Report of the Greater Manchester/Lancashire/Preston PHL Liaison Group
Survey on the Microbiological Examination of Black Pudding
K. Williamson, G. Allen, F. J. Bolton, PHLS North West FESL – Preston PHL
Date of Report: 12/03/02
Survey Code No: 104015
Introduction
Black Puddings are usually purchased from butchers shops, market stalls or
delicatessen counters as a cooked product. They are almost always sliced and served
fried with eggs, sausages, bacon and other breakfast meats, or as a fried topping to
some ‘hotpot’ dishes. Black puddings are made from minced pork fat, pig’s liver, a
high content of pigs blood, oats, spices and breadcrumbs. They are considered a
traditional tasty dish particularly by locals in Northern England and in Brittany, and
occasionally by visitors and tourists.
Black Puddings are retailed as a cooked preparation and considered to be a ready to
eat food which are sometimes consumed without further cooking. Environmental
Health Officers in Lancashire and Greater Manchester have expressed concern
relating to the storage and display of black puddings and have observed that some
retailers handle them as a raw product and others as a cooked product.
Black puddings are not specified in the PHLS Microbiological Guidelines for some
ready to eat foods (1).
Hence the purpose of this survey was to determine the microbiological quality of
Black Puddings from retail outlets and recommend an aerobic colony count category
in the PHLS guidelines (1). Additionally the survey aimed to provide retail display
details so as to assist EHO’s with their task of ensuring food safety.
Materials and Methods
Sample Collection
This survey was carried out as part of the Greater Manchester FLG/Lancashire
FOG/Preston PHL sampling programme during September – December 2001.
Samples of Black Pudding were purchased from delicatessen counters, market stalls
or butchers shops by local authority sampling officers. Information relating to the
premises, sample details and in particular where the product was served from i.e. raw
meat, cooked meat or separate display, was recorded on a modified PHL food request
form (Appendix 1).
The samples were placed in food grade plastic bags and transported to the laboratory
in a cool box with sufficient ice packs so as to maintain a 0-5°C temperature.
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Sample Examination
A total of 301 samples of Black Pudding were submitted from 25/26 authorities in
Greater Manchester and Lancashire as detailed in Appendix 2.
Samples were examined for aerobic colony count/g (ACC), Enterobacteriaceae/g,
E. coli/g, Staphylococcus aureus/g, Bacillus cereus and other Bacillus spp/g,
Clostridium perfringens/g, Listeria monocytogenes/g, Listeria spp/g and for the
detection of Salmonella/25g, Campylobacter/25g and E. coli O157/25g, using UKAS
accredited PHLS NW FESL food methods.
Results
Table 1.
Microbiology results (n=301)
Not
detected
ACC 30oC 48h/g
Enterobacteriaceae/g
E.coli/g
S.aureus/g
B.cereus/g
B.spp (not B.cer)/g
C.perfringens/g
Listeria mono/g
Listeria spp (total)/g
Salmonella/25g
Campylobacter/25g
E. coli O157/25g
Table 2.
Detected
<10,
<20,<102
5
187
297
291
293
251
295
301
301
301
300
301
10,20,<102
102-<103
103-<104
104-<105
105-<106
106-<107
26
30
2
1
6
36
4
0
0
56
14
1
0
1
10
2
0
0
51
12
0
0
0
2
0
0
0
46
5
0
0
0
2
0
0
0
59
0
0
0
0
0
0
0
0
53
1
9
0
0
0
107
58
0
0
0
1
0
0
0
0
0
1
0
PHLS guidelines for some ready to eat foods sampled at point of
sale (1)
Microbiological quality (cfu/g) unless stated
Aerobic colony count (Category 1)
Aerobic colony count (Category 2)
Aerobic colony count (Category 3)
Aerobic colony count (Category 4)
Enterobacteriaceae
E.coli
S.aureus
B.cereus and other pathogenic Bacillus spp
Cl. perfringens
Listeria monocytogenes
Listeria spp (total)
Salmonella
Campylobacter
E. coli O157
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Satisfactory
Acceptable
Unsatisfactory
<103
<104
<105
<106
<100
<20
<20
<103
<20
<20
<20
Not detected/25g
Not detected/25g
Not detected/25g
103 –104
104-<105
105-<106
106-<107
100-<104
20-<100
20-<100
103-<104
20-<100
20-<100
20-<100
104
105
106
107
104
100
100-<104
104-<105
100-<104
N/A
100
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Unacceptable/
Potentially
hazardous
N/A
N/A
N/A
N/A
N/A
N/A
104
105
104
100
N/A
Detected/25g
Detected/25g
Detected/25g
Table 3.
Microbiological quality of black pudding using categories 2, 3 and
4 of the PHLS microbiological guidelines (1) (n = 301)
Category
Satisfactory
2
3
4
75 (25%)
112 (37%)
145 (48%)
Table 4.
No. of Samples
Acceptable
Unsatisfactory
56 (19%)
62 (21%)
83 (28%)
166 (55%)
123 (41%)
69 (23%)
Unacceptable/
Potentially
hazardous
4 (1%)
4 (1%)
4 (1%)
Microbiology results using category 4 of the PHLS microbiological
guidelines and premise/sample/display details
Satisfactory
Acceptable
Unsatisfactory
Unacceptable/
potentially
hazardous
Samples from butchers shops (n=198)
95 (48%)
54 (27%)
46 (23%)
3 (2%)
Samples from deli counters (n=55)
28 (51%)
12 (22%)
14 (25%)
1 (2%)
Samples from market stalls (n=48)
22 (46%)
17 (35%)
9 (19%)
0
Whole black pudding (n=200)
84 (42%)
62 (31%)
52 (26%)
2 (1%)
Sliced black pudding (n=96)
59 (61%)
19 (20%)
16 (17%)
2 (2%)
Raw meat display (n=58)
32 (55%)
12 (21%)
14 (24%)
0
Cooked meat display (n=192)
90 (47%)
54 (28%)
46 (24%)
2 (1%)
Separate display (n=43)
20 (47%)
14 (33%)
7 (16%)
2 (4%)
Total samples (n=301)
145 (48%)
83 (28%)
69 (23%)
4 (1%)
Table 1 demonstrates that the majority of black pudding samples produced indicator
organism counts of acceptable microbiological quality i.e. Enterobacteriaceae 284/301
(94%), E. coli 298/301 (99%), Staphylococcus aureus (99.7%) and Listeria spp
(100%).
Campylobacter was detected in one sample.
Five samples produced unsatisfactory (3) and unacceptable (2) counts of pathogenic
Bacillus spp including B. cereus (1), B. licheniformis (2) and B. subtilis (2).
Six samples (2%) produced unsatisfactory counts of Clostridium perfringens.
Salmonella and E. coli O157 were not detected in any of the samples.
Table 1 also demonstrates a wide range of aerobic colony counts (ACC) which are the
main cause of unsatisfactory results regardless of which category is used in the PHLS
guidelines (Table 2).
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Table 3 highlights the fact that the choice of ACC category greatly affects the
interpretation. ACC is the only parameter causing the significant difference between
unsatisfactory results in Category 3 (41%) and Category 4 (23%).
According to Category 4 of the PHLS guidelines, Table 4 demonstrates that:
(a)
Similar numbers of acceptable microbiological results were obtained from
black puddings purchased from butchers shops and delicatessen counters
(75%, 73% respectively), whereas 81% were acceptable from market stalls.
Of the 12 unsatisfactory/unacceptable samples due to food poisoning
organisms i.e. Campylobacter (1), Bacillus spp (5), Clostridium perfringens
(6), 11 were purchased from butchers shops.
(b)
More unsatisfactory/unacceptable results were obtained from whole (27%)
than sliced black puddings (19%) .
(c)
Black puddings purchased from raw meat or cooked meat displays gave
similar results (76% and 75% acceptable), whereas 80% were acceptable from
a separate display.
Discussion
The questionnaire results indicated that butchers shops were the commonest source of
black puddings. Whole black pudding was more frequently retailed, and cooked meat
displays (192/301 (64%)) were more frequently used. Raw meat displays were used
for (58/301 (19%)) of the samples examined in this survey.
The sample from which campylobacter was detected was a whole black pudding
served from a cooked meat display in a butchers shop.
The 5 black pudding samples of unsatisfactory/unacceptable quality due to high
Bacillus spp counts were served from cooked meat displays (3) and separate displays
(2). One was from whole and 4 were from sliced black pudding. Four were from
butchers shops and 1 from a delicatessen counter.
The 6 black pudding samples of unsatisfactory quality due to high Cl. perfringens
counts were served from cooked meat displays (4) and separate displays (2). One was
from whole and 5 were from sliced. All 6 were from butchers shops.
It has been observed that shelf life information of whole black puddings is often not
available at the retail outlet and often lost when the links are cut, whereas the sliced
product is frequently derived from a plastic sleeved product with labelled details
including producer and use by date. Hence whole black puddings may inadvertently
have longer display times accounting for the higher number of unsatisfactory results
(23%) compared with the sliced (19%). The higher number of acceptable results from
market stalls (81%) may be due to smaller stock levels and quicker turn over times
due to lack of storage facilities. Butchers shops and delicatessen outlets have access
to storage refrigeration.
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It is proposed that category 4 of the PHLS guidelines (1) is used to interpret the
microbiological quality of black puddings for two reasons. Firstly category 4 (23%)
produced almost half as many unsatisfactory results than category 3 (41%) but still
produced a significant number to cause concern. Category 3 ACC levels would be too
stringent. Secondly black puddings could be included in the current meat product
type i.e. tripe and other offal which are listed as category 4 products.
It has been suggested that the high counts of Clostridium perfringens and Bacillus spp
may be attributable to the survival of a high number of spores which can be produced
by both of these organisms.
However a detailed investigation carried out from production to retail by Wyre EHD
concluded that black puddings were cooked appropriately and post production counts
were satisfactory. It was only after wholesale storage and delivery and retail storage
and display that unsatisfactory Bacillus and Clostridia counts occurred. Advice was
subsequently issued to their local businesses, informing them of the importance of
temperature control and adherence to use by dates which may have to be obtained
from the producer.
Conclusion
1.
It is proposed that category 4 of the PHLS ready to eat food guidelines (1) is
used to interpret the microbiological quality of black puddings.
2.
Overall the microbiological quality of black puddings is of concern due to
24% of the samples examined in this survey producing
unsatisfactory/unacceptable results including 4% containing significant counts
of food poisoning organisms.
3.
At the point of retail there appears to be a lack of knowledge relating to the
product and measures expected to ensure its safety.
Black pudding is a cooked food and should be handled, stored and displayed
accordingly. It is of concern that 19% of samples in this survey were
displayed and served from raw meat displays.
4.
There is a risk that black pudding served from raw meat displays could
become
contaminated
from
raw
meat
and/or
shared
utensils/equipment/surfaces etc.
When black pudding has been in contact with raw meat products, it should be
clearly labelled to inform the purchaser that further heating to 82°C is
required.
5.
It is recommended that the retailers obtain and adhere to ‘use by’ dates
stipulated by the producer, and that traceability of production details is not
lost.
References
(1)
Guidelines for microbiological quality of some ready to eat foods sampled at
the point of sale, PHLS ACFDP Working Group, Communicable Disease and
Public Health. Sept 2000, Vol 3, No. 3 : 163-167.
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Appendix 1
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-
Request Form
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Appendix 2
-
Survey Participants
Authority
Barrow
Blackburn
Blackpool
Bolton
Burnley
Bury
Chorley
Fylde
Hyndburn
Lancaster
Manchester
Oldham
Pendle
Preston
Ribble Valley
Rochdale
Rossendale
Salford
South Lakes
South Ribble
Stockport
Tameside
Trafford
West Lancs
Wigan
Wyre
TOTAL
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Number of
samples
8
15
35
12
9
6
13
20
10
15
14
9
0
6
7
3
10
14
11
12
12
13
11
12
12
12
301
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