PRINCIPLES OF MEAT DRYING
Drying meat under natural temperatures, humidity and circulation of the air, including direct influence of sun rays, is the oldest method of meat preservation. It consists of a gradual dehydration of pieces of meat cut to a specific uniform shape that permits the equal and simultaneous drying of whole batches of meat.
Warm, dry air of a low humidity of about 30 percent and relatively small temperature differences between day and night are optimal conditions for meat drying. However, meat drying can also be carried out with good results under less favourable circumstances when basic hygienic and technological rules are observed. Intensity and duration of the drying process depend on air temperature, humidity and air circulation. Drying will be faster under high temperatures, low humidity and intensive air circulation.
Reducing the moisture content of the meat is achieved by evaporation of water from the peripheral zone of the meat to the surrounding air and the continuous migration of water from the deeper meat layers to the peripheral zone (Fig. 6).
There is a relatively high evaporation of water out of the meat during the first day of drying, after which it decreases continuously. After drying the meat for three or four days, weight losses of up to 60–70 percent can be observed, equivalent to the amount of water evaporated. Consequently, moisture losses can be monitored by controlling the weight of a batch during drying.
Continuous evaporation and weight losses during drying cause changes in the shape of the meat through shrinkage of the muscle and connective tissue. The meat pieces become smaller, thinner and to some degree wrinkled. The consistency also changes from soft to firm to hard.
In addition to these physical changes, there are also certain specific biochemical reactions with a strong impact on the organoleptic characteristics of the product. Meat used for drying in developing countries is usually derived from unchilled carcasses, and rapid ripening processes occur during the first stage of drying as the meat temperature continues to remain relatively high. For that reason the specific flavour of dried meat is completely different from the characteristic flavour of fresh meat. Slight oxidation of the meat fats contributes to the typical flavour of dried meat.
Undersirable alterations may occur in dried meat when there is a high percentage of fatty tissue in the raw meat. The rather high temperatures during meat drying and storage cause intensive oxidation (rancidity) of the fat and an unpleasant rancid flavour which strongly influences the palatability of the product.
Meat drying is a complex process with many important steps, starting from the slaughtering of the animal, carcass trimming, selection of the raw material, proper cutting and pre-treatment of the pieces to be dried and proper arrangement of drying facilities. In addition, the influence of unfavourable weather conditions must also be considered to avoid quality problems or production losses. The secret of correct meat drying lies in maintaining a balance between water evaporation on the meat surface and migration of water from the deeper layers.
Dehydration process of a piece of meat suspended under drying conditions (schematic).
In other words, care must be taken that meat surfaces do not become too dry while there is still a high moisture content inside the meat pieces. Dry surfaces inhibit the further evaporation of moisture, which may result in products not uniformly dried and in microbiological spoilage starting from the areas where the moisture content remains too high.
Adherence to the following meat-drying techniques should avoid failures in the production of dried meat and ensure obtaining products of good quality with a long shelf-life. The following description of the basic technology of meat drying includes the salting of the meat before drying. Presalting is not absolutely necessary, but has certain advantages, particularly for the drying of meat strips and large flat meat pieces and is therefore strongly recommended for this type of product.
SELECTION OF MEAT FOR DRYING
As a general rule only lean meat is suitable for drying. Visible fatty tissues adhering to muscle tissue have a detrimental effect on the quality of the final product. Under processing and storage conditions for dry meat, rancidity quickly develops, resulting in flavour deterioration.
Dry meat is generally manufactured from bovine meat although meat from cameloids, sheep, goats and venison (e.g. antilopes, deer) is also used. The meat best suited for drying is the meat of a medium-aged animal, in good condition, but not fat. Meat from animals in less good nutritional condition can also be used for drying, but the higher amount of connective tissue is likely to increase toughness.
It is very important that raw material for the manufacture of dry meat is examined carefully for undersirable alterations such as discoloration, haemorrhagic spots, off-odours, manifestation of parasites, etc. Such defects must be trimmed off.
Carcasses have to be properly cut to obtain meat suitable for drying. Owing to their size, beef carcasses are more difficult to handle under rural conditions than carcasses of sheep, goats or game. In the absence of chilling facilities, beef carcasses must be cut and deboned immediately after slaughter.
BEEF CARCASS CUTTING, TRIMMING AND DEBONING
The carcass is first split into two sides along the spinal column and then cut into quarters. Fore- and hindquarters are separated after the last rib, thus leaving no ribs in the hindquarter. For suspension the hindquarter is hooked by the Achilles tendon and the forequarter by the last two ribs (see Fig. 5).
After the quarters are suspended so that they do not touch the floor or anything around them, they are trimmed. Careful trimming is very important for the quality and shelf-life of the final product. The first step is to remove with a knife all visible contamination and dirty spots. Washing these areas will spread bacterial contamination to other parts of the meat surface without cleaning the meat (Fig. 7).
Trimming a beefcarcass.
After completing the necessary cleaning of the meat surfaces, knives and hands of personnel must be washed thoroughly. Using a sharpened knife, the covering fat from the external and internal sides of the carcass and the visible connective tissue, such as the big tendons and superficial fasciae, are carefully trimmed off.
It is recommended that this operation should start with the hindquarters and follow with the forequarters. The aim is to remove the bones with the least possible damage to the muscles. Incisions into the muscles are inevitable but only at spots where the bones adhere and have to be cut off.
Deboning of the suspended hindquarter should start from the leg and proceed to the rump and muscles along the vertebral column.
Deboning of the forequarter must start with cutting and deboning the shoulder separately, followed by cutting off the rib set, together with the intercostal muscles.
Deboning of the forequarter is completed by removing the meat from the neck and the breast region of the spinal column.
TECHNIQUE OF CUTTING MEAT PIECES FOR DRYING
Anatomic cuts, which were separated from the carcass, are suspended again (Fig. 8) and the big individual muscles are carefully cut out, while the smaller muscles are left together. The next step consists in cutting the muscles into thin strips. This operation is crucial for the appearance and quality of the final product. All strips to be dried in one batch must be cut to an identical shape. Care must also be taken to obtain rather long strips of meat.
There are two ways of cutting muscles or smaller muscle groups into strips:
In both cases the muscles have to be split exactly along the muscle fibres. The strips must be cut as uniformly and as smoothly as possible and the diameter of the strip must remain the same throughout the length.
The length of the strips may differ, though it should not be less than 20 cm and not more than 70 cm. Meat cut into shorter strips requires considerably more time for hooking than the same quantity cut into longer strips. However, strips which are too long may break because of their weight.
Beef muscles suitable for drying are usually no longer than 50 cm (except the sirloin strip attached to the spinal column). However, strips longer than 50 cm can be produced by cutting the muscle along the fibre in one direction, without cutting through the end of the muscle (Fig. 11). Using this technique long strips can be obtained, but their length should not exceed 70 cm for reasons of stability. The thickness of the strips determines the duration of the drying process. Since thick strips take considerably more time to dry than thin ones, it is important that strips to be placed in the same batch are of the same cross-section, with only the length differing. Insufficiently dried or overdried pieces will be the result if this rule is not followed.
Suspended anatomic cut from the hindquarters (“silverside”)(A) and splitting into individual muscles (B) which result in (C).
Cutting meat streeps from the muscle on a chopping board.
Cutting meat streeps from a suspended muscle.
Special cutting technique to obtain long meat streeps.
Cutting muscles into long, thin and uniformly shaped strips requires experience and skill. Knives with broad blades are best suited for this purpose.
Under dry climatic conditions two basic shapes of meat pieces proved to be the most suitable for natural drying:
RECOMMENDED TREATMENT BEFORE DRYING
Because meat is always consumed slightly salted, the raw material may be presalted before drying. This procedure not only contributes to a more tasty product, but is also desirable from the technological and hygienic standpoint. Pure common salt is used for this purpose, either dry or dissolved in water. In the case of meat for drying cut into strips or flat pieces, the use of a 14-percent salt solution is preferred.
Dipping the meat into the salt solution serves first of all to inhibit microbiological growth on the meat surfaces. For that reason salting has to be carried out within five hours after slaughter, as after that period massive microbiological growth occurs which cannot be reduced by salt treatment. Secondly, presalting is a protection against insects during drying. The freshly cut meat surfaces are very attractive to various insects, in particular domestic flies, which feed on the moisture excreted from muscle fibres. These insects cause considerable contamination of the meat and may also deposit their eggs into it. Meat is no longer such an attractive environment for insects after it has been dipped into the salt solution. The salt concentration on the meat surfaces keeps them away.
Furthermore, a thin layer of crystalline salt is formed on the surface of the meat during drying. The salt crystals are hygroscopic and absorb part of the water excreted from the meat, preserving the meat surfaces by keeping them dry. Dry meat surfaces inhibit the growth of bacteria and moulds which is one reason for the preservability of presalted and dried meat.
The salt solution is prepared by adding the necessary amount of edible common salt to water and dissolving it by intensive stirring. To obtain the recommended salt concentration of about 14 percent the amount of salt necessary for different volumes of water (expressed in litres) is indicated below:
As soon as the salt is dissolved in the water, the meat strips are dipped into the solution (Fig. 12), soaked for about five minutes and then drained. Draining should be done by placing the strips into a plastic sieve in order to allow the brine to drop off for collection and re-use (Fig. 13).
The handling of the meat strips before drying has to be carried out under strictly clean conditions in order to avoid contamination and ensure a long shelf-life of the dried product. However, if accidental contamination of certain pieces occurs, further processing can only be undertaken with certain precautions. A special bucket with salt solution should be available in order to soak the contaminated pieces of meat, after having rinsed them previously in clean water. However, it must be borne in mind that the original quality of contaminated pieces cannot be restored. For that reason such pieces should always be dried separately, and not stored for a long period, but should be used as soon as possible in the preparation of meals.
METHODS OF SUSPENDING MEAT STRIPS FOR DRYING
The traditional way of suspending meat for drying by hanging strips over tree branches, wire or rope is not recommended because meat remains in contact with these supporting devices or may touch each other and thus not dry properly in these contact areas. Consequently, the chosen method should be to suspend the meat strips individually from one end, thus ensuring, through appropriate arrangement on the drying facility, free air circulation along the whole length of the pieces and fast and uniform drying. The contact of meat pieces with each other during drying must absolutely be avoided, since these areas will remain wet and humid for a prolonged period, thus making them a favourable environment for spoilage, bacteria and flies.
Meat strips are soaked in a 14-percent salt solution for five minutes.
Draining the brine from the meat strips after soaking using a plastic sieve.
The suspension of the meat strips can be done in different ways, either with hooks, loops or clips (Fig. 14).
Suspension using metal hooks
This is a very simple but efficient way of suspending the meat strips. The meat strips are hooked at one end, always the thicker end for stability, and suspended on a horizontal wooden stick, tightrope or wire.
The metal hooks can easily be made, preferably from galvanized (non-corrosive) wire. Wire of 1 to 1.5 mm diameter is cut into pieces 15 cm long with a slanting cut so that the ends are sharp to allow piercing of the meat. In order to obtain an S-shaped hook, both ends of each piece are simply twisted around a circular stick (Fig. 15).
Suspension using loops
For this purpose a thin string or a somewhat stronger thread is best suited (Fig. 16). The string is divided into pieces about 30 cm long with the ends knotted. The string is fixed to the stronger end of the meat strip by a double loop and pulled tight in order to prevent the meat from slipping out of the loop (Fig. 16D/E).
Suspension using metal clips
Clips 4 to 7 cm wide are best suited. They are easily placed on the stronger end of the meat strips. Whereas metal hooks and rope loops can only be used for the suspension of rectangular or similar shaped strips, the metal clips are very practical for the suspension of flat, leaf-shaped pieces. The special advantage of hanging leaf-shaped pieces by means of a clip is that the edges of the meat do not fold in during drying.
INSTALLATION FOR DRYING ENTIRE BATCHES OF MEAT
It has already been pointed out that placing meat pieces for drying over wire, ropes or branches of trees is not recommended. Apart from problems of free air circulation under trees, some pieces may be intensively exposed to direct sun, whereas others are screened by the foliage. Furthermore, wind will transfer dust, twigs or leaves on to the meat and insects and birds will cause further damage. A general disadvantage of this very simple method of meat drying is that it is practically impossible to shelter the meat in case of storm or rain.
Suspension of meat strips on hooks (A), loops (B), and by means of clips (C).
Preparing hooks from galvanized wire.
Preparing loops from string or thread and fixing the meat strips.
It is therefore recommended that natural meat drying be done by using simple premises and equipment, which can be made locally. The following descriptions give the different types of meat dryers.
These meat dryers are constructions of wood, metal and/or concrete, stationary or mobile, without or with a roof. For strips suspended by hooks or with a loop attached or fixed by clips, removable horizontal bars, either made of wood or metal or horizontal wire strings are needed.
Sun meat dryer made of wood or metal
This dryer consists of four wooden forks planted into the ground which are connected with two longitudinal, wooden traverses of about 4 m. Wooden or metal sticks for hanging the meat streeps are placed on the traverses at a distance of 15 cm from each other (Fig. 17A). If there are not sticks available, strong metal wire or plastic rope can be spanned between the two longitudinal traverses and two additional transversal traverses should be fitted for reinforcement (Fig. 17B). Similar constructions, but with iron parts and traverses instead of the wooden ones are suited for the more industrial type of meat drying (Fig. 18A/B). These constructions can also easily support a roof and meat drying can be done on two or more levels. However, care has to be taken that the traverses at the lowest level are not less than 1 m from the ground.
Mobile meat dryer
This type of dryer, which can be easily assembled or dismantled, can be moved to places where the animals are slaughtered. Although wooden constructions can be used for this purpose, for easy assembly and for a firm base metal constructions using 40-mm tubular iron bars are more convenient (Fig. 19).
This type of dryer consists of two rectangular frames (2 x 2 m) placed 4 m apart from each other. They are connected with four longitudinal and eight transversal metal traverses in two levels from the ground (approx. 1 m and 2 m), thus permitting meat drying on the two levels (Figs 19 and 20).
Simple wooden construction for meat drying using sticks (A) or wire/plastic rope (B) to suspend the meat strips.
Simple metal construction for meat drying using sticks (A) or wire/plastic rope (B) to suspend the meat strips.
This dryer has the capacity for drying the meat of two beef carcasses at the same time. It is recommended that the upper level of the dryer be used for the suspension of meat from the hindquarters and the lower level for meat from the forequarters.
Meat dryer with protection against external influences
In regions with strong and frequent winds, meat placed on the dryer must be protected from contamination by dirt, dust, sand, etc. In these cases it is recommended that the side walls of a roofed dryer (e.g. roof of corrugated aluminium, Fig. 21) be covered with plastic foil up to a height of 0.80 m to 1.20 m from the floor. It is important to ensure that the upper parts of the dryer remain open for air circulation. Protection against insects is provided by covering the sides of the dryer with insect screen (Fig. 22).
Movable metal construction for meat drying.
Suspending meat strips on the lower level of the dryer on wooden sticks by means of metal hooks.
ARRANGEMENT OF THE MEAT STRIPS IN THE DRYER
In the dryer the meat strips are hung on horizontal plastic ropes, wires or sticks by means of hooks, loops or clips. As shown above, ropes and wires have often to be supported because of the heavy load of suspended meat, and they are not easily removable, which may cause difficulty in handling the meat to be dried.
Compared to flexible wires or ropes, firm wooden or metal sticks (Figs 15 and 16) have proved to be the better solution for the following reasons:
The round wooden sticks can be made locally; they are usually 2 m long and 2 cm in diameter. This size permits the suspension of 25 to 30 pieces of meat. Metal sticks are in two different shapes, one tubular, made of galvanized water-pipes, and the other T-shaped. They are more expensive than wooden sticks but they last much longer.
The following rules for the arrangement of the meat pieces apply to both wooden or metal sticks:
Roofed meat dryer (corrugated aluminium).
Protecting the sides of a meat dryer with an insect screen.
Arranging meat strips in the dryer along sticks or wires for suspension.
QUALITY OF THE FINISHED PRODUCT
Drying of meat of the shape described in this chapter takes four to five days. After this period the dried meat is ready for consumption and can be packaged, stored or transported (Fig. 24). At this stage the product should meet the following quality criteria.
The appearance of the dried meat should be as uniform as possible (Fig. 25). The absence of large wrinkles and notches indicates the desired steady and uniform dehydration of meat.
The colour of the surface, as well as of the cross-cut, should be uniform and dark red. A darker peripheral layer and bright red colour in the centre indicates incorrect, too fast drying, with the formation of hard rind which hinders evaporation from the deeper layers of the product. In this case the central parts have a brighter colour and softer consistency and are, because of the higher water content, more susceptible to microbiological spoilage when packaged or otherwise stored. A softer consistency can also be recognized by pressing the meat with the fingers. These pieces should be kept for one more day in the dryer for finishing. The consistency of properly dried meat must be hard, similar to frozen meat.
Taste and flavour are very important criteria for the acceptance of dried meat by the consumer. Dried meat should possess a mild salty taste which is characteristic for naturally dried meat with no added spices. Off-odours must not occur. However, a slightly rancid flavour which occurs because of chemical changes during drying and storage is commonly found in dried meat. Dried meat with a high fat content should not be stored for a long period but used as soon as possible in order to avoid intensive rancidity.
Dried meat must be continuously examined for spoilage-related off-odour, which is the result of incorrect preparation and/or drying of the meat. Meat with signs of deterioration must be rigorously sorted out.
PACKAGING AND STORAGE
After taking the dried meat strips out of the dryer, a selection of the pieces based on length can be undertaken.
Packaging serves to protect the product from contamination to which the meat might be exposed on its way from the producer to the consumer.
Numerous materials are used for packaging dry meat, such as paper, plastic foils (Fig. 26), aluminium foils, cellophane and textiles (Fig. 27). The longest shelf-life is obtained using vacuum-packaging. Transparent plastic material and cellophane are more appealing to the consumer. For details about packaging see Chapter 4.
Dried meat strips.
Properly dried meat with a smooth surface and uniform cross-section.
Packaging is employed for both the retail and wholesale trade. The weight per package of dry meat for retail sale usually does not exceed 1 kg, whereas those for the wholesale trade weigh 5, 10, 25, or 50 kg.
If plastic bags are used for packaging, the pieces of dry meat should be cut to a certain length so that they can be best arranged in the bags. Cardboard boxes are very useful for additional packaging.
During storage special care has to be taken to prevent dried meat, which is not packaged in water-proof containers, from becoming wet, resulting in rapid growth of bacteria and moulds. For this reason the premises for storing dry meat have to be rain-proof. It is further advisable to cover the piles of packaged dry meat with plastic sheets, as additional protection against moisture and dust. Dry meat protected in this way can be stored for more than six months.
Dried meat strips packed in plastic bags with the opening heat sealed (above) or tied (below).
Dried meat in jute sacks for wholesale trade.
During storage individual packages must be opened at least once a month and the organoleptic quality of the goods examined. These controls enable the persons responsible to evaluate storage conditions and to assess the shelf-life of the dry meat.
For controlling temperature and air humidity, it is useful to have a thermometer and hygrometer installed on the premises (see also Chapter 5). A maximum-minimum thermometer is recommended to obtain the highest and lowest temperatures recorded between two readings. The temperature and relative air humidity should be carefully registered bearing in mind that dry meat is extremely sensitive to changes in environmental conditions, especially of the ambient temperature and relative humidity.
PREPARATION OF DRIED MEAT FOR CONSUMPTION
Dried meat manufactured as described above has to be rehydrated to resemble fresh meat again. Rehydrated dried meat has almost the same nutritive value as fresh meat.
Rehydration is in most cases combined with cooking. The procedure usually starts by putting the dried meat, which may be cut in smaller pieces, into a pot (Figs 28 and 29). The meat in the pot is then covered with water and boiled. The rehydrated and cooked meat and the broth are used, together with other additives which may vary according to local consumption habits, for the preparation of tasty dishes.
Other types of dried meat, which are manufactured by a combination of drying with special treatments, are consumed raw, without rehydration and cooking. Some examples of this group of products are given below.
MEAT DRYING IN COMBINATION WITH ADDITIONAL TREATMENT
Meat drying after presalting, as described above, is the simplest and most efficient method of meat dehydration. Additional treatments used for some special dried meat products are curing, smoking and the utilization of spices and food additives.
Specific antimicrobial agents in smoke or spices or the antimicrobial properties of the curing substance, nitrite, may allow a less intensive dehydration of the meat. The resulting “semi-dry” products are in most cases consumed without rehydration, whereas rehydration is indispensable for common dried meat. In many countries, including developed countries, “semi-dry” products such as unsmoked and smoked raw hams (e.g. Parma ham, jamon serrano or smoked hams of the central European type), unsmoked or smoked dry sausages (e.g. salami, dry chorizo) or dried cured beef (Bündnerfleisch of Switzerland) are not only popular because of the products’ durability but particularly because they are delicious, high-quality meat specialities.
In developing countries, where the preservation aspect is even more important because of the lack of a cold chain, treatment carried out in addition to the drying of meat will be somewhat different and in some cases (e.g. intensive smoking over fire) the product quality is lowered rather than improved. The reasons for this additional treatment are in many cases adverse climatic or environmental conditions which do not allow the drying of meat without additional treatment. There are also of course other reasons for additional treatment, such as special flavours or special mixtures with non-meat ingredients, which may be preferred locally.
Cured dried meat
Curing is the impact of nitrite on meat, in particular on the muscle pigment, myoglobin, which results in the formation of the pigment myochromogen and gives a stable red colour to muscle tissue. In addition, nitrite inhibits to some extent microbiological growth in the meat, but does so efficiently only in combination with low temperatures and/or low water activity (see Chapter 4). These effects are of particular importance for the shelf-life of raw hams and dry sausages and may also be of importance for non-intensively dried biltong, the South African dried meat, which may also be manufactured with nitrite or nitrate.
Apart from occasional use in biltong, it can be concluded that curing is not important in the manufacture of traditional dried meat products. The reasons are that a bright red colour is not desired in dried meat (because it will be rehydrated and used for cooking meals) and drying is generally so intensive that the inhibiting effect on microbiological growth is unnecessary. Curing substances must be handled very carefully as they are toxic even in low concentrations. Very small dosages are sufficient for the curing effect, about 200 ppm, that is, 2 g or less in 10 kg meat.
Whole strips and flat pieces of dried meat and dried meat comminuted to fragments of different sizes for preparing meals.
Preparing a meal of dried meat. As a first step the dried meat is put into boiling water.
Smoked dried meat
Smoking of meat is a technique in which meat is exposed directly to wood smoke which may be generated by a variety of methods. In smoke produced from wood there are various substances which contribute to the flavour and the appearance of the smoked meat product and which have a certain preserving effect on the product.
However, the preserving effect of common smoking is not very significant when storing the product without a cold chain. On the other hand, intensive or prolonged smoking may considerably increase the shelf-life of the product, but it also has an unfavourable effect on flavour. Whereas a light smoke aroma generally enhances the organoleptic properties of the product, intensive smoking has a negative influence on the quality, especially in the case of prolonged storage in which concentrated smoke compounds develop increasingly unpleasant tarry flavours.
In view of the above, smoking in order to preserve meat can only be considered as an emergency measure when no other preservation methods can be carried out. This may be the case during wet weather or generally under a humid climate, or when the preservation has to be completed as fast as possible because of the need of immediate transport, for instance after game-hunting.
Intensive meat smoking is always a combination of two effects, drying the meat by reducing its moisture content through hot air and the condensation of smoke particles on the meat surface together with their penetration into the inner layers of the product. Both have preservative effects and prolong the shelf-life of the product.
To smoke the meat, large strips and/or pieces, with and without bones, are dried by smoking in special drying/smoking places. The smoke is produced in these cases by glowing wood. Often, meat is prepared quickly by drying and smoking over a fire. In this case, the meat is not only smoked, but “half-cooked” or roasted. Normally, meat from this treatment is not well prepared and has to be consumed soon after drying, otherwise it will spoil quickly.
The quality of traditionally smoke-dried meat is generally poor. This is not only owing to poor meat quality or inadequate smoking devices, but mainly because smoke-drying is a rather rough treatment for the meat. The process is fast and has a certain preserving effect, but at the cost of quality.
Quality losses are even more obvious when failures in preparing the raw material occur. When, for example, the thickness of the meat parts to be smoked ranges from about 3 cm to 15 cm, uniform drying will not be achieved. The smaller pieces will be overdried and the thicker ones may still remain with a high moisture content in the product centre. The results of faulty drying and smoking are a too strong smoke flavour, lack of rehydration capacity of the smaller parts and fast spoilage of the thicker parts. For effective smoke-drying, the meat thickness should not exceed 7 cm to achieve products which are stable for a certain period without refrigeration.
Apart from primitive smoking places with just a fire below the meat, the construction of special smoking kilns has been suggested for smoke-drying of meat.
The effect of light smoking could be of interest for the production of dried meat. Light smoking is not suitable for meat preservation without a cold chain, but it adds a smoke flavour to the product and inhibits the growth of moulds and yeasts on the product's surface owing to the fungistatic smoke compounds. Thus light smoking may be used for the prevention of growth of moulds during the storage period of dried meat, especially under humid climatic conditions.
Dried meat with spices and additives
Various methods, typical for different regions, exist to produce this type of product. General guidelines for manufacture cannot be given because of the great variety of preparations, but the idea behind all of them is to combine the necessary preservation of meat with a typical flavour. In some cases the additives act as an absorbent with the aim of faster drying, and some spices may also act against bacterial growth.
TYPICAL DRIED-MEAT PRODUCTS WITH OR WITHOUT ADDITIONAL TREATMENT
Some examples of dried meat or dried and further processed meat manufactured in Africa, America and the Near East are described. No mention is made of the various dehydrated meat products well known in the Far East. These products are somewhat different owing to their sugar component. They will be the subject of future FAO studies.
(Somalia and other East African countries)
Odka is basically a sun-dried meat product made of lean beef and is of major importance to nomads in Somalia. In the face of perennial incidence of drought in the Horn of Africa, odka has become important since it is often prepared from drought-stricken livestock.
The production of odka is similar to the simple drying technique described earlier. However, the meat strips cut for drying are bigger and dry salting is usually applied instead of brine salting. After only four to six hours' sun-drying the large pieces of meat are cut into smaller strips and cooked in oil. After this heat treatment drying is continued and finally sauces and spices are added. For storage odka is again covered with oil and, when kept in a tightly closed container, it has a shelf-life of more than 12 months.
(Ethiopia and other East African countries)
Qwanta is manufactured from lean muscles of beef which are further sliced into long strips ranging from 20 to 40 cm and are hung over wire in the kitchen to dry for 24 to 36 hours. Prior to drying, the strips are coated with a sauce containing a mixture of salt (25 percent), hot pepper/chilli (50 percent) and aromatic seasoning substances (25 percent). After air drying the meat pieces may be further exposed to a light wood smoke and are then fried in butter fat and dried again to some extent. At this stage the product is ready for consumption or storage.
(Nigeria and other arid or semi-arid zones of West Africa)
Kilishi is a product obtained from sliced lean muscles of beef, goat meat or lamb and is made on a large scale under the hot and dry weather conditions prevailing from February to May. It is produced by sun-drying thin slices of meat. However, recent experience indicates that kilishi can also be produced industrially using tray-drying in a warm air oven. Connective tissue and adhering fatty material are trimmed off the meat which is cut with a curved knife into thin slices of about 0.5 cm thickness, 15 cm length and as much as 6 cm width.
Traditionally, the slices of meat are spread on papyrus mats on elevated platforms or tables in the sun for drying. However, these papyrus mats may lead to hygienic problems, especially after repeated use. Therefore, easily washable corrosion-free wire nets or plastic nets are recommended for horizontal drying. The vertical drying method is also recommended in this case.
Sun-drying of kilishi could also be improved by the use of solar dryers as shown in Figs 19 and 20. These devices will increase the rate of drying of the product and keep insects and dust from the product.
In the first stage of drying, which takes two to six hours, the moisture of the meat slices has to be reduced to about 40 to 50 percent. The slices are then put into an infusion containing defatted wet groundnut cake paste or soybean flour as the main component (about 50 percent), and is further composed of water (30 percent), garlic (10 percent), bouillon cubes (5 percent), salt (2 percent) and spices such as pepper, ginger and onion. The “dried” slices of meat should absorb the infusion up to almost three times their weight.
After infusion, the wet product is again exposed to the sun to dry. Drying at this stage is much faster than at the first stage. When the moisture content of the slices has been reduced to 20 to 30 percent, a process which takes two to three hours depending on weather conditions and the dimensions of the product, the slices are finally roasted over a glowing fire for about five minutes. The roasting process helps to enhance desirable flavour development and to inactivate contaminating micro-organisms. Roasted kilishi is therefore superior in flavour to the unroasted version.
After roasting, the final moisture content ranges between 10 to 12 percent. It will decrease during storage at room temperature to as low a level as 7 percent. When packaged in hermetically sealed, low density plastic bags the product remains remarkably stable at room temperature for a period of about one year (see Chapter 4).
(Southern African countries)
Biltong is a well-known salted, dried meat prepared from beef or antilope meat. Most muscles in the carcass may be used but the largest are the most suitable. The finest biltong with the best flavour is made from the sirloin strip and the most tender is derived from the fillet.
The meat is cut into long strips (1 to 2 cm thick) and placed in brine, or dry-salted, which is actually the most popular method. Common salt, preferably coarse salt (1 to 2 kg for 50 kg of meat), or salt and pepper are the principal ingredients used, although other ingredients such as sugar, coriander, aniseed, garlic or other spices are included in some mixtures to improve flavour. In most cases nitrate or nitrite is added to achieve a red colour and the typical flavour of cured meat. The addition of 0.1 percent potassium sorbate to the raw meat is permitted in South Africa as a preservative. The salt/spice mixture is rubbed into the meat by hand and the salted strips are then transferred to a suitable container. It is recommended that a little vinegar be sprinkled on each firmly packed layer in the container.
Biltong is left in the curing brine for several hours, but not longer than 12 hours (otherwise it will be too salty), and then dipped into a mixture of hot water and vinegar (approx. 10:1). The biltong is now ready for sun-drying for one day. Then the strips are moved into the shade for the rest of the drying period. The product is usually not smoked, but if it is smoked only light cold smoking is recommended, which takes one to two weeks under sufficient air circulation. The biltong is ready when the inside is soft, moist and red in colour, with a hard brown outer layer.
Biltong is sold in sticks or slices. The usual shelf-life is several months without refrigeration and packaging, but in airtight packages the product stores well for more than one year. Biltong is not heated during processing or before consumption. It is eaten raw and considered a delicacy.
(Turkey, Egypt, Armenia)
Pastirma is salted and dried beef from not too young animals. In some areas camel meat is also used. The meat is taken from the hindquarters and is cut into 50 to 60 cm long strips with a diameter of not more than 5 cm. The strips are rubbed and covered with salt and nitrate. The dosage of the nitrate in relation to the meat is 0.02 percent, that means 2 g of nitrate for 10 kg of meat. Several incisions are made in the meat to facilitate salt penetration.
The salted meat strips are arranged in piles about 1 m high and kept for one day at room temperature. They are turned over, salted again, and stored in piles for another day. Thereafter the meat strips are washed and air-dried for two to three days in summer and for 15 to 20 days in winter. After drying the strips are piled up again to a height of 30 cm and pressed with heavy weights (approx. 1 tonne) for 12 hours. After another drying period of two to three days the meat pieces are again pressed for 12 hours. Finally the meat is again air-dried for 5 to 10 days.
After the salting and drying process, the entire surface of the meat is covered with a layer (3 to 5 mm thick) of a paste called cemen, which consists of 35 percent freshly ground garlic, 20 percent helba (i.e. ground trefoil seed), 6 percent hot red paprika, 2 percent mustard, and 37 percent water. Helba is used as a binder of the paste; the other ingredients are spices, but garlic is the most important as it is antimycotic. The meat strips covered with cemen are stored in piles for one day, and thereafter are dried for 5 to 12 days in a room with good air ventilation, after which the pastirma is ready for sale. Thus, the production of pastirma requires several weeks. However, not much energy is required since most of the salting and drying is done at room temperature. The final product has an average water activity (aw) of 0.88 (see Chapter 5). The aw should not fall below 0.85 or the meat will be too dry. The salt content should range between 4.5 and 6.0 percent. The product is mould-free for months at ambient temperature even in summer. Pastirma thus has a better microbiological stability than biltong.
(Brazil and other South American countries)
Charque consists of flat pieces of beef preserved by salting and drying. The fresh, raw meat from the fore- and hindquarters is cut into large pieces of about 5 kg, which should not be more than 5 cm thick. The pieces are submerged in a saturated salt solution for about one hour in barrels or cement vats. On removal from the brine, the meat is laid on slats or racks above the brine tank to drain.
For dry-salting, the flat meat pieces are piled on a sloping, grooved, concrete floor under a roof. To form a pile, salt is spread evenly over the floor about 1 cm high. Then a layer of meat is put on the salt. The meat is covered with another (1 cm) layer of salt followed by adding another layer of meat, and so on until the alternate layers of salt and meat reach a height of about 1 m. The pile is then covered with a few wooden planks and pressed with heavy stones.
After eight hours the pile is restacked so that the top meat goes to the bottom of the pile. The restacking process with fresh layers of salt is repeated every day for five days.
The salted meat is then ready for drying. Before initiating drying, the meat pieces are subjected to rapid washing to remove excess salt adhering to the surface. The meat pieces may also be passed through a pair of wooden rollers or a special press to squeeze out some surplus moisture and flatten the meat slabs. The meat is then spread out on bamboo slats or loosely woven fibre mats in a shed or, in industrial production, exposed to the sun on wooden rails which are oriented north-south, thus permitting an even solar coverage.
Initial drying, directly in the sun, is limited to a maximum period of four to six hours. This period of exposure may be subsequently lengthened to a maximum eight hours. Temperatures in excess of 40°C on the meat surface should be avoided. To ensure even drying over the extended muscle pieces, the meat is placed on the rails during the morning and removed again in the afternoon. The meat pieces are exposed to the sun each day over a period of four to five days. After each period of exposure the pieces are collected, stacked in piles on concrete slabs and covered with an impermeable cloth to protect them against rain and wind and to hold the heat absorbed.
When sufficiently dry, the meat pieces are either sold without prior packaging or wrapped in jute sacks. Plastic sacks are not suitable, because the product still contains a certain proportion of its original moisture content, and this moisture must be allowed to drain freely from the product. Charque keeps for months under ambient room conditions and is resistant to infestation by insects and growth of moulds.