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to the smell of the layers of muscle tissue adjacent to the bones. The results of the
analysis are assessed for each carcass or part of the carcass separately and compared
with the requirements of the regulatory and technical document for a specific type of
poultry meat.
Determining broth clarity and aroma
From a sample (carcass or its part), except for the wing and neck, 70 g of
muscles are cut with a scalpel to the entire depth of the muscle tissue and, without
mixing them according to the samples, they are ground twice in a meat grinder. The
minced meat obtained from each sample is thoroughly mixed. Take a sample of
minced meat weighing 20 g, weighed with an accuracy of ± 0.1 g, place it in a
conical flask with a capacity of 100 cm3 and fill it with 60 cm3 of distilled water. The
contents of the flask are thoroughly mixed. The flask is covered with glass and placed
in a boiling water bath for 10 minutes.
The aroma of the meat broth is determined during heating to a temperature of
80–85 °C by the aroma of the vapors escaping from the slightly open flask.
The degree of transparency of the broth is determined visually by examining
20 cm3 of broth poured into a transparent cylinder.
Characteristics of organoleptic indicators of poultry meat of varying degrees of
freshness are presented in table 3.
Table 3
Organoleptic characteristics of poultry meat of varying degrees of freshness
Indicator name
Characteristics of the indicator
fresh meat
meat of questionable
freshness
stale meat
Appearance and
color:
- carcass surface
Whitish-yellow in color,
with a pinkish tint; in
lean carcasses —
yellowish-gray with a
reddish tint; in skinny
ones — gray with a
bluish tint
Sticky under the wings,
in the groins and folds of
the skin; whitish-yellow
with a gray tint
Covered with mucus,
especially under the
wings, in the groins and
folds of the skin;
whitish-yellow with a
gray tint, sometimes
with dark or greenish
spots
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Indicator name
Characteristics of the indicator
fresh meat
meat of questionable
freshness
stale meat
- subcutaneous
and internal
adipose tissue
Pale yellow or yellow
color
Pale yellow or yellow
color
Pale yellow in color, and
the inner fabric is
yellowish-white with a
gray tint
- serous
membrane of the
thoracoabdominal
cavity
Moist, shiny, free of
mucus and mold
No shine, sticky, may
contain a small amount
of mucus and mold
Covered with mucus,
possible presence of
mold
Condition of the
muscles on the
cut
Slightly damp, do not
leave a wet spot on the
filter paper; pale pink in
chickens and turkeys,
red in ducks and geese
Wet, leaves a wet spot
on filter paper, slightly
sticky, darker in color
than fresh carcasses
Wet, leaves a wet spot
on filter paper, sticky,
darker in color than
fresh carcasses
Consistency
The muscles are dense,
elastic, when pressed
with a finger, the
resulting hole quickly
levels out
The muscles are less
dense and less elastic;
when pressed with a
finger, the resulting hole
is leveled out slowly
(within 1 min)
The muscles are flabby;
when pressed with a
finger, the resulting hole
does not level out
Smell
Specific, characteristic
of fresh poultry meat
Musty in the abdominal
cavity
Putrefactive from the
surface of the carcass
and inside the muscles,
most pronounced in the
abdominal cavity
Broth clarity and
aroma
Transparent, fragrant
Transparent or cloudy
with a slight unpleasant
odor
Cloudy, with a lot of
flakes and a strong
unpleasant odor
Determining the degree of freshness of poultry meat
by laboratory methods
Only poultry meat recognized by the results of an organoleptic study as being of
questionable freshness is subjected to laboratory (biochemical, microscopic) studies.
Determination of volatile fatty acids
The analysis is carried out according to the method described on pp. 22–23 of
this publication. Fatty poultry meat is not analyzed.
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Poultry meat is considered fresh if it contains up to 4.5 mg KOH of volatile
fatty acids.
Meat is considered to be of questionable freshness if it contains VFAs
between 4.5 and 9.0 mg KOH.
Stale meat contains over 9.0 mg of KOH volatile fatty acids.
Reactions to ammonia and ammonium salts with Nessler's reagent
Putrefactive decomposition of proteins is accompanied by deamination of
amino acids with the formation of ammonia and its compounds.
Ammonia and ammonium salts are capable of forming with Nessler's reagent
(double salt of mercury iodide and potassium iodide) a substance colored yellowbrown — mercurammonium iodide.
Analysis procedure
Add 40 cm3 of distilled water to a sample of minced meat (minced meat)
weighing 10 g and leave for 15 minutes, shaking three times. The resulting extract is
filtered through a paper filter.
Add 10 drops of Nessler’s reagent to 1 cm3 of filtrate, mix and observe the
change in color and transparency of the solution.
Meat is considered fresh if the extract acquires a greenish-yellow color while
maintaining transparency or becomes slightly cloudy.
Meat is considered to be of questionable freshness if the extract becomes
intensely yellow, sometimes with an orange tint; significant turbidity is observed with
the formation of a thin layer of sediment after settling for 10–20 minutes.
Meat is considered stale if the extract becomes yellowish-orange in color;
There is a rapid formation of large flakes that precipitate.
Determination of peroxidase activity in poultry muscle tissue
To conduct the study, use an extract prepared for the reaction with Nessler's
reagent. The implementation of the research methodology and evaluation of its
results are carried out in the same way as in the study of meat from slaughtered
animals (pp. 24–25 of this publication). The reaction is not carried out during the
examination of waterfowl and chicken meat.
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Determination of acid number of fat
When conducting chemical studies of poultry meat, along with indicators
characterizing changes in proteins, the degree of hydrolysis and oxidation of fat is
assessed. In accordance with this, the acid and peroxide values of adipose tissue are
assessed in poultry meat.
The acid number of fat is expressed by the number of milligrams of potassium
hydroxide used to neutralize the free fatty acids contained in 1 g of fat.
The method is based on the titration of free fatty acids in an ether-alcohol
solution of fat with an aqueous alkali solution in the presence of an indicator. Ether
serves as a fat solvent, and ethanol is used to homogenize the system formed by an
aqueous solution of alkali and fat in the process of titration.
Analysis procedure
Preparation of fat: Take at least 20 g of internal adipose tissue, grind it with
scissors and melt it in porcelain cups in a water bath, filter through 4 layers of gauze
into a beaker and cool to a temperature of 20 °C.
A sample of fat weighing 1 g is weighed in a conical flask with a capacity of
250 cm3 with an accuracy of 0.001 g, and 20 cm3 of a neutral mixture of ethyl ether
and ethyl alcohol (2:1) containing 5 drops of a 1 % alcohol solution of
phenolphthalein is added. The contents of the flask are thoroughly shaken until the fat
is completely dissolved. If the fat has not completely dissolved, the flask is slightly
heated in a water bath while constantly stirring the solution. After cooling to a
temperature of 20 °C, the solution, constantly shaking, is quickly titrated with a 0.1N
solution of potassium hydroxide until a crimson color appears, which does not
disappear within 1 minute. In case of cloudiness, add 10 ml of a neutral mixture to
the flask, shake the contents and heat the flask slightly in a water bath until clear,
then cool to 20 °C and continue titration.
The acid number of fat (X) is expressed in cm3 of potassium hydroxide and
calculated using formula (3):
V К 5.61
Х = , (3)
М
where:
V is the amount of 0.1N potassium hydroxide solution consumed for
titration, cm3;
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K — correction to the titer of a 0.1N solution of potassium hydroxide;
5.61 — amount of potassium hydroxide contained in 1 cm3 of 0.1N solution, mg;
M is the mass of the fat sample, g.
The arithmetic mean of three parallel determinations is taken as the result. The
calculation is made with an error of no more than 0.01 mg KOH.
The results are assessed in accordance with the data presented in table 4.
Table 4
Acid number of fat, mg KOH
Fat
Meat
fresh
of questionable freshness
stale
Chilled carcasses
Chicken
up to 1
1.0–2.5
more than 2.5
Goose
up to 1
1–2
more than 2
Duck, turkey
up to 1
1–3
more than 3
Frozen carcasses
All types
up to 1
1.0–1.6
more than 1.6
Determination of fat peroxide value
The peroxide value of fat is expressed by the number of grams of iodine
released in an acidic environment from potassium iodide under the influence of
peroxides contained in 100 g of fat.
The method is based on the oxidation of hydroiodic acid with peroxides
contained in fat, followed by titration of the released iodine with sodium thiosulfate.
Analysis procedure
A sample of fat prepared for determining the acid number of fat, weighing 0.5 g,
is weighed in a conical flask with an error of no more than 0.001 g and dissolved in
10 cm3 of a mixture of glacial acetic acid and chloroform (1:1). Add 1 cm3 of freshly
prepared saturated potassium iodide solution to the solution and keep in a dark place
for 5 minutes. Then 30 cm3 of distilled water is added to the solution. The released
iodine is titrated with a 0.002N solution of sodium thiosulfate in the presence of an
indicator — starch — until the blue color disappears.
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Simultaneously, under the same conditions, a control experiment is carried out,
in which the same amounts of reagents are taken, but without fat.
The peroxide value of fat (X) as a percentage of iodine is calculated using
formula (4):
К (V — V1) 0.0002538 100
Х = , (4)
М
where:
K is the correction to the titer of a 0.002N sodium thiosulfate solution;
V is the amount of 0.002N sodium thiosulfate solution consumed for titration
of the test solution, cm3;
V1 is the amount of 0.002N sodium thiosulfate solution consumed for titration
of the control solution, cm3;
0.0002538 — amount of iodine corresponding to 1 cm3 of 0.002N sodium
thiosulfate solution, g;
M is the mass of the fat sample, g.
The arithmetic mean of three parallel determinations is taken as the result of
the analysis. The calculation is made with an error of no more than 0.01 % iodine.
The results are assessed in accordance with the data presented in table 5.
Table 5
Peroxide value of fat, % iodine
Fat
Meat
fresh
of questionable freshness
stale
Chilled carcasses
Chicken
up to 0.01
0.01–0.04
more than 0.04
Goose
up to 0.01
0.01–0.1
more than 0.1
Duck, turkey
up to 0.01
0.01–0.1
more than 0.1
Frozen carcasses
All types
up to 0.01
0.01–0.03
more than 0.03
Microscopic examination of poultry meat
The method is based on determining the number of bacteria and the degree of
breakdown of muscle tissue by microscopy of fingerprint smears.
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Analysis procedure
The surface of the hip muscles is sterilized with a hot spatula or burned with a
swab dipped in alcohol, pieces measuring 1.5 × 1.0 × 1.5 cm or 2.0 × 1.5 × 2.5 cm are
cut out with sterile scissors and surfaces. The cut surfaces are applied to a glass slide
(3 prints on two glass slides). The specimen are air dried, fixed, Gram stained and
microscopically examined.
Meat is considered fresh if no microflora is detected in the fingerprint smears
or single specimens of cocci or rods are visible in the field of view of the preparation
and there are no traces of muscle tissue decay.
Meat is considered to be of questionable freshness if no more than 30 cocci or
rods, as well as traces of muscle tissue decay, are found in fingerprint smears.
Meat is considered stale if more than 30 cocci or rods are found in fingerprint
smears, and significant tissue decay is observed.
Rationale for veterinary and sanitary assessment
of poultry meat depending on freshness
According to the “Rules for veterinary inspection of slaughter animals and
veterinary and sanitary examination of meat and meat products,” veterinary and
sanitary assessment of fresh poultry meat is carried out on a general basis.
Poultry meat of questionable freshness, after preliminary cleaning (removal
and disposal of altered areas) and, if necessary, washing, is processed into boiled
sausages or boiled.
Stale poultry meat is disposed of.
Test questions and assignments
1. Describe the rules for sampling poultry meat for research.
2. What organoleptic indicators are determined when assessing the freshness of
poultry meat?
3. What should be done with poultry meat if, according to the results of an
organoleptic study, it is found to be of questionable freshness?
4. What laboratory methods for determining the degree of freshness of poultry
meat do you know?
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5. How much VFA is contained in poultry meat of varying degrees of
freshness?
6. What characterizes the acid number of fat?
7. What are the acid number of fat for poultry meat of varying degrees of
freshness?
8. How is the peroxide value of fat measured?
9. What are the fat peroxide values for poultry meat of varying degrees of
freshness?
10. How many microbial bodies are contained in prints from deep layers of
poultry meat of varying degrees of freshness?
39
CHAPTER 4. VETERINARY AND SANITARY EXAMINATION
OF THE RABBIT MEAT
Rules for sampling rabbit meat for freshness testing
3 samples (carcasses) are selected from the batch boxes for organoleptic,
chemical and microscopic analyses. For bacteriological analyses, 3 samples
(carcasses) are taken.
Each selected sample is packaged in parchment or cling film. When sending
samples to a laboratory located outside the place of collection, the samples are placed
in a container (box, bag), which is then sealed.
Determining the degree of freshness of rabbit meat according
to organoleptic indicators
Organoleptic examination of rabbit meat involves determining and assessing
the appearance, condition of the muscles on the cut, consistency, smell, transparency
and aroma of the broth.
Determination of the appearance and color of the surface of the carcass,
subcutaneous and internal adipose tissue and peritoneum is carried out visually.
Determination of the condition of the muscles on the cut. The thigh muscles
are cut across the muscle fibers. To determine muscle moisture, filter paper is applied
to the surface of the muscle cut for 2 s.
To determine muscle stickiness, touch the surface of the muscle cut with
fingers.
Determination of consistency. On the surface of the rabbit carcass in the area
of the thigh muscles, lightly pressing a finger creates a hole. Mmonitor the time it
takes to level it out.
Definition of smell. To determine the smell of fat, take at least 20 g of internal
adipose tissue, chop it with scissors, melt it in a beaker in a water bath and cool it to a
temperature of 20 °C. The smell of fat is determined organoleptically by stirring it
with a glass rod.
The smell of the surface of the carcass and the abdominal cavity is determined
organoleptically.
To determine the smell of the deep layers of meat, a knife is used to cut the
muscles down to the bone. Particular attention is paid to the smell of the muscles
adjacent to the bone.
40
Determination of broth clarity and aroma. From the carcass, with a scalpel,
pieces of muscle weighing 25 g are cut out from the area of the thigh, shoulder blade,
back, butt and grinded in a meat grinder.
The minced meat is thoroughly mixed, weighed out 20 g, placed in a conical
flask and filled with 60 cm3 of distilled water. The contents of the flask are stirred.
The flask is covered with a watch glass and placed in a boiling water bath for
10 minutes.
The smell and aroma of the broth is determined by heating it to 80–85 °C at the
moment of the appearance of vapors escaping from the slightly open flask. The
transparency of the broth is determined visually after placing 20 cm3 of broth in a
glass cylinder with a capacity of 25 cm3 and a diameter of 20 mm.
Characteristics of organoleptic indicators of rabbit meat of varying degrees of
freshness are presented in table 6.
Table 6
Organoleptic characteristics of rabbit meat of varying degrees of freshness
Indicator name
Characteristics of rabbit meat (carcasses)
fresh
dubious freshness
stale
Appearance and
color:
- carcass surface
Has a drying crust of
pale pink color
Moistened in places,
slightly sticky, slightly
darkened
Covered with mucus,
grayish-brown in color
- integumentary
and internal
adipose tissue
Yellowish-white color
Pale yellow or yellow
color
Grayish-white color
- serous
membrane of the
abdominal cavity
Wet, shiny
No shine, sticky, may
contain a small amount
of mucus and mold
No shine, covered with
slime, mold
Muscles in
section
Slightly damp, do not
leave a wet spot on the
filter paper; pale pink
with a reddish tint
Wet, leaves a wet spot
on the filter paper,
slightly sticky, dark red
in color
Wet, leaves a wet spot
on the filter paper, sticky,
red-brown in color
Consistency
The muscles are dense,
elastic, and when pressed
with a finger, the
resulting hole quickly
levels out; dense fat
The muscles are less
dense and less elastic
than those of fresh
carcasses; when pressed
with a finger, the
The muscles are flabby,
and when pressed with a
finger, the resulting hole
does not level out; the fat
is soft, in thawed
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