Handling and storage of Offals

Offals must be inspected for abnormalities and disease conditions prior to further handling. Blood, liver, trachea, oesophagus, spleen, brain, kidneys and fat should be collected under hygienic conditions. They should be used immediately or stored at 4-7 C in stainless steel containers. Blood should be transported within four to six hours for processing. Skin and hide should be transported within eight hours of collection. Pancreas and endocrine glands should be collected in ice and preserved under frozen conditions. Bones should be free of adhering flesh and dried Green bones should be broken, boiled, dried and stored at room temperature. The intestines and stomach should be cleaned in the unclean section of abattoir. 

Due to higher glycogen content and lesser fat covering, edible offals are pore perishable than carcass, therefore, it is essential to remove the edible offals soon after slaughter from the carcass, cooked and served preferably on the day of slaughter. High degree of care is to be taken to handle them to prevent contamination.

Carbon dioxide gas/dry ice accelerates chilling of offals . Freezing arrest the growth of organisms. vacuum packing double the refrigerated shelf life of organs like liver, kidneys  and heart. However it is advisable to utilize the organ meat  without delay .

In advisable to freeze the liver,heart,oxtail  and giblets for longer keeping quality. But care should be taken that these organs are thawed refrigerators. Similarly , sweetbreads and brains are also stored in frozen condition but thawing is done in hot water . For organs such as kidney ,tongue and tripe , it is advisable to use as fresh or within 24 hours of refrigeration. tongue may be smoked and refrigerated or pickled and refrigerated to use with in 3 days or 7 days  respectively. Giblets kept under refrigeration should be consumed with in 12 hours.   

Classification of offals

There are various basis of classification of offals such as their use, appearance etc. On the basis of utility as human food the offals are classified as edible or inedible. However, this depends on socioeconomic conditions of the consumers. For example, the head, feet, and blood are utilized as food by some people while many others do not consider these by-products as edible. Another basis of classification is appearance. The Red offal includes head, heart, liver, lungs, melt (spleen), sweetbreads, tail, thick skirt (diaphragm) and tongue. The White offals are fats, many plies (third stomach), set of guts and bladder, set of tripe (weasand, first, second and fourth stomach and rectum), fore feet and trimmings. Blood, hides and pharmaceuticals are usually considered as a separate category. 

The English Food standards committee have separated offal into two categories: 

List A: Items which may be used in cooked or uncooked products from mammalian species contain tissues such as diaphragm (skirt, cattle only), head meat (ox cheek, cattle only), heart, kidney, liver, pancreas (sweetbreads), tail meat (oxtail, skinned, cattle only), thymus (sweetbreads, cattle and sheep only), and tongue and avian parts such as heart and liver (giblets, when gizzard and neck are included). 

List B: Items which may not be used in uncooked products contain portions of the mammalian species such as blood, blood plasma, brains, feet (cow heel, cattle only; sheep trotters, sheep only; pig trotters, pig only), large intestines (chitterlings, pigs only), small intestines, lungs (lites), oesophagus meat, rectum, spinal cord, stomach (non-ruminant), first stomach (tripe, after cooking), second stomach (tripe, after cooking), fourth stomach, testicles (lamb fries, lamb only), udder and parts of avian species such as gizzard (giblets, when the heart and liver are also included) and neck. 

Utilization of Offals- Edible and Inedible

"Offals" means everything from slaughter of an animal that is not directly sold as consumable meat. 'By-product' is synonymous to offals and is used for broader sense where as 'offals' is used for various visceral organs and parts other than carcass. Animal by-products utilization is important from economic as well as public health point of view. Industry that turns wastes to valuable products has to be , encouraged. An industry can run successfully when it utilizes both edible and inedible by-products of its factory. Just selling the meat is hardly profitable. It is said, profit comes by utilization of by-products as one of the major source of income.

When an animal is slaughtered, it provides meat with well balanced protein as a major source. The byproducts of the animal are more than 50 per cent which are edible and inedible and requires efficient processing and utilization. The byproducts may be calculated by deducting the dressing percentage of an animal from 100. The dressing percentage of various animals ranges from 45 to 70 per cent. 

The by-products of meat industry if not utilized properly, the income is lost and and Meat Inspection adds cost for its disposal about which you have read earlier. Fortunately all the integrated abattoir and meat processing plants in India are utilizing byproducts effectively. You will study the utilization of animal by-products in detail in course- BPVI.

Carcass Yield

Carcass yield is one of the criteria of the grading. Generally sheep, goat, cattle and buffalo carcasses include the portions of body after removal of the blood, hide/skin, head, feet, digestive tract, bladder, pluck and adhering tissues etc. In case of pig carcass, skin and head are included in the carcass. Carcass mainly consists of muscular tissues, fatty tissues, bones, tendons and other connective tissues, large blood vessels etc. Approximately, 50,55 and 75 per cent of the live weight of sheep, cattle and pigs respectively remains in the carcass.

It provides information about the amount of meat and different by products obtained from alive animal after slaughter and dressing.

Percentage of meat and Different by-products available from cattle,pig and sheep carcass

source : Hald-Christensen(1986) Bengtson Holmquist (1984) Gerard(1977),Filstrup(1976).

From a study of buffalo carcass,following observation regarding meat yield and yield of other by-products are obtained

yield of meat and by-products based on live weight of buffalo

Dressing percentage is a comparison of the carcass weight in relation to the live weight of the animal and it is calculated as follows: 

Dressing percentage =(Dressed weight(carcass weight)/ Live weight of the animal)x 100

Sometimes edible offals like heart, liver, kidney, spleen etc. are also included in the dressing percentage because these are sold with the meat at same price. 

Dressing percentage of meat animals ranges from 45 to 70 per cent. The animals with heavy fat and the carcass with skin usually provide dressing percentage above 60 per cent. Generally pig carcass with skin and heavy subcutaneous fat provides dressing percentage more than 60 per cent. In some animals, muscles exist in double i.e., dopplender condition and these animals produce higher dressing percentage. This condition is more common in cattle. 

Dressing percentage of meat animals depends on the following factors: 

(i) Species: Dressing percentage varies from species to species. For example, dressing percentage of pig is generally higher than that of cattle. 

 Dressing percentage of different meat animals and poultry 

(ii) Breed: The animals from same species but from different breed produce different dressing percentage. For example, large white Yorkshire pig yields more meat than indigenous pig breed. 

(iii) Stage of maturity: Matured i.e., adult animal produces higher dressing percentage than young (i.e., immature) animal. 

(iv) Degree of finish: Finish represents external, internal and intramuscular fat of a carcass. Higher finish gives higher dressing percentage. 

(v) Intestinal content: As dressed carcass is free from intestinal content, the animal with more intestinal content produces the carcass of less dressing percentage. For example, intestinal content of calf is relatively more (percentage wise) than that of adult cow and calf produces less dressing percentage than adult cow. 

Dressing of Animals

Generally sheep, goat, cattle, buffalo, pig and poultry are slaughtered in India. In our country, slaughter of buffalo is much prevalent as compared to cattle. Sheep and goats have no religious taboos compared to cattle and pigs. Poultry meat is acceptable to many due to lower price compared to other meats and lesser chances of adulteration with other meat. Beef, veal, pork, lamb, mutton, chevon are known as red meat whereas chicken i.e., poultry meat is known as white meat. In India, Halal method for Muslim and Jhatka method for Sikh are more prevalent than other method of slaughter.

You have already studied about stunning and bleeding of different meat animals in unit-9. So we will learn here the steps involved in dressing of these animals.

Dressing of Cattle/Buffalo

Dressing of cattle and buffalo after stunning and bleeding, involves following steps:

Dehiding: Dehiding is the removal of hide or skin. At first the head is flayed by making an incision with knife from the poll to the muzzle. From the base of the neck, another incision is made to the middle of lower jaw. After reflecting the hide over head, atlanto-occipital joint is cut to separate the head. Then an incision is made from the mid ventral line of the base of the neck to the brisket, belly and base of the tail. The medial aspect of the fore limbs is incised from the knee joint to the mid ventral incision. Similarly, medial aspect of hind limb is also incised. The shanks are removed at flat joint. Then the hide/skin over the fore limb and hind limbs is removed and followed by the skin/hide of belly, chest and neck. Practically, flaying of back or butt region is difficult because the skin is highly adherent to underlying tissues in this area. The tail is removed from the base of the tail.

Evisceration: Evisceration is process of removal of visceral organs. A circumcision is made around the anus by a sharp knife and the attachments of large intestine are removed. This helps in easy pulling of intestines from the ventral aspect. The distal end of the anus is tied with a small rubber band to prevent the contamination of the carcass by intestinal contents. A sharp knife is used to make mid ventral incision from the mid point of pubic symphysis to the level of sternum. After exposing the abdominal cavity, o mental and mesenteric fats are removed and then abdominal contents are removed. Care should be taken not to puncture the visceral organs accidentally. The attachments of diaphragm to liver are cut to separate the liver without puncturing the gall-bladder. Then thoracic cavity is opened by a mid ventral incision from the sternum to midpoint of neck. Diaphragm and the thoracic organs are removed. In case of cattle and buffalo carcass, laryhx, trachea, lungs, heart and liver are collectively known as 'pluck'. All these are placed for post-mortem examination along with the carcass. You will study the post-mortem examination in detail in unit-12.

Splitting: The beef(cattle) and buffalo carcasses are split vertically & from the pelvis up to the neck by sawing or cleaving. This splitting of carcass makes two halves (right and left). The saw or cleavers should be sterilized properly before use.

Carcass washing: Carcass is washed to remove soil, blood, stains etc. Only potable water should be used for carcass washing. Carcass may be washed before or after splitting. Surface of the carcass and thoracic and abdominal cavity are washed by spraying of potable water. Then the carcass should be dried as far as possible to avoid the bacterial growth.

Sometimes, by quartering, each side(left or right half) is divided into fore quarter and hind quarter. After postmortem examination of the carcass and offals, the carcass is placed in a chilling room for proper setting of the carcass and further storage. You will learn about chilling and freezing storage in next course.

Slaughter of cattle

Dressing of Sheep/Goat 

You have studied the stunning and bleeding of sheep and goat in previous unit. After bleeding, the carcass is dressed in the following way:

Decapitation: It is the removal of the head. Head is separated with skin at atlanto- occipital joint.

Removal of legs: The fore legs are disjointed at the knee joint.

Skinning/flaying: Skinning or flaying is started by making an elliptical incision around the hock joint on either side of hind legs. Skin is reflected on both sides by twisting and thumbing and this process is called fisting. Flaying is continued in this manner up to the level of sternum and finally the whole skin is removed by pulling out in a single flap. Skin is also removed by putting air in between the skin and underlying tissue.

Evisceration: For removal of visceral organs, same process is followed as in case of cattle but the composition of 'pluck' is slightly different in case of sheep/goat. Here, the 'pluck' includes larynx, trachea, heart, liver, lungs and spleen. Paunch i.e., stomach is first removed, then 'pluck' is removed. In sheep and goat, the kidneys remain attached to the carcass until the carcass is split down the back bone. Generally, the sheep and goat carcasses are not split and sold entire. Dressed carcass and offals are placed for postmortem inspection.

Carcass washing: Sheep and goat carcasses should be washed by spraying Dressing Techniques and Carcass Yield potable water on the surface of the carcass and on the thorasic and abdominal cavity .

Slaughter of Goat

Dressing of Pig 

Dressing of pig is slightly different from cattle or sheep because the skin of the pig is not removed during dressing. We have discussed the stunning and bleeding of pig in the previous unit of this course. Steps involved in the dressing, are discussed below: 

Scalding: As the skin of the pig is consumed with the meat, skinning or flaying is not done. Instead of that the carcass is exposed to hot water treatment which is known as scalding. Scalding is done to loosen the attachment of hair/bristles by partial cooking of hair follicles.Scalding temperature for pig is about 62-64 C. 

Dehairing: Hairs or bristles of the pig can he removed either by dehairing machine i.e., mechanical scrapper or manually. Dehairing should be done in the direction of the hair follicles. When it is done manually, a blunt knife is used for this purpose. All the bristles and fine hairs may not be removed by scrapping. Then the skin surface is exposed to blow lamp which chars the remaining bristles and hairs. This process is called as singeing. Then the charred bristles and hairs are removed by shaving with a fine knife. 

Rinsing: The entire carcass is rinsed thoroughly with cold potable water to give the carcass a clear appearance. 

Evisceration: The procedure is almost same as followed in case of cattle. A sharp and Meat Inspection end knife is used to make incision through subcutaneous fat from mid point of pubic symphysis to midpoint of neck. A knife is introduced through the opening of the pelvic cavity towards abdominal cavity and all the pelvic and abdominal organs are pulled out except the kidneys. To open the thoracic cavity, sternal cartilage is cut by a cutting knife. Then diaphragm along with other thoracic organs is removed. The carcass and the organs are then placed for postmortem examination. 

Final washing: Clean, cold and potable water is used to remove blood and dirt adhering to the carcass. 

The carcass is then kept in the chilling room for proper setting. Sometimes the carcass is divided into  two equal halves.

slaughter of pig

Line Dressing System

After stunning of the animal, bleeding and complete dressing is carried out speedily on overhead rail. This is called as line dressing or rail dressing systems. Line method of dressing is essential for high rate of production. This is achieved by combination of several machines, tools and equipments to reduce cost Line dressing is useful for buffalo/cattle, sheep and goat, pig and poultry. Without the line method of slaughter, it would not be possible to reach the production level achieved in a modern meat plant which may be as high as 5000 cattle/buffalo or 10000 sheep/goat every 10 hours. 

Advantages of rail slaughter system 

This system is safer to operators than conventional system 

This is hygienic method as carcasses do not touch the floor 

It is easy to handle mechanical heavy tools on conveyors/rail 

It saves space and reduces unnecessary movement of the carcass movements 

It enhances the value of hide/skin and organs as the overhead line removes the hurdles of floor dressing 

It systematically synchronizes inspection of carcasses and organs with their identification 

It increases the throughput i.e., slaughter rate as there is no chance of idleness for workers. 

Disadvantages of rail slaughter system 

The rail system requires high engineering skill and any dislocation on the line will totally stop the production. Absence of particular skilled worker may adversely affect the production. 

The repetitive nature of work leads to loss of job interest. 

Meat inspection is sometimes said to be more difficult and possibly less efficient as the carcasses and their respective viscera follow different ways and require marking to match at the time of conclusion. 

It requires a large capital investment

The line dressing system has been classified into four categories on the basis of mode of operation. 

(i) Gravity rail system: Here the movement of spreader and single wheel trolley or runner is under the influence of gravitational force. The carcass is gravitated to each station and manually stopped at each station for operation. 

Advantages 

• Simplest in design, so less chances of serious breakdown with consequent loss of production. 
• Various items of equipment may be used with the gravity rail, e.g., a moving top viscera inspection table or a paunch truck. 

Disadvantages 

Low slaughter rate i.e., 10 to 40 beef/hour 

Adequate ceiling height is necessary because of pitch of the rail to gravitate carcass. 

(ii) Intermittent powered system: Here the suspended carcasses on spreader (gambrel) and trolley are moved along a level rail at interval by mechanical means of variable timing device which can be preset to suit the slaughter rate. 

Advantages 

• Faster slaughter rate (10 to 75 beef/hour) as compared to gravity rail system 
• Leveled rail and therefore height of ceiling is not a major problem. 

Disadvantage

• The timing as per slaughter rate is to be fixed previously. 

(iiii) Continuous powered system: Here the movement of carcass is by mechanical means but continuous. 

Advantages 

• A much higher slaughter rate i.e., 40 to 120 beef/hour. 
• The carcass can be revolved a fu11 360 degrees as per convenience of the worker. 
• Efficiency of worker is increased. 

Disadvantage 

Same as those discussed for line dressing system. 

(iv) Can pak System: This system is a continuous conveyorised method in which the carcasses are spread by trolley or runner from the overhead rail and no spreader or gambrel is used. This system has been developed by Canada Packers Limited, Toronto, Canada. Probably this is the most common system used in large modern plant. 

Advantage 

A very higher rate of slaughter i.e., 50-150 beefs/hour

Disadvantage 

Same as those discussed for live dressing system

Dressing Techniques and Carcass Yield

In unit-5 of this course you have already studied that the slaughter and dressing of livestock may be carried out either on the rail or on the floor. Dressing of the animals involves various steps like removal of skin, leg, head and visceral organs (lungs, liver, heart, spleen etc.) and washing of the carcass etc. through which an animal after stunning and bleeding becomes ready for marketing or further processing. The storage life of meat depends on conditions during slaughter and dressing. A uniform approach to dressing technique in all the countries is not possible due to climatic conditions, stage of development, social differences and religious practices. In general, following are essential during slaughter and dressing of animals:

• Proper ante-mortem examination to ensure that the animals are healthy and free from diseases. 
• Humane slaughter which refers to stunning of animal prior to bleeding. 
• Complete bleeding to prevent growth of microorganisms and to improve the appearance of carcass. 
• Hygienic dressing (i.e., dehiding, evisceration etc.) to obtain good quality meat. 
• Proper postmortem inspection to ensure the production of hygienic and wholesome meat. 

In this unit we will discuss line dressing system, dressing techniques for different meat animals, carcass yield and dressing percentage of different meat animals in detail.