Number 142 February 1998 (revised April 1998)
MAFF UK - SURVEY OF NITRITE AND NITRATE IN BACON AND CURED MEAT PRODUCTS
This is a revised information sheet, reissued in April 1998, because
the original version contained an error in identifying a Danepak bacon product
as exceeding permitted limits.
Index to MAFF UK Food Surveillance Information
Sheets, 1998
See also:
91: MAFF UK -
Nitrate in vegetables (July 1996)
121: MAFF UK - 1996/97 UK Monitoring
Programme for Nitrate in Lettuce and Spinach (August 1997)
132: MAFF UK - Survey of Added Water in
Cured Pork Products (November 1997)
137: MAFF UK - 1994 Total Diet Study -
Nitrate and Nitrite (December 1997)
154: MAFF UK - 1997/98 UK Monitoring
Programme for Nitrate in Lettuce and Spinach (August 1998)
158: MAFF UK - Nitrate in Vegetables
(September 1998)
163: MAFF UK -
1997 Total Diet Study: Nitrate and Nitrite. (October 1998)
165: MAFF UK - Duplicate Diet Study of
Vegetarians-Nitrate Analyses (November 1998)
177: MAFF UK - Nitrate in Lettuce and
Spinach (May 1999)
Summary
A survey of the preservatives nitrite and nitrate in 200 samples of bacon
and cured meat products, from retail outlets in England and Wales, has recently
been completed. Only one of the samples was found to contain levels above the
maximum permitted residual limits which applied at the time the samples were
taken. The full results, including brand names, are provided at
Annex A. Trading Standards Officers have been informed of
the results via the Local Authorities Co-ordinating Body on Food and
Trading Standards (LACOTS). The retailer who sold the sample with a level above
the permitted residual limits has also been informed. The company concerned was
given the opportunity to provide a summary of its comments for inclusion in this
Information Sheet. No comments were received.
The nitrite levels found were similar in both prepacked and freshly-sliced
ham or bacon, whereas nitrate levels were on average higher in bacon and ham
from delicatessens than in prepacked samples. Total levels of both nitrite and
nitrate were generally similar across England and Wales and comparable with
those obtained in the previous survey of cured meat products carried out in
1989.
Dietary intakes of nitrite and nitrate from cured meat products for high
level consumers were estimated to be 19 per cent and 1 per cent of the
respective Acceptable Daily Intakes (ADIs) for these chemicals. These data
suggest that intake of nitrate was a quarter of that found for meat products in
the Total Diet Study carried out in 1994,
whilst intake of nitrite was the same.
Background
Traditionally a wide range of different types of meat have been preserved by
the addition of chemicals such as common salt, sugar, salts of nitrate and
nitrite and vinegar. These agents can also improve the colour and flavour
characteristics of the product, although their primary function is that of a
preservative.
Nitrite is a relatively strong reducing agent with antibacterial properties,
although much of the preservation of the foodstuff is attributable to the high
concentration of salts employed during the curing process, as is also the case
for nitrate. In addition nitrate may act as a reservoir from which nitrite may
be formed by microbiological reduction.
This survey was carried out to see if levels of nitrite and nitrate in cured
meats had changed since these were previously considered, in 19891.
It also provided the opportunity to see if any products had levels above those
permitted at the time the samples were taken.
This is the latest in a series of surveys of nitrite and nitrate in food1-4,7. The
previous survey of nitrite and nitrate in cured meats was undertaken in 19891. One sample out of 213 contained levels of
nitrite and nitrate that exceeded the combined statutory limit in force at that
time. In 1994, as part of the Total Diet
Study, intakes for high level consumers of nitrite and nitrate from all
dietary sources were estimated to be 3 and 137 mg/person/day respectively2. Vegetables were considered to be the single
greatest contributor to these estimated intakes.
In Great Britain the use of nitrite and nitrate in meat products is
currently controlled by the Miscellaneous Food Additives Regulations 1995, as
amended (parallel legislation exists for Northern Ireland). These Regulations
limit the maximum residual concentration of nitrite in cured bacon to 175 mg/kg
and to 100 mg/kg in other cured meat products (in both cases as sodium nitrite).
The maximum permitted residual concentration of nitrate in all cured meat
products is 250 mg/kg (as sodium nitrate). However, the timing of this survey
meant that, because of a transitional provision in the 1995 Regulations, the
maximum levels of nitrite and nitrate specified in the Preservatives in Food
Regulations 1989, as amended, could still be permitted. These 1989 Regulations
limited the combined amount of nitrate and nitrite in cured meats to between 150
and 500 mg/kg depending upon the type of processing and packaging used.
This survey of nitrite and nitrate in cured meats is covered by transitional
arrangements5 which have been put in place for
surveys commissioned prior to September 1997. Samples were obtained before
these arrangements were considered, and thus information on 'best before' dates
was not recorded. However, brand names were recorded and are included in
Annex A. The company whose product contained residues
which were above the current maximum permitted levels has been advised of its
result and given the opportunity to provide a 100 word summary of its comments
for inclusion in this Information Sheet. No comments were received. The
results of this survey have been provided to the Local Authorities Co-ordinating
Body on Food and Trading Standards (LACOTS) and the Food Advisory Committee.
The Committee's statement is as follows:
The Food Advisory Committee noted that the results of this survey were
similar to those obtained from the previous one. However, they also noted that
in a small percentage of samples the levels found were greater than the maximum
permitted residual limits (since found to be the case for only one of the
samples) and they therefore welcomed the action that has been taken to ensure
that the respective traders and enforcement authorities had been informed of
these. The Committee observed that the levels of these preservatives found in
some samples were low and, whilst recognising that they are sometimes used in
combination with others, stressed the need for manufacturers to ensure that
their products contain adequate overall levels of preservatives to guarantee
microbiological safety.
Methodology
Samples were obtained from supermarkets and other outlets in England and
Wales. A total of 200 samples, 40 each from Wales, Northern England, South East
England, South West England, and the Midlands, were purchased and analysed
between December 1996 and February 1997. The sampling programme was designed to
reflect recent changes in shopping patterns towards freshly sliced produce
available from supermarket delicatessen counters or local butchers' shops.
Samples were transported to the laboratory and processed immediately. Each
sample was finely chopped and divided into two, both parts being separately
extracted using a hexane-water/borax mixture. Potassium ferrocyanide and zinc
acetate were added to each sample, which was then cleaned up on a disposable
cartridge. Samples were analysed by high performance liquid chromatography
(HPLC) with photo-diode array detection. To ensure that false results were not
obtained due to other substances present in the sample, peak purity testing was
carried out for positive analyses. Confirmation was carried out using a
different HPLC column. The analytical method was based upon that described by
Dennis et al6.
The samples were analysed in batches of 20 to 25 and a four level
calibration set was included at the beginning and end of each batch. Two
samples containing both nitrite and nitrate, were selected as in-house reference
materials. These were analysed with each batch of samples to ensure that the
batch performance was acceptable, i.e. within three standard deviations
of the analytical quality control set mean. Each result represents the mean of
at least two duplicate analyses reported to one decimal place.
The repeatability of the method for both nitrite and nitrate was found to be
at least as good as that quoted by Dennis et al6.
The limit of quantitation was 0.2 mg/kg for both nitrite and nitrate, and the
recovery values obtained for nitrite and nitrate added to fresh samples of cured
cooked meat were 92 per cent and 97 per cent respectively.
Results
The results are summarised in Tables 1,
2 and 3 and individual
results for each product are listed in Annex A.
The majority of samples contained concentrations of nitrite and nitrate at
less than half of the maximum permitted levels. However, in one sample the
level of nitrite was above the maximum level laid down in both the 1995 and the
1989 Regulations.
The results of the survey were entered into a dietary intake computer
programme and an estimation of nitrite and nitrate intake from cured meat
products was obtained. The nitrate intakes for this survey represented a
quarter of those reported for meat products in the
1994 Total Diet Study2.
For nitrite, the intakes were similar to those reported for meat products in
1994. These findings suggest that current levels of nitrite and nitrate in meat
products will not have a significantly greater impact on total dietary intake
compared to those reported in 1994. A dietary intake was not estimated using
the results from the previous survey of cured meat products as these were
reported at the same time as the 1985 Total Diet Study7
which included a more extensive range of meat products.
A summary of the levels of nitrite and nitrate in the range of sample types
analysed is given in Table 1. In both this and the
previous survey, carried out in 19891, bacon
and ham products were the largest categories in both surveys with over 50
samples in each group. Mean nitrite levels in these products in the 1989 survey1 were broadly similar to those reported here.
The ranges of nitrate levels were similar for both surveys, although the mean
levels in the bacon and ham categories were higher in the present survey. The
results for other meat products varied considerably between the two surveys.
Overall means (for all products analysed) for both the surveys indicate that
nitrite levels were approximately the same, whereas the mean nitrate levels
reported in this survey were somewhat higher than in 1989. However, this was
probably due to a few outlying results rather than a general increase in nitrate
levels in meat products.
Table 2 shows that total levels of nitrite and
nitrate were generally similar across England and Wales. Samples from the
Midlands had a lower mean nitrite content, whereas those from Wales gave the
lowest mean value for nitrate. Nitrite levels were similar in both prepacked
and freshly-sliced ham or bacon (Table 3). Nitrate
levels were on average higher in bacon and ham from delicatessen counters than
in prepacked samples.
Interpretation
Nitrate intakes calculated from this survey were a quarter of those reported
for meat products in the 1994 Total Diet
Study2. For nitrite, intakes from cured
products were similar to those reported in 1994. Nitrite and nitrate levels in
the majority of samples were within the maximum permitted levels. Generally the
concentrations of nitrite and nitrate were below 50 per cent of their current
maximum permitted level and, in around half of the samples, the concentrations
of both nitrite and nitrate were below 10 per cent of their respective current
limits. These latter samples were largely from a subset of miscellaneous meat
products such as corned beef and turkey. Such levels may be below a
concentration that, unaided, would normally be expected to effectively control
microbiological contamination. However, most of the pre-packaged samples were
found to include an antioxidant, sodium ascorbate (which is used as an adjunct
to nitrite) amongst the ingredients listed on the label. This, together with
the presence of salt, reduces concerns regarding the microbiological safety of
the samples. It was not possible to determine if this was the case for loose
samples.
In general terms, the data indicated that the concentration of nitrite
ranged from less than 0.2 mg/kg to 120 mg/kg for bacon and less than 0.2 mg/kg
to 170 mg/kg for other meat types. The levels of nitrate ranged from 1.4 mg/kg
to 440 mg/kg for bacon and less than 0.2 mg/kg to 450 mg/kg for other types of
cured meat. The average concentration of nitrite was found to be 24 mg/kg and
that for nitrate was 62 mg/kg. These mean values for both nitrite and nitrate
were well within the statutory limits, and are similar to those obtained in the
previous survey of nitrite and nitrate in cured meat products1.
References
- Survey of nitrate and nitrite concentrations in samples of
retail cured meat (1989). Steering Group on Chemical Aspects of Food
Surveillance, Nitrate, nitrite and N-nitroso compounds in food: Second
Report. Food Surveillance Paper No. 32. p 58, (1992) HMSO.
- Food Safety Information Bulletin, No. 91, December
1997, MAFF.
- Working Party on Nitrate and Related Compounds in Food
(1987) Nitrate, nitrite and N-nitroso compounds in food. Food
Surveillance Paper No. 20. HMSO.
- Steering Group on Chemical Aspects of Food Surveillance
(1993) Dietary intake of Food Additives in the UK: Initial Surveillance.
Food Surveillance Paper No. 37. HMSO.
- Food Safety Information Bulletin, No. 88,
September 1997, MAFF.
- Dennis, M.J., Key, P.E., Papworth, T., Pointer, M. and
Massey, R.C. (1990) The determination of nitrate and nitrite in cured meat by
HPLC/UV. Food Additives and Contaminants, 7, 455-461.
- Estimated total dietary intakes of nitrate and nitrite in
the UK in 1985, Steering Group on Chemical Aspects of Food Surveillance, Nitrate,
nitrite and N- nitroso compounds in food: Second Report. Food
Surveillance Paper No. 32. pp 62 & 66 (1992) HMSO.
Contact Point
For further information please contact:
Dr W A Matthews
MAFF, Joint
Food Safety and Standards Group
Additives and Novel Foods Division
Room
228 Ergon House
c/o Nobel House
17 Smith Square
LONDON SW1P 3JR
Tel:
+ 44 (0) 171 238 6229
Fax: + 44 (0) 171 238 6263
Spreadsheet Tables
Annex A
Annex A Table A1: Concentrations of Nitrite and Nitrate in
bacon products
Click here to download the Excel version of Annex A
Table A1
Shift-Click here to download the .csv
version of Annex A Table A1 (if you have any other spreadsheet package)
Annex A Table A2: Concentrations of Nitrite and Nitrate in
ham products
Click here to download the Excel version of Annex A
Table A2
Shift-Click here to download the .csv
version of Annex A Table A2 (if you have any other spreadsheet package)
Annex A Table A3: Concentrations of Nitrite and Nitrate in
other cured meat products
Click here to download the Excel version of Annex A
Table A3
Shift-Click here to download the .csv
version of Annex A Table A3 (if you have any other spreadsheet package)
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