Bacteriological Status of Minced Beef

Bacteriological Status of Minced BeefAuthor(s): J. F. Dempster, L. McGuire, J. Sherington, E. M. Brady, P. Dempsey and P. V.JenningsSource: Irish Journal of Food Science and Technology, Vol. 10, No. 1 (1986), pp. 61-66Published by: TEAGASC-Agriculture and Food Development AuthorityStable URL: http://www.jstor.org/stable/25558127 .

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Bacteriological Status of Minced Beef

Abstract: Samples of minced beef (250 g each) were collected from each of five outlets

(retail butchers' shops and the meat counter of a supermarket) in four regional areas (Letterkenny, Sligo, Galway, Dublin) on four or five occasions between December 1983 and April 1985 to give a total of 90 samples. They were examined for total count, coliform count (E. coli) and salmonellae by conventional methods and the pH of 60 was

measured.

Results showed that the Galway mince had the lowest total count (log 5.57 g_1) while the Dublin mince had the highest total count (log 8.45 g_1). Surprisingly, the Galway samples were the most faecally contaminated (log 3.71 E. coli g_1) while the Letterkenny samples were the least faecally contaminated (log 1.2 E. coli g_1). Only 5/90 (5.5%) of the

samples were salmonella positive. The pH value of the mince ranged from 5.75 (normal) to

6.85 (high) with a mean of 6.25 (high). Results are discussed in relation to national and international standards (guidelines) for

this product.

Introduction A previous survey of the bacteriological status of comminuted meat (beef mince) sold in the Dublin metropolitan area in 1977-78 showed that 8/102 samples

(7.88%) were salmonella positive (Dempster and Cody, 1978). Total bacterial numbers

per gram ranged from 9.4 x 106 to 6.2 x 109 and numbers of Escherichia coli from less than 100 to 3.24 x 105 per g. Daly et al (1976) reported that the aerobic plate count of mince sold in Cork ranged from a low' of 3.5 x 105 to a 'high' of 1.3 x 109/ g. They did not examine the meat for salmonellae but *coliform' numbers ranged

from 1.9 x 103 to 5.3 x 106/g. In Ireland, other surveys have been conducted on the

bacteriological status of mince meat in recent years, but the results have not been

published (Pierse, personal communication,

1984). This investigation was carried out to

obtain current information on the quality of

mince sold in Dublin and other regions of

the country.

Materials and Methods

Three regional laboratories (Letterkenny, Sligo, Galway) located in the local

Technical Colleges collaborated with this

laboratory (Agricultural Institute, Dublin). A format was agreed whereby samples (250

g) of freshly-produced minced beef were

collected from each of five outlets (retail butcher and/ or meat counter in super

market) over periods as shown belqw: Dublin Jan-May 1984

Letterkenny Dec 1983-May 1984

Sligo March-April 1984

Galway Nov 1984-Apr 1985 AH samples were refrigerated (+4?C) until

tested when the following were carried out:

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IRISH JOURNAL OF FOOD SCIENCE AND TECHNOLOGY, VOL. 10, NO. 1,1986

Total aerobic viable count (5?C) and salmonella screening as described by

Dempster and Cody (1978). E. coli: One ml of meat macerate (10 g

mince in 90 ml quarter Ringers solution + 0.1% peptone diluent) was added to 9 ml of the above diluent and tested for E. coli as described previously (Dempster etal, 1973).

pH: The pH value of the meat was measured

on the macerates using portable meters.

Statistical analysis: An analysis of variance

was carried out to examine differences

between regions and between shops

within regions.

Results

The mean counts (total aerobes at 25?C) of

the different mince samples are presented in

Table 1. Results indicated that the mince

sold in the Dublin region had the highest mean count, 281 x 106 (l?g 8.45 per g) while the Galway samples had the lowest

count, 37 x 104 (log 5.57 per g). Sligo was

second and Letterkenny was tliird. These

regional differences were highly significant

(p<0.001) as were the differences between

shops within regions (p<0.01). The numbers of E. coli in the mince are

shown in Table 2. The Letterkenny samples had the lowest mean count (log 1.2 per g) and the Galway samples the highest count

(log 3.71 per g). The differences between regions were

highly significant (p<0.001) and within

regions between shops (p<0.01). However,

direct comparisons cannot be made between

these and results of other surveys since

different methodologies were employed in each case. For example, Foster, Fowler and

Ladiges (1977) in the USA incubated plates for aerobic count at 32?C/48 h and obtained numbers of microorganisms ranging from

6.9 x IO4 (log 4.84) to 8.3 x 107 (log 7.92) per g while Roberts et al (1980) in the UK recorded counts ranging from 155 x 105

(log 7.19) to 43 x 106 (log 7.63) per g after incubation at 20?C/96 h. We employed 25?C/72 h.

The 'Salmonella status' of the samples is

presented in Table 3. No salmonellae were

recorded in any of the Dublin or Letterkenny samples but 1/25 and 4/20 were positive in Galway and Sligo respectively. In Sligo,

the four positives Wi?re obtained in four

of the five shops sampled. The pH values of the Dublin and Letter

kenny samples are shown in Table 4. No pH

measurements were made on the Sligo or

Galway samples. The Dublin mince ranged

from a low pH of 5.75 to a high value of 6.85 with a mean of 6.25. The corresponding

figures for the Letterkenny samples were

5.1 and 6.41 with a mean of 5.79.

TABLE 1: Mean total viable microbiological count (log jq count g ) of minced beef between different

regions and within different retail outlets

No. samples Shop

per shop-_ Region (n) A B C D Ex SEof mean

Sligo 4 7.43 7.97 8.39 6.98 6 94 7.54 0.33

Letterkenny 5 6.24 7.22 7.29 5.53 i 35 6.73 0.3

Dublin 4 9.13 9.36 7.98 8.67 7.19 8.45 0.33

Galway 5 5.33 6.2 5.88 5.26 5.19 5,57 0.3

F-values for difference between region means =14.9 (p<0.001) F-values for difference between shops within region

= 2.66 (p<0.01)

62




TABLE 2: Mean E. coli count Gog jq count ~*) of minced beef between different regions and within different retail outlets

No. samples Shop

per shop - - -

_

Region (n) A B C D Ex SEof mean

Sligo 4 1.84 1.42 2.06 1.64 0.62 1.52 0.3

Letterkenny 5 2.02 0.46 0.63 1.03 1.85 1.2 0.27

Dublin 4 2.01 0.58 2.85 2.08 1.07 1.72 0.3

Galway 5 3.48 4.11 3.74 3.42 3.78 3.71 0.27

F-value for difference between region means =17.2 (p<0.001) F-value for difference between shops within regions

= 2.61 - 5 (p<0.01)

TABLE 3: Salmonella in minced beef

No. samples tested No. No.

Region 2 X 25 g positive positive

Galway 25 1/25* 4.0

Sligo 20 4/20* 20.0

Letterkenny 25 0/25 0.0

Dublin 20 0/20 0.0

*Serotype/s not determined (in Sligo, isolations

were made in 4 out of the 5 shops sampled)

are those issued by the Department of

Health 1978, revised in 1984. They are

reproduced in Table 5 for ready comparison

with the results of this study. However,

direct comparison is not possible since the

present samples were 'fresh chilled' and, in

the above guidelines for this product, the

designation is 'frozen'. But even if the guide

line (not to exceed 3 x 106 per g) for

frozen comminuted meat were to be applied

here, then 2/20 (10%) Dublin samples,

TABLE 4: pH values of minced beef

Sample number

Shop 1 2 3 4 5 x

Dublin A 5.75 6.05 6.0 5.95 5.94 5.94

B 5.95 6.85 6.8 6.25 6.46 6.46

C 6.0 6.85 6.75 6.5 6.4 6.5

D 6.05 6.75 6.25 5.93 6.3 6.3

E 6.0 6.05 5.95 6.1 6.03 6.03

Letterkenny A 5.96 5.88 6.2 5.45 6.09 5.92

B 6.04 6.07 6.06 5.52 6.41 6.02

C 5.88 5.56 5.8 5.1 6.05 5.68

D 5.68 5.69 5.78 5.25 5.69 5.62

E 5.71 5.55 6.4 5.17 5.81 5.73

Discussion

The guidelines available in Ireland in relation to microbiological quality of minced meat

4/20 (20%) Sligo samples, 13/2: (52%;; Letterkenny samples and 22/25 (88%) Galway samples would comply. Thus 41/90

63



IRISH JOURNAL OF FOOD SCIENCE AND TECHNOLOGY, VOL. 10, NO. 1,1986

TABLE 5: Microbiological guidelines (An Roinn Slainte) for fresh meat, including chilled

and frozen meats*

Standard Plate Count

Category (30?C/72 h) Salmonella**

Carcass meat, fresh, chilled- 2 X 106/g Absent

Carcass meat, frozen 1 X 10?/g Absent***

Boneless meat, frozen 2 X 10"/g Comminuted, frozen 3 X 106/g Edible offal, frozen 2 X 106/g

Source: Department of Health, Dublin (1984) **A11 analyses based on 2 X 25 g samples or subsamples from each unit/pack

***For all frozen meats, a pre-enrichment phase (for resuscitation) is essential

(45%) of the samples would fall within the

guideline with the majority originating outside the Dublin metropolitan area.

Presumably the percentage compliance rate

would decrease, though, if the guideline was for *fresh chilled comminuted' instead

of 'frozen meat'.

Guidelines promulgated in Northern

Ireland for products such as minced meat,

sausage meat and other raw products should

comply with a standard of 5 x IO5 per g and never exceed 2 x IO6 per g (Murray,

1975). Salmonellae should be absent in 100

g. This is a rigorous standard and if applied to the present results, only 33 (37%) of the

samples would comply on total count. On*

the other hand, if our guideline (Dempster and Cody, 1978) were applied, then 45/90

(50%) of the samples would comply. The E. coli count (Table 2) ranged from a

low of log 1.2 per g (Letterkenny) to a high of log 3.71 per g (Galway). This indicates a very wide range of faecal contamination in

mince, of the order 15 to 5,100 E. coli

organisms per g of sample. It is significant

that all the Galway samples fell within a

narrow band (3,000 to 13,000 per g) or

about one to three hundred times higher than all the others. Reasons for this were

not investigated.

Faecal coliforms are not included in the

Department of Health Guidelines (1984) for this product; the only figure (5/g) refers to heated products in open pack including pastas, pates and pasteurised canned meats.

Likewise Murray (1975) did not include faecal coliforms in his guidelines but he did cite a standard for coli-aerogenes

bacteria of 1,000 per g. When numbers exceeded 5,000 per g, the sample was

deemed unsatisfactory.

That only 5/90 (5.5%) of the samples were 'salmonella-positive' is reassuring and is

a small improvement on the 1978 figures cited by Dempster and Cody. On this

occasion, no Dublin sample was positive

whereas in 1978, 8/102 Dublin samples had

salmonellae in 100 g of sample.

Conclusions

Current microbial evidence indicates that actual limits for total viable numbers in

meat products as a measure of quality and/

or safety are unworkable and unrealistic.

Firstly, none of the Indicator' tests (total count, total coliforms, or faecal coliforms) can serve as a food safety assurance test for

raw or ready-to-eat meats, Miskimmin et al

(1976). They found that none of these tests

was suitable as a screening agent for food

64




safety. However, they suggested that a total

aerobic plate count would be the most suit

able method for the evaluation of micro

biological safety of foods. Further evidence of the above was pro

vided by Dempster (1978) who examined 115 samples of 11 different products for a

relationship between viable count E. coli and

salmonellae. Correlations (?0.96: -0.78) were found in only two samples. According to Roberts et al (1980) ... "if a measure of

overall microbial quality is needed, TVC/ 37?C would supply it quickly". This

suggestion seems to concur with that of

Miskimmin et al (1976). Secondly, the experiences of the State of

Oregon in the USA are well documented

(Carl, 1975). This was one of the first states to legislate for microbiological quality of ground meat. However, the law was un

workable , the standards were abandoned and

replaced by bacteriological criteria which are

only advisory and do not carry criminal

liability (Wehr, 1978). Until there is clearer evidence that minced beef is frequently implicated in food-borne illness there seems

little point in applying bacteriological criteria.

It is perhaps significant that the 'Dublin' meat with the highest mean count (log 8.45

per g) also had the highest pH value in 4 of

the 5 shops sampled. This relationship was

noted earlier by Dempster and Cody (1978). Roberts et al (1980) noted that the pH of minced beef was significantly and positively correlated with count, that is, there was a

trend to higher bacterial numbers with

increase in pH value. With the proviso that meat with a high pH is clearly not necessarily a reflection of bacterial status, pH can be a

reasonable measure of bacteriological quality

and accordingly should be measured when this and similar meats are studied.

J. F. Dempster, L. McGuire The Agricultural Institute, Meat Research

Department, Grange/Dunsinea Research Centre,

Castleknock, Dublin 15

J. Sherington1 The Agricultural Institute, Statistics Department, 19 Sandymount Avenue, Dublin 4

E.M.Brady Regional Technical College, Ballinode, Sligo

P. Dempsey Regional Technical College, Letterkenny, Co.

Donegal

P. V. Jennings Regional Technical College, Galway

Present address: P. O. Box 417, Konedobu, Papua New Guinea

References

Car], K. E. (1975). Oregon's experience with

microbiological standards for meat. Journal

of Milk and Food Technology 38: 483-486.

Daly, Michele C, Morrisey, P. A. and Buckley, D. J. (1976). Quality of raw minced beef.

Irish Journal of Agricultural Research 15:

280-286.

Dempster, J. F. (1978). Bacteriological relation

ships in raw and processed meats and associated

products. Proceedings XXIV European Meeting

of Meat Research Workers, Kulmbach, Paper

B9,3-6.

Dempster, J. F. and Cody, O. H. (1978). Bacterio

logical and chemical status of minced beef.

Irish Journal of Food Science and Technology 2: 1-11.

Dempster, J. F., Reid, S. N. and Cody, 0. H.

(1973). Sources of contamination of cooked,

ready-to-eat cured and uncured meats. Journal

of Hygiene (Cambridge) 71: 815-823.

Department of Health, Dublin (1984). Micro

biological guidelines for meat and meat

products, milk, cream, ice cream, eggs and fish.

An Roinn Slainte, Dublin, 17 pages.

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IRISH JOURNAL OF FOOD SCIENCE AND TECHNOLOGY, VOl . 10. NO. 1,1986

Foster, J. F., Fowler, J. L. and Ladiges, W. C.

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794.

Miskimmin, D. K., Berkowitz, K. A.. Solberg. M..

Rhia, W. E. Jr., Franke,W. C, Buchanan, R. L.

and O'Leary, V. (1976) Relation between indicator organisms and specific pathogens in potentially hazardous food. Journal of Food

Science 41: 1001-1006,

Murray, 3. G. (1975). Microbiological standards for

f ood. Institute of Food Science and Technology

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(1980). The bacteriological quality of minced

beef in the UK. Journal of Hygiene (Cambridge) 85:211-217.

Wehr, H. M. (1978). Attitudes and policies of state

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foods). Food Technology 32: 63-67.

Received March 11,1986

66



Radiation (gamma), responses to, of selected

microorganisms in sterile water and

bovine muscle, 57.

Rancidity (lipolytic), quantification and

identification of flavour components

leading to, in stored butter, 1.

Ripening, influence of cheese geometry on

the movement of sodium chloride and

water during, 97.

Sodium chloride, influence of cheese

geometry on the movement of, 73; 97.

Sports nutrition - a review, 135.

Sterile water, responses to gamma radiation

of selected microorganisms in, and

bovine muscle, 57.

Water, influence of cheese geometry on the

movement of sodium chloride and,

during brining, 73; influence of cheese

geometry on the movement of sodium

chloride and, during ripening, 97.

Water (sterile), responses to gamma radiation

of selected microorganisms in, 57.

IRISH JOURNAL OF FOOD SCIENCE AND TECHNOLOGY

VOLUME 10, NO. 1,1986

ERRATA

Page 57. Abstract, Line 4. Delete 'at room temperature'

Page 58. Lines 21-22. Delete 'at room temperature' Page 62. Line 1. For 5?C read 25?C



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Bacteriological Status of Minced Beef