REPORT OF THE GREATER MANCHESTER FLG/LANCASHIRE FOG/
PRESTON MICROBIOLOGY SERVICES LIAISON GROUP
SURVEY OF THE EXAMINATION OF LOW FAT SPREADS FROM
RETAIL OUTLETS FOR LISTERIA SPECIES
K Williamson, G Allen, F J Bolton
Food and Environmental Microbiology Services, Preston
Date of Report : October 2004
Survey Code: 404005
Introduction
The HPA reported in 2003 that cases of Listeria monocytogenes had been
associated with butter in the Yorkshire and Humberside area. In addition, an outbreak
of L. monocytogenes was associated with consumption of butter in Finland.
L monocytogenes is ubiquitous in various environments including soil, sewage and
water.
It can cause life-threatening illnesses including septicaemia,
meningoencephalits in immunocompromised patients, and septic abortion in neonates.
Listeria species are able to multiply slowly at refrigeration temperature although if
present in butter growth should be limited due to a strongly dispersed water phase in
such a high fat product. Margarine is a solid emulsion of water on oil with a high fat
content similar to butter, about 81g per 100g, and as with butter, the addition of salt
also precludes the growth of most micro-organisms.
There is now an increased demand for low fat spreads which often contain
unsaturated fats and a lower salt content as part of the health agenda for change. Low
fat spreads with a fat content of less than 80% cannot be called margarine and have a
higher content of water and may therefore be more susceptible to bacterial growth.
There is a scarcity of published information on the prevalence and types of Listeria
that may be found in reduced fat table spreads. The aim of this study is to establish if
these health driven modifications have caused a microbiological risk particularly in
relation to L. monocytogenes.
Materials and Methods
Sample Collection
This survey was carried out as part of the Greater Manchester FLG/Lancashire FOG/
Preston Microbiology Services sampling programme during May – August 2004.
For the purpose of this survey a low fat spread was defined as any type of low fat
table spread which may be blended with a dairy product and contains 60g or less fat
per 100g.
Samples were purchased as unopened packs from a wide range of retail outlets,
packed in a food grade-sampling bag, labelled and transported to the laboratory at 080C.
KW/KLM (60/04)
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Information relating to the premises, sample details including salt and fat content was
recorded on a modified FEMS – NW food request form.
Sample Examination
A total of 367 samples were submitted from 25/26 authorities in Greater Manchester
and Lancashire as detailed in Appendix 1.
All samples were examined for the presence of (in 25g) and enumeration of
L. monocytogenes and other Listeria species using UKAS accredited FEMS North
West food methods.
Results
Table 1.
Microbiology results. (n = 367)
Detected
Not detected
Listeria monocytogenes/25g
0
367
Listeria Spp (total)/25g
0
367
Table 1 demonstrates that Listeria species was not detected in any of the 367 samples
examined.
Discussion
Potentially hazardous foods support rapid and progressive growth of pathogens, have
a pH >4.6, a AW.0.85, and require refrigeration. Although low fat table spreads have
pH and Aw values within this range, the results obtained in this study in relation to
Listeria spp indicate that table spreads should not be considered a potentially
hazardous food. However it must be emphasised that samples examined were from
unopened retail packs and, further investigations may be useful on ‘in use’ opened
catering packs which may be susceptible to environmental contamination.
Conclusion
Listeria species were not detected in any of the samples examined in this study,
supporting the view that low fat spreads at retail are not a potentially hazardous food.
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Appendix 1 – Participants
Authority
Barrow
Blackburn
Blackpool
Burnley
Chorley
Fylde
Hyndburn
Lancaster
Pendle
Preston
Ribble Valley
Rossendale
South Lakes
South Ribble
West Lancs
Wyre
LANCASHIRE TOTAL
Number of samples
16
16
30
8
15
17
8
16
15
9
20
6
13
19
20
17
245
Bolton
Bury
Manchester
Oldham
Rochdale
Salford
Stockport
Tameside
Trafford
Wigan
GT MANCHESTER TOTAL
0
15
7
14
16
16
8
20
14
12
122
TOTAL FOR LANCASHIRE
AND MANCHESTER
367
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