlan

N‐nitrosamines in foods

N‐nitrosamines are an extremely hazardous class of compounds. The possibility of the occurrence of these compounds in our food and in other environmental situations has caused concern over the past decade. This review examines the literature which provides an understanding of the chemistry of N‐nitrosamine formation. Particular attention is paid to the more recent reports concerning methodology for determining N‐nitrosamines and to the reports since 1970 on the occurrence of N‐nitrosamines in foods. The literature concerning factors which influence N‐nitrosamine formation in foods is evaluated and discussed.

N-Nitrosodimethylamine in beer

Abstract Commercially-available bottled and canned beer was analysed for volatile nitrosamines using a chemiluminescence detector. N -Nitrosodimethylamine, the only volatile nitrosamine found, was detected in 23 of 25 samples analysed. The range of levels was 0–14 ppb (μg/kg) while the mean was 5·9 ppb. The identity of N -nitrosodimethylamine was confirmed by mass spectrometry.

N-nitrosodimethylamine in Spanish beers

A survey of 21 beers produced in Spain during 1994 was conducted to assess contamination with volatile N-nitrosamines. N-Nitrosodimethylamine (NDMA), the only volatile N-nitrosamine detected, was found in 52% of Spanish beers at or above the detection level (0.05 microgram/kg). The mean NDMA level for all samples was 0.11 microgram/kg, and the range was from not detected to 0.55 microgram/kg. No differences in the NDMA content were observed between the different beer types. Individual daily intake of NDMA may reach up to 0.021 microgram/person/day for Spanish people.

N-Nitrosodimethylamine in dried dairy products

Abstract Commercially available non-fat dried milk and dried buttermilk were analysed for volatile nitrosamines using a chemiluminescence detector. N-Nitrosodimethylamine, the only volatile nitrosamine that could be confirmed to be present by mass spectrometry, was detected in eight out of nine samples analysed. The range of levels was 0 to 4·5 ppb (μg/kg) while the mean was 1·9 ppb. The identity of N-nitrosodimethylamine was confirmed by mass spectrometry in five of the samples.

Null carcinogenic effect of large doses of nitrosoproline and nitrosohydroxyproline in Wistar rats.

Summary The nitrosamino acids, nitrosoproline or nitrosohydroxyproline, were given orally to weanling rats in four weekly doses totalling 290 mg/animal and the rats were observed for their lifetime. Negative controls received water and positive controls were given diethylnitrosamine. The rats were maintained on a basal semi-purified diet or a basal diet containing cyclopropenoid fatty acids. No tumorigenic effect was seen in rats given nitrosoproline or nitrosohydroxyproline. Diethylnitrosamine produced a high incidence of hepatomas, as expected. Cyclopropenoid fatty acids had no significant effect on the carcinogenicity of the nitrosamino acids.

Isolation and characterization of products from the nitrosation of the alkaloid gramine

The nitrosation of gramine, a tertiary amine alkaloid present in barley malt, was carried out by reaction with sodium nitrite in buffered acetic acid (pH 3.4) for 1 hr at room temperature. Two major non-volatile products of the nitrosation reaction were isolated by preparative HPLC and characterized as indole-3-carboxylic acid and N1-nitroso-3-nitromethylindole. This interpretation was supported by spectral data. The nature of these products indicated that gramine did not undergo nitrosation by the expected mechanism of nitrosative dealkylation. A mechanism is offered to explain the labile nature of the dimethylamino group found in gramine.

Mutagenicity of nitrosamines formed from nitrosation of spermidine

5 nitrosamines formed from the nitrosation of spermidine were investigated for mutagenicity using various strains of Salmonella typhimurium in the presence and absence of S9 mix. Using the plate incorporation method, 3-butenyl-(2-propenyl)-N-nitrosamine, 3-hydroxybutyl (2-hydroxypropyl)-N-nitrosamine, 4-hyroxybutyl-(2-hydroxypropyl)-N-nitrosamine, 4 hydroxybutyl-(3-hydroxypropyl)-N-nitrosamine, and in the liquid test 3-hydroxybutyl-(3-hydroxypropyl)-N-nitrosamine were mutagenic in the absence of S9 mix.

Volatile nitrosamines in foods-an update

Abstract Nitrosamines form when the precursors, amines and nitrosating agents, are present in food. The three most common situations for nitrosamine occurrence are the addition of nitrite in the manufacture of cured meats, direct-fire drying of foods, and migration of nitrosamines or precursors from various materials. Reliable analytical methods exist for the measurement of volatile nitrosamines in foods at the sub-μg/kg level. Use of these anlytical methods has demonstrated that certain volatile nitrosamines, such as N-nitrosodimethylamine, occur at low μg/kg levels in a number of foods such as fried bacon, cured meats, beer and nonfat dry milk. Over the past decade nirosamine and nitrosamine precursor migration to foods from bady bottle rubber nipples and from rubber netting used in the manufacture of cured meats has been demonstrated. Nitrosamine formation in certain foods has been reduced by using reduced levels of certain food additives (e.g., nitrites), adding inhibitors (e.g., ascorbic acid), and changing manufacturing processes (e.g., direct to indirect-fire drying of malt).

Identification of minor nitrosation products of the alkaloid gramine by mass spectrometry

The nitrosation of gramine, a tertiary amine alkaloid present in barley malt, was carried out by reaction with sodium nitrite in buffered acetic acid (pH 3.4) for 1 hr at room temperature. Following the previous isolation and identification of the major nitrosation products (Ahmad et al. Fd Chem. Toxic. 1985, 23, 841), two minor products were isolated by HPLC and identified as indolin-3-one oxime and indole-3-aldehyde. Identification was based on mass spectrometry. The results give strong support to the hypothesis that gramine does not undergo nitrosation by nitrosative dealkylation.

Synthesis of N 1‐nitroso‐3‐nitromethylindole: A nonvolatile N‐nitroso compound isolated from the nitrosation of the alkaloid gramine

An approach to the synthesis of N1-nitroso-3-nitromethylindole, a nitrosation product of the alkaloid gramine, is described. The method involves a few reaction steps starting from indole-3-carbinol.