Meat Processing and Utilization in Tropical Africa: A Review

Review Article

Meat Processing and Utilization in Tropical Africa: A Review

Corresponding author: Kubkomawa, H.I., Department of Fisheries Technology, Federal Polytechnic, Mubi Adamawa State, Nigeria; E-mail: kubkomawa@yahoo.com, Tel: 07066996221

Abstract

The objective of the paper was to review meat processing methods and consumption rate in tropical Africa. Meat is a major animal product which has high quality in human nutrition. It is a balanced source of protein, having essential amino acids of lysine, methionine, B vitamins (especially B12) and iron. Meat in Nigeria and elsewhere in Africa is processed locally in a traditional way in the public abattoirs. It is usually cooked fresh at homes for households’ meals, restaurants for sale, festivals and ceremonies for celebrations. Meat is occasionally preserved by smoke and sun drying, frying and refrigeration for future use. Meat consumption of Nigeria increased from 21g/person/day in 1992 to 23g/person/day in 2007 growing at an average annual rate of 3.23 %. This also falls below the recommended minimum standard of animal protein intake by FAO. Therefore, African government and Nigeria in particular should wakeup to the reality of the moment by improving the per capital income of the citizenry to enable them improve their animal protein intake for healthy living and high productivity around the continent.

Keywords: Flesh Processing, Consumption Rate, Tropical Africa

Introduction

Meat is generally refers to the edible flesh of those animals which are acceptable to be eaten or for consumption by man. Meat is superior to vegetable food because vegetables are deficient in B vitamins, lysine, methionine and iron. Iron in meat is readily absorbed compared to poorly absorbed iron from plants sources [1].

White meats like ostrich, chicken, fish and rabbit contain less fats and cholesterols and have higher health benefits. Apart from fish, rabbit meat has the highest amount of protein and contains the lowest fat than all other types of meat. It contains less calories and Sodium than other meats but contains more calcium and phosphorus which is very good for body functioning [2].

Meat consumption is the amount of flesh available for human consumption. However, the actual flesh consumption may be lower than the quantity recommended by FAO as meat availability depending on the magnitude of wastage and losses in the household, e.g. during processing, storage, preparation and cooking, as plate-waste or quantities fed to domestic animals and pets, thrown or given away. Meat consumption per person is the amount of flesh, in terms of quantity, for each individual in the total population.

The Federal Ministry of Agriculture and Rural Development said in 2018 that Nigerians consume about 360,000 tonnes of beef yearly. This conservative figure is projected to rise to 1.3 million tonnes per year by 2050. Poultry meat accounts for 30% of global meat consumption. The worldwide average per capita consumption of poultry meat has almost quadrupled since 1960s, 11kg in 2003 compared to 3kg in 1963 [3]. Pork is another meat most commonly consumed in the world, accounting for about 38% of meat production worldwide. In Nigeria and elsewhere in Africa, meat per capital consumption is far lower than the recommended level by FAO which grossly affects the health of the work force, general mental and physical productivity of the continent. Though, excessive beef consumption is one of the factors that lead to the development of cardiovascular diseases, obesity, hypertension and cancer. These effects are directly related to the fat present in beef, which has an elevated concentration of saturated fatty acids (SFAs) and a lower ratio of polyunsaturated to saturated fats when compared to white meat [4]. The objective of the paper was to review meat processing methods and consumption rate in tropical Africa.

 Reasons for Eating Meat:

Olawoye and Kubkomawa (2018) reported that, meat is similar to human flesh in composition. It is a protective food. It ensures protection against nutrients deficiencies. Nutrients found in meat are, therefore, directly useful in nourishing human body [5]. Meat is concentrated in essential nutrients such as essential amino acids, especially lycine and methionine, both of which cannot be found in adequate amounts in any one plant origin. It is a source of all minerals, especially iron and vitamins [1, 2].

Similarly, it is palatable and consumed for pleasure e.g. in social gathering. Eating meat is associated with high social class, wealth and affluence [1]. It is consumed on religious grounds. Those who cannot consume meat always can go to the extent of taxing themselves during religious festivals to get their share of meat. Meats of different kinds are also used during marriage, naming ceremonies, funerals and birthday ceremonies.

Meat can temper with the toxic effects of alcohol. Meat contains protein and fats which digest slowly and are absorbed slowly. They tend to reduce the rate at which alcohol is absorbed in the blood stream, hence reduce the degree of alcoholic intoxication, therefore, meat provides high satiety to human beings [1]. Meat or fish is used to import some intrinsic, desired flavour to soups. Soup flavours are improved when they contain certain meats. It is a tribute to meat as palatable food. It transcends all other food in aroma, causing watering of the mouth. It causes a flow of saliva and gastric juice.

Example of meat is shown in figures 1, 2, 3 and 4.

Figure 1: Beef                                                               Figure 2: Pork

       Figure 3: Rabbit Meat                                            Figure 4: Chicken Meat

 

Per Capital Meat Consumption

It is recommended by FAO (1970) that, the total minimum protein intake for adults is 85.9g per day of which about 34g or 40% should be of animal origin. In Nigeria, a total protein intake is below the FAO recommended minimum standards. Animal proteins contributed only 8.6g or 16.6% of an estimated 51.7g daily total protein intake of an average Nigerian. This ration went down to 6.5g or 14% of a total of 46.7g total protein intake by 1984.

Slaugtering and Dressing Techniques

According to [1, 4, 6], there are five main stages involved in converting live animal to carcass.  In the United States, the humane treatment of animals during each of these stages is required by the Humane Slaughter Act. The main steps are: Pre-slaughter handling, stunning or immobilization, bleeding, skinning and evisceration. These steps ensure through human slaughter that, the animal is clean externally of hair and skin or internally of blood and digesta or gut contents.

Steps in Slaugtering Animals

Pre-Slaughter Handling

Giovani et al. (2012); Adamu, S. M.; Olawoye and Kubkomawa (2018) [1, 6, 7] reported that, pre-slaughter handling is a major concern to the livestock industry, especially the pork industry. Stress applied to livestock before slaughter can lead to undesirable effects on the meat produced from these animals as shown in Figure 4. Pre-slaughter stress can be reduced by preventing the mixing of different groups of animals, by keeping livestock cool with adequate ventilation, and by avoiding overcrowding. Before slaughter, animals should be allowed access to water but held off feed for 12 to 24 hours to assure complete bleeding and ease of evisceration (the removal of internal organs).

Figure 4: Manual Restraining of Beef Cattle

Stunning or Immobilization

As the slaughter process begins, livestock are restrained in a chute that limits physical movement of the animal. Once restrained, the animal is stunned to ensure a humane end with no pain. Stunning also results in decreased stress of the animal and high meat quality. It is a means of rendering the animal unconscious before bleeding. It is a human act of killing which makes the animal completely unconscious in a minimum excitement or discomfort. It also renders the animal helpless and easy for the operator to bleed the animal with minimal effort. Four methods of stunning are identified: mechanical, chemical, electrical and ritual as described by Giovani et al. (2012); Adamu, S. M.; Olawoye and Kubkomawa (2018) [1, 6, 7].

Mechanical stunning is the penetrating type, such as the captive bolt gun or the concussion type, such as compression stunner. Compression stunners deliver high velocity blow with penetrating or non-penetrating or mushroom hairs. It is effective in painlessly stunning cattle, swine and sheep. In the case of the captive bolt gun, the captive bolt enters the skull while in the concussion type, the force will be delivered through a mushroom head through the head of the bolt. The stunning can be administered to the forehead or in the back of the poll [1, 6, 7].

Chemical stunning uses carbondioxide gas which can be held in pit with a minimum loss of gas as it is heavier than air, the chamber holds 65-75% CO2. It is commonly used for pigs which are driven into the chamber of CO2 and rendered unconscious [1, 6, 7].

Electrical stunning involves high voltage of 400 – 600volts. The voltage is applied between the ears or back of the poll in pigs [1, 6].

Ritual bleeding involves tying the hoofs of the animal before it is bled. Animals are not stunned where ritual bleeding is employed. For example, the Kosher or Islamic slaughter method. Usually the animal is oriented to face the east [1, 6].

Bleeding

After stunning, animals are usually suspended by a hind limb and moved down a conveyor line for the slaughter procedures. They are typically bled (a process called sticking or exsanguination) by the insertion of a knife into the thoracic cavity and severance of the carotid artery and jugular vein. This method allows for maximal blood removal from the body. At this point in the process, the slaughtering procedures begin to differ by species. Bleeding is achieved by making a full cut across the throat below the jaw line, severing the jugular of an animal while it’s on the floor or hanging upside down from a hoist. Another method of bleeding is sticking. This involves inserting a sharp knife in to the breast or brisket at an angle of 45° and severe the carotid arteries and jugular vein. Only about 50% of the blood value can be removed from the body, the remainder is held in vital organs as described by Giovani et al. (2012); Adamu, S. M.; Olawoye and Kubkomawa (2018) [1, 6, 7]. Examples of manual slaughtering of livestock are demonstrated in figures 5, 6, 7, 8 and 9.

 

 

Figure 9: Manual Slaughtering of Chickens

Hogs are usually stunned by electrical means or CO2 gas. Mechanical stunning is not generally used in hogs because it may cause serious quality problems in the meat, including blood splashing (small, visible hemorrhages in the muscle tissue) in the lean meat as reported by Giovani et al. (2012); Adamu, S. M.; Olawoye and Kubkomawa (2018) [1, 6, 7]

Hogs are one of the few domesticated animals in which the skin is left on the carcass after the slaughter process. Therefore, after bleeding, the carcasses undergo an extensive cleaning procedure. First they are placed for about five minutes in a scalding tank of hot water that is between 57 and 63 °C (135 and 145 °F) in order to loosen the hair and remove dirt and other materials (called scurf) from the skin. The carcasses are then placed in a de-hairing machine, which uses rubber paddles to remove the loosened hair. After de-hairing, the carcasses are suspended from a rail with hooks placed through the gambrel tendons on the hind limbs, and any residual hair is shaved and singed off the skin [1, 6].

An exception to this procedure occurs in certain specialized hog slaughter facilities, such as “whole hog” sausage slaughter plants. In whole hog sausage production, all the skeletal meat is trimmed off the carcass and, therefore, the carcass is routinely skinned following exsanguination [1, 6].

After cleaning and de-hairing, heads are removed and carcasses are opened by a straight cut in the center of the belly to remove the viscera (the digestive system including liver, stomach, bladder, and intestines and the reproductive organs), pluck (thoracic contents including heart and lungs), kidneys, and associated fats (called leaf fat). The intestines are washed and cleaned to serve as natural casings for sausage products. The carcasses are then split down the center of the backbone into two “sides,” which are placed in a cooler (called a “hot box”) for approximately 24 hours before fabrication into meat cuts [1, 6].

Cattle, calves, and sheep are usually stunned mechanically, but some sheep slaughter facilities also use electrical stunning. The feet are removed from the carcasses before they are suspended by the Achilles tendon of a hind leg for exsanguination. The carcasses are then skinned with the aid of mechanical skinners called “hide pullers.” Sheep pelts are often removed by hand in a process called “fisting.” (In older operations, hides and pelts are removed by knife.) The hides (cattle and calves) or pelts (sheep) are usually preserved by salting so that they can be tanned for leather products. Heads are removed at the first cervical vertebra, called the atlas joint. Evisceration and splitting are similar to hog procedures except that, kidney, pelvic, and heart fat are typically left in beef carcasses for grading. Carcasses are then placed in a cooler for 24 hours (often 48 hours for beef) prior to fabrication into meat cuts [1, 6].

Skinning or External Cleaning

This involves removing the hide in cattle, skinning in goat and sheep, de-hairing in swine and removing feathers or de-feathering in poultry. This is flayed on the floor or on a flayed rug, while sheep and goat are flayed hanging upside down by the archine-tendon. In the tropics, cleaning many sheep and goats involves burning of the hairs by roasting. Roasting is also applied to pigs dogs, donkeys, horses and rabbits processed in homes and farms. Poultry is de-feathered after loosening the feathers in hot water at 62°C, while that of pig at 65-71°C [1, 6]. Manual Flaying and Processing of farm animals are shown in figures 10 and 11.

Figure 10: Manual Flaying of Beef Cattle                       Figure 11: Manual Flaying of Camel

Evisceration

It is the process of removing the visceral contents. The breast and the abdomen are openned up at midline. The intestine is pulled out. The pluck, lungs and liver are also removed and gall bladder is also removed. The carcass is washed. The viscera, gut and stomach are cleaned for human consumption in most tropical countries [1, 6].

Other three (3) steps expected to be followed are washing of carcass, meat inspection for wholesomeness and cutting of the carcass into wholesale or retail cuts. In countries where tenderness of carcass is desired and the cold-room facilities are available, carcass is chilled at 1.6 – 4°c for 24 – 48hours. This enables the carcass to be firm and tender [1, 6].

Manual Evisceration and Processing of livestock are shown in figures 12, 13, 14, 15 and 16.


Figure 16: Processing and Weighing of Chicken Meat

Evaluation of Dressed Carcass

Carcass is the portion of animal left after the external and internal offals have been removed. It consists of the muscle, fat, connective tissue and bones. The yield of the carcass depends much on edible offal which has been left intact on the carcass. This is true of carcass of roasted goats, pigs, rabbits and chicken, where the skin, feet and head are left on the carcass. In traditional European method of slaughtering animals, the head, skin, feet are removed and designated as offals. This practice lowers the yield of the carcass [1, 6].

The Average Carcasses of Some Animals:

Carcass dressing percentage = dressed carcass weight x 100

Live weight of animal

If a goat’s weight is 25kg and the carcass weight is 11.25kg, the carcass dressing percentage:

X = carcass weight x 100 = 11.25 x 100 = Dressing % = 45%

Live weight                    25

This goat is dressed in a typical European style, where the head, skin, feet and Visceral contents were removed. Where the head, feet and skin were left on the carcass, carcass yield is 64.6%. The significance of dressing percentage is in estimating carcass yield of an animal without actually weighing the carcass [1, 6].

 Principles of Meat Identification

It is important that, meat cuts are well separated and identified for the following reasons: Proper identification is a prerequisite for more profitable merchandising as meaty and tender cuts cost more than bony and less tender cuts. Proper utilization of meat depends on identifying a cut for a specified type of cooking. Some cuts from the shoulder are rich in collagen and are better cooked on dry heat. Since, the various cuts differ in composition and tenderness, lean cuts are separated from fat cuts and tender from less tender cuts. Also, thick cuts designated as roasted are distinguished from thin cuts which are designated as steak. Meat identification is vital for checking pilfering of carcass fats which is common among some butchers. It is also used for identifying joints or cuts which sell faster than others. Some large carcasses from beef, large pork and goats are impractical to transport from the abattoir to the wholesale or retail market places in one piece. Hence, carcass must be split into halves, fore and hind quarters or smaller identifiable cuts for ease of transportation as stated by Giovani et al. (2012); Olawoye, U. H. [1, 7]

The names of wholesale or retail cuts are related to and are named after bone structures. The location of retail cuts are also a clue to cuts tenderest. The supporting muscles along the backbone are generally tenderer than those of the shoulder, legs, breast and flank. Hence, the meat along the backbone is considered as the tenderness. There are essentially seven basic retail cuts of meat based on skeletal locations in the carcass. The seven basic cuts are from the arm, rib, sirloin, loin, leg or round breast cuts and blade. The retail cuts from the seven (7) basic areas are common to beef, hog, lamb and goat as can be seen in table 1 and figure 17. Whether retail cut is called a roast or a steak is based on the thickness of the cuts and the recommended cookery method as reported by Giovani et al. (2012); Olawoye, U. H. [1, 7]

 

Table 1: The Names of Cuts of Carcass in Three Major Languages in Nigeria (Hausa, Igbo, Yoruba)

 

Chemical Composition and Chemistry of Meat

According to Giovani et al. (2012); Olawoye, U. H. [1, 7], the chemical composition of fresh meat and their reactions to physical, chemical, physio-chemical or thermal treatments are the fundamental principles of meat processing. The term fresh meat includes that product which has gone through physical characteristic changes from slaughter to certain stage of rigor but which has not been further processed by freezing, burning or smoking. The characteristics or properties of meat include its potential usefulness to the processor, home merchandise and consumers; it shows its adaptability for further processing in other products. The important active components are water, protein, carbohydrate, lipids and inorganic components. The physio-chemical and thermal reaction of this meat component that could lead to a new product, better shelf life or improved eating quality of meat are considered.

 

Water and Water Holding Capacity (WHC) of Meat

Meat contains about 75% water. Water holding capacity is the ability of meat to retain its water during application of external forces such as cutting, heating, grinding or pressing. The power with which this water is bound by the muscle proteins is of great importance for quality of meat and meat products. Many physical properties of meat such as colour, texture and firmness of raw meat and the juiciness and tenderness of cooked meat are partially depended on water holding capacity. Procedures for storing and processing of meat are influenced by the WHC of meat and the procedures can change the WHC of the meat. Some of the procedures include storage, grinding, transportation, salting, curing, cooking, canning, freezing, thawing or drying as described Giovani et al. (2012); Olawoye, U. H. [1, 7]

Proteins

Meat contains about 19% protein on wet weight basis. The major fractions of the protein include myofibrillar 11.5%, sarcoplasmic 5.5% and connective tissue 2%. Myosins is the most abundant of the myofibrillar protein. It has a high content of glutumics, aspartic and dibasic amino acids, which make it highly charged and has a strong affinity for calcium and magnesium ions. The other major myofibrillar is active, the myofibrillar protein are soluble in concentrated salt solution. Sarcophomic proteins are soluble in water or diluted salt solution. Myofibrillar is a sarcophomic protein responsible for colour of meat. Connective tissue proteins form the major supportive ligament of the body and are insoluble in salt solution at low temperatures. Connective tissue proteins include collagen and elastin [1, 7].

Lipids in Meat

Meat contains a large number of fats-like substance called lipids. Fats, the glycerol esters of fatty acids, constitute over 95% of the total lipid in the body. Although, the total body fats are next in abundance to water, it is about 40% of carcass depending on dietary regime [1]. Fats contain fatty acids, 7 of which comprise more than 98% of the total fatty acids in meat. This fatty acids are; palmitic, stearic, palmitoleic, oleic, linoleic, limolenic and arachidonic. Linoleic and arachidonic are a dietary essential for humans, occurring in animal fats [1, 7].

Nutritive Content and Food Value of Meat

Meat is a very rich source of high quality protein, B-complex vitamin, minerals such as iron and copper and essential fatty acids such as linoleic (C18:2), linoleic (C18:3) and arachidonic (C20:4). The CHO content is low and fats content varies, depending on the plane of nutrition of the animal and the amount of trimming during feed preparation. Meat has prestige value, its taste and aroma appear to be particularly attractive and it is generally having high nutritive value. It is a highly regarded component of any balanced meal. Meat is known to be good for body building and resistance to disease [1, 7].

There is a remarkable similarity in the protein and amino acids of meat of animals and man, despite differences in species and diet. The lysine and methionine content in muscle of various sizes vary from 0.1 – 0.57% and 0.14 –0.16%, respectively. This indicates the essential amino acids requirements of man and these essential amino acids can be met easily from meat of any animal species [1].

The biological values of individual plant proteins are generally lower than those of animal protein with the exception of gelatine which has BV of 0.1. Hides and skin are very rich in gelatine. Meat has BV of 75% while soya has BV of 70% [1].

Vegetarians may balance their amino acids by consuming soyabeans and sesame. Soya is a good source of lysine but low in methionine, whereas sesame has high methionine content, as high as that of white fish meal. However, vegetarians can develop anaemia through lack of iron and vitamin B12.  Vegetable sources of iron are poorly absorbed [1].

It can be seen that, the nutrient content of meat has protein and amino acids and these two contain high quality proteins with all the essential amino acids required by the human body. The protein is highly digestible and is easily absorbed. These essential amino acids are those that cannot be synthesised by the body in amounts sufficient to meet its requirement. Adult human beings need 8 amino acids. When soya bean is compared with animal protein, it is found to be low in methionine and thryptophan. Sesame or beniseed is low in lysine but it is high in methionine in equivalent amounts to that in animal protein. This shows that, vegetable proteins are not as balanced in amino acid as animal proteins [1].

Food and nutrition board of the National Research Council prescribed that, a grown man requires 56gramms of protein per day as the recommended dietary allowance.

Meat Preservation

Fresh meat is a very rich nutritive medium for micro-organisms, if it is not protected [1]. Therefore, there is a need for preservation of meat so as to protect it from bacterial damage (spoilage).

Reasons for Meat Preservation

Preserved meat is attractive, maintains its good flavour, aroma and its nutritive protein is intact. Meat is usually transported for long distances from the area of slaughter. Preservation ensures that, meat reaches customers in an acceptable form. Meat must be preserved from spoilage in tray or cold room/vehicle. Preserved meat ensures that abundance of meat could be available at all times to prevent scarcity, i.e. it stabilizes demand and supply. It also ensures availability of variety from which customers will select from. When organized hunting is practiced, carcass is preserved by smoking while in the hunting camp. Preserved meat ensures the convenient and instant source of meat when needed [1, 2].

Principles of Meat Preservation

The principal factor in meat preservation is micro-organisms. Their growth or proliferation requires warmth, moisture, optimum PH and oxygen. Therefore, create an unfavorable condition to prevent their multiplication or provide a lethal condition for their elimination. The controlled factors are temperature, which include refrigeration and thermal processing, dehydration and direct microbial inhibition, which include ionization radiation, antibiotics and chemicals such as salts, nitrates, wood smoke, sugar and organic acid [1, 2].

Different Preservation Methods

Temperature – it involves refrigeration.

Refrigeration: – refrigeration temperature is between -2°C and -3oC. Period of refrigeration storage or shelf life is between 3 – 4 days. Weight loss is ensured during refrigeration due to moisture lost. The moisture is called chilling lost. A length of storage depends on bacterial load, temperature and humidity condition, the size of the animal etc [1, 2].

Storage below freezing point: – meat freezes at approximated -2°C to -3°C instead of at 0°C because of concentration of salt which lowers the freezing point.  Some microbial and enzyme activities occur at temperature up to -10°C but below -10°C most deterioration due to enzymatic activity is curtailed. At -10°C beef and lamb remained resistant to oxidative activity after 18months storage. In general, the recommended storage time in months is 6 – 12 for beef, 6 – 9 for veal, 3 – 6 for pork, 6 – 9 for lamb, ground beef 3 – 4months and ground pork 1 – 3months etc [1, 2].

Storage by Moisture Control or Dehydration

Deprivation of available moisture prevents growth of micro-organisms found in meat and may kill them. Water may be removed from meat by sun drying, smoke drying, freeze drying or water may be made unavailable to micro-organisms by increasing the extra cellular osmotic pressure as in curing or salting [1, 2].

Methods of Drying Meat

Sun Drying

 It is practiced with lean or low fat meat such as grass fed animal beef that is cut into slices, rubbed with mixture of spices and then sun dried. Quick drying is achieved if the slices are placed on wire mesh to dry. The wire mesh allows hot air movement on both sides of the meat, application of spices reduces contamination by flies, for example, it is called kilishi in Nigeria [1, 2].

Figure 18: Kilishi

In order to improve the process of finished products, the meat is pre-cooked before drying. Sometimes, the meat is dried after smoking in salt solution and heated in water at 72°C-75°C for 10 – 15 minutes, then drained and sun dried [1, 2].

Smoke Drying

Smoking and drying are often combined in developing countries. Hot smoke is generated by burning hard wood in combination with saw dust. The hard wood generates the heat while saw dust generates the smoke. The heat dehydrates the meat while smoke deposits some degree of penetration. Smoke components, aldehydes, acetic and other acids, phenols, resins, exert preservative action and impregnate the meat surface giving a smoky taste and a desirable flavour. Usually, the meat to be smoked is suspended above the source of smoke at a distance so that, the heating can be effective. Meat dries faster when it is thinned very well [1, 2].

Moisture Control by Curing or by Characteristically Dehydrating

The principal ingredient in a cure mixture is common salt. At salt concentration of 9-11%, microbial growth is inhibited as a result of the increased osmotic pressure of the meat and in lowering of the water activity. Salt is acting as a characteristically dehydrating agent. The biochemical mechanism of curing is that, water and solubles flow out of the meat because salt diffuses instantly. The accumulation of the salt is linear with the salt concentration of the brine [1, 2].

Freeze Dehydration

This is the removal of water vapour from frozen meat without throwing it or going through the liquid state. This is a process of rapid dehydration by gentle heating under a vacuum. The process of passing from solid state to vapour phase without going through a liquid state is called sublimation, for example, freeze dry products are stock fish, meat, dehydrated soup mixture etc. Heat of sublimation is supplied by a plate heat exchanger through which warm water is circulated. The vacuum chamber is operated at a pressure of 1.0 – 1.5mm/hg to a temperature of 43°C [1, 2].

Preservation by Direct Microbial Inhibition or Destruction

There are two (2) ways: Radiation or thermal method of preservation [1, 2].

(i)Radiation consists of two (2) types: Corpuscular and electromagnetic radiation, both use energy which travels through space. Ionizing radiation kills micro-organisms in and on meat without raising the temperature of the product. The thermal method of preservation is the application of heat to kill micro-organisms; this is employed in canned foods. Canned meat and meat products may be subjected to heat at two (2) levels:- pasteurisation and sterilization. Pasteurisation stops microbial growth with minimum damage, while in sterilization all or most bacteria are killed and meat is altered considerably.

(ii)Thermal processing is done at high temperature (120°C) and pressure (32kg/cm2) e.g. electric or gas cookers.

Processed Meat

Processed meat products are those with the properties of fresh meat which have been modified by the use of one or more procedures such as grinding, addition of seasonings, alteration of colour or heat treatment. It includes curing by smoking and any treatment or process resulting in two (2) substantial changes on the natural state of the meat, but does not include burning, cutting or trimming [1, 2].

Reasons for Processed Meat

Processed meat provides products with desired texture, flavour and aroma. It is a means of providing meat variety other than fresh meat. Processing transforms raw meat to products with longer shelf life e.g. salted and smoked beef. Examples of processed products: sausage, kebab, it may also be referred to as kilishi, smoked meat, roasted meat, frozen meat, canned meat, sun dried meat, fried meat, cooked meat [1, 2].

Methods of Cooking Meat and their Effects on Cooked Meat Quality

Reasons for Cooking Meat

Meat is cooked to improve its palatability factors of flavour, aroma, tenderness, juiciness and appearance. Meat is cooked in liquid to release its nutrients juice as soup. This is because meat protein coagulates, shrinks on heating to secrete meat juice rich in lipids. Meat is also cooked for wholesomeness as heat used is sufficient to kill parasites and micro-organisms. Other reasons include creating variety of products, improving nutritive requirement value, social requirements or religious customs. It is also cooked in order to preserve it [1, 2, 8, 9].

Palatability Parameters of Cooked Meat

The overall impression of the palate to how tough (tenderness), how much liquid (juiciness) and tasty (flavour) a meat may be is called palatability. If all impression is that of satisfaction, the meats appeals to the palate and as it is palatable more meat will be consumed. If the overall impression is dry, tough and one needs much saliva before he can experience any flavour from the meat, the meat will not appeal to the palate, and as it appears less palatable, less meat will be consumed. This is because the jaws will be tired from chewing dry and leathery meat before enough is eaten to quench hunger [1, 2, 8].

Tenderness

The overall impression of tenderness is obtained from the ease with which the teeth sinks into the meat when chewing, the ease with which the meat breaks into fragments and the amount of residue remaining after chewing.

Meat tenderness is not a problem in meat eating culture of Nigerians, tough meat with strong flavour is prepared to vary tenderness and juiciness of the meat as found with broilers. Broilers have to be deep-fat-fried or roasted to some degree of toughness to be accepted by an average Nigerian customer. Tenderness can be reduced by the addition of vinegar, lemon juice or some plant enzymes such as bromine, fascines etc [1, 2, 10]

Juiciness

The principal sources of juiciness in meat are the intra-muscular lipids and water content. In combination with water, the melted lipid constitutes a broth that when retained in meat is released upon chewing. The broth may stimulate the flow of saliva and improve the meat’s apparent juiciness. The main source of juiciness is water remaining in cooked meat. Minimizing moisture loss to keep the meat tender should be considered when cooking [1, 2, 10].

Flavour and Aroma

The flavour perception involves the detection of four basic sensations (saltiness, sweetness, sourness and bitterness) by the nerve endings on the surface of the tongue. Aroma is detected when numerous volatile materials stimulate the nerve endings in the lining of the nasal passage [1, 2, 10].

Methods of Cooking Meat

There are six (6) basic methods, which involve two (2) types of heat:- dry heat (without water), moist heat (with steam or liquid water). Examples of dry heat are roasting, broiling, frying and pan-broiling [1, 2, 8].

Roasting

It was used before the days of efficient ovens; the meat was hung or placed on top of a wire mesh before an open fire and cooked by radiant heat. In order to prevent burning and scorching before it is cooked, the meat had to be turned continuously [1, 2, 8].

 

 Ovens are devices that produce enclosed heat in which the heat surrounds the meat which needs no burning but is cooked.

Boiling

This is appropriate only for tender cuts such as steaks chops and ground meat because the heating period is usually of short duration and there is inadequate time to achieve connective tissue breakdown, for example, heating desired takes about 15minutes for 1 – 15cm meat thickness  [1, 2, 8].

 

Pan Boiling

This is suitable for some thin cuts as in broiling but not more than 2.5cm thick. The meat is placed in a heavy frying pan and heated, the meat is turned occasionally until the desired degree and tenderness is achieved, the pan is never covered throughout the cooking period [1, 2, 8].

Frying

It includes pan-frying in which the fat never covers or submerges the meat as in deep-fat-frying, in which the meat is covered in fat. In deep-fat-frying, there is no need to turn the meat as both sides are immersed in fat and cooked at once. The meat is coated with egg or flour [1, 2, 8].

 

Braising

This involves, mostly, cooking meat with small amounts of water added to the meat or juice from the meat during cooking, usually the pot is covered. Extra water is added if the meat contains relative large amount of connective tissue. This provides water for the complete hydrolysis of collagen connective tissue together, for example, pork meat. Salt is added before braising, for example, pepper meat [1, 2, 8].

Cooking in Liquid or Water

Here the meat is covered in liquid. It is for large, less tender cuts and stew meat; it is applied when making meat soup [1, 2, 8].

Conclusion and Recommendations

Processing of meat in Nigeria and elsewhere in Africa is still at the primitive level. Poor processing and storage facilities have made meat industry handicapped while the product is wasted in millions of tones every year. This process affects the living standard of the stakeholders and economy of the continent at large. Meat consumption in Africa is below minimum standards operated in developed world. Good meat processing method is therefore paramount for best presentation of transformed end product to the consumers. This, also, helps in packaging the product in acceptable, palatable and convenient way. Meat processing again helps to promote longer shelf life and ease of storage of the product. Meat consumers should therefore, intensify effort to meet up with the recommended minimum rate and not to over consume the product for healthy and high productivity at all levels of the economy.

References

  1. Olawoye, U. H., & Kubkomawa, H. I. (2018). Feed requirements of livestock and product processing for agricultural science and related disciplines, pp. 1 – 200.
  2. Olumide, A. & Carlos, E. C. (2017). Household Demand for Meat in Nigeria. Selected Paper prepared for presentation at the Southern Agricultural Economics Association’s 2017 Annual Meeting, Mobile, Alabama, February, 2017; 4-7.
  3. FAO (2009). Food and Agriculture Organization Statistics Division, Rome, Italy.
  4. French P., Stanton C., Lawless F., O’Riordan E.G., Monahan F.J., et al. Fatty Acid Composition, Including Conjugated Linoleic Acid, of Intramuscular Fat From Steers Offered Grazed Grass, Grass Silage or Concentrate Based Diets. J Anim Sci. 2000; 78(11):2849-55.
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  6. Adamu SM., Kubkomawa, HI (2018) Beef Production and Marketing in Tropical Africa: Entrepreneurship in Animal Agriculture. 1st ed, Published by Tapass Institute of Scientific Research and Development Ezeogidi Estate, Nigeria, pp. 131-145.
  7. Giovani F, Telma TB, Márcia CAS, Paulo HMD, Ricardo AR, et al. Qualitative Characteristics of Meat from Confined Crossbred Heifers Fed with Lipid Sources. Sci. agric. Piracicaba, Braz. 2012; 69 (5): 1-15.
  8. Koohmaraie M, Kent PM, Shackelford SD, Veiseth E, Wheeler TL. (2002). Meat Tenderness and Muscle Growth: Is There Any Relationship? Meat Sci. 2002; 62(3): 345-52.
  9. Rotta PP, Prado RM, Prado IN, Valero MV, Visentainer JV, et al. The Effects of Genetic Groups, Nutrition, Finishing Systems and Gender of Brazilian Cattle on Carcass Characteristics and Beef Composition and Appearance: A Review. Asian-Australasian Journal of Animal Science 2009; 22 (12), 1718–1734.

Webb, E.C. (2006). Manipulating Beef Quality through Feeding. South African Journal of Animal Science. 2006; 7 (1): 5–15.

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