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Файл:Veterinary and sanitary examination of meat and meat products. Study aid
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development of proteolytic microflora. Therefore, in smears — imprints from the
meat of animals killed in an agonal or severely pathological state — rods
predominate. Their number will depend on the severity of the disease. In smears of
old, tired animals, the ratio of rods and cocci is 50:50.
The amount of microflora. The meat of sick animals is susceptible to
contamination with microflora, including putrefactive ones. Therefore, even when
fresh, it has a higher degree of microbial contamination than meat from healthy
animals. The reservoir of microflora is the gastrointestinal tract. As a result of the
weakening of the body's resistance during the disease, intravital bacteremia occurs,
when the intestinal microflora enters the blood and spreads to all organs and tissues.
The meat of sick animals may contain pathogenic microflora.
The number of microorganisms in the field of view depends on the severity of
the animal’s disease. In the meat of sick, dead, and overworked animals, microflora
in the deep layers is detected immediately after slaughter. If in 25 fields of view of a
fingerprint smear an average of 10 to 30 microbial bodies are found, then such meat
is classified as obtained from sick animals. If more than 30 microbial bodies are
detected, it is considered that the meat was obtained from animals killed in agony or
dead, and subsequently it is sent for technical disposal.
Biochemical methods for recognition of meat, obtained
from the slaughter of sick animals
Determination of pH (according to GOST R 51478-99)
The pH value of meat depends on the carbohydrate content in it at the time of
slaughter of the animal, as well as on the activity of intramuscular enzymes. During the
life of the animal, the reaction of the muscle environment is slightly alkaline. After
slaughter, as a result of the accumulation of acidic breakdown products of glycogen,
adenosine triphosphate acid, a sharp shift in the concentration of hydrogen ions occurs
in the acidic direction. So, after a day, the pH of the meat drops to 5.6–5.8. In ripened
meat from healthy animals, the pH is 5.7–6.2.
In the meat of animals that are sick or killed in an agonal state, such a sharp
decrease in pH does not occur. In the muscles of poorly fed, emaciated and sick
animals, glycogen is 2–3 times less than in the muscles of healthy animals. With
prolonged illness, the body's energy supply decreases and the process of glycolysis is
limited. When meat ripens, a small amount of acidic decomposition products is
formed. Due to the lack of lactic acid, the pH level increases. Meat from sick and
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overworked animals has a pH in the range of 6.3–6.5, and meat from animals killed
in a severely pathological or agonal state has a pH of 6.6 or more.
The pH of muscle tissue is determined using the methods described on pp. 19–21
of this book.
Peroxidase reaction
Peroxidase is an enzyme in muscle tissue; its activity depends on the pH of the
environment and the content of oxidizing substances in the extract.
The activity of peroxidase depends on the pH of the medium and the content of
oxidizing substances in the extract, as a result of which complete correspondence
between the benzidine reaction and the concentration of hydrogen ions is not
observed. However, at a pH of the extract corresponding to the value of the indicator
for fresh meat of a healthy animal, peroxidase activity is high (positive reaction), and
at pH 6.3 and higher, corresponding to the meat of a sick animal, peroxidase activity
is reduced (negative reaction).
The peroxidase reaction is carried out according to the method described on pp.
23–24 of the study aid.
Formol reaction
In severe diseases, intermediate and final products of protein breakdown
(polypeptides, albumoses, amino acids) accumulate in the muscles while the animal is
still alive. The essence of this test is the precipitation of protein breakdown products
with formaldehyde. This technique is mainly used to study beef.
Analysis procedure
A meat sample weighing 10 g is freed from fat and connective tissue, minced,
placed in a mortar, 10 cm3 of physiological solution and 10 drops of 0.1N sodium
hydroxide solution are added. The meat is ground with a pestle, the resulting mass is
transferred into a flask with a glass rod, and heated to a boil to precipitate the proteins.
The flask is cooled with tap water, its contents are neutralized.
5 drops of 5 % oxalic acid solution added and it’s filtered through a paper
filter. 2 cm3 of the prepared extract is poured into a test tube, 1 cm3 of neutral
formaldehyde is added. Formaldehyde is neutralized with a 0.1N solution of sodium
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hydroxide using an indicator consisting of equal parts of aqueous solutions of neutral
and methylene blue until the color changes from violet to green.
Reaction assessment. If the filtrate is clear or slightly cloudy, the meat is
considered to have come from a healthy animal. If flakes form and a jelly-like clot
falls out, it means that the meat was obtained from a sick animal or an animal killed
in an agonal state.
Determination of acidity-oxidability coefficient
(according to G.V. Kolobolotsky)
Immediately after the slaughter of a healthy animal, the breakdown of glycogen
in meat begins through the glucose stage to lactic acid. ATP breaks down into
orthophosphoric and monophosphoric acids, and the acidity of the meat increases. In
ripened meat of sick animals, titratable acidity remains at a low level, since due to the
low glycogen content, less ATP of the breakdown products of these substances
accumulates.
The oxidability of meat depends on the presence of microorganisms and
decomposition products of organic substances in it. In the ripened meat of sick
animals it is much greater than in the meat of healthy animals.
Thus, the change in titratable acidity and oxidability values is inversely
proportional. The acidity-oxidability coefficient (ACO) of cooled meat from healthy
animals is usually 2–3 times higher than that of meat from sick animals.
Analysis procedure
To determine titratable acidity, pour 10 ml of meat extract 1:4 into a flask,
dilute it with 40 cm3 of distilled water, add 3 drops of an alcohol solution of
phenolphthalein and titrate with a 0.1N solution of sodium hydroxide to a slightly
pink color.
To determine oxidability, pour 50 cm3 of distilled water into the flask, add 5 cm3
of a 0.4N solution of sulfuric acid, add 1–2 drops of a 0.1N solution of potassium
permanganate until it turns slightly pink. The solution is heated in a water bath to
40–50 °C. Add 2 cm3 of meat extract 1:4 to the warm solution and immediately
titrate with a 0.1N solution of potassium permanganate until a pink color does not
disappear within 30 s. A recalculation is made per 10 cm3 of meat extract, that is, the
amount of cm3 of potassium permanganate used for titration is multiplied by 5.
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To obtain the CEC value, divide the first indicator (titratable acidity) by the
second (oxidability):
- CEC of fresh meat is 0.15–0.20;
- The CEC of ripened meat from healthy animals is 0.40–0.60;
- The CEC of ripened meat from sick animals is 0.20–0.40.
Determination of amino-ammonium nitrogen content
(according to A.M. Sofronov)
The accumulation of protein breakdown products (amino acids and ammonia)
in the muscles of sick animals occurs during life, therefore, by the amount of aminoammonium nitrogen in meat, one can judge the condition of the animal at the time of
slaughter.
The method for determining amino-ammonium nitrogen in meat is described
on p. 26 of this publication.
Benign meat of a healthy animal contains no more than 1.26 mg of aminoammonium nitrogen per 10 cm3 of extract, meat of questionable freshness —
1.27–1.68 mg, stale meat and meat from sick animals — more than 1.68 mg per
10 cm3 of extract.
Rationale for veterinary and sanitary assessment
of sick animals’ meat depending on the results of the examination
Meat and other products from the slaughter of sick animals in their raw form
pose a danger to human health or may cause the spread of infectious diseases among
farm animals. In this regard, slaughter products of forcedly killed animals are allowed
to be released from the facility only after neutralization. According to the “Rules for
the veterinary examination of slaughter animals and the veterinary and sanitary
examination of meat and meat products” (1983), during forced slaughter, regardless
of its reason, bacteriological and biochemical examinations of the meat are carried
out. If necessary, resort to toxicological analysis.
Veterinary and sanitary assessment. If, according to the results of
bacteriological and physical-chemical studies, meat and other slaughter products are
found suitable for food purposes, then they are sent for boiling or for the production
of meat loaves or canned food. The sale of meat from forced slaughter animals in
food markets is prohibited. The release of such meat and other slaughter products,
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regardless of the results of laboratory analysis, in raw form, including into public
catering networks (canteens, cafes, etc.), without prior neutralization is prohibited.
If salmonella is found in the carcass or organs, the internal organs are disposed
of, and the meat is sent for boiling, processing into meat loaves or canned food.
If E. coli is found in muscle tissue or lymph nodes, then the meat is sent for
processing into boiled or boiled-smoked sausage. When E. coli is isolated only from
internal organs, the latter are boiled and the carcasses are released without
restrictions.
If bacteria of the coccal group, as well as putrefactive microbes (especially
from the Proteus group) are detected in the deep layers of muscles or lymph nodes,
but with good organoleptic characteristics, the meat is sent for boiling or processing
into meat loaves. If organoleptic indicators indicate putrefactive decomposition of
meat and meat products, or if there is an unusual smell that does not disappear when
tested by cooking, such meat and meat products are sent for disposal or destruction.
Until the results of bacteriological examination are obtained, meat and offal
must be stored in isolated conditions at a temperature not exceeding 4 °C. If,
according to the results of a veterinary and sanitary examination, meat and other
slaughter products obtained from the slaughter of sick animals are found suitable for
use as food, then they are sent for disinfection under the following regimes.
1. The meat is boiled in pieces weighing no more than 2 kg, thickness no more
than 8 cm in open boilers for 3 hours; in closed boilers (pressure 0.5 MPa) —
2.5 hours. Meat is considered disinfected if the temperature inside the piece has
reached at least 80 °C, the color of the pork on the cut has become white-gray, and
the meat of other types of animals has become gray, without signs of a bloody tint,
the juice flowing from the cut surface of a piece of meat is colorless. By-products are
boiled under the same conditions. Internal fat and lard are melted: the temperature in
the melted fat should be brought to 100 °C, at this temperature it is kept for
20 minutes.
2. Processing into canned food. The meat of forcedly killed animals is sent for
the production of canned foods such as “Goulash” and “Meat Pate.” Cutting up
carcasses, preparing minced meat, and filling jars is carried out on separate tables,
in separate rooms or in a special shift, under the supervision of a veterinarian. Upon
completion of work, the premises, containers and equipment are disinfected.
Sterilization modes: temperature from 115 to 125 °C, sterilization duration —
40–115 minutes.
3. Processing into meat loaves is carried out in electric or gas ovens (product
weight no more than 2.5 kg, baking temperature not lower than 120 °C) for
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2–2.5 hours. By the end of baking, the temperature inside the product should not be
less than 85 °C.
4. Carcasses of birds and rabbits are boiled at 100 °C until cooked, but not less
than an hour (for salmonellosis — 1.5 hours), or fried on open baking sheets at
100 °C for 30 minutes (until ready).
Test questions and assignments
1. List the cases in which the slaughter of animals for meat is prohibited.
2. What visual signs can be used to determine the degree of exsanguination
of meat?
3. What laboratory methods for determining the degree of exsanguination of
meat do you know?
4. What biochemical indicators are determined during the biochemical study of
meat from forcedly slaughtered animals?
5. What is the pH value of the muscle tissue of sick and killed animals in the
agonal state?
6. What characterizes the acidity-oxidability coefficient of meat? What is its
significance for the meat of a healthy, sick or agonized animal?
7. What indicators are determined during bacterioscopic examination of meat?
8. Describe the smear-imprint of the meat of a sick animal.
9. What methods of detoxifying meat do you know?
10. Name the modes under which meat is cooked.
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CHAPTER 6. VETERINARY AND SANITARY EXAMINATION OF MEAT
FOR SUSPECTED PRESENCE OF FOOD TOXIC INFECTIONS
In case of a wide variety of animals and poultry’s diseases, slaughter products
are often contaminated with microorganisms that can cause specific infectious diseases
in humans, as well as food diseases, which include toxic infections and toxicoses.
Foodborne toxic infections are human diseases caused by microorganisms in
combination with toxic substances formed during their life processes (mainly
endotoxins). These are acute diseases that occur when consuming food products
containing a large number of living cells of a specific pathogen. Foodborne toxic
infections are caused by bacteria of the genus Salmonella, some opportunistic
microorganisms (Escherichia coli, Proteus), B. cereus, Cl. perfringens, etc.
Foodborne toxic infections must be distinguished from foodborne toxicoses —
diseases caused by enterally acting exotoxins that accumulate in foods as a result of
abundant proliferation of microbes. Food toxicosis can be caused by a toxin without
the participation of a microbe. Coccal microorganisms (staphylococci, streptococci),
anaerobic microorganisms (Cl. botulinum), as well as toxigenic fungi that produce
mycotoxins in products of plant and animal origin when they mold have the ability to
produce exotoxins in food products.
The purpose of bacteriological examination of meat is to confirm or exclude a
diagnosis of infectious diseases, as well as to identify microbes that cause foodborne
toxic infections and toxicoses.
Cases in which bacteriological examination of meat is carried out
Bacteriological examination is carried out in cases provided for by the “Rules
for veterinary examination of slaughter animals and veterinary and sanitary
examination of meat and meat products” (1983) and other current regulatory and
technical documentation.
Bacteriological examination of meat is carried out in the following cases:
- if acute infectious diseases (anthrax, emkar, etc.) are suspected;
- for foot and mouth disease, if single necrotic foci are found in the muscles;
- for swine fever, erysipelas, pasteurellosis and Aujeszky's disease, if there are
no pathological processes in the muscles of the carcass and in the internal organs;
- in case of necrobacteriosis, if several organs are affected and the fatness of
the carcass is satisfactory;
- with leukemia, if individual organs are affected, but no changes in the skeletal
muscles are detected;
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- with strangles (equine distemper);
- with white muscle disease and ketosis, if changes in the muscles are weakly
expressed;
- for infectious rhinotracheitis, parainfluenza-3, viral diarrhea, adenoviral
infection with the presence of pathological changes in the carcass and internal organs;
- with stachybothricosis, if there are no necrotic areas;
- with a complicated course of onchocerciasis with signs of purulent-necrotic
processes;
- for piroplasmosis, if jaundice disappears within 2 days;
- for mastitis, endometritis, parametritis of cows and sheep;
- in all cases of forced slaughter, regardless of the reasons for the slaughter;
- during septic-pyemic processes;
- in cases of poisoning of animals, suspicion of poisoning by toxic substances
of chemical or plant origin;
- for diseases of the gastrointestinal tract;
- for severe diseases of the respiratory tract and internal organs;
- in case of questionable freshness of meat and meat products in cases where a
sanitary assessment cannot be given based on the results of a veterinary examination;
- when removing the intestines from the carcass later than 2 hours from the
moment the animal was exsanguinated;
- upon detection of serous and fibrinous pericarditis in pigs;
- for extensive burns, hemorrhages with inflammatory phenomena;
- for swelling of internal organs and parts of the carcass;
- in the presence of purulent foci in the liver, kidneys, spleen, lungs;
- if contamination with salmonella and toxigenic Cocci is suspected;
- in the absence of brands, head and internal organs or a certificate from a
veterinarian;
- at the request of veterinary or sanitary authorities.
Rules for sampling meat and meat products for bacteriological analysis
Depending on the expected diagnosis and the nature of the pathological
changes, the following is sent to the veterinary laboratory for bacteriological
examination.
1. Two muscle tests; part of the flexor or extensor of the front and hind limbs, a
piece of muscle along with the fascia covering it. Sample size 8 × 6 × 6 cm.
2. Lymph nodes (at least 2): from cattle carcasses — superficial cervical, or
actually axillary, external iliac; from pork carcasses — submandibular, superficial
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cervical dorsal, axillary 1st rib and popliteal fold, together with the surrounding
connective and adipose tissue.
3. Internal organs: the entire spleen and kidney, part of the liver with a hepatic
lymph node or an emptied gall bladder. The cut surface of the liver lobe is cauterized
until a scab forms.
4. Tubular bone (to clarify the diagnosis in order to isolate a pure culture of the
pathogen).
5. When examining half-carcasses or quarters, a piece of muscle, lymph nodes
and tubular bone are sent to the laboratory.
6. When studying the meat of rabbits, nutria, and poultry, whole carcasses are
sent to the laboratory.
7. If pasteurellosis is suspected, a lobe of the lung is additionally directed, and
for listeriosis — the brain.
8. If the presence of an anthrax pathogen is suspected, an ear from the side on
which the animal lay, a lymph node from the affected area, edematous tissue, or, in
pigs, a submandibular lymph node are sent from corpses and forcedly killed animals.
9. When examining corned beef, two samples of meat are taken from different
places, the existing lymph nodes, and brine.
Samples are taken with sterile instruments. The samples are packaged
individually in parchment paper or plastic film, placed in a moisture-proof container,
and sealed.
The accompanying document indicates the name of the facility and its address,
the name and number of the sample, the type of animal, the purpose of the research,
brief pathological data, the intended diagnosis, the date of sampling, the position and
signature of the person in charge.
If it is impossible to deliver samples within 24–30 hours, they are preserved to
prevent the proliferation of microflora with a 30 % aqueous solution of glycerol.
Until the results of microbiological studies are obtained, meat and offal must
be stored in isolated conditions at a temperature not exceeding +4 °C.
Scheme of meat and meat products’ bacteriological research
Bacteriological examination of meat is carried out according to a certain
scheme. In the laboratory of veterinary and sanitary examination of markets, only
bacterioscopy of the fingerprint smear is carried out, and if necessary, the samples are
sent to a veterinary laboratory, where bacteriological examination of the meat is
carried out for three days or more.
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On the first day of bacteriological examination the following is carried out:
1) organoleptic assessment of the degree of freshness of meat samples (only
fresh meat is suitable for bacteriological analysis);
2) bacterioscopy of fingerprint smears from deep layers of meat;
3) sowing on MPB and MPA nutrient media;
4) sowing on differential diagnostic nutrient media.
On the second day:
1) taking into account growth on the MPA in order to exclude anthrax;
2) taking into account growth on differential diagnostic media (Endo’s
environment);
3) preparation of a “pure culture” suspension (“microbial suspension”);
4) morphological typing of isolated microorganisms:
a) bacterioscopy of colonies suspicious for salmonella;
b) determination of bacterial mobility in a hanging drop;
5) serological typing of isolated microorganisms;
6) sowing on “variegated row” media.
On the third day:
1) biochemical typing of Salmonella;
2) a conclusion about the nature of the microflora isolated from meat;
3) veterinary and sanitary assessment of the studied products.
Procedure and methodology for bacteriological examination of meat
in the presence of foodborne pathogens
The first day
1. Organoleptic assessment of the degree of freshness of meat (material of
questionable freshness, stale material is disposed of).
2. Bacterioscopy of fingerprint smears from deep layers of meat.
From the middle of the test sample, after burning the surface with alcohol, a
piece of material is cut out with sterile scissors and applied to the surface of a flamed
glass slide. Prepare 2–10 smears of prints from parenchymal organs, kidneys, spleen,
and lymph nodes. The preparations are dried, fixed and stained. During microscopy,
the morphological features of the microflora (shape, size, Gram stain, presence of
spores and capsules) and the number of microbial bodies in the field of view of the
microscope are determined. If gram-positive rods with chopped ends or rods with
capsules are present in the smears, the detection (bacterioscopically) of the causative
agent of anthrax is reported (preliminary response).
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