Number 57      February 1995

MAFF UK - NDMA AND ATNC IN RETAIL MALT WHISKY

Index to MAFF UK Food Surveillance Information Sheets, 1995

Background

N-nitrosodimethylamine (NDMA) is one of a group of chemicals collectively referred to as N-nitroso compounds and is known to be carcinogenic to a wide range of animal species. However there is no proof of its carcinogenicity to humans. It was found in the late 1970s that NDMA can be formed during the kilning of malt. As a result, changes to the malting process were introduced by brewers to reduce the formation of NDMA. Whisky undergoes a long maturation period and may be blended from products with a range of ageing periods from three years. Malt whisky is usually left to mature for approximately ten years and older stocks may still contain elevated levels of NDMA. As a result, the reduction in the levels of NDMA in malt whisky reaching the retail market has been delayed. Previous surveillance for NDMA in whisky samples supplied by the industry showed that median levels fell from 1.8 µg/kg in 1983 to 0.3 µg/kg in 1989. However for one brand of malt whisky the median level of NDMA in 1989 remained significantly higher than the overall median, with some samples slightly exceeding the 'action level' of 5 µg/kg adopted by the alcoholic drinks industry. The current survey has been carried out to check whether concentrations of NDMA have fallen since 1989 in this brand (A in the Table 1, below) and other brands of malt whisky.

It is known that non-volatile N-nitroso compounds can be formed during the fermentation process in the production of beer. These compounds are determined as a group by analysis of the Apparent Total N-Nitroso Compounds (ATNC) content. Previous whisky samples taken by MAFF have not been analysed for ATNC. In view of the distillation involved in the production, it was considered unlikely that non-volatile products would be present in the resulting beverage. The current samples were analysed for ATNC to ensure this view was correct.

Results

Five bottles of each of four brands of single malt whisky were purchased from seven retail outlets covering both supermarket chains and independent off-licences during August 1994. Between them the brands sampled account for over 50 percent of the UK market for single malts. The samples were analysed at the CSL Food Science Laboratory, Norwich using gas chromatography with a capillary column separator and thermal energy analyser (GC-TEA). The median level of NDMA found (see table 1, below) in Brand A was 0.6 µg/kg. This is much lower than that (4.7 µg/kg) found in the samples of the same brand in 1989. The median levels of NDMA found in the other brands were in the range 0.3-3.4µg/kg. None of these brands have been analysed previously for NDMA by MAFF. ATNC were not detected in any of the samples (detection limit of 14.5 µg (N-NO)/kg).

Interpretation

Much lower concentrations of NDMA in Brand A malt whisky were found in the current survey compared with 1989. All the whiskies sampled were below the 'action level' of 5 µg/kg adopted by the alcoholic drinks industry. This indicates that the measures taken by the industry to reduce the extent of NDMA formation in malt during the kilning process have been effective and continue to ensure that concentrations of NDMA in whisky are low.

Contact Point

For further information, please contact:

Dr Nigel Harrison,
MAFF, Food Safety and Science Group,
Food Contaminants Division,
Room 234, Ergon House, c/o Nobel House,
17 Smith Square
London SW1P 3JR

Tel: +44 (0) 171 238 6235
Fax: +44 (0) 171 238 5331

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