Physical and chemical quality characteristics of warthog (Phacochoerus africanus) meat

L C Hoffman and J Sales

Department of Animal Sciences, University of Stellenbosch, PO Bag X1, Matieland, 7602, South Africa
lch@sun.ac.za

Abstract

The warthog (Phacochoerus africanus), a game species from Africa, has been evaluated in this study as a potential meat source according to carcass and meat quality characteristics.

Dressing percentage, calculated on the basis of cold carcass weight without skin and head, presents a value of 52 %. The contribution of the shoulder (37 %), loin (7 %), back (9 %), belly (14 %) and hind legs (32 %) to the cold carcass weight also differ substantially from that found for the domestic pig.  However, pH_60min (6.32), pH_24h, (5.49), drip loss (2.76 %), cooking loss (16.79 %), shear force (3.36 kg), colour characteristics CIEL (46.37), CIEa^* (5.06) and CIEb^* (9.21), moisture (74.04 %), lipid (1.69 %), protein (22.14 %) and ash (1.29 %) compared well to literature values for meat from other pig species.  The fatty acid profile of the meat differs substantially from other pig species, with unsaturated, mono-unsaturated, and polyunsaturated fatty acid contents of 35.75, 16.70 and 47.56 %, respectively, resulting in a polyunsaturated:saturated fatty acid ratio of 1.33.

It has been concluded from this study that warthogs provide a meat source suitable for human consumption that can also be promoted on its health properties.

Key words: carcass characteristics, chemical composition, physical characteristics, warthog meat

Introduction

The warthog, (Phacochoerus africanus), belonging to the Suidae family, has a natural distribution in Africa from Senegal and Guinea in West Africa, in the Sudan, Sahelian zones and Guinea savannas, to Ethiopia and south to the northern parts of the Republic of South Africa (Skinner and Smithers 1990).  Characterised by a high fecundity, the warthog has a mean of four to five piglets per litter and a gestation period of 167 to 175 days.  Mature males can attain a body weight of 100 kg and females up to 70 kg.  The growth of warthogs (Mason 1985; Somers and Penzhorn 1992) has been documented, and Somers (1997) calculated a sustainable harvesting rate using simulation modelling.  However, all the research conducted to date has concentrated on the biological and conservation status of this species.  Regarding meat quality characteristics, a preliminary study (Hoffman 2001) has found that warthogs, similar to the domestic pig, are prone to produce pale, soft and exudative (PSE) meat when exposed to ante mortem stress.  As noted by Somers (1997), in South Africa, as in other parts of Africa, poverty is widespread and use of wildlife as a source of income and food is important to local communities.

Hoffman et al (2005) have noted that warthog is a species regular consumed by locals in South African restaurants and is also a game species frequently consumed by tourists visiting South Africa (Hoffman et al 2003a).  However, no literature could be sourced where the nutritional composition of this species has been reported. Therefore, the objective of the present investigation was to collect base line data of the yield and chemical composition of the meat from the warthog.
 

Materials and methods

Warthogs were hunted in July (they normally breed in the September to November, with a peak in October in Southern Africa) in the Leeukop Nature Reserve (27˚25’ 31˚55’) in KwaZulu Natal, South Africa.  In this investigation, a single sharp-shooter fired all the shots using a .243 Winchester fitted with a telescopic sight and silencer.  The shots invariably caused the remainder of the herd (flounder) to run, although not at an alarming rate, still only one pig was shot per herd.  All the shots were fired in the daytime and utilized a flank, neck or head-shot to kill the warthog.  Directly after shooting, the animals were exsanguinated by sticking.

Immediately after killing, the animals were weighed to obtain a hot body weight.  After the targeted number of hogs (n = 5) had been harvested the animals were transported to a commercial small scale game processing plant where they were further processed according to standard South African and Zimbabwean practices.  This consisted of skinning (it is standard practice to skin both warthogs and wild pigs in Africa as very few game processing plants have the facility to remove the hair), removal of the head, evisceration, and cleaning of carcasses (Hoffman 2000).  Most of the subcutaneous fat is removed with the skin (the warthog is similar to the domestic pig in having a “thick” widely spread subcutaneous fat depot).  After cooling overnight in a cooler (1 °C), the carcasses were cut into the following commercial cuts: shoulder, loin, back, belly and hind legs.  The hind legs were removed after loosening the flanks on the inside of the legs (following the curve of the leg muscles) to an imaginary line perpendicular to the ilium (seen from the inside of the carcass).  The leg was then removed by cutting along this line, just missing the ilium (through the last lumbar vertebrae).  The weight of the two legs was recorded before the two legs were split along the sacral vertebrae using a bandsaw.  The rest of the carcass was halved prior to separating into trade joints.  The shoulder was removed by sawing along an imaginary line from the elbow joint to a point below the spinal column, between the 5^th and 6^th ribs.  The carcass was then swiveled so that the spinal column was sawn through at right angles.  The belly was removed by sawing from the Muscularis obliquus abdominis internus muscle parallel to the spine.  The loin and back was separated perpendicularly to the spinal column at the junction of the thoracic and lumbar vertebrae.  All commercial joints were weighed on a digital computing scale (Digi DS-680) to the nearest gram.

The pH and carcass temperatures were measured within 10 minutes of death, and 45 minutes thereafter at regular periods until the pH decline had reached a plateau.  The pH was measured in the lumbar region of the Musculus longissimus dorsi using a calibrated (standard buffers at pH 4.0 and 7.0) Crison 506 portable pH meter. 

Thirty-six hours after cropping, two ca. 2 cm thick loin sub-samples (the first at the first lumbar vertebrae and the second, caudally adjacent to it) were taken for determination of drip and cooking loss (Honikel 1998).  Drip loss was expressed as the percentage moisture loss relative to the weight of the fresh sample after a 48 hr hanging period in the cooler (1 ˚C).  Cooking loss (%) was determined by placing weighed samples of approximately 70 to 100 g, sealed in plastic bags, in water at 70°C for 60 min. This allowed for sufficient heat penetration without causing excessive denaturation of collagen present in the meat.  The bagged samples were allowed to cool down in running water to ca. 25°C.  Weight of the dried cooked samples were determined after decanting the liquid phase, and the cooking loss calculated as total fluid lost, expressed as a percentage of the fresh (uncooked) sample.  Thereafter, five 1.27 cm diameter samples (from the centre of each Musculus longissimus thoracis et lumborum sample) were randomly removed for determining of Warner-Bratzler shear force values.  The samples were cut parallel to the muscle fibre direction in order to measure the influence of the myofibrillar proteins.  Maximum shear force values (kg/1.27 cm diameter) were recorded for each sample (repeated five times) and a mean was calculated for each individual animal.  The colour of the Musculus longissimus thoracis et lumborum was evaluated using a Color-guide 45º/0º colorimeter (Cat no: 6805; BYK-Gardner, USA) to determine L*, a* and b* values (Commission International de l' Eclairage 1976) with L* indicating brightness, a* the red-green range and b* the blue-yellow range. 

The rest of the loin sample (Musculus longissimus dorsi) was minced and used for chemical analysis.  Moisture content was determined by drying 2.5g samples at 100 °C to constant weight, ashing at 500 °C for 5 h, protein (N x 6.25) content by the block digestion method (AOAC 1997).  The total lipid content was determined by chloroform/methanol solvent extraction (Lee et al 1996). 

The fatty acid and cholesterol content was determined as follows: After extracting the lipids, fatty acid methyl esters (FAME) were prepared according to Morrison and Smith (1964).  The FAME were analysed with a GLC: Varian Model 3300, equipped with flame ionization detection and two 30m fused silica megabore DB-225 columns of 0.53 mm internal diameter (J & W Scientific, Folsom, CA).  Gas flow rates were: hydrogen 25 ml/min; air 250 ml/min and nitrogen (carrier gas) 5-8 ml/min.  The temperature program was linear at 4 ºC/min with initial and final temperatures of 160 ºC and 220 ºC (held for 10 min), respectively.  The injector temperature was 240 ºC and the detector temperature 250 ºC.  The FAME were identified by comparison of the retention times to those of a standard FAME mixture (Supleco TM 37 Component FAME Mix, Catalogue Number 18919-1AMP, Lot number, LB-16064. Sigma Aldrich Inc. North Harrison Road, Bellefonte, PA 16823-0048, USA).  
 

Results and discussion

Carcass characteristics of animals are presented in Table 1. 

A dressing percentage, expressed as cold carcass weight as a percentage of body weight, of 52 % was lower than 76 % obtained for Landrace X Large White pigs that were reared in South Africa under either free-ranging (body weight 86.4 kg) or conventional housing (body weight 78.7 kg) systems (Hoffman et al 2003b).  Furthermore, carcass weight in warthogs, in contrast to domestic pigs, does not include the head, skin and adjacent subcutaneous fat layers, accentuating the fact that dressing percentage is lower in warthogs compared to domestic pigs.  The head and skin form nearly 9 and 6 %, respectively, of the body weight of warthogs.  Cold carcass weight consists of 37 % shoulder and 14 % belly (Table 1), compared to 14 and 6 %, respectively, for Landrace X Large White pigs (Hoffman et al 2003b) reared under South African conditions.  However, in contrast to the present study, shoulder and belly percentages were determined without bone in the latter study.  A value of 15 % has been reported for loin as a percentage of cold carcass weight in wild pigs shot in Poland (Mijewski and Korzeniowski 2000), compared to 7 % for warthogs found in the present study.  Carcass weight in the former study also included skin, as with domestic pigs.  The above demonstrated the difficulty in comparisons of warthog carcass characteristics with literature values for other pig species due to differences in processing methodology.

Values for pH_60min (Table 2) fall outside the range considered critical (below 5.6) for developing PSE meat, and are also below the critical limit (above 6.4) for dark, firm and dry (DFD) meat. 

Meat not subjected to either PSE or DFD has a pH_24h range of 5.5 to 5.8 (Lawrie 1985).  However, an exponential decay model fitted to the pH decline data (Wiklund et al. 1995) presented evidence that three of the five warthogs showed a rapid pH decline (Table 3; Figure 1), a phenomenon associated with PSE type meat.  Furthermore, there was a positive correlation of 0.772 between the rate of pH change (c-value in the exponential equation) and the percentage drip loss. 

Values for warthog (Table 2) compare well to values of 6.16 and 5.53 reported for pH_45min and pH_24h, respectively, in meat from Landrace X Large White pigs (Hoffman et al.2003b).  Marchiori and de Felício (2003) found values of 6.18 and 5.57 for pH_60min and pH_24h, respectively, in the Musculus longissimus of wild boars raised in Brazil (members of the European wild boar subspecies), Müller et al (2000) determined a value of 5.45 for pH_24h in wild pigs from Germany, whereas Mijewski and Korzeniowski (2001) reported a value of 5.44 for pH_24h in meat of wild boars from Poland.

Under South African rearing conditions with similar laboratory techniques for analysis, drip loss of 4.11 %, cooking loss of 22.59 %, CIEL* of 55.32, CIEa^* of 2.81 and CIEb^* of 10.10 have been reported (Hoffman et al 2003b) in the Musculus longissimus lumborum of the domestic pig.  Similar drip losses (3.42 to 4.55 %), and higher values for colour (CIEL* of 51.30, CIEa^* of 7.94 and CIEb^* of 13.24) have been reported for Musculus longissimus of Brazilian wild boars (Marchiori and de Felício 2003).  Ranges for colour in normal meat have been suggested as 52.2 to 54.8 for CIEL*, 5.1 to 7.5 for CIEa^*, and 12.9 to 14.5 for CIEb^* (Van der Wal et al 1988).  Although it seems that meat from warthog has a lower lightness (CIEL*) than either domestic or wild pigs, intermediary red colour intensity (CIEa^*), and yellow colour intensity similar to meat from domestic pigs (CIEb^*), direct comparisons are eliminated by differences in time post-mortem that measurements have been taken.

Comparable to values reported in Table 4, values of 74.54, 1.82, 22.31 and 1.20 % for moisture, lipid, protein and ash, respectively, have been determined in the Musculus longissimus lumborum of the domestic pig in South Africa (Hoffman et al 2003b). 

This is in agreement with values of 74.04, 1.95, 21.80 and 1.01 reported for wild pigs from Poland (Mijewski and Korzeniowski 2001), although it was not mentioned if fat extraction in the latter study was performed by ether or methanol/chloroform extraction.

The most abundant fatty acid found in warthog meat was the polyunsaturated linoleic (C18:2n-6) acid (Table 4).  Not only the amount of fat consumed, but also its saturation is important in prevention of coronary diseases (Girolami et al 2003).  Fatty acid composition of dietary fat influence cholesterol levels in humans in that high dietary level of long-chain saturated fatty acids increase plasma cholesterol levels compared with high levels of mono- and polyunsaturated fatty acids (Grundy and Denke 1990).  With a similar fatty acid analysis than technique to that used in the present study (Table 4), Hoffman et al (2003b) found contents of saturated, mono-unsaturated, and polyunsaturated fatty acids as 42.39, 39.19 and 18.43 %, respectively, in the Musculus longissimus lumborum of Landrace X Large White pigs kept under conventional housing conditions in South Africa.  A similar tendency has been found when domestic pigs have been kept under free-ranging conditions.  This clearly illustrates the influence of diet on meat fatty acid composition, which is especially profound in monogastric animals (Wood et al 2004).  The polyunsaturated: saturated fatty acid ratio in meat from warthogs was found to be 1.33 (Table 4), compared to 0.46 to 0.64 in domestic pigs (Hoffman et al 2003b).  Whereas Raes et al (2004) suggested a polyunsaturated: saturated fatty acid ratio of 0.7 or higher in meat, Wood and Enser (1997) recommended a ratio of 0.45 as the minimum.

Conclusions

• It can be concluded from this study that warthogs can be used as a meat source for human consumption. 

  
  

• Meat from this species is not only comparable that that of other pig species regarding physical meat characteristics, but also supply a meat that can be promoted on a favourable fatty acid profile for human health concerns. 

  
  

• Presently, warthogs are found in abundance within southern Africa and are readily consumed within the local restaurant trade. There are also no hunting restrictions on this species.

  
  

• The only restriction on this species according to the Animal Diseases Act (Act 35 of 1984) and its regulations is the movement of carcasses out of African Swine Fever control areas.
   

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Received 11 February 2007; Accepted 14 March 2007; Published 5 October 2007

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