121. MICROBIOLOGICAL CRIT€RtA FOR FRESH MEAT' A. W. KOTULA UNITED STATES DEPARTMENT OF AGRICULTURE .............................................................................. Though concern about microbial contamination of meat and con- comitant standards for microbiological quality, can be traced to the turn of the century, as far as can be ascertained there are no microbiological standards that are presently being enforced for fresh meat. Elliott and Michener (1961) reviewed the literature relative to microbiological. standards and handling codes for chilled and frozen foods up to 1960. Table 1 sum- marizes the portion of his review which deals with fresh meat. bacteriological limits are as high as lo6 or lo7 viable aerobes per gram. Because off odor will develop at about lo8 organisms per gram (Kirsh -- et al., 1952, Barnes 1957) only a few days shelf life can be expected for such a product even under optimum storage temperatures. But extended shelf life is not our only concern during the consideration of microbiological criteria. The purpose of microbiological criteria are threefold: Some of the 1. To identify and eliminate slaughter and marketing practices which might allow meat to reach marketing channels, when it might be deleterious t o consumer health by virtue of its microbial content. 2. To increase the level of wholesomeness of all meat and meat products . 3. To enhance consumer satisfaction and confidence in meat as a food. Table 2 shows the microbiological limits for fresh meats that have been proposed since the Elliott review of 1961. used to mean meat that has not been cured, smoked, or canned, not t o express time post mortem. rather than "standards" to more readily relate to other groups such as the Food Protection Committee of the National Research Council, who already have spent many years evaluating microbiological levels and have developed a precise terminology for microbiological criteria. logical criterion as "any specification, recommended limit, or standard". Further, a specification is a maximum level set by an agency or firm purchas- ing food for its own use; a limit is a recommended l e v e l , and a standard is that part of a law or administrative regulation designating the maximum acceptable number of microorganism. The term "fresh meats" is The proposals of Table 2 are referred to as "limits" They define a microbio- - 1/ Appreciation is expressed t o members of the Microbiology Committee, Drs. J. A. Carpenter, R. H. Gothard and J. M. Jay for the information which they contributed for this presentation.
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121.
MICROBIOLOGICAL C R I T € R t A FOR FRESH MEAT' A. W . KOTULA
U N I T E D S T A T E S D E P A R T M E N T O F A G R I C U L T U R E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Though concern about microbial contamination of meat and con- comitant standards f o r microbiological qua l i ty , can be t raced t o the tu rn of t he century, as far as can be ascertained there are no microbiological standards t h a t are present ly being enforced f o r f r e sh meat. E l l i o t t and Michener (1961) reviewed the l i t e r a t u r e r e l a t i v e t o microbiological. standards and handling codes f o r ch i l l ed and frozen foods up t o 1960. Table 1 sum- mar izes t h e port ion of h i s review which dea ls w i t h f r e s h meat. bac te r io logica l l i m i t s are as high as lo6 or l o 7 viable aerobes per gram. Because off odor w i l l develop at about lo8 organisms per gram ( K i r s h -- e t al., 1952, Barnes 1957) o n l y a few days shelf l i f e can be expected f o r such a product even under optimum storage temperatures. But extended shelf l i f e i s not our only concern during t h e consideration of microbiological c r i t e r i a . The purpose of microbiological c r i t e r i a are threefold:
Some of t h e
1. To iden t i fy and eliminate slaughter and marketing prac t ices which might allow meat t o reach marketing channels, when it might be de le te r ious t o consumer heal th by v i r tue of i t s microbial content.
2. To increase the l e v e l of wholesomeness of all meat and meat products .
3. To enhance consumer s a t i s f a c t i o n and confidence i n m e a t as a food.
Table 2 shows the microbiological l i m i t s for f r e sh meats t h a t have been proposed since the E l l i o t t review of 1961. used to mean m e a t t h a t has not been cured, smoked, or canned, not t o express t i m e post mortem. r a the r than "standards" t o more r ead i ly r e l a t e t o other groups such as the Food Protect ion Committee of the National Research Council, who already have spent many years evaluating microbiological l e v e l s and have developed a precise terminology for microbiological c r i t e r i a . l o g i c a l c r i t e r i o n as "any specif icat ion, recommended l i m i t , or standard". Further , a spec i f ica t ion i s a m a x i m u m l eve l s e t by an agency or f i r m purchas- ing food f o r i t s own use; a l i m i t i s a recommended leve l , and a standard i s t h a t p a r t of a l a w or administrative regulat ion designating the m a x i m u m acceptable number of microorganism.
The term "fresh meats" i s
The proposals of Table 2 are re fer red t o as " l i m i t s "
They define a microbio-
- 1/ Appreciation i s expressed t o members of t h e Microbiology Committee, D r s . J . A. Carpenter, R. H. Gothard and J. M. Jay for the information which they contributed f o r t h i s presentation.
122.
E l l i o t t (1970) proposed the use of y e t another term, "guideline", which i s a l e v e l of bac te r i a i n a f i n a l product t h a t necess i ta tes ident i - f i c a t i o n and cor rec t ion of caus i t ive f ac to r s i n current or fu ture production and handling.
Table 2, therefore , dea ls with microbiological l i m i t s f o r f r e sh m e a t . The limits involve both spoilage and pathogenic microorganisms.
Table 2 does not include the pos i t ion statement by the Consumer and Marketing Service of the U. S. Departnent of Agriculture concerning Salmonella i n r e d meats and t h e i r products. This statement ind ica tes t h a t ready-to-eat and warm-and-eat meat products must be free of salmonellae. R a w red mat products found t o be heavily contaminated w i l l be re ta ined and improvements i n san i t a t ion w i l l be required t o protect fu tu re production. Heavy contamination i s indicated by (1) a high incidence of pos i t ive findings, (2) a high l e v e l of Salmonella c e l l s or (3) a higher incidence of Salmonella i n the product than i n the animals from which it i s produced.
The microbiological l imits proposed i n Table 2 would probably be of l i t t l e use t o the meat industry. There appears t o be a lack of agreement as t o which organisms, other than t o t a l aerobes, are important. Also the proposed l i m i t s are incomplete f o r some of t he f r e sh meat categories . Rather than t o f u r t h e r evaluate t h e limits proposed i n the s i x t i e s , l e t ' s look at t h e s teps t o be taken, if indeed such s teps are warranted, t o develop and improve the usefulness of microbiological l i m i t s i n the seventies.
Mossel (1969) suggests t h a t t he f i r s t s tep i n developing micro- b io logica l c r i t e r i a should be a carefu l study of t he microorganisms associated with a pa r t i cu la r food. bac te r ia , actinomycetes, molds, and yeasts i so la ted from ref r igera ted beef. Two minor modifications have been made i n Table 3. Aerobacter and Paracolo- bactrum were r ec l a s s i f i ed as Enterobacter according t o Edwards and Ewing (1966). organisms. i l l n e s s i n 1968 w e r e :
Table 3, compiled by A p e s (1960), c l a s s i f i e s
This grouping can be broken down f u r t h e r i n t o pathogens and spoilage Hall (1969) s t a t ed t h a t t he bac te r i a responsible f o r f oodborne
Number of I l l n e s s e s Percent
- C perf ringens S t aDhvloc occus , ." S almone 11 a Streptococcus E. c o l i
5,966 4,419 1,287 1,282 1,234 - -
Shige l la 407 Brucel la 12 C . bolulinum 10
Total 14,617 -
40.8 30.2 8.8 8.8 8.4 2.8
< l . O <l.O
Mossel (1969) would add Baci l lus cereus and Vibrio parahemolyticus t o t h i s l i s t of pathogens as being of current i n t e r e s t from the standpoint of out- breaks of food-borne diseases, r ea l i z ing t h a t Vibrio parahemolyticus has been associated with f i s h .
123
Van Schothorst (1970) recognized t h a t no pathogens should be allowed i n food, but there would not be much food t o eat if regulat ions were t h a t s t r i c t . Mossel (1969) indicated t h a t t o obtain czrcasses with a t o l e r - able degree of Salmonella contamination, the meat industry must consider pathogen-free young animals, bacter iological control of feed, and consider- able improvement of the san i ta ry conditions of the a n i m a l s on the farm, during t ransportat ion, and while awaiting slaughter.
Fortunately, while the industry i s s t r iv ing towards t h i s g o a , proper san i ta t ion and inherent microbial. antagonisms help t o maintain patho- gens a t low leve ls . For example, mil l ions of viable - C . perfringens bac ter ia must be ingested t o cause i l l n e s s (anonymous, 1970). meat product at less than 10°C w i l l i nh ib i t t h e development of such numbers (Patterson, 1967, H a l 1 and Angelotti, 1965) . Patterson (1967) , indicated t h a t growth of Salmonella and Staphylococcus a u e u s are a l s o inhibi ted below 10°C. the danger from pathogens i s avoided.
Refrigeration of the
Thus if meat i s not abused by improper storage temperatures, much of
Hartman (1968) indicated t h a t t he Committee on Environmental Health of the Cal i forn ia Conference of Local Health Off icers concluded t h a t standasds based on b a c t e r i d counts associated with disease, although desirable , were not f eas ib l e at present. It seemed more p rac t i ca l t o proceed t o e s t ab l i sh standards, based on b a c t e r i a l counts i n foods, associated with current production prac t ices .
How do current prac t ices a f f ec t t he microbiological qua l i ty of meat? Vanderzant and Nickelson (1969) reported t h a t muscle t i s sue of healthy l i v i n g animals contains f e w or no microorganisms and t h z t there are no psychrotrophic bac te r i a i n f r e s h t i s s u e s of pork, lamb, or beef. S t r inger 5 &., (1969) found t h a t contamination occurs immediately a f t e r slaughter, and t h a t moist carcass areas axe contaminated most highly. rump, br i ske t , and fore legs are l i k e l y t o show the grea tes t contamination according t o Murray (1969).
The
The generic d i s t r ibu t ion of i so l a t e s between f r e sh and spoiled beef as found by Jay (1967) includes:
Genus
Pseudomonas Achr omob ac ter Aeromonas - Proteus F 1 avob ac t e r i u n Alcoliaene s
No. of beef i so l a t e s Fresh Spoiled
34 4 2 3 1 2 2 1 1
16 1 1 0 1 0 0 0 0
Table 4 summarizes bac te r i a l numbers found i n f r e sh m e a t as reported during the l as t decade. uniform among the various researchers and i n some instances was not reported at all. The usefulness of such da ta f o r developing microbiological c r i t e r i a i s limited unless sampling methods, treatment of samples, and methods
Methodology i n the determinations w a s not
124.
of bac ter io logica l examination are r i g i d l y followed (Murray 1969). paper presented methodology, as shown i n Table 5 taken from Rey e t al., (1970), comparison of t h e counts would be simplified. In te rna t iona l Association of Microbiological Soc ie t ies has published methods f o r de tec t ion of food-borne pathogens and indicator organisms (Thatcher and Clark, 1969): an agreement on the optimum methodology f o r non-pathogens.
If each
A committee of the
It would be highly desirable f o r microbiologists t o come t o
The Association of Food and Drug Of f i c i a l s of the U. S. have developed the microbiological c r i t e r i a f o r beef pot pies, shown i n Table 2, using what appears t o be the most s c i e n t i f i c approach t o date . Four independent labora tor ies cooperated t o provide microbiological da t a on f i v e beef p i e s from each of 2 4 commercial l o t s . Sampling, plat ing, and incubating procedures were standardized before the study was i n i t i a t e d . The labora tor ies then determined coliform, E . co l i , Staphylococcus, and Streptococcus by the most probable number m e t h g (m and also viable aerobes, coliforms, Staphylococcus and Streptococcus by p l a t e count. Results of t h i s study are reported i n the l a t t e r past of Table 4. The Committee on Research and Methodology decided not t o recommend examination f o r staphylococci because the level of contamination w a s t oo low t o serve as a sens i t ive index of qua l i ty . p i e s because the labora tor ies encountered d i f f i c u l t y with the KF Medium from one commercial source. The Committee's f i n a l recommendation s ta ted t h a t a t o t a l z r o b i c p l a t e count of l O O , O O O / g and 200 coliform/g by the MPN method should be used t o evaluate the qua l i ty of precooked frozen beef pie. p i e s from each l o t would be sampled and if the average of the log 10 count exceeded the l i m i t s , t he l o t would be unacceptable. means of 150,000 aerobic organisms/g and 380 coliform/g would be accepted 5 times i n 1000. aerobes/g and 50 coliform/g would not r i s k exceeding the limits i n more than 1 l o t of 1000. Though t h i s approach i s sound, it would have been advantageous if a grea te r number of p lan ts could have been included i n the study t o repre- sent a greater divergence i n f i n a l product qual i ty . The effect iveness of the c r i t e r i a a l so could have been strengthened if microbial counts had been r e l a t ed t o t h e standards of s an i t a t ion practiced within each plant. This idea i s not new. (1963), and E l l i o t t (1969) f o r many years because, u n t i l improved biological techniques of evaluation are developed, it i s more f eas ib l e t o control qua l i t y by a preventative system of plant san i ta t ion than by the ana ly t ica l approach.
Fecal s t reptococci were not used as an index of q u d i t y of beef
Ten
By t h i s method l o t s with
A processor who regular ly produces p i e s having 43,000
It has been advocated by Mossel (1969), Shiffman and Kronick,
summary
Microbiological limits proposed f o r f r e sh meats are reviewed. None of t he suggested limits are idea l standards f o r the following reasons: (1) methodology f o r sampling and p l a t ing w a s nei ther uniform nor w a s it described i n d e t a i l ; (2) decisions were based on too few samples; ( 3 ) some f r e sh m e a t i t e m s were not evaluated; (4) samples representing grea te r divergence i n f i n a l product qua l i t y were needed; and (5) microbiological counts should have been correlated t o standards of san i ta t ion practiced within each plant . References describing microbial counts associated with f r e sh meats are l i s t e d . However, counts i n these repor t s are of l imited value f o r use i n formulating micro- b io logica l limits because procedures were not uniform and sampling w a s , i n some instances, inadequate. Thus, if microbiological standards or limits are deemed necessary, a cooperative e f f o r t involving industry, university, and government microbiologists should be i n i t i a t e d t o standardize and publish
125.
preferred sampling techniques and methods of enumerating microorganisms. Furthermore, each f r e s h meat i t e m should be evaluated systematically t o ensure t h a t samples representing many l e v e l s of qual i ty , as r e l a t ed t o in- plant san i ta ry pract ices , are included i n the t e s t i n g by the various labora tor ies . Data from such s tudies would reflect the "state of the a r t " i n t he meat packing industry and could then become t h e basis for microbio- l og ica l l i m i t s f o r f r e s h meat.
126.
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Table 3. C las s i f i ca t ion of Microorganisms Iso la ted from Refrigerated Beef. (Ayres 1960).
Bacter ia and Actinomycetes
Sc h i z omyc e t e s Pseudomonadale s
Pseudomonadace ae Pseudomonas Aeromonas
Eub ac t e r i d e s Achromobac t e r i ac e ae
Alcaligenes Achromobac t e r Flavobacter im
Ent erobac t e r i ace ae E scher ich i a Enter obact e r S e r r a t i a Proteus Sdmone 11 a
Micrococcaceae Microc oc c u s Staphylococcus Sarcina
Lac t ob ac t e r i ace ae S t re p t oc oc c us
Corynebacteriaceae Microbacterium
B ac ill ace ae Bacil lus Clostridium
Actinomycetales
Molds and Yeasts
Phycomycetes Muc or ale s
Mucor ace ae Rhiz opus Mucor
Thamnidiaceae Thamnidium
Fungi Imperfecti Moniliale s
Monili ace ae Monilia Aspergil lus Penicil l ium Sporotrichum
D e m a t iace ae Cladospor iwn Alternar ia
Kreger-van R i j (33)-/ - Crypt oc occ ace ae
T orulop s i s
C r y p t o w A f t e r Lodder &
Candida Rhodot orul a
S t r e i t omycet aceae S t r e p t omyc e s
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