Species of animals. species affiliation. Laboratory methods for establishing the species of meat

14.11.2019

3 DETERMINATION OF THE SPECIES OF MEAT

An attempt to pass off the meat of one type of animal for the meat of another type of animal, usually more valuable, is called species falsification and can take place in the markets in trading network and institutions Catering. That's why veterinarian must be able to determine the species of meat. Usually, in case of species falsification, carcasses of animals similar in size, shape and other indicators are used. So they usually try to pass off horse meat as beef and vice versa (in some countries where horse meat is valued higher), carcasses of large dogs are passed off as sheep, cats are tried to pass off as rabbits and nutrias. Objective and subjective methods are used to determine the species of meat.

Subjective methods for determining the species of meat. Subjective methods include such as configuration, morphological and organoleptic indicators of meat, etc. So, for example, during visual inspection, a horse carcass has a longer neck, a well-muscled croup, while in cow carcasses the neck is shorter than the croup, flatter, maklocks often bulge and ischial tubercles; horse meat is darker in color, although aged or poorly bled beef may be dark red, horse meat visually has whiter large and well-defined muscle fibers compared to beef.

Table 1

Species features of the structure of the bones of the cow and horse skeleton

bone	cow	horse
atlas	No rear wing openings, there is a rear wing notch	There are front and rear wing holes
Epistrophy	The odontoid process is hollow, semilunar in shape	The odontoid process is convex, chisel-shaped
sternum	Flat without a ridge, has 6 articular fossae on each side	Laterally compressed has a good pronounced crest and 8 articular fossae
Sacrum	The sacrum is flat, consists of 5 fused vertebrae, the spinous processes are located separately from each other	The sacrum is convex, fully fused, consists of 5 fully fused vertebrae, the spinous processes fuse into a solid ridge
ribs	Wide, flat, 13 pairs	Narrow, barrel-shaped in section, 18 pairs
scapula	The neck is short, the awn is high hanging over the neck, ending with an acromion, the ratio of the supraspinous and infraspinous parts is 1:4	The neck is long, the spine is low, descending to the neck of the scapula, there is no acromion, the ratio of the supraspinous and infraspinous parts is 1:3
shoulder	Has two block-shaped process and roughness instead of a swivel	It has three, block-shaped processes, and a highly developed trochanter
Radial and ulnar	The radius and ulna are the same length	The radius comes to the middle of the ulna
femoral	Processes and protrusions are smoothed, the greater trochanter is monolithic, the lesser trochanter is in the form of a blunt tubercle, the third trochanter is absent	The greater trochanter is divided into two parts, clearly defined lesser and third trochanter
Tibia	The tibia is bent to the medial side, the tibia is in the form of a rudimentary process	The tibia has a trihedral section, the fibula accompanies it to the middle
Thoracic and lumbar vertebrae	The spinous processes of the vertebrae are flat, located vertically, their upper part is directed forward.	The spinous processes end in a cone-shaped thickening and touch each other

Objective methods for determining the species of meat methods for determining the species of meat

Of greatest importance are the objective methods that must be used in drawing up official opinions. These methods include: the anatomical features of the structure of the bones of the skeleton, the melting point of fat, the glycogen content in meat, and the precipitation reaction with species-specific precipitating sera.

Determination of species affiliation by the anatomical features of the structure of the bones of the skeleton and internal organs

By any bone of the skeleton and even by its fragment, one can determine the species of meat. The main distinguishing features of similar skeletal bones in the compared animals are presented in Table. 12.

Table. 2

Species features of the structure of the bones of the skeleton of a cat, rabbit and nutria


shoulder blade	Ratio	Length ratio	Diamond shape
	length and width	and blade width	we, ratio
	shoulder blades 1:3, neck-	1:2, neck short,	length and width
	ka long, awn	awn is high, navi-	shoulder blades 1:1, spine
	low,	sits over the neck,	low, acromion
	branches into	offshoot	long starts-
	two parts	ed and directed	Xia from the middle third
		way down	shoulder blades
femoral	Has a large	Has one pain	Has a large and
bone	lesser and third trochanter	shoy skewer	lesser trochanter third missing
Tibia	The fibula is rudimentary	Tibia and fibula	Tibial and peroneal braids
	tiirovana and coalesces with pain	connected movably by articular	they are connected by movable articular
	tibial ending in its upper third	surfaces, the tibia is much thicker than the fibula	surfaces, the tibia and fibula are almost the same thickness.
Sacrum	Long, consists of four vertebrae with high separate spinous	Short with three low cones different processes at the ends	Consists of four massive vertebrae with separate spinous processes
	processes

When determining small meat cattle and dogs should take into account the fact that the bones of small cattle in their shape resemble those of a cow.

According to the anatomical features of the structure of the internal organs, it is also possible to accurately determine the species of meat and slaughter products.

The liver of a cow is massive, convex-concave in shape, dark brown in color, lobulation is weakly expressed, on the right, on the ventral side, there is an interlobar notch in which the gallbladder is located. In a horse, the large liver is clearly divided into three lobes, the right lobe is separated from the middle one by a deep notch, and the left one is separated from the middle one by a round ligament, the gallbladder is absent. The dog's liver is larger than that of small cattle, divided into seven lobes. The lungs of a cow have a clear mesh pattern, are clearly divided into cranial, medial and caudal lobes, the cranial anterior lobe is divided into two halves, there is an additional lobe in the right lung. In the horse, the lobulation of the lung is weakly expressed, the sharp edge of each lung has a gentle interlobar fissure separating the caudal lobe from the cranial lobe. In dogs, unlike sheep and goats, the mesh pattern on the lungs is invisible, and the lobes of the lungs are separated by deep interlobar fissures that go all the way to the bronchi.

The kidneys of a cow consist of 16-18 lobes. In horses, the kidneys are single-papillary, the left one is oblong or bean-shaped, and the right one is heart-shaped.

The spleen of a cow is flat, elongated, with rounded edges. The horse has a flat crescent-shaped spleen. The anterior margin is concave and pointed, the posterior margin is convex and obtuse. In a dog, the spleen is flat, irregularly triangular in shape, its lower end is expanded, and its upper end is narrowed.

The heart of a cow has a sharper apex than that of a horse; in addition, the wall of the left ventricle of a horse is 2.5 times thicker than that of the right one. The heart of sheep and goats has a pointed top, while dogs have a rounded heart.

The tongue of a cow has a thick end pointed, in the middle third there is a roller-like thickening, an oval-shaped epiglottis. The horse's tongue is longer and flatter, its end is rounded, the epiglottis is rounded. In dogs, unlike small cattle, the tongue is wide, flat, with pointed edges; on its upper surface there is a median furrow.

Determination of the melting point of fat The melting point of fat is strictly individual for animals of different species and therefore is an objective indicator for determining the species of meat. Moreover, this indicator in the compared animal species differs by 1.5-2 times, which significantly facilitates the diagnosis.

Statement of the reaction The studied fat is melted and collected in transparent glass capillaries with a diameter of 1.5 mm. The height of the fat column should be 5-7 mm. Capillaries with fat will be placed in the refrigerator for 1-2 hours. After cooling, the capillary with fat is fixed with a rubber band on the thermometer in such a way that the column of fat is at the same level with the head of the thermometer. After that, the thermometer, together with the capillary, is fixed on a tripod and lowered into a transparent beaker filled with water and standing on an electric stove so that the upper part of the capillary is above the water surface (see Fig. I). Then they begin to heat the water by stirring it with a glass rod. Heating is continued until the column of fat becomes transparent and under the pressure of water begins to rise up the capillary. At this point, take the thermometer reading. The measurement is repeated five times and the arithmetic mean is found. The result obtained is considered the melting point of the studied fat. The melting temperature of the fat of some mammals and birds is given in Table. 3.

Determination of glycogen content in muscles

In the meat of the compared animals, the content of glycogen differs by 2-3 times. So, for example, the content of glycogen in the meat of horses, dogs and cats is significantly higher than in the meat of cows, small cattle and rabbits, which makes it possible to use a qualitative reaction for glycogen to determine the species of meat. However, it should be remembered that the glycogen content is not constant and depends on the state of the animal at the time of slaughter, the conditions of maturation and the duration of storage of meat.

Statement of the reaction

A sample of the studied meat is taken, crushed to the state of minced meat, poured with distilled water in a ratio of 1: 4 and boiled in a flask for 30 minutes. The broth is filtered through a paper filter and cooled. Take 5 ml of broth into a test tube and add 5-10 drops of Lugol's solution.

Reaction accounting

With a positive reaction (typical for a horse, dog and cat), the contents of the test tube turn cherry red or lilac.

With a doubtful reaction (it happens in cats), the color will be orange

With a negative reaction (typical for cows, sheep and goats), the contents of the test tube will be yellow.

Precipitation reaction with species-specific sera

The reaction with species-specific precipitating sera is one of the most accurate methods for identifying the species of meat. With the help of this reaction, it is possible to investigate not only meat, but also minced meat and even semi-finished products and determine the addition of meat from another type of animal to these products.

Statement of the reaction 4z of the studied meat, minced meat, semi-finished products, an extract is prepared. To do this, a sample of the product is crushed to the state of minced meat and poured with 0.9% sodium chloride solution in a ratio of 1:1 and extracted for 3 hours, after which it is filtered through a paper filter (the extract should be transparent).

Melting temperature of animal fat of different species


Kind of animal	T ° C melting external fat	1°С melting internal fat
Cattle	48	49,5
Horse	28,5	31,5
small cattle	49,5	54
Dog	23	27
Pig	37,5	45,5
Deer	48,5	52
Camel	36	48
Bear	32	30
Rabbit	26	22
Cat	39	42
Nutria	36	37
Human	22	21
Goose	29	34
Chicken	33	40

Optimal for setting up the reaction is the ratio of protein and extract1:1000.

To set up the reaction, three rows of Ulengut test tubes are placed in a rack. Using a pipette, 0.9 ml of the studied extract is collected into the test tubes of the first row, 0.9 ml of 0.9% sodium chloride solution into the test tubes of the second row, and 0.9 ml of standard sera into the test tubes of the third row. various kinds animals having the same dilution as diagnostic precipitating sera. Then, 0.1 ml of diagnostic serum precipitating with the protein of this animal species is added to each of the three test tubes using a Pasteur pipette.

Reaction accounting

Accounting for the reaction is carried out after 10 minutes. The reaction is considered reliable if the contents of the tube with saline remain clear, and a precipitating ring forms in the tube with standard serum.

If the same ring is formed in a test tube with the extract under study, then the reaction is considered positive, and the species of meat is established. If the contents of this tube remain clear, the reaction is considered negative and studies are continued with sera from other animal species.

Organization and methodology of post-slaughter veterinary and sanitary examination of carcasses and internal organs of agricultural and wild game animals (birds)

Certificate in form No. 2, without which the products are not allowed for inspection and sale. Help is not valid. Veterinary and sanitary examination on the market is subject to: - meat of slaughtered farm animals of all kinds, including poultry and rabbits, as well as meat of wild game animals and game birds in a cooled, chilled, frozen or salted form (internal organs and other offal ...

Meat and offal of animals bitten by snakes, tarantulas and scorpions are also released for food without restrictions, but those tissues into which the poison has penetrated are removed. 4. Features of the veterinary and sanitary examination of meat and meat products in food markets (documentation, delivery rules, inspection sequence and research methods). Veterinary sanitary examination of carcasses and internal organs is carried out by...

... ; 3) control the quality of products entering the market; 4) prevent the spread of infectious and parasitic diseases through livestock products. Veterinary and sanitary examination and technology of livestock products as academic discipline also considers issues of hygiene and technology food products and raw materials of animal origin (meat, ...

Definition specific belonging to blood - the solution of the question of its belonging (to an animal or a person). Determining the type of blood is a prerequisite for subsequent research to determine blood groups and the possibility of its origin from a particular person. Such a study also allows you to check the suspect's version of the origin of blood on clothes and crime instruments from a particular animal. Establishing the fact of the origin of blood from a particular animal or bird can also be an independent study in case of poaching, an air accident, and under other circumstances.

Rice. 93. Reaction Chistovich.
Left - positive; on the right is negative.

The type of blood is determined using the precipitation reaction. This reaction involves hood from the spot (blood proteins - antigens) and precipitating serum(antibodies), capable of reacting only with a protein of a person or a certain animal - a horse, dog, pig, cattle, etc. The specific interaction of species antigens and antibodies is manifested by precipitation (precipitate). The expert establishes with which of the sera introduced into the reaction a precipitate is formed, and on the basis of this determines the type of blood in the stain. For control, experiments are also performed with extracts from an object outside the blood stains (Fig. 93).
The precipitation reaction is very sensitive. Its result depends largely on the state of blood proteins, mainly their solubility. Therefore, improper handling of physical evidence, in particular, drying them at high temperatures, can lead to the transition of blood proteins into an insoluble state, which prevents their type from being established. Sending wet clothing with traces of blood leads to its decay and denaturation of proteins, which also makes it impossible to determine the type of blood.

Rice. 94. Precipitation reaction in agar (explanation in the text).

Reaction precipitation is usually carried out in test tubes with a thin end. An extract from the test spot is first placed in them, and then the precipitating serum is lowered to the bottom of the test tubes with a pipette. With a positive reaction, a precipitate forms in the form of a disc-shaped turbidity at the interface between the serum and the extract. The absence of sediment in the control tube with an extract of the carrier object allows in such cases to draw a conclusion about a certain type of blood in the test spot. A negative result of the precipitation reaction when using all precipitating sera may be due to the destruction or insolubility of blood proteins, its insufficient amount, or the presence of the blood of any other animal. In such cases, they resort to concentration of extracts and the use of more sensitive methods for determining specific blood accessories - precipitation reactions on special paper for chromatography, precipitation reactions in agar, methods of electroprecipitation, etc. The precipitation reaction in agar is also used in cases where the turbidity of the extract prevents the study in a liquid medium. A layer of molten agar is poured onto the glass, after it solidifies, recesses are made in it, into some of which an extract from the stain is placed, and into others - precipitating serum. They diffuse into the agar and when the extract (antigens) and the precipitating serum meet, if they are homologous, a precipitate is formed in the form of a whitish band. If a hood and serum heterologous, no precipitate is formed (Fig. 94).
To distinguish the blood of humans and animals (according to the content of a number of inorganic elements), the method of emission-spectrum analysis can also be used. Currently, in order to increase the sensitivity and resolution of the precipitation reaction, a laser indicator is used as a recorder of the formation of a precipitate. The method allows you to determine the type of blood in mixed and hardly soluble stains, in traces of blood on contaminated carrier objects.
Currently, to determine the type of blood, the immunofluorescence method is also recommended, in which agglutinating serum is combined with fluorochrome. In the case of a positive result, when examining the object in ultraviolet rays, a glow is visible with a color corresponding to the fluorochrome, with which the serum was previously combined.

System solutions for species identification of meat and fish products

STYLAB offers the SureFood® test systems for identifying the species of animals whose meat has been used to make food.

Animal species must be determined in order to prevent or establish the fact of falsification of more expensive types of meat with cheap ones, as well as to contaminate meat products that do not contain (not allow, in accordance with the standards) meat in general or meat of certain types of animals. Many of these situations are related to forensic veterinary expertise. First of all, this is the falsification of meat and fish products, including violation of the requirements for kosher and halal products (in particular, such products should not contain pork). Adding cheap varieties of meat (fish) to products or replacing raw materials with those similar to those declared in terms of visual and taste qualities is called assortment falsification.

Assortment falsification allows you to reduce the cost of production and thereby increase profits. However, it is a violation of consumer rights and can exacerbate allergies and other diseases. In addition, raw materials for falsification are often of dubious origin, do not pass veterinary control and may contain pathogens of dangerous diseases.

Permissible standards for the content of third-party varieties of meat (fish) in food products does not exist. This necessitates the use of highly sensitive techniques. qualitative analysis. Anatomical definition is considered the most accurate method for determining species. To do this, the specialist evaluates the structure of the bones of the animal. However, this is not always possible, especially when analyzing finished products, semi-finished products, minced meat and fish. In addition, an unscrupulous manufacturer can get rid of the bones. Methods such as determining the melting point and solidification of fat, density, refractive index, glycogen content and iodine number, as well as the analysis of the organoleptic properties of the product, do not always have sufficiently high accuracy. The precipitation reaction, based on the interaction of precipitating serum with antigen, is accurate and allows the analysis of even thermally processed or salted products, but it requires a set of sera. Moreover, this method is labor intensive.

Currently, one of the most sensitive methods for determining species is DNA analysis by real-time PCR (real-time PCR). With proper sample preparation, it can be used to analyze both raw materials and raw products, as well as semi-finished products and processed products.

Another area of application of this method is the analysis of animal feed. In connection with, among other things, “mad cow disease”, many countries have adopted a legislative ban on the presence of impurities in ruminant tissues in feed for ruminants.

Currently, immunochemical methods are being developed for the analysis of the species of feed, food raw materials and finished products. One of these methods is enzyme immunoassay. Test systems are designed for the analysis of feed and bone meal. With the help of test systems, impurities in raw materials and finished products are analyzed. The technique is based on the interaction of species-specific proteins in the sample with antibodies to them.

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Hosted at http://www.allbest.ru

1. Determination of the species of meat

The veterinarian and sanitary doctor has to determine the species of meat in case of falsification, theft, poaching. In order to establish the species affiliation of slaughter products, organoleptic, chemical and microbiological research methods are carried out.

Organoleptic research methods.

Meat obtained from animals of various species has a characteristic color of muscle and adipose tissue, as well as a certain configuration of the carcass.

Meat is identified by type, sex, age, fatness and thermal state of a warm-blooded herbivore.

Depending on the type of slaughtered herbivore, there are: beef, pork, lamb, goat meat, horse meat, venison meat, rabbit meat, meat of wild animals, etc.

By gender, beef meat is divided into meat: oxen, cows, bulls.

By age, cattle meat is divided into: beef from adult cattle (cows, oxen, heifers over three years old, bulls), beef from first-calf heifers, beef from young animals (bulls, heifers) and veal (from two weeks to three months) .

Identification signs of meat of oxen and cows. It has a color from bright red to dark red, a fine-fibrous structure of muscle tissue, deposits of subcutaneous and intermuscular fat. Marbling of meat is especially pronounced in meat breeds livestock. The color of fat is from white to yellowish (depending on age).

Identification signs of meat of young animals. It has a pink-red color, a delicate, fine-fibered structure, marbling is weakly expressed. In some areas, there may be deposits of subcutaneous fat - white, dense, crumbling consistency.

Identification signs of veal - has a color from pale pink to grayish-pink, delicate texture, fine-fibrous muscle structure. Marbling is absent.

Pork is divided by age into pig meat (from 1.3 to 12 kg), gilt meat (12-34 kg) and pork (more than 34 kg).

The meat of young pigs has a pale pink or gray-pink color, middle-aged pigs are pale red and old pigs are red. The texture is soft, fine-grained. Fat is white, soft.

Lamb of young animals has a light red color, delicate texture, fine-grained muscle tissue. The meat of old animals is brick-red in color, coarser in texture, with a pronounced specific smell. The fat is white, refractory, crumbly.

Goat meat differs from lamb in a more elongated dorsal part of the carcass. The bones of the pelvis and the chest part are narrower, the withers are pointed, the neck is long, the color of the meat is brick red. It has a strongly pronounced specific smell. Goat meat is fried and stewed.

Horse meat has a dark red color of meat with a bluish tinge, muscle tissue is coarse-fibred, without marbling, there are no deposits of subcutaneous fat. The taste of meat is sweetish. The fat is yellow, more fusible than beef. The most valuable is the meat of foals (under the age of one year).

Rabbit meat has a color from white to pink, delicate texture, fine-grained structure. Fat in a significant amount is deposited in the abdominal cavity.

Public catering enterprises also receive meat from wild animals - bears, wild boars, elks, hares, etc. The color of the meat is dark red, the consistency is dense, tough. Fat is most often deposited in the kidney area, there is almost no subcutaneous and intermuscular fat. It has a specific smell and taste, depending on the feed of the animal.

The basis for identifying meat by fatness is the degree of development of muscle tissue and the deposition of subcutaneous fat.

Beef, lamb, goat meat, rabbit meat are divided into categories I and II according to fatness.

Category I beef has satisfactorily developed muscles; the spinous processes of the dorsal and lumbar vertebrae, ischial tubercles and maklaki stand out not sharply; subcutaneous fat covers the carcass from the eighth rib to the buttocks, significant gaps are allowed, the neck, shoulder blades, front ribs, thighs, pelvic cavity and groin area have fat deposits in the form of small areas.

In young beef, the muscles are well developed, the shoulder blades are without depressions, the hips are not pulled up, the spinous processes of the vertebrae, ischial tuberosities and maklaks slightly protrude Carcass weight (in kg): from selected young animals - over 230,

1st class - over 195 to 230; 2nd class - over 168 to 195; 3rd grade - 168 or less.

Category II beef has less satisfactorily developed muscles (thighs have depressions); spinous processes of the vertebrae, ischial tuberosities and maklaki protrude, subcutaneous fat is present in the form of small areas in the area of the ischial tuberosities, lower back and last ribs

In young animals, the spinous processes of the vertebrae, ischial tuberosities and maklaki protrude distinctly.

Category I veal (from dairy calves) has satisfactorily developed muscles of pink and milky color. Fat deposits in the region of the kidneys, pelvic cavity, on the ribs and in some places on the thighs, the spinous processes of the vertebrae do not protrude.

Category II veal (from fed calves) has less satisfactorily developed muscles, fat deposits in the kidney and pelvic cavity, in some places on the lumbosacral part, spinous processes of the dorsal and lumbar vertebrae slightly protrude.

Category I lamb has satisfactorily developed muscles, the spinous processes of the vertebrae in the back and withers slightly protrude, subcutaneous fat covers the carcass with a thin layer on the back and slightly on the lower back, on the ribs, in the sacrum and pelvis, gaps are allowed.

Category II mutton has poorly developed muscles, the bones protrude noticeably, on the surface of the carcasses in some places there are slight fat deposits in the form of a thin layer, which may be absent.

Pork fatness is divided into five categories:

I (bacon), II (meat - young animals), III (fatty), IV (for industrial processing), V (meat of pigs).

Category I pork (bacon) has a well-developed muscle tissue, especially on the dorsal and hip parts. The mass of carcasses in the skin in the paired state should be from 53 to 72 kg. The thickness of the fat above the spinous processes between the 6th and 7th dorsal vertebrae should be between 1.5 and 3.5 cm, not counting the thickness of the hide.

Category II pork (meat - young animals) includes carcasses of meat pigs (young animals) in the skin weighing from 39 to 86 kg; carcasses without skin weighing from 34 to 76 kg; carcasses without croup weighing from 37 to 80 kg. The thickness of the bacon for all carcasses should be from 1.5 to 4.0 cm. Carcasses of gilts in the skin weighing from 12 to 38 kg and without the skin weighing from 10 to 3.3 kg, with 1.0 cm thick bacon and more and trimmed pork.

Category IV pork (for industrial processing) includes carcasses in the skin weighing more than 86 kg, carcasses without skins; weighing more than 76 kg and carcasses without croup weighing more than 80 kg. The thickness of the bacon for all carcasses should be from 1.5 to 4.0 cm. Carcasses in the skin are worked out with the hind legs.

The color of meat cooked in water has two types: white and gray. This color, of course, will vary in its shades, and although in practice it has a modest recognition value, it still allows you to sharply distinguish animal meat into two types: white and gray.

Typical white meat comes from pigs, calves, and fish; then many kinds of birds (hens, mainly on the chest).

Gray meat is given by: cattle, horses and other animals, not excluding game. Thus, we see that the color of cooked meat makes it possible to divide animals into groups (group trait), but does not at all make it possible to distinguish the meat of individual genera of animals from each other.

The color and structure of muscle tissue are not sufficiently reliable indicators of the species of meat, since they change depending on the sex, age, fatness of the animal and other reasons. This indicator varies widely within one animal species and significantly depends on the age of animals, breed, sex, conditions of keeping, exploitation and feed ration. This feature is not a sufficiently reliable criterion.

Beef: Meat from calves up to 6 weeks of age has a pale pink color.

meat of young animals up to 1-2 years of age - light raspberry color

meat of cows and oxen aged 2-7 years - bright red color with

pronounced "marbling". The meat of old animals (over 7 years old) is red or dark red. Meat of bulls - dark red color, "marbling" and subcutaneous fat is absent.

Mutton: the meat of young animals has a reddish color; the meat of adult animals is from light red to red, sometimes to brick red; the meat of old sheep is dark red.

Goat meat: The meat has a brick-red color, darkens in the air. The meat of wild goats is darker in color.

Pork: The meat has a pink or rose-red color in different parts of the carcass. Uncastrated boars have dark red meat.

Horse meat: the meat of foals up to one year of age is red. The meat of young animals (up to 3 years of age) is red or dark red in different parts of the carcass; the meat of adult animals is dark red, sometimes with a purple tint. The meat of working horses has a darker color. In the air, horse meat tends to acquire a black-red color with a bluish tint.

Venison: The color of meat can vary from pale to intense red, depending on the age of the animal (the older the animal, the more intense the color), often the meat has a bluish tint.

Buffalo meat: It has a dark red color, on the cut the meat has a purple hue and shine. After cooling, the color intensity decreases. Camel meat: the meat has a dark red color Elk meat has a dark red color with a purple tint. Rabbit meat - pale pink meat The meat of well-fed animals is almost white

The hare has a dark red color. Sobachina (meat of dogs) is red or dark brick in color to dark brown. Nutria meat is pale pink in color, appearance resembles a rabbit. Bear meat has a dark red color with bluish connective tissue is poorly developed.

2. Determination of the species of meat by the appearance and structure of the hair

This is an insufficiently accurate method of differential diagnosis of meat from different animal species, but in the presence of reference material and established hair samples, it allows you to obtain reliable results. Hair examination is carried out by macroscopic and microscopic examination of the hair shaft.

Macroscopic examination determines the shape, length, color, and type of hair. To determine the color, a contrasting background is used: dark ones are examined on a light background, light ones on a dark one.

According to the structure, the hair is divided into 3 types: integumentary, long and sensitive (sinuose). Integumentary hair is divided into vellus, woolly and bristly (guard hair). Vellus hair is developed in fine-fleeced sheep and fur-bearing animals, in other animals they are found in the form of an undercoat. Woolly hair is distributed throughout the body. They are soft and not long. Bristly - rough and hard. Long hair is relatively thick and coarse, forming bangs, mane, brushes and tail. Sensitive hair is developed on the lips, cheeks, chin and around the eyes.

Microscopic examination is the main method of hair examination. With its help, the structure of the hair, the pattern of the cuticle are established, and a comparative study is carried out. In the hair shaft, the cuticle (the outer scaly layer of the hair), the cortical layer (the thickest, containing long cells with pigment) and the core are determined.

Method of microscopic examination of hair.

The contaminated hair is washed with warm soapy water and dried with filter paper. After that, the hair is clarified by placing it in one of the liquids: turpentine, xylene, benzene, glycerin, Canadian balm and lactic acid. The hair treated in this way is placed on a glass slide, 1-2 drops of glycerin are applied, a cover slip is placed and examined under a low magnification microscope.

Microscopically, the cuticle is a series of flat transparent cells (scales) devoid of pigment, which are located in a tile-like manner and cause the serration of the optical edge of the hair. The bulk of the hair is the bark. It consists of keratinized spindle-shaped cells interspersed with pigment grains. Depending on the location of these cells different types animals have different bark striations. Pigment grains along the length of the hair can be arranged in the form of thin or coarse strands, clumps or chains, clusters in the form of strokes, giving the hair a “spotted” look.

The core (medulla) - is not always noted. The medulla is poorly developed in woolly hair, may be completely absent in vellus hair, and is very well developed in bristly hair. The core of the hair contains air bubbles, therefore, under microscopic examination, it has a black appearance, in transmitted light it looks transparent and colorless. When determining the type of animal to which the hair belongs, attention is paid to the size and location of the cells of all layers of the hair shaft, the results obtained are compared with reference material.

response to glycogen.

In the ripened meat of various animals, glycogen is contained in the following quantities: beef - 0.2-0.3% (approximately the same amount in lamb and pork), horse meat - about 1, dog meat - about 2, cat meat - - about 0.5%. Therefore, the reaction for glycogen is used to distinguish lamb from dog meat and horse meat from beef.

The course of determination: a sample of meat (15 g) is crushed in a mortar with scissors, transferred to a flask and 60 ml of distilled water are added. The meat sample may be larger or smaller, but the ratio of meat to water should be 1:4. Bring the contents of the flask to a boil and boil for 30 minutes. The broth is filtered through a paper filter and cooled.

Pour 5 ml of the filtrate into a test tube and add 5-10 drops of Lugol's solution.

With a positive reaction, the broth turns cherry red.

with negative - in yellow, with doubtful - in orange.

The meat of a dog, horse, camel, bear and cat in most cases gives a positive reaction to glycogen (extract from cat meat can also turn orange).

The meat of sheep, goat, cattle, rabbit and pig for glycogen gives a negative reaction.

It should be borne in mind that the meat of young animals of all kinds gives a positive reaction to glycogen, but the meat of old and sick animals, as well as taken from the head and neck area, as a rule, gives a negative reaction to glycogen.

Some distinguishing features of the meat and internal organs of horses and cattle

Index
		cattle

First cervical vertebra Epistropheus	On the wings there is a transverse hole. The dentate process is chisel-shaped.	There is no transverse opening on the wings. The odontoid process is semicylindrical.
Thoracic vertebrae	The body is short, spinous processes with thickened ends. Number of vertebrae - 17-19	The body is long, spinous processes without thickenings, lamellar. Number of vertebrae - 13
breast bone	Compressed laterally. On the ventral surface there is a keel-shaped cartilaginous ridge (falcon)	Compressed dorso-ventrally, the crest is absent.
	The crest of the scapula gradually passes into the neck	At the cervical scapula, the ridge forms a strong protrusion (Acromion)
Brachial bone	At the upper end there are three bony tubercles and a double intertubercular groove.	At the upper end there are two bony tubercles and a single intertubercular groove.
Ulna and radius	The ulna is short, ending at the level of the upper third of the radius. The body is long, the spinous processes are without thickening, lamellar. Between them there is one interosseous space	The ulna is long, the same length as the radius. Between them there are two interosseous spaces.
	Narrow, evenly wide.	Wide, strongly expanding downwards.
Femur	The proximal end has a forked greater trochanter	The greater trochanter is not bifurcated
	Consists of the tibia and fibula	Consists of the tibia (the fibula is rudimentary)
sacrum	The spinous processes are not fused	spinous processes fused along the middle ridge
Cutting tubular bones	Tubular bones with bony crossbars	Tubular bones without bony bars
	Narrow, long, there may be fat deposits in the upper part	Wide, short, no fat deposits in the upper third of the neck
	Convex
meat color	Dark brown with a bluish (violet) tint
fat color	intense yellow	Light yellow to yellow
Fat consistency at +20°С

Some Distinguishing Characteristics of Sheep and Dog Meat

Index


First cervical vertebra	With thick wings	With thin, strongly divergent wings, instead of a wing hole, there is a wing notch.
epistropheus	Tooth-like process of a chisel-shaped form	Dentoid process of cylindrical shape
Thoracic vertebrae	The vertebral bodies are long	The vertebral bodies are short, the caudal vertebral notch is clearly expressed
	triangular shape	Anterior edge arched
		hoop-shaped
Lumbar vertebrae	Number of vertebrae 6, transverse costal processes directed horizontally	Number of vertebrae, transverse costal processes directed cranioventrally
Brachial bone	Flattened laterally, the lateral tubercle hangs over the medial one, forming an almost closed ring	Curved S-shaped, lateral and medial tubercles are poorly developed
sacrum	Long, consists of 4 fused vertebrae	Short, consists of 3 fused vertebrae
	Consists of 1 bone (the fibula is rudimentary)	Consists of 2 bones
	Thin, long
meat color	Light red to dark red	Red, dark brown
fat color		grayish white
Fat consistency at +20°С	Dense, crumbles between fingers	Soft, melts between fingers

outdoor
internal
Iodine number of fat

Some distinguishing features of rabbit and cat meat

Index


First cervical vertebra	The wing opening is located under the wing of the atlas	The wing opening is located on the wing of the atlas, from above
Thoracic vertebrae	Spinous processes high	Spinous processes low
breast bone	6-7 separate, the handle ends bluntly	9-split, the handle ends sharply
	The length is twice the width, the acromial process is divided into two parts	The width is twice the length, the acromial process is elongated, straight, not bifurcated
Brachial bone	Deltoid roughness is well defined at the proximal end	Deltoid roughness is absent
Lumbar vertebrae	The mastoid processes have protrusions at the ends, directed forward	The mastoid processes terminate sharply
sacrum	Long, with high spinous processes	Short, with low cone-shaped spinous processes
Femur	Large and small skewers available	There is only a large skewer
Fibula	Free in the proximal third, and then merges with the tibia.	Free throughout.
Fat melting point, °C:
outdoor
internal
Refractive index of fat at +20°С

meat glycogen fat

3. Determination of the melting point of fat

Melted and filtered fat of the test sample is collected into a clean dry glass capillary with a diameter of 1.4-1.5 mm. The length of the column of fat in the capillary should be about 20 mm. Capillary for complete solidification of fat in it is kept for 1-2 hours in a household refrigerator or on ice. After cooling, the end of the capillary tube filled with fat is cut off (break off), leaving a column of fat at least 5 mm long. The capillary is attached with a rubber ring to a chemical thermometer in such a way that its end, filled with fat, is turned up, and free from fat - down. A thermometer with a capillary is placed in a test tube (diameter 20-25 mm) and fixed in it with a stopper with a hole for the thermometer. The thermometer should not touch the walls of the test tube. The test tube is fixed in a tripod, lowered into a glass of water, while the water level in the glass should be above the upper end of the capillary. The water in the glass is slowly heated and on a dark background, through a magnifying glass, the thermometer reading and the state of the fat in the capillary are observed. The reading of the thermometer at the moment when the fat begins to flow down the capillary and free space forms in its upper part is noted as the melting point of the fat. The determination is carried out twice and the result is the arithmetic mean of the two tests, they should not differ by more than 0.5 ° C.

Determination of the pour point of fat.

The pour point is the highest temperature that remains constant for a short time during the transition of fat from a liquid state to a solid state. The pour point depends on the chemical composition of the fat and is used not only to assess the degree of purity of fats, but also to roughly determine the species. The test fat is melted in a water bath, filtered, dried and poured into a test tube. The fat temperature should be 12-15°C above the expected pour point. The test tube is closed with a stopper, into which a thermometer with a scale divided into fifths or tenths of a degree is inserted. The thermometer is strengthened so that its mercury ball is in the middle of the fat layer and does not come into contact with the walls and bottom of the test tube.

The test tube is fixed in the throat of a glass jar so that it does not touch the bottom; the jar is immersed in a vessel with water and ice.

The melted fat is stirred with a thermometer until it cools evenly. After the loss of fat transparency, the thermometer is left alone and a drop in temperature is noted every 2 minutes.

From the moment of crystallization of fat, the drop in temperature slows down, then it can stay at the same level or increase slightly and fall again. Since fats are not pure substances, their pour point is unstable.

The maximum reading of the thermometer observed during the crystallization of fat is taken as the temperature of its solidification.

Determination of the refractive index (refraction) of fat.

The studied fat must be in a liquid state, so dense animal fats are melted. The determination is carried out using various refractometers. Light-refractive properties (refraction) of fat depend on the amount of triglycerides contained in it, saturated and unsaturated fatty acids.

First, the refractometer is set to distilled water (n = 1.333). The refractive index of fat is found at a temperature close to its melting point. If the melting point is above 20°C, then the refractive index is recalculated according to the formula n 20°C = n + (TC - 20°C) * 0.00035, where n 20°C is the refractive index at 20°C; n is the refractive index at the temperature under study; (TC - 20°C) - temperature difference; 0.00035 is a constant value.

A drop of the studied fat is applied to the lower prism of the refractometer. An illuminator directs a beam of light into an illuminating prism. Observe through the eyepiece.

The division of the scale is set through which the border of chiaroscuro passes - this will be the refractive index of the studied fat.

Determination of the iodine number of fat.

By the value of this indicator, the predominance of saturated or unsaturated fatty acids in fat is judged. The more unsaturated fatty acids a fat contains, the higher its iodine value.

Refractory fats have a low iodine number, low-melting fats - high, therefore, by the value of the iodine number, one can roughly determine its species.

precipitation reaction.

With the help of the precipitation reaction, it is possible to recognize the species of meat even in cases where it has undergone salting, freezing or heat treatment.

The titer of precipitating sera is preliminarily established and their specificity is determined. The serum titer is checked as follows: serial dilutions of 1:100, 1:1000, 1:5000, 1:10000 and further are made from the normal blood serum of a certain animal (depending on the titer indicated on the ampoule label). Dilutions are made in small test tubes (more convenient with a tapering end). To 0.9 ml n. Serum in the indicated dilutions is added with a Pasteur pipette to 0.1 ml of precipitating serum. Layering can be done with one pipette, starting with the minimum dilution. The specificity of precipitating serum is determined in the same way, but with sera from different animals.

Precipitating serum is considered suitable if it has a titer of 1:10000. that is, it precipitates the serum protein of the animal of the species for which it is made, in a dilution of 1: 10,000 for 10 minutes and does not precipitate with the sera of other animal species in dilutions of 1: 1,000 for 1 hour.

First prepare the studied extract (extract). The sample of the studied meat is carefully freed from fat and connective tissue, finely ground in a porcelain mortar, placed in a wide test tube. Then the contents of the cork are poured with saline so that it covers the meat with a layer of several millimeters. The tube is not shaken. Raw meat is extracted for 3 hours, dried (dried) and boiled - 24 hours After that, the extract is sucked off with a pipette and passed through a sterile paper filter or centrifuged until completely transparent.

The concentration of protein in the extract should be approximately 1:1 000. This is determined as follows: a glass capillary about 10 cm long is lowered into the extract, and the latter, due to capillarity, rises along the tube (not completely). Then the same capillary is introduced obliquely into concentrated nitric acid poured onto a watch glass. Nitric acid, like the extract, enters the capillary. At the point of contact of liquids in the capillary, a protein precipitate forms in the form of a white ring. If the precipitate is thick and massive, then the extract must be diluted with saline and the test repeated again. This is done until the white ring of coagulated protein is barely visible. The complete absence of sediment when setting up a capillary test indicates that the protein concentration in the extract is less than 1: 1000. With such an extract, the reaction can be set, since the titer of precipitating sera is higher than I: 1000.

Definition progress. Prepare 4-7 rows of small tubes, three tubes in a row. In the first tubes of each row, 0.9 ml of the extract from the test meat is poured, in the second - 0.9 of physiological saline, and in the third - the same volume of normal sera of various animals. Serums are taken in a dilution of 1: 1000.

In all three test tubes of the first row, 0.1 ml of serum, precipitating cow protein, are added with various Pasteur pipettes, 0.1 ml of serum, precipitating horse protein, in test tubes of the third row, 0.1 ml pig serum, in test tubes of other rows - for the same amount of sheep, goat and dog serum.

The reaction is read against a dark background. A positive reaction is the appearance at the site of contact of liquids during the first minutes after the addition of the precipitating serum of a cloudy white ring.

The reaction will be specific if a cloudy white ring appears within 1 hour after adding the precipitating serum to the extract. Precipitation after 1 hour is considered non-specific.

A positive reaction in the first and third test tubes of the same row indicates that the test meat belongs to an animal that corresponds to the specificity of the serum. In all other rows in the first test tubes, the reaction should be negative, and in the third - positive. In the second test tubes of all rows (control sample with physiological saline), the reaction should be negative.

For example, if the extract under study turned out to be prepared from horse meat, then the result of the reaction in all test tubes should be as follows:

Hosted on Allbest.ru

Species of animals. species affiliation. Laboratory methods for establishing the species of meat

Send your good work in the knowledge base is simple. Use the form below

Similar Documents