1. Slaughtering and raw materials for meat preservation
Product quality and shelf-life of preserved meat and meat products depend on the microbiological and biochemical status of the carcass meat used for processing. In other words, the raw material must be as clean as possible and derived from slaughter animals in good and healthy condition.
Obviously the way of slaughtering animals plays an important role. Many irreversible quality losses, especially with regard to the hygienic quality, originate from improper slaughtering and carcass handling. Slaughter techniques, particularly under rural conditions, cannot and need not be sophisticated, but they must allow carcass meat which complies with basic hygienic requirements to be obtained whether slaughtering at the farm, or in slaughterslabs or slaughterhouses.
Careless slaughter and meat handling result in:
- improper and insufficient bleeding of the animals, leaving a relatively high amount of blood in the muscle. As a consequence the meat does not reach the necessary degree of acidity and its shelf-life is reduced;
- improper dehiding of the carcass, leading to heavy contamination of the meat surfaces by frequent contact with the personnel, polluted floors and dirty tools and equipment;
- improper evisceration through accidental opening of stomachs and tripes, leading to contamination spreading to internal and external surfaces of the carcass;
- contamination of the meat when carcasses are split on the ground;
- contamination of the meat during transport, when carcasses or parts of them make contact with unclean clothes, hooks, bars or containers;
- contamination of the meat stored under unhygienic conditions and because of faulty handling in meat markets, shops and processing plants.
It has to be borne in mind that faulty meat handling, apart from affecting the quality and shelf-life of meat and processed products, may also endanger the health of consumers. Massive contamination will not only enhance meat deterioration caused by food-spoiling bacteria, but may also cause poisoning of consumers by toxin-producing micro-organisms. Toxin-producing micro-organisms find a favourable environment not only in fresh meat stored for a prolonged period at ambient temperatures, but also under certain circumstances in processed meat or even in preserved meat. Appropriate hygienic measures during slaughtering and meat handling are therefore indispensable.
A proper way of improving the slaughter hygiene is to carry out as much of the slaughter operations as possible with the carcass in a hanging position.
RURAL SLAUGHTERING ON THE FARM
Slaughter operations of small animals can easily be performed with the carcass in a hanging position. Problems may arise when slaughtering large animals such as cattle. The bleeding of the animal and cutting off the hind feet is done on the ground and the opening of the skin of the belly and leg region may also have to be done in this position. To complete skinning, evisceration and splitting, simple wooden structures and ropes to gradually hoist up the carcass are strongly recommended (see Figs 1 and 2).
Remarkable improvements in slaughter hygiene can be achieved by this technique with much less visible contamination (dirt) and a lower degree of invisible contamination. The structure built for slaughtering can also be used for cutting and deboning the carcass.
Slaughterslabs are used in rural communities where the throughput of animals is very small, but where slaughtering in the field should be avoided.
Animals should be suspended from a wooden or metal frame using a gantry hoist to ensure that carcasses are kept off the floor.
The simplest slaughterslab consists of a concrete platform with gantryhoist facilities. The platform should be approximately 50 cm above the ground and sloped to a drain. A roof should be added as protection against adverse weather conditions.
Slaughterslabs should be fenced and roofed and have facilities for hygienic slaughtering and adequate disposal of effluents. If pigs are to be killed a scalding vat should be provided.
FAO'S SMALL-SCALE MODULAR SLAUGHTERHOUSE
The Animal Production and Health Division of the Food and Agriculture Organization of the United Nations (FAO) has developed a model project for village meat industry in which one of the main components is a smallscale modular slaughterhouse. The design incorporates the use of locally available construction materials and unsophisticated equipment. The slaughterhouse can be built in modules, adding units to the central slaughterhall for operations such as by-product utilization, meat preservation, processing and butchering. Designs have also been prepared for the construction of a meat market in order to facilitate the integration of production, processing and marketing.
It is intended that from the basic nucleus a number of small-scale industries be developed consecutively, e.g. meat preservation by low-cost technologies, traditional tanning, handicrafts based on hides, skin, bone and horns, etc. The objective is to increase employment, in particular for rural women, create market outlets for livestock products and increase the income of small producers.
The project could become a focus for farmer organization and a centre of technical assistance for producers. The organization of small producers is indispensable to ensure their participation and for the success and continuity of the project.
FAO is promoting the establishment of slaughterhouses of this type in some rural areas because this would increase the availability and quality of meat, improve the utilization of by-products, avoid rural migration and increase employment. The slaughterhouses may, therefore, constitute a tool for rural development, increasing the income level in the countryside and villages, thus improving the living conditions of the rural communities.
Rural slaughterhouses can also facilitate veterinary control of livestock (ante-mortem inspection) and carcass meat (post-mortem inspection). Slaughtering can be organized to follow a determined daily or weekly time schedule for which compulsory veterinary controls can be arranged. In addition, adequate technical facilities for efficient meat inspection can be provided, i.e. vertical position of the carcasses and special platforms for the personnel. Special hooks or inspection tables can be provided for the inspection of internal organs.
The detailed design for a small-scale modular slaughterhouse was developed by FAO. It includes designs, specifications, and schedule of quantities for a slaughterhouse and meat market suitable for small communities.
Provision is made for slaughter of all species: cattle (or buffalo), sheep, goats and pigs, though because of space limitations, concurrent slaughter of
different species is not possible. The abattoir capacity will be dependent on the mix of animals being slaughtered. Daily throughputs of approximately 10 large stock (e.g. cattle) or 50 small stock (sheep, goats or pigs) or a combination thereof could be achieved with this design.
The facilities are divided into modules which can be combined as required to suit a particular location.
The following modules are included:
- Slaughter floor
- Tripe room
- Meat cutting and processing room
- Solid waste and blood disposal
- Hides and skin processing
- Effluent disposal
- Electric light and power
- Water supply
- Meat market
A possible overall abattoir layout based on these modules is shown in Fig. 3. This layout shows a typical arrangement for a facility designed to handle beef, small ruminants and pigs. Modifications for a large beef kill and/or the elimination of pig slaughter (e.g. for Muslim communities) are possible.
It is evident that when establishing slaughterhouses each country or even separate localities must adopt a solution incorporating special local conditions, locally available materials and manpower, etc.
The designs foresee procedures for slaughter of each species as follows:
The animal is led into the bleeding area where it is restrained by a tether through the floor ring prior to stunning (using a captive bolt pistol). After stunning the animal is shackled by one leg and hoisted with a rope pulley block. The animal is then stuck and allowed to bleed in this position and the blood collected in a drum for disposal.
Once bleeding is complete the head can be removed and the animal lowered on to the cradle for dressing. It is also possible to dress the hanging animal. The feet are then removed, the skin opened up along the breastbone and the hide partially flayed. Leg hooks are attached and the carcass raised to a half-hoist position on the spreader. Flaying can then be completed and the hide removed. The paunch can then be removed to the inspection buggy and the red offal (including lungs if treated as edible) placed on hooks or the inspection table for inspection.
After inspection the carcass can be split and quartered, the quarters being individually hung on the low rail.
Once the carcass has been partially flayed and half-hoisted a second animal can enter the bleeding area.
Pigs are first stunned in the stunning area then hoisted for sticking and bleeding and then transferred to the scald tank. After scalding for approximately five minutes at 60°C the carcass is removed to the scraping table. After scraping a gambrel can be inserted into the hind legs and the carcass transferred to the overhead rail for final scraping and evisceration. Once a pig is clear of the scraping table the next pig can be placed in the scalding tub.
Sheep and goats
These would be slaughtered and dressed on the rail in the pig area in a similar manner to pigs. The scraping table is removed to one side during processing of sheep and goats.
After slaughter carcasses should be chilled in chilling rooms. Chilled meat is a requirement for many methods of further processing. However, in rural areas of developing countries refrigeration facilities are generally lacking. Before cutting, carcasses should therefore be carefully examined for signs of taint caused by microbial spoilage.
Unchilled meat as a raw material is suitable for dried meat and certain meat products which undergo a heat treatment immediately after processing.
When dealing with hot carcasses, cuts and trimmings should be either consumed or processed (dried) on the day of slaughtering. It is obvious that under these conditions good hygiene during slaughtering and meat handling is of great importance for the quality of the final product. The higher the initial contamination, the faster the meat deterioration, especially under high ambiental temperatures.
In this context a new way of short-term meat preservation that could be especially beneficial for prolonged periods of handling of carcasses or meat cuts during transport, etc. should be mentioned. Meat surfaces are treated with organic acids such as acetic, lactic, citric, tartaric and ascorbic acid, as well as sodium sorbate. These compounds are from different natural foods and not toxic and may be used alone or in combination as dipping solutions or sprays on the surface of meat and meat products. Treatment of carcasses with these products has proved to be successful under conditions in developing countries. With an aqueous solution of 20 percent sodium sorbate, 5 percent sodium acetate and 5 percent sodium chloride sprayed on warm beef carcasses, the shelf-life of meat at 25° to 35°C was doubled. However, more work is needed on the subject, especially for tropical conditions.
As whole carcasses of beef or pork are too large to be easily transported in one piece, they are split into sides or cut into fore- and hindquarters. The development of meat processing introduced the need for cutting quarters, halves or whole carcasses into smaller pieces which, according to their quality and market value, are used for culinary purposes and processing respectively.
The culinary meat in the form of primary cut is mostly sold to wholesale dealers who bone and cut it into sub-primals and finally into retail cut. The point at which wholesale cutting ends and retail cutting begins is not clearly defined. In the traditional, small, independent butchers' shops these operations may take place on a cutting table behind the counter in order to give the butcher the maximum opportunity to select the most suitable piece of meat and prepare it in a manner which is most likely to satisfy the consumer.
Meat for processing comprises parts of lower quality but also high-quality meat for the manufacture of special products like hams, smoked pork loins and dried meat. It can be divided into different classes according to the amount of fat and connective tissues.
There are several regional, country, and local differences in cutting the animal carcass into primary or retail cut and butchery practices vary depending on geographical location, tradition and habits, and demand for high-quality meat.
For the preparation of dried meat, two methods have been recommended. In both, carcasses are divided into two sides along the backbone. Each side is cut crosswise into two quarters which are divided into primal and retail cuts, and then boned and trimmed.
The pistola cutting system, with the side of beef quartered between the fifth and sixth ribs, allows the complete separation of all first-quality meat cuts in the hindquarters and loin regions. Fig. 4 illustrates primal cuts in the beef carcass.
After separation of the forequarters, the flank piece is removed by freeing the muscles of the abdomen from those of the proximal pelvic limb. Separation is completed by extending the cut down the side, parallel to and at a distance of some 20 cm from the backbone.
The hindquarter piece, which contains all the first-quality muscles, may be separated into the hind leg, rump and loin cuts by cutting and sawing directly across the Bicepsfemoris at a point just below the exposed point of the pelvic bone. The forequarter is similarly divided into two by removing the foreleg and blade cut from the thorax and neck. Table 1 illustrates the distribution of primal cuts within the carcass.
According to the second method the carcass is split into sides, along the spinal column. After that, the sides are cut horizontally into two quarters: hindquarters and forequarters. The cut line runs immediately after the last rib, which excludes leaving any ribs on the hindquarters. The hindquarters are hooked by the Achilles tendon and the forequarters by the last two ribs (Fig. 5).
In both cutting systems further division into commercial or retail cuts is usually necessary in order to separate the muscles or groups of muscles most suitable for drying from those which, by nature of their characteristics and retail value, should be sold fresh or processed by other methods.
|Flank and rib||14|
|Rump and loin||20|
|Foreleg and blade||15|
|Thorax and neck||22|
Hindquarter (top) and the forequarter (bottom) separated behind the last rib. (Procedure recommended for meat for drying.)
Hindquarter (top) and the forequarter (bottom) separated behind the last rib. (Procedure recommended for meat for drying.)
After boning, the meat is trimmed to improve the quality of the finished product. Trimming consists of removing all or part of the extra fat layers, coarse tendons, fascia, nerves and blood vessels and, where necessary, bits of muscle which have been improperly cut or superficially damaged. Infiltrated fat, particularly melted fat, must also be removed to ensure a high-quality finished product which keeps well. Not only does this fat have a peculiar taste, it is sticky, unpleasant, easily becomes rancid and often forms a barrier which can interfere with the drying process.
The bones can be dried as well. They should be cut into smaller pieces on a clean clog. However, care should be taken to leave the connective tissue and ligaments intact, so that the pieces of the bones can be suspended for drying after having been dipped into a salt solution (see Chapter 2).
SOME IMPORTANT NON-MEAT INGREDIENTS FOR MEAT PROCESSING
Salt is an important ingredient in the preparation of meat emulsions for imparting the typical flavour of processed meats and to contribute to keeping quality. The salt content of most processed meats ranges between 2.5 to 5.0 percent of the final product. A higher salt content would produce a salty taste. To function as a preservative, salt concentrations in the product of about 17 percent would be necessary, far too high for a palatable product.
Nitrates and nitrites are curing ingredients. The development of the red or pink colour is their most obvious effect. In addition, nitrites:
- affect the flavour of the products through their action as anti-oxidants; and
- have bacteriostatic properties, particularly in canned products (sodium nitrite is an effective inhibitor of the growth of the bacterium Clostridium botulinum).
Nitrate in itself is not effective in producing the curing reaction until it is first broken down into nitrite. This is a slow process which depends upon the presence of bacteria in brine and meat. Therefore nitrate has largely been replaced by nitrite.
Nitrite provides the ultimate source of the nitric oxide that reacts with the myoglobin pigment of the muscle tissue. Levels in excess of 200 parts per million of sodium nitrite should not be used. Since nitrate and nitrite are added in small amounts, it is recommended that they are first dissolved in water to ensure uniform distribution.
Extenders in general are added to lower-quality products for economic reasons. Some of them improve binding properties, cooking yields, slicing characteristics and flavour. The ones most often used are:
- dried skim milk and milk proteins;
- various cereal flours such as wheat, rice, oats, corn;
- soy products such as flours (containing about 50 percent protein), grits (which are similar to soy flour in composition but they are larger in particle size and more adaptable to meat products), textured soy protein (similar to grits except that the texture is changed to more closely resemble the texture of ground meat), soy protein concentrates (containing about 70 percent of protein, that is available either in a coarse granular form or as a flour), soy protein isolates (containing about 90 percent protein), useful both as binders and emulsifiers.
Various non-meat proteins are being developed for use in sausage and processed meats. These include protein from oil seeds other than soya, such as cotton seed and peanuts, as well as from single-cell plant source such as torula yeast. Most extenders are usually limited to 3 percent in the dry state or to 10 percent after swelling.
Seasoning is a comprehensive term for ingredients which improve the flavour of processed meats. Salt and pepper form the foundation upon which many seasoning formulae are built. Other ingredients such as spices, herbs and vegetables are supplementary, although necessary to obtain the distinctive flavour associated with various products.
Spices are aromatic substances of vegetable origin and include cinnamon, cassia, clove, ginger, mace, nutmeg, paprika, pepper, cardamom, coriander and mustard. They vary in composition. The aromatic and pungent components which render them valuable are present in volatile oils and resins. Some success has been achieved in extracting these components. Spice extracts offer the advantage of being easier to dose and to store.
Condiment herbs include sage, savory, bay leaves, thyme and marjoram. The dried leaves of any of them can be used in the preparation of sausages and other meat products. Condiment vegetables are onion and garlic.
All spices and seasonings should be stored under dry conditions and possibly in sealed containers. They should not be exposed to direct sunlight and should only be ground or crushed on the day of manufacture.