A bulletin for the Australian Food Industry August 1999
Contents: Refrigerated retail cabinets | Cheese from unpasteurised milk and listeriosis | Alicyclobacillus spp. - a source of flavour taints in acidic foods | Dioxins in food | Volatile nitrosamines in food and drink | Disinfection of seeds for sprouting
Volatile nitrosamines in food and drink
Many readers will recall the concerns raised in the 1970s and 80s about the possible hazards of N-nitrosamines in cured meats and other foods. Nitrosamines are carcinogenic compounds formed by the reaction of nitrites with secondary amines in food and other materials notably tobacco smoke. They may also be formed endogenously.
Nitrite is an essential ingredient in the curing process as it produces the characteristic pink colour in cured meats, contributes to flavour, and most importantly inhibits outgrowth of bacterial spores especially those of Clostridium botulinum.
The outcome of much scientific research in the 70s particularly in the United States was that every attempt was made to minimize the amount of nitrite used to cure meat without compromising the microbiological safety of products. Formulation changes which maximize the retention of the antioxidant ascorbates were also made. Residual antioxidant activity in the meat matrix helps to inhibit nitrosation reactions leading to nitrosamine formation. At the same time, greater controls over roasting and drying processes for foods and ingredients were introduced.
In a 1997 paper (Food Technology 51 (2) 1997 53), Cassens reported an apparent dramatic decrease in the residual nitrite level in cured meat products in the United States. He estimated an approximate 80 per cent reduction from the levels common in the 1970s. No comparable data is available for Australia. However interesting results have been obtained by the Australian Government Analytical Laboratories (AGAL) and published in Research and Development Report 98-31. This report, Determination of volatile nitrosamines in various foods and malted alcoholic drinks, is part of a series of publications produced by AGAL highlighting the outcomes of work it does as part of its public interest activities.
The work reported is the development of a suitable analytical methods for the determination of volatile nitrosamine levels in beer, smoked meats, dried milk powder, cereal products and dried seafoods on the market in Australia. No attempt was made to obtain a large range of samples as the aim of the work was to refine and validate the method of analysis not conduct a survey.
The results obtained during the validation of the methodology are encouraging. Sixteen domestic and imported beers were found to contain only trace amounts of common volatile nitrosamines (below 1 ug/kg). Samples of fried bacon, cooked ham, nonfat dry milk powder and cereals also contained below 1 ug/kg of volatile nitrosamines.
Following different sample preparation techniques, nitrosamine levels in dried fish and dried prawn products imported for commercial distribution were also measured. Levels in dried fish were generally low (2 ug/kg) although one sample contained 67 ug/kg. Of greater concern was the level found in commercial dried prawn products ranging from less than 5 ug/kg to 313 ug/kg.
While these products are not usually a major component of the diet, many samples had nitrosamine concentrations 5-10 times that permitted in some overseas countries. Australia has no legislative standards for nitrosamines in foods.
For further information contact:
Australian Government Analytical Laboratories,
tel 02 6275 3450, fax 02 6275 3565.
Food Science Australia
PO Box 52, North Ryde 1670. Tel +61 2 9490 8397 Fax +61 2 9490 8499
Email enquiries@csiro.au