Improving the meat quality of venison and other exotic game

19 Improving the meat quality of venison and other exotic game L. C. Hoffman, Stellenbosch University, South Africa and K. W. McMillin, Louisiana State University Agricultural Center, USA Abstract: The effect of various external factors on the sensory quality of venison and game meat is reviewed. As cervid species and wild boar have been domesticated and farmed for a number of years, there are more data available on these effects than there are for the wild free-roaming African game species. Most of these effects are similar in magnitude to that experienced in the traditionally farmed monogastric animals and ruminants, e.g. change in fatty acid profiles to reflect that of the diet in monogastrics. With the farmed species, greater control over the transport, lairage and stunning/ slaughter processes is possible, resulting in more uniform practices being developed that ultimately lead to a more consistent meat quality. However, with the wild game species this is not the case and research has focused on finding methodologies that best control the harvesting of the various species. Various value-added techniques used in the traditional red meat processing have been adapted and are used successfully in these wild species. Key words: deer, wild boar, African game, fatty acids, value adding, wildlife utilization.

19.1 Introduction A large number of the deer species found in the world have adapted well to domestication because most of the deer harvested for human consumption originate from herds where man has some form of control over the production process. The production may be in the form of a free-ranging herd under the control of herdsman, as found in Alaska (Wiklund and Malmfors, 2004) or a herd finished in a feedlot (Volpelli et al., 2002). Fletcher (1994) reported on a historical perspective of why farmers choose to domesticate deer and farm with these cervids; some advantages and disadvantages that are still relevant today to the semi-intensive domestication of deer are also listed. The history of reindeer

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production (particularly by the Saami people) in the Northern hemisphere has changed from an intensive herding system to a more extensive system using modern aids such as trucks, helicopters, motorbikes and snowmobiles to help with the herding (Malmfors and Wiklund, 1996; Wiklund and Malmfors, 2004). A production system that could be considered as an intermediate between the wild animals in Africa and intensively farmed deer is the herding of semi-domestic reindeer (Rangifer tarandus tarandus) in the Nordic countries and Alaska. Reindeer are free-ranging out in the forest or mountain tundra, but handled twice a year, in July, for marking of new calves and in December to be slaughtered (Hoffman and Wiklund, 2006). The Africa game species that are harvested, on the other hand, are either feral or loosely confined in large commercial farms by various forms of fencing (Eloff, 2002). Confinement of many African game species is difficult, however, as many of them, such as the kudu (Tragelaphus strepsiceros) are able to jump over 2 m high fences. The concept of ranching African game arose in the late 1950s with research being conducted in Zimbabwe (Dasmann and Mossman, 1960). Prior to this, game was found throughout Africa, but had very little commercial value. It was only in the late 1960s that the potential of game for meat production was recognized (Ledger, 1963; Ledger, Sachs and Smith, 1967; Von la Chevallerie, 1970). Most of the studies conducted towards the end of the 1900s consisted of recording basic information such as growth and yields (Von la Chevallerie and van Zyl, 1971; Von la Chevallerie, 1972), and any data collected on the meat composition (or quality) were focused more towards the effects of extreme environmental conditions, such as the droughts experienced towards the end of winter in Africa (see, for example, Van Rooyen, 1993). Some of the attributes required by wild ungulate species for domestication include non-territorial behaviour, a tolerance for other males, a high fecundity, a pre-disposal towards herding, and social behavioural patterns compatible with that of humans (Clutton-Brock, 1992). Such species should be gregarious, breed readily in captivity, and have a wide home range and a short flight distance. An example of such a species is the eland (Taurotragus oryx). However, a trial in Zimbabwe that began in the early 1950s and ran for 30 years in an attempt to domesticate this species and farm it, together with cattle, failed due to a number of reasons. The dominant causes for the lack of successful domestication were parasite burdens, a density-dependent decrease in their fertility, and a decrease in their overall body condition because most wild ungulates are concentrate selectors whilst the farmed animals are generalized feeders (Kyle, 1994). Goats and sheep and most cervids fulfil these conditions, but gazelles (such as the Springbok Antidorcas marsupialis) do not and thus are not suitable candidates for domestication (Skinner and Louw, 1996). The wild boar (Sus scrofa scrofa L.) has been present in parts of Europe and Asia since historical times and has disappeared from regions due to man’s influence (normally due to deforestation) and then reappeared again, either from wild invasions or from man’s introduction. Various strategies have been employed to manage these wild populations by means of hunting – normally by hunting

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teams using hound packs (The third issue of the Ibex Journal of Mountain Ecology, 1995, provides a good overview of the management strategies employed to control population numbers). McIlroy (1995) reviews the various strategies such as use of helicopters for shooting and poisoning campaigns that have been used to control feral wild boar populations in Australia. By contrast with most European countries, the European wild boar has not existed in the wild in the UK for 700 years (Booth, 1995). In the late 1980s, people started to farm with wild boar in the UK. The communication by Booth (1995) provides an overview of the history and progress of wild boar farming in the UK. Most of the farmed systems now consist of an extensive system with large paddocks (over 1 ha each) for a family herd, e.g. a boar with up to 10 sows, dry sows and weaners/growers, rotated to new paddocks after 1 year. These animals are fed a mixture of commercial feed and forage vegetables. As wild boars do not occur in the wild in the UK, they are classified as pig meat and therefore they have been slaughtered in abattoirs. However, this is a hazardous procedure for both the animals and the handlers, and shooting on the farm (as for deer) is now considered the most desirable method. These carcasses then go through the normal veterinarian health inspections to ensure that they are fit for human consumption. In the review of the prevalent microbes found on wild boar and feral pig meat, Gill (2007) also noted that these animals are normally skinned (and not scalded, dehaired and singed as is the practice with commercially farmed pigs). This is mainly to remove the thick black hairs found in these ‘wild’ pigs. This is also the practice for the wild warthog (Phacochoerus africanus) found in Africa. As soon as a species has become domesticated, man can then start manipulating the ante-mortem factors (diet, age at slaughter, selection of breeding stock for a specific trait, etc.) that can improve the meat and sensory quality of the end product. Similarly, the factors prior to the slaughter of the animal are under control resulting in a better quality product. This is the reason why a large number of the deer species are farmed and managed under a production system very similar to that used for the traditionally farmed domestic species. On the other hand, the African ungulate species are, with a few exceptions, not suitable for domestication, and the control over the end product is not always ideal. Most of the exotic game species are inherently wild and have developed survival instincts that make them successful in the wild. Thus, these species are perhaps even more pre-disposed to the effects of stress than many of the domesticated species because the first reaction to any external stimuli (such as the stress induced during harvesting) typically is the flight or fight reaction, which increases the associated hormone levels. For this reason, behaviour must be considered when designing the handling, transporting (if applicable), and holding facilities at the farm and/or abattoir if optimal meat quality and the welfare of the animal are to be achieved (Renecker et al., 2001). Of the species harvested in southern Africa, the Springbok is the most prevalent and most of the research to date has been conducted on the growth and production, and lately, on the meat quality of this species.

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19.2 Improving meat quality by means of the production system 19.2.1 Genetic selection Although deer farmers do select the stags that they wish to use as future breeding stock according to size, growth rate, antler characteristics and other desired traits, there are no reports of the effects of selection on the meat quality of the offspring. Hybrid (75% red deer Cervus elaphus: 25% Elk) stags and hinds had significantly high growth rates, carcass weights and dressout percentages when slaughtered at the same age and fed the same diet. The stags also grew faster and were heavier than the hinds (Hoskin et al., 1999). Similar results were also found with Scottish red deer (C. elaphus scoticus) compared with hybrids containing Père David’s deer (Elaphurus davidianus, PD) (Goosen et al., 1991). The stags were also noted to contain less total carcass fat than the hinds. An interesting phenomenon in that study was the significantly different muscle tissue distribution in Père David’s hybrids than in the red deer. The authors postulated that the 5% larger hind leg total in the hybrids could be indicative of a major gene effect similar to double-muscling observed in cattle and callipyge in sheep. The hybrids had larger vastus (6%), rectus femoris (6%), semitendinosus (9%), gastrocnemius (10%) muscles compared with the red deer. There were no significant differences in shear force values of muscles between the genotypes, but the M. longissimus dorsi of the stags were tougher than the hinds. Bison (Bison bison) and their hybrids with cattle (Bos taurus) had more lean meat and less fat trim than purebred cattle. However, the bison had a thicker fat depth at the 12th rib than cattle since most of the carcass fat of bison is located over the thoracic area. The bison and their hybrid also had a lower proportion of their carcass in the hindquarter than the Bos taurus. Bison meat was more tender as shear force and tenderness scores and had a flavour different from that of Bos taurus (Koch et al., 1995). Most of the African wildlife species have musculature similar to that of the general bovid pattern. There are, however, some species-specific variations. For example, the springbok has exceptionally large M. longissimus thoracis et lumborum (Skinner et al., 1971), but the fibre diameter is very small compared to other African ungulates, resulting in it having a low level of toughness (Table 19.1). Most of the increase in fibre diameter in the springbok occurs within the first 28 weeks of age (Von la Chevallerie and van Zyl, 1971). The only anecdotal report of improvement of African game species is that where a number of farmers have imported the larger Kalahari springbok (body weights of males 41.6 and females 35.4 kg) into the Karoo region in South Africa to breed with the smaller local animals (body weights of males 31.2 and females 26.5 kg, Skinner and Louw, 1996), the resulting offspring are larger, although this is attributed to heterosis as their offspring are once more smaller in weight. It is postulated that the South African springbok are smaller due to insufficient nutrition. Wild boar readily cross-breed with domestic pigs and this phenomenon has been

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Table 19.1 Dressing percentage and meat quality in mature males of four antelope species (adapted from Skinner and Louw, 1996) Springbok Number of animals Dressing (%) Moisture content (%) Buttock fat content Colour Fibre diameter (µm) Toughness (g/cm)

72 56 74.5 1.7 7.3 45.5 1181

Eland 6 51 74.8 2.4 5.9 66.3 3366

Impala

Blesbok

18 59 75.7 1.4 7.4 56.7 2751

23 53 75.5 1.7 7.9 53.8 2323

9 4.0 5.2

11 4.9 5.8

Taste panel scores for flavour (10 points = highest) Number of animals Intensity Acceptability

36 4.2 6.1

3 4.4 5.3

exploited by producers/farmers/hunters (even in Japan – Kanzaki and Kodera, 1995) to improve the litter size, growth rate and survival rate of the offspring. Using the wild boar in a cross-breeding program, Muller and co-workers (2000) showed that lean cuts and meat-to-fat ratio indicated a higher meat percentage in wild boar than for Meishan (the latter were more fat), although the wild boar (and its crosses) had slower growth rates. The cooling loss was also significantly higher for the wild boar than for the Meishan or Pietrain breeds. Wild boar also had the lowest dressing yield – caused by their heavier heart and liver weights. As pertaining to the meat quality, the wild boars and their crosses had darker meat (this was ascribed to a higher red fibre proportion – 28.4% for wild boar compared to 14.7% for Large White breeds; Essén-Gustavsson and Lindholm, 1984). The authors also noted that all the Wild boars tested were stress resistant (CK20-, CRCand Halothane tests). Marchiori and de Felicio (2003) characterized the meat quality of wild boar (raised in a semiconfinement area) found in Brazil with local domestic breeds (crosses between Large White, Landrace and Pietrain, raised in a confinement system) and found that the muscle pH decrease was more gradual in the wild boar. The commercial pigs also had a lower 48 h pH than the wild boar. A comparison of the L*, a* and b* values indicated that the wild boar also had the darker muscles (in both the Longissimus dorsi and Semimembranosus muscles). There have been indications that game meat sold as Japanese wild boar is adulterated by cross-breeding between pigs and wild boars or by contamination with meat from domestic pigs or European wild boars (Naya et al., 2003). In Japan there are two subspecies of wild boar: the Japanese wild boar (S. s. leucomystax) and the Ryukyu (S. s. riukiuanus). Nii and co-workers (2005) analysed the quantitative trait loci (QTL) of a number of meat traits in a cross-population of wild boar × Large White pigs and found that for muscle fibre composition, wild boar alleles had favourable effects on meat quality. These authors further speculated that wild boar containing these

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Table 19.2 Mean values for fatty acid composition (g/kg total fatty acids) in M. longissimus from pasture and pellet-fed reindeer (Rangifer tarandus tarandus L) and red deer (Cervus elaphus), respectively Fatty acid Pasture (n = 9) Polar lipids 14:0 16:0 16:1 17:0 17:1 18:0 18:1 18:1 (trans) 18:1 (n-9) 18:1 (n-7) 18:2 (n-6) 18:3 (n-3) 20:3 (n-3) 20:4 (n-6) 20:5 (n-3) 22:4 (n-6) 22:5 (n-3) 22:6 (n-3) SFA MUFA PUFA (n-6) PUFA (n-3) (n-6)/(n-3)

Reindeera Pellets Degree of Pasture (n = 6) significance (n = 7)

2.1 12.6 0.6 0.4 0.4 12.4 3.4 0.4 11.5 1.0 21.1 6.1 6.0 10.2 2.7 6.0 4.6 2.0 25.4 17.3 31.9 14.2 2.2

2.9 13.8 0.9 0.2 0.2 13.4 2.0 0.3 12.0 1.7 27.6 1.2 8.0 9.5 1.6 6.0 3.3 2.0 26.3 16.0 39.4 7.5 0.53

n.s. n.s ** *** *** * *** ** n.s *** *** *** *** n.s *** n.s. *** * n.s. * *** *** ***

4.5 1.7

3.5 1.8

** n.s.

23.8 0.3 0.9 1.0 21.4

27.2 0.3 1.6 0.8 21.0

*** n.s. *** *** n.s.

1.3 34.1 1.0 2.2 1.0 0.5

0.6 35.6 1.1 2.1 0.2 0.2

*** * * n.s. *** ***

0.4

0.2

***

4.0

0.1

***

Red deer b Pellets Degree of (n = 7) significance

10.1 1.1

10.3 0.4

n.s. **

15.8 12.3

14.1 12.4

* n.s.

20.3 5.2 1.0 9.0 3.0

29.8 0.2 1.3 12.1 0.8

*** *** *** *** ***

4.0 0.9 25.9 13.8 29.3 14.2 2.1

1.9 0.2 24.4 12.4 41.9 4.5 9.3

*** *** n.s. n.s. *** *** ***

5.0 1.6 0 33.3

6.1 2.2 0.1 34.6

n.s. * n.s. n.s.

9.3 0.6 15.7 24.7

11.9 0.4 9.3 25.7

* n.s. *** n.s.

3.8 1.5 0.1 0 0.7 0.3 0.6

5.3 0.3 0.1 0.1 0.8 0 0.2

* *** n.s. * n.s. *** ***

Neutral lipids 12:0 14:0 14:1 15:1 16:0 16:1 (trans) 16:1 17:0 18:0 18:1 18:1 (trans) 18:1 (n-9) 18:1 (n-7) 18:2 (n-6) 18:3 (n-3) 20:0 20:3 (n-3) 20:4 (n-6) 20:5 (n-3) 22:5 (n-3)

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Table 19.2 continued Fatty acid Pasture (n = 9) SFA MUFA PUFA (n-6) PUFA (n-3) (n-6)/(n-3)

53.0 37.6 2.6 1.4 1.9

Reindeera Pellets Degree of Pasture (n = 6) significance (n = 7) 54.6 39.2 2.3 0.3 7.7

n.s. * n.s. *** ***

54.7 36.4 4.3 2.5 1.7

Red deer b Pellets Degree of (n = 7) significance 50.6 39.8 6.6 0.6 11.0

** * ** *** ***

a

adapted from Wiklund et al. (2001c). Wiklund et al. (2003a). n.s. Not significant, * P < 0.05, ** P < 0.01, *** P < 0.001.

b

alleles are expected to be used in breeding programs, such as marker-assisted introgression, to improve meat quality traits of pork.

19.2.2 Artificial feeding The farming systems for deer range from wild, extensive to intensive systems that utilize strategic feeding such as over-wintering (Webster et al., 2001) or strategic feeding for finishing (Volpelli et al., 2002). In the Cervids, a large number of experiments have compared the meat quality of wild/free range deer to that from feedlot finished animals. Although venison is renowned for its low muscle lipid content (Aidoo and Haworth, 1995; Wiklund et al., 2001c), higher levels (4.5% in red deer; Kay et al., 1981; 4.2% in female reindeer, Sampels et al., 2005) than in meat from African ungulates have also been noted. The later phenomenon is particularly noted when the animals have been finished on pelleted diets (Wiklund et al., 2001c, 2003a; Phillip et al., 2007; Table 19.2). The effects of age, gender (including castration), region, and production system on the meat composition (Volpelli et al., 2002; Stevenson et al., 1992), including the fatty acid profile of the meat (Garton and Duncan, 1971; Manley and Forss, 1979; Wiklund et al., 2003a; Sampels et al., 2005), have been reported for fallow deer, red deer and reindeer. By and large, deer respond in a manner similar to any ruminant (Raes et al., 2004; Wood et al., 2003). The effects of these factors on the palatability and sensory characteristics of the venison have also been explored (Britten et al., 1982; Stevenson et al., 1992; Forss et al., 1979; Wiklund et al., 2003a). Those findings were similar to findings on the traditionally farmed ruminant species, viz large variation between animals within a treatment. A sensory panel could distinguish between the meat from animals that had been fed grain-based pellets and those grazed on natural pasture as pertaining to the attribute ‘grassy flavour’, with significantly higher scores for this attribute in meat from deer grazing pasture (Wiklund et al., 2003a). Similar results have been reported for reindeer venison, where both a trained panel and consumers found that meat from

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free-ranging reindeer had a stronger gamey flavour compared with meat from animals fed commercial grain-based pellets (Wiklund et al., 2003b). The consumer preference test showed that 50% of the consumers preferred meat from grazing reindeer and 50% preferred meat from pellet-fed animals. Recently, seasonal variation in sensory attributes has been studied in meat from Alaskan free-ranging reindeer slaughtered at three different times of the year: July, November and March. The strong and gamey flavour of the meat increased over the season, so that reindeer slaughtered in July produced meat with a milder flavour, while meat from animals killed in March had a clear gamey flavour (Wiklund et al., 2006a). It is also suggested that these results were related to the variation in diet composition over the year for the free-ranging reindeer. Free-range red deer had higher muscle pigment than pellet fed deer, although the pigment content of the meat samples did not seem to have an influence on the colour stability or oxidation product formation (Wiklund et al., 2006b). Type of diet also did not have an influence. As expected, the oxidation products (TBARS) increased during refrigerated storage. However pasture-fed fallow deer (Dama dama) had a longer colour display life after 2 and 3 weeks under refrigerated conditions than deer fed a barley and hay diet (Wiklund et al., 2005). Although it is known that diet influences the fatty acid profile of ruminants to a lesser degree than that of monogastric animals (MacRae et al., 2005), dietary effects can still be noticed (Table 19.3). An illustration is the comparison of values of the kudu, predominantly a browser, to those of the springbok, predominantly a grazer. The influence of diet has been further reported in impala, an ungulate that grazes and browsers, depending on the available food. Animals from two different habitats (predominantly grass and predominantly bush) had different fatty acid profiles (Hoffman et al., 2005). Comparison of the muscle tissue lipids of domestic cattle with those of African buffalo (Synceros caffer), giraffe (Giraffa camelopardalis), eland (Taurotragus oryx), kongoni (Acephalus buselaphus) and topi (Damaliscus korrigum) in East Africa showed that meat of the game species reflected the lipid composition of the diet (Crawford et al., 1970). The game species also contained high amounts of the long chain (C>20) unsaturated fatty acids. The fatty acid profiles of the species in Table 19.3 all had P:S ratios above 0.4 and n-6:n-3 ratios below 4.0. With a desirable fatty acid profile, game meat can compete well with domesticated meat as it contains high levels of PUFA, yet has high P:S and low n-6:n-3 ratios (Table 19.3). The game species listed have high levels of linoleic acid and knowledge of the concentrations of the different isomers would allow quantification of the potential health aspects of the isomers in game meat (Schmid et al., 2006). As early as 1968, it had been noted that the proportion of polyunsaturated to non-essential fatty acids in tissues was in the order of 1/50 for domestic bovids whilst that in the free-living animal was 1/2.3 (Crawford, 1968), but no data has been found on the muscle chemical composition of African ungulate game species fed formulated diets. The chemical composition, especially the fatty acid profiles of monogastric animals, is strongly influenced by diet. Townsend and co-workers (1978) evaluated the chemical, physical and sensory properties of loins from Yorkshire,

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cross-bred and wild pigs that had all been reared under the same conditions, and found differences between the breeds in the percentage moisture, protein and total lipids. The loins of the wild pigs had significantly higher levels of pentadecanoic acid (C15:0) and palmitoleic acid (C16:1), although the total percentage of the former was less than 1.3 and the difference between the breeds of the latter fatty acid was less than 1.5%. A trained taste panel could not distinguish among the three genotypes as pertaining to the juiciness, flavour intensity and flavour desirability. However, the wild pigs had a lower overall desirability which was due mainly to the meat being perceived to be significantly less tender, a finding that also correlated to the higher (less tender) measurements of the Warner–Bratzler apparatus. The meat of the wild pigs was also darker than that from the cross-bred or pure Yorkshire breed.

19.2.3 Effect of animal age and gender on meat quality Similar to other animals, the meat quality of the exotic species, especially tenderness, tends to decrease with age, although the effect does not seem as pronounced in the wild ungulates as in the traditionally farmed species. The meat from 13–16 month Blackbuck antelope (Antilope cervicapva) stags was leaner, had higher ultimate pH, and was slightly less tender than that of castrates or younger (7–10 months) stags (Woodford et al., 1996). In fallow deer (Dama dama), older (30-month-old) animals had more insoluble collagen and higher shear force values than 18-month-old animals (Volpelli et al., 2003). The M. longissimus thoracis et lumborum in older animals were fatter and the M. semitendinosus provided lower PUFA, both in the n-6 and n-3 fraction. In freerange reindeer (Rangifer tarandus), the older animals had less tender meat (sensory as well as shear force values) than younger animals (Renecker et al., 2005). The taste panel noted no significant differences between age and gender for either juiciness or gamey flavour of the loin steaks. Although the older males were found to be more lean in all their fat reserves, this was attributed to the fact that they had just completed their rut. For the African game species, an extensive study on meat quality with springbok age indicated that the loins from young animals (24–60 weeks old) were deemed to be too tender! (Zondagh et al., 1995). Remember that young springbok reach their growth inflection point at 28 weeks (Skinner and Louw, 1996). In another study, however, neither age nor gender had an effect on the shear values of Springbok meat, which varied from 2.04 to 2.31 kg/1.27 cm diameter for the different age categories (Hoffman et al., 2007a). The shear force values obtained for springbok were low compared with values of 3.21–4.08 reported for impala (Aepyceros melampus) (Hoffman, 2000), 3.23– 4.28 for black wildebeest (Connochaetus gnou), 3.77–4.60 for blue wildebeest (C. taurinus), 2.95 –3.00 for mountain reedbuck (Redunca fulvorufula) (Van Schalkwyk, 2004), and 2.03–7.74 for beef (Belew et al., 2003) as kg/1.27 cm diameter. Females had higher intramuscular fat than males and, although fat levels increased as animals aged, the fat levels were still below 3.5% (Hoffman et al., 2007b). The specific fatty acids

Table 19.3 Mean total fat (%), fatty acid composition (%) and total cholesterol content (mg.100 g–1) of the M longissimus dorsi of the common duiker (Sylvicapra grimmia), kudu (Tragelaphus strepsiceros), blesbok (Damaliscus dorcas phillipsi), springbok (Antidorcas marsupialis), impala (Aepyceros melampus), red hartebeest (Alcelaphus buselaphus caama), black wildebeest (Connochaetes gnou), blue wildebeest (Connochaetes taurinus), warthog (Phacochoerus aethiopicus), buffalo (Syncerus caffer) and zebra (Equus zebra) (from Hoffman and Wiklund, 2006) Fatty acid

Common duiker (male)a

Kudu (male)b

Total fat 14:0 16:00 16:1 (n-7) 18:00 18:1 (n-9) 18:2 (n-6) 18:3 (n-6) 18:3 (n-3) 20:00 20:1 (n-9) 20:2 (n-6) 20:3 (n-9) 20:3 (n-6) 20:3 (n-3) 20:4 (n-6)

2.12 0.75 0.86 18.58 19.68 18.70 19.91 0.12 4.10 0.81 0.23 0.29 – 2.94 0.19 7.83

1.58 – 16.10 0.52 19.72 19.91 20.53 0.05 4.85 0.11 0.06 0.15 – 1.14 – 8.44

Blesbok Springbok (male)c (male)d 0.76 – 16.44 0.00 24.7 17.98 18.89 0.08 3.72 0.31 0.04 0.03 – 1.85 – 10.96

1.07 – 13.93 0.07 25.32 16.33 21.62 0.13 3.37 0.31 0.10 0.28 – – – 9.30

Impala (male)e – 0.32 15.04 0.57 22.25 19.34 19.67 0.14 5.09 0.14 0.10 0.18 – 0.86 0.09 7.87

Red Black Blue Warthogg hartebeest wildebeest wildebeest (male)c (male)f (male)f 4.69 – 18.27 0.00 36.08 16.01 14.55 0.26 4.06 0.49 0.38 0.08 1.11 – – 7.01

0.97 – 13.2 0.19 26.21 14.37 20.97 0 4.47 0.39 0.19 0.19 0.78 – – 9.9

2.94 – 16.12 0.18 21.47 16.75 20.45 0.13 4.57 0.33 0.12 0.20 – – – 7.72b

– 0.80 20.00 0.70 14.7 15.8 26.10 0.20 7.30 0.10 0.10 0.30 – 1.10 0.90 7.50

Buffalog

Zebrag

– 0.64 18.03 1.50 18.83 30.02 12.93 0.08 3.79 0.62 0.31 1.00 – 0.95 0.20 5.71

– 1.13 22.50 2.02 10.22 20.55 24.01 0.11 11.46 0.14 0.30 0.39 – 0.75 0.59 3.29

20:5 (n-3) 22:00 22:2 (n-6) 22:3 (n-3) 22:4 (n-6) 22:5 (n-3) 22:6 (n-3) 24:00 24:1 (n-9) SFA MUFA PUFA PUFA:SFA (n-6)/(n-3) Cholesterol (mg.100 g-1 meat sample)

2.10 0.08 0.01 0.14 0.31 1.14 1.09 0.06 – 22.24 37.51 40.26 1.81 – –

3.17 0.31 – – – 2.75 2.50 – – 35.93 20.48 43.59 1.23 2.29 –

2.39 0.31 – – 0.22 2.43 0.39 0.57 0.49 42.33 18.51 40.96 0.97 3.62

2.38 0.26 – – 0.27 2.60 0.94 0.53 0.17 40.35 16.67 31.59 0.79 3.28

51.38

56.9

Adapted from: a Hoffman and Ferreira (2004). b Mostert and Hoffman (2007). c Smit (2004). d Hoffman et al. (2007c). e Hoffman et al. (2005). f van Schalkwyk (2004). g Unpublished data chemically analysed as described in Hoffman et al. (2005).

3.44 0.16 0.14 – 0.43 2.82 1.00 0.19 0.14 38.11 20.15 41.74 1.10 – –

2.38 0.46 – – 0.28 2.31 0.37 0.88 11.71 56.18 28.1 32.41 0.58 2.75

3.11 0.39 – – 0.58 3.69 0.58 0.78 0.58 40.97 15.33 44.27 1.01 2.82

3.28 0.22 – – 0.28 5.38 0.98 0.41 0.18 38.55 17.23 42.99 1.15 2.07

50.9

46.05

51.08

0.90 0.10 0.10 – 0.40 2.40 0.40 0.10 0.10 35.8 16.7 47.6 1.33 – –

1.55 0.56 0.06 0.30 0.27 1.65 0.83 0.10 0.78 38.78 31.61 29.32 0.76 – –

0.41 0.07 0.06 0.00 0.26 1.24 0.39 0.06 0.04 34.12 22.91 42.96 1.26 – –

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were also quantified (Hoffman et al., 2007c) and the major fatty acid of the M. longissimus dorsi was stearic acid (C18:0), which contributed 23.92–27.02%. Oleic acid (C18:1) represented the largest component (16.33–20.45%) of the mono-unsaturated fatty acids (MUFA). The major n-6 polyunsaturated fatty acid (PUFA) was C18:2n-6, which formed 18.77–21.62%, whereas C18:3n-3 (3.33– 4.00%) was the most abundant n-3 PUFA. The n-6:n-3 ratio of the meat varied from 3.02 to 3.35, with an average ratio of 3.2. Polyunsaturated to saturated (P:S) ratios varied between 0.96 and 1.18 and averaged at 1.06. Total MUFA was found to be higher in males (20.99%) than females (16.67%). In the same study, the regional effect was greater on the sensory characteristics of springbok than either gender or age (Hoffman et al., 2007d). Production region influenced the game meat aroma, initial juiciness, sustained juiciness and residual tissue ratings of the meat, whilst gender and age had only a significant effect on the residual tissue rating of the meat. Gender had no effect on the chemical (proximate, amino and fatty acids, minerals) composition of kudu (Tragelaphus strepsiceros) (Mostert and Hoffman, 2007). • Zochowska and co-workers (2005) quantified the effect of carcass weight (age) on the muscle fibre characteristics of free ranging wild boar aged either 0.5 or 3 yrs (carcass weights of 20 or 60 kg, respectively). The young animals showed significantly lower muscle texture (hardness, cohesiveness, springiness, chewiness) than the older animals, which was linked to the latter having thicker perimysia and endomysia, fibres of higher cross-sectional area and also a higher • content of red fibres (Type I). In a later study, Zochowska-Kujawska et al. (2007) found similar results as pertaining to the age effects on wild boar muscle. They also found that the older animals had lower percentages of Type IIB fibres. No effect of age on the rheological properties was found.

19.2.4 Other farming strategies There have also been reports of deer farmers’ velvetting as well as castrating stags to ensure less fighting and more space at the feed trough (MacDougall et al., 1979; Mulley and English, 1985; Woodford et al., 1996; Sookhareea et al., 2001). A shift in muscle distribution between castrate and entire red deer showed the castrate forequarter muscle to be proportionately 7% lighter and hindquarter muscle proportionately 7% heavier than entire males (Tan and Fennessy, 1981). With castration and intensive feeding, the next logical steps are concerns for herd health and vaccination programmes, the use of AI (artificial insemination) and embryo transfer, as well as the inclusion of growth promotants to improve the productivity of the animals (Knox et al., 1991; Mulley et al., 1996). However, the deer industries worldwide have rejected use of growth hormones to increase meat production.

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19.3 Transport, lairage and slaughtering techniques As deer have become more domesticated, greater control has been practised on the transport, lairage and slaughter techniques to minimise the effects of stress on meat quality. However, it must still be remembered that these are wild animals and therefore they have more highly developed flight or fight reflexes than most domesticated species. The instinctive behaviour of these species must be known when the handling, transporting (if applicable), and holding facilities at the farm and/or abattoir are designed if optimal meat quality and the welfare of the animal are to be achieved (Renecker et al., 2001). Evaluation of the bruising of deer carcasses at a slaughter plant over a three-year period revealed that transport and lairage were the main causes of the down grading of carcasses (Jago et al., 1996). The effects of different pre-slaughter handling routines (reindeer: Wiklund et al., 1996a; Wiklund et al., 1997), transport (reindeer: Wiklund et al., 1995; Wiklund et al., 2001a; red deer and fallow deer: Pollard et al., 1999) and lairage (red deer: MacDougall et al., 1979; Pollard et al., 1999; reindeer: Wiklund et al., 1996b) on several of the physical meat quality attributes have been reviewed (Hoffman and Wiklund, 2006). Most of the responses of the animals to these ante mortem stressors are similar to those noted for domesticated animals. For example, diet had a stronger influence on muscle metabolism post-mortem than transport or lairage (Wiklund et al., 1996b). The reindeer (Rangifer tarandus tarandus L.) that had received a supplementary diet two months prior to transport and lairage had lower blood metabolites indicative of stress than non-supplemented deer. In red deer killed either in a pasture or in a slaughter plant, pre-slaughter handling created moderate stress (as determined by measuring various biochemical parameters in the blood) and the high levels of muscular exertion or damage noted on the deer killed in the slaughter plant were possibly related to antagonism during lairage (Pollard et al., 2002). However, muscle glycogen, pH and meat quality measurements showed only minor muscle specific differences between the two treatments. These various ante-mortem factors and their effects on the meat quality of deer has also been reported and reviewed by Malmfors and Wiklund (1996), Renecker et al. (2001) and Wiklund and Malmfors (2004). Conclusions of all these studies were identification of possibilities to improve pre-slaughter handling routines for all of the included deer species that would further reduce the frequency of DFD (Dark, Firm, Dry) meat with high ultimate pH values. The harvesting techniques used for African game species have been reviewed in detail (Hoffman and Wiklund, 2006). The normal harvest at night is the least stressful while harvesting in the day time from a hide creates little stress, but the harvest rates are very restricted. Shooting in a boma gives high take-off rates but is stressful to the animals and shooting from a helicopter is highly stressful and results in a large amount of bullet damage in the neck and back region of the animals. Meat from most game animals tends towards DFD due to the stress of the cropping process; however, PSE meat has been observed in animals that have experienced acute stress during the killing process (Hoffman, 2001). For example,

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Table 19.4 The effect of ante-mortem stress on the rate of pH change and drip loss of warthogs (Hoffman and Sales, 2007e) No.

Description of antemortem stress

Meat class

1

Shot behind the shoulder, run 100 m before dying Head shot, died immediately Shoulder shot, dropped immediately Head shot, paralysed, frantic kicking movements Neck shot, dropped immediately, frantic kicking movements

Pale, soft, exudative Slightly dark, firm, dry Normal

2 3 4 5

Constants for the exponential % Drip loss function (y = a + bect) a b c 5.41

1.27

–0.31

3.35

5.24

1.65

–0.06

2.45

5.53

1.17

–0.14

2.16

Pale, soft, exudative

5.34

1.18

–0.65

6.76

Pale, soft, exudative

5.47

0.84

–0.58

3.14

Note: y = pH at time t; a = ultimate pH; e = base of natural logarithm and b and c are the function parameters describing the shape of the curve.

buffalo (Syncerus caffer) that were killed using scoline had meat that was PSE (Hoffman, 2001). This phenomenon was also similar to a condition called white muscle myopathy that is sometimes found during the live capture of game (Harthoorn and van der Walt, 1974). Warthogs, similar to the domesticated pig, can be prone to PSE (Hoffman and Sales, 2007e) depending on the ante-mortem stress that is experienced (Table 19.4, Fig. 19.1). The time and manner of harvesting does have an impact on the meat quality of the wild animals (Kritzinger et al., 2003). A light calibre silenced rifle used at night seems to have the least effect on the meat quality and also has the least effect on the herd behaviour as a whole (Lewis et al., 1997).

19.4 Post-mortem intervention to improve the meat quality Some of the post-mortem interventions that have been utilized to improve quality attributes (mainly meat tenderness) include electrical stimulation (Chrystal and Devine, 1983; Wiklund et al., 2001b) combined with ageing (Drew et al., 1988). Studies have also focused on some of the interactions between muscle glycogen and technological meat quality attributes (Wiklund et al., 2004). 19.4.1 Pelvic suspension The technique of pelvic suspension (‘tenderstretching’) of the carcass resulted in positive effects on tenderness in several valuable cuts from fallow deer carcasses (Woodford et al., 1996; Sims et al., 2004).

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7.00 6.80 6.60 6.40

1

6.20 pH

2 3

6.00

4

5.80

5

5.60 5.40 5.20 5.00 1

5

9

13

17

21

25

Time (hours)

Fig. 19.1 Post-mortem pH change in the M. longissimus dorsi of warthogs (Warthogs 1, 4 and 5 showing a post-mortem pH decrease characteristic of the pale, soft, exudative condition, Warthog 2 a pattern illustrating a slightly dark, firm, dry condition, and Warthog 3 a pattern of normal meat). From Hoffman and Sales (2007e).

19.4.2 Electrical stimulation (ES) As mentioned in other chapters, a chilling rate that is too rapid may induce cold shortening and thus result in tougher meat. This is particularly pronounced when the carcasses have very little, or only localized, subcutaneous fat. Conventional carcass chilling is also a lengthy and energy-expensive process. Blast chilling can reduce cooling time and associated shrink loss, although its application may compromise meat quality, particularly in lean carcasses or those with localized finish such as most exotic game species (with the exception of zebra and very fat eland). Low voltage electrical stimulation (LVES) can reduce the risk of decreased meat quality by inducing rapid rigor onset prior to exposure of the musculature to extreme cold temperature. Blast chilling (–20 ºC, 3 m/s air velocity, 2 h) accelerated the temperature decline of bison (Bison bison bison) Longissimus lumborum muscle and significantly reduced the cooler shrink loss when compared to conventional chilling (0 ± 2 ºC, 24 h) (Janz et al., 2001). Although blast chilling tended to produce darker bison meat, this effect was tempered by the application of LVES, and samples from the combined treatments were significantly lighter than conventional chilling. Blast chilling also resulted in reduced tenderness in the M. Longissimus lumborum, as assessed by shear force measurement, in part due to significantly shorter sarcomere length in blast-chilled samples. Taste panellists,

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however, were unable to detect a significant or detrimental blast chilling effect. Where LVES was incorporated, there was an improved tenderness response with ageing. The combined LVES/blast chilling treatment of bison carcasses was thus recommended for rapid processing of bison without compromising meat quality. Low ES (80 V peak, unidirectional half sine-wave pulses of 10 ms duration) for a 90 s period resulted in beef loin muscles having a ‘conditioned’ status with tenderness similar to muscles that had been maintained at 10 ºC for 24 h followed by 24 h at 2 ºC (Chrystall and Devine, 1983). The control muscles, chilled rapidly at 2 h post mortem, were very tough and showed characteristics typical of cold shortening. LVES also increased the rate of post-mortem glycolysis in red deer (Wiklund et al., 2001b). This improvement in tenderness was maintained for at least 3 weeks post-mortem, but the differences disappeared by 6 and 12 weeks post-mortem. After 1 week of refrigerated storage, ES significantly reduced the display life (hours of Minolta a* value 512), but this difference disappeared at 3, 6 and 12 weeks of ageing. ES did not affect drip at any ageing time point during that study. High voltage electrical stimulation (HVES) may be used instead of LVES. The efficiency of high voltage electrical stimulation (700 V, 1400 V peak, pulses 1 s on/1 s off, 60 Hz, 2 A) on buffalo (Bubalus bubalis) carcass muscle conditioning during nine days storage resulted in a significantly more rapid pH fall as compared with controls (Soares et al., 1995). The IMP/ATP ratio clearly indicated that ES reduced the time period necessary for the onset of rigor mortis. Myofibrillar fragmentation index differences between the control and ES muscles increased throughout storage at 2 ºC. On the 6th day of post-mortem conditioning, the SDS electrophoretic patterns of the myofibrillar proteins indicated light weakening of Troponin T (37 000D). Another alternative to ES for alleviation of cold shortening effects is elevated temperature conditioning (ETC: 10 ºC until 10 h post-mortem) until the critical decrease in energy reserves required to minimize cold shortening is achieved. ETC allowed avoidance of the cold-induced meat quality defects that are a risk with conventional bison carcass chilling (0 ± 2 ºC for 24 h) (Janz et al., 2000). The ETC treatment maintained internal M. Longissimus lumborum and M. Semimembranosus temperatures above 10 ºC within the first 10 h post mortem. The time/ temperature combination did not result in significant evaporative loss, although loss of weight during carcass cooling can represent a practical economic loss. ETC accelerated post-mortem glycolysis and pH decline, and resulted in samples of lighter, more intense red colour than those conventionally chilled. Significant improvement in both initial tenderness and tenderization during ageing was also realized with the use of ETC. In Africa, the various game species are frequently harvested during winter when the ambient temperatures are below 4 ºC and cold shortening of muscles in smaller game species may occur. A pilot study on tenderization of tenderloin muscle in Springbok with LVES indicated that, although there was a tendency for the meat from ES carcasses to have less Warner–Bratzler shear force, a trained taste panel could not distinguish any differences with treatments. The results may have been

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confounded by the freezing of the muscles prior to preparation for sensory analysis, with the small differences becoming undetectable due to physical damage caused by ice crystal formation. Most of the research results demonstrate that the benefits of ES on tenderness are not permanent, and the procedure is not necessary for a product that is to be maintained in chilled storage for a long period.

19.5 Improving or maintaining the meat quality post-mortem 19.5.1 Colour It has been well recorded in the literature that most of the free-ranging exotic species have higher muscle pigmentation (myoglobin; Mb) and thus are darker than the animals farmed and/or finished in a feedlot. This darker pigmented muscle is usually attributed to a higher level of exercise. The retail storage time of a meat product is generally limited by colour deterioration, which occurs at some time before microbial spoilage. Such colour deterioration severely restricts the possibilities for widespread distribution of retail-ready cuts because the deterioration process commences immediately when a meat surface is exposed to O2. Venison and game meat have high concentrations of myoglobin (7.3 mg/g muscle for impala – Hoffman et al., 2005) and mitochondria that increase the rate of metabolic oxygen consumption, so the bloomed appearance does not last long and thus results in poor colour stability when compared to meat from other species. Venison has a short retail display life, which was decreased even further by the duration of storage under vacuum prior to being displayed under oxygen (Seman et al., 1988). This was linked to the extended period of auto-oxidation and lipid oxidation that occurs whilst the meat is stored under vacuum (Pietrasik et al., 2006). The rapid formation of metmyoglobin (MetMb) is enhanced when the meat has been stored frozen for long periods prior to being thawed, cut and displayed under chilled retail conditions. The colour stability of previously frozen bison meat cuts was very low in the retail case compared with stability of beef (Dhanda et al., 2002). The formation of ice crystals in the meat causes structural damage in the muscle cells, thereby allowing cellular components that are normally kept apart to mix. Also, as ice crystals exclude salts, the ionic strength of the remaining unfrozen water is increased. In the event of exposure to oxygen, these events lead to the formation of free radicals that accelerate tissue degradation and oxidation, which is linked to colour deterioration. It was concluded that vacuum packaging appeared to be the most economic method used and produced meat of better colour stability (Seman et al., 1988). However, this method entails repackaging into oxygen permeable packages for retail display. Investigations on the post-mortem MetMb reduction in fresh venison to gain more insight into methods suitable for regenerating the bright red oxymyoglobin state resulted in the conclusion that the MetMb reducing activity occurs

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Improving the sensory and nutritional quality of fresh meat

anaerobically in completely discoloured venison following storage display (Bekhit et al., 2007). Any visible effects of MetMb reducing activity would only be possible when oxidative processes were slowed down or eliminated by techniques such as vacuum packaging. However, it was also noted that, in a vacuum system for regenerating the red colour in venison, any practical benefits from the packaging reduction system to regenerate the desirable cherry-red colour, which only lasts for a short time (<30 h), may be negated or prohibited by the cost of repackaging for retail sale.

19.5.2 Sensory attributes Similar to other red meat types, venison and game meat becomes more tender as refrigerated time increases. However, some of the sensory characteristics also become less desirable with storage, with the negative characteristics enhanced by the auto-oxidation reactions caused by the higher myoglobin and mitochondria levels. Similarly, as venison and game meat have a low lipid level, there is a higher proportion of phospholipids (Sampels et al., 2005) that cause higher susceptibility to lipid oxidation. For example, red deer loin samples became significantly more tender, less desirable, more intense in flavour and exhibited a higher degree of offflavour as storage time increased from 1 to 18 weeks (Seman et al., 1988). The animals of non-domesticated species are wild and thus susceptible to antemortem stress that may result in DFD meat. In evaluations of the proteolysis and tenderization in reindeer (Rangifer tarandus tarandus L.) M. longissimus thoracis, the muscles in the high pH (> 5.80) group had significantly higher activity of µcalpain compared with the low pH group (< 5.79) at 1 day post-mortem (Wiklund et al., 2003b). No differences in shear force, myofibrillar protein degradation by SDS-PAGE, m-calpain and calpastatin activities, cathepsin B + L activities or the levels of cystatin-like inhibitors were found between the two pH groups. In the three carcasses with the highest ultimate pH values (6.11, 6.34 and 6.38), the sarcomere lengths were around or below 40% of the resting length (1.37 µm, 1.25 µm and 1.25 µm, respectively), which was presumed to be associated with the occurrence of heat shortening.

19.5.3 Packaging In the meat industry, vacuum packaging (VP) is used to maximize the shelf-life of meat, whereas modified atmosphere packaging (MAP) containing high levels of O2 is used to attain the bright red colour of meat through oxygenation of deoxymyoglobin. As with other red meat species, the evaluation of MAP has also enjoyed some attention in venison and bison. Vacuum packaging resulted in a lower incidence of off-odours and higher colour acceptability scores than did 100% CO2 flushed packaging systems (Seman et al., 1988). MAP with CO2 conferred little additional shelf-life to chilled venison loins if the fabrication methodology was such that minimal microbiological contamination took place (Seman et al., 1989).

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Beef Longissimus lumborum steaks in MAP (70% O2/30% CO2) retained their bright red colour longer than bison steaks (Pietrasik et al., 2006). Bison steaks had developed higher 2-thiobarbituric acid reactive substances (TBARS) during storage, which may have influenced the resulting rapid loss of redness from the bloomed meat. It was also noted that storage under MAP resulted in higher TBARS than storage under vacuum. Storage at –1 °C in MAP provided greater colour stability and a longer storage-life for both beef and bison. Steaks stored overnight under MAP before retail display maintained the highest a* values for up to 5 d, compared with those stored under vacuum. MAP steaks stored overnight generally maintained the highest oxymyoglobin content for up to 5 d during retail display compared with those stored under vacuum. Nevertheless, oxymyoglobin levels were significantly lower in bison steaks compared with those of beef, irrespective of packaging treatments. The greatest changes in the instrumental values of the parameters occurred during the first 9 days post-packing in evaluations of the effects of different gas mixtures in MAP on the quality (pH, colour as L* a* b* values, drip loss (DL), cooking loss (CL) and shear force (SF) of deer (Cervus elaphus)(Vergara et al., 2003). The pH and water loss increased in all treatments (40% CO2 + 60% N2; 80% CO2 + 20% O2; 80% CO2 + 20% N2), thus making it impossible to maintain the initial meat quality in any of the groups tested. Also, the samples in all the groups turned yellow with time (increased b* value), with the change more rapid in groups packed in MAP containing oxygen. The colour values (redness and yellowness) of the meat in MAP containing 40% CO2 + 60% N2 suggest that this mixture is the most appropriate for the preservation of deer meat.

19.5.4 Microbiological shelf-life It would seem that, with modern slaughter and processing technologies, microbiological spoilage would be less of a problem than auto-oxidation and lipid oxidation. A recent review on the microbiological contamination of exotic meats indicates that the slaughter techniques play an obvious role in microbiological contamination (Gill, 2007). When springbok were harvested by standard commercial techniques (Hoffman and Wiklund, 2006), the microbiological status (mean total count and initial bacterial composition) indicated that introduction of certain critical control points into the harvesting system will be necessary to produce a fresh product with an acceptable shelf-life (Buys et al., 1996). Ageing of springbok meat had no influence on bacterial counts (Buys and Kruger, 1995). As the ageing period increased beyond 12 days of refrigeration storage, vacuum packaging inhibited the growth of spoilage bacteria and the Enterobacteriaceae group. Muscles of bison attain final pH values <5.7 (Janz et al., 2001) and bison steaks vacuum packed or displayed in oxygen permeable packaging had storage lives comparable to that of beef steaks prepared under good hygienic conditions (Janz and Aalhus, 2006). Similarly, the storage life of ground bison meat maintained at chiller temperatures was comparable to that of ground beef (Li and Logue, 2005).

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Improving the sensory and nutritional quality of fresh meat

Venison can remain acceptable for up to 18 weeks when stored and distributed at temperatures around –1 ºC (Seman et al., 1989). This has allowed the development in the meat trade of chilled venison transport from New Zealand and chilled game meat transport from South Africa and Namibia. Wild boar meat proved to have a much better storage life than pork and resembles that of beef (Boers et al., 1994). This was attributed to a high level of glucose in the wild boar muscle which may contribute to its long shelf-life through a delay of glucose limitation and subsequent amino acid breakdown by microorganisms.

19.5.5 Improving meat quality by means of injecting/enhancement The beef and pork industries have recently adopted moisture enhancement of fresh meat for widespread commercial use to help ensure a more consistent, juicy, and tender product. This technology has also been used on exotic meat types, with similar results as noted for beef. A salt/phosphate blend injected into bison steaks had a beneficial effect on the colour stability of steaks during retail display (Pietrasik et al., 2006). However, this positive effect was more pronounced for bison steaks compared with those of beef injected steaks, with steaks stored at –1 °C having significantly higher oxymyoglobin levels compared with noninjected counterparts and those stored at +4 °C, respectively. The TBARs values were also found to be lower in the injected bison samples than in the non-injected steaks. The palatability of bison semimembranosus muscle and the effects of injection with sodium chloride (0.5%) and sodium tripolyphosphate (0.3%) on cooking yield, colour, shear force and consumer acceptability has been investigated (Dhanda et al., 2002). Although the Hunter Lab a* (redness) and b* (yellowness) values did not differ between injection treatments, the injected steaks had lower L* values (were darker) compared with the controls. Control samples were very lean and high in protein, but not very tender. Marination by injection significantly reduced shear force values compared to control samples. Cooking yields for the steaks/ roasts from the injected sections were also significantly higher compared with control non-injected sections after being cooked to either 71 or 77 ºC. Bison samples cooked by moist heat had significantly lower cooking losses and shear force values compared with those cooked by dry-heat. As expected, steaks/roasts were more tender and had higher cooking yields when cooked to a medium level of doneness (71 ºC) compared to an internal temperature of 77 ºC (well done). A panel of 80 consumers preferred injected steaks cooked to 77 ºC over other treatment combinations, followed by non-injected steaks cooked to 71 ºC, whereas injected steaks cooked to 71 ºC and non-injected steaks cooked to 77 ºC were equally, but least, preferred. Hence, injection seems to be protecting against moisture loss at high end-point cooking temperatures. Enhanced (injected) springbok and Blesbok samples were more tender (W–B shear values and taste panel) and more juicy, with consumers preferring the enhanced muscles (Du Buisson, 2006). The enhancement of game meat with an

Improving the meat quality of venison and other exotic game

467

inorganic salt solution might be a useful processing tool to further improve the acceptability of game meat tenderness and juiciness, since game meat is often perceived as being dry and less tender because of its lower fat content and the use of slaughter techniques that stress the animals and subsequently lower meat quality. • Zochowska-Kujawska et al. (2007) evaluated the effect of injecting a standard brine solution and then massaging the wild boar muscles intermittently, on the hardness, rheological properties and structure of four muscles. They concluded that the lower the initial values of textural and structural parameters and percentage of Type I fibres of a muscle were (typically as found with a young animal compared to an old animal), the higher was the muscle’s susceptibility to massage.

19.6 Value-added products as a means to improve the quality attributes of exotic meats Venison and game meat are not only consumed fresh but also in various processed forms (Paleari et al., 2000). A large number of these processed forms are from traditional recipes and few of the processed meats have had a scientific analysis of their nutritional and sensory quality characteristics. However, increased globalization of the food market will allow a large number of these products to move from being a local or domestic product to becoming a niche market item. One of the most popular meat products is dried meat, which is known in South Africa as biltong and in the US as jerky. The meat can be in various forms, as whole muscles, muscle strips, or ground/mince for structuring into desired forms prior to processing for dried, salted and dried, or salted, smoked and dried products. Most jerky in the US is cured with sodium nitrate, whereas salt and pepper form the basis of the spices added to biltong. A hot smoking process slightly changes the fatty acid composition, lipid class composition and vitamin content, whereas drying results in major changes in these chemical components in reindeer M. semimembranosus (Sampels et al., 2004). With curing and/or fermenting and drying, there is normally an increase in most of the chemical constituents due to the drying process. Comparison of fermented and dried cured products (similar to the traditionally prepared beef bresaola) with fresh meat showed that, surprisingly, the amount of lipid between the fresh and cured deer product was similar whilst lipid in the boar meat (and other meat species used) was higher in the cured product (Paleari et al., 2003; Soriano et al., 2006). The protein and ash contents in the cured products were also higher, with a high content of free amino acids and high levels of polyunsaturated fatty acids. Evaluation of the microflora of the cured products in the same study revealed only flora typical of processed products (Paleari et al., 2002). Sausages are another group of popular products where the meat is minced and then restructured into the final product. These are then either fermented and dried (typical salami-like products) or dried. During the ripening of fermented sausages, the proteins and lipids undergo major changes. For example, ten commercial

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Improving the sensory and nutritional quality of fresh meat

chorizos and saucissons (dry sausages found in Spain) were made from either wild boar or deer meat (Soriano et al., 2006). These sausages are made following similar procedures and are mainly differentiated by the higher concentration of spices, particularly paprika in chorizo, which gives the typical red colour. The proteins in the myofibrillar fraction were higher than in the sarcoplasmic fraction. The chorizos made with deer or wild boar meat had higher percentages of polyunsaturated free fatty acids, linoleic and linolenic acids and lower percentages of the mono unsaturated 11-eicosenoic acid than the saucissons. Ripening of venison (Cervus elaphus) chorizo sausages was influenced by stage of the hunting season and natural or controlled drying rooms (Ruiz et al., 2007). The myofibrillar protein decreased and proteolysis indices were between 4.6 and 14.4% after ripening, but variations were minimal after 45 days in vacuum packaging. Processing in controlled conditions showed similar myofibrillar changes, but there was more variation with natural drying rooms, with pH of sausages lower with controlled than natural drying. Hunting season stage influenced the initial meat pH before sausage production and the relative density of the 49 kDa band after 21 days of ripening. Changes in proteins profiles were found after storage of the four treatment batches.

19.7 Future trends Storage of raw chilled venison, bison and game meat under MAP is an excellent option for short-term storage due to its positive effects on meat colour, but VP may be necessary for longer storage with minimal quality changes. An option to increase shelf-life and have retail display with desirable colour might be storage of meat under vacuum and then placing it under MAP just before retail display (Pietrasik et al., 2006). The marketing of portions derived from individual muscles is a strategy followed by the South African game meat export industry and has been adapted from the marketing of ostrich meat, which is another form of exotic meat discussed in Chapter 18. The enhancement of meat quality traits through infusion, marination or injection or massaging (frequently under vacuum) of various lactate, salt, and phosphate blends would improve the tenderness and juiciness of most game meats, particularly if harvest and chilling conditions are not tightly controlled. Information on meat quality during extended shelf-life and subsequent consumer preferences is needed. Consumers increasingly desire more convenient and value-added meat products. There may be a niche market for precooked ready to heat or ready-to-eat (RTE) products made from game, venison or other exotic meats. The large sales portion of meat in prepared form through in-store or restaurant purchases rather than raw form indicates that there is increased purchasing power for value-added items, particularly by the patrons who regularly consume game or exotic meats. Continued attention to sanitary harvest and processing conditions is necessary

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for all of the game, venison, and exotic species to maintain the highest possible meat quality through marketing channels. The increased production of the deer species and bison and wild boar (and its hybrids with domesticated swine breeds) under more controlled farm practices will allow management over the harvest and processing factors that affect food safety and meat quality. However, producers will have to remain sensitive to the fact that, as their husbandry management practices increase, their product may lose its ‘exotic’ image and become perceived to be yet another farmed animal species. Different training and practices will also be necessary to minimize the potential for a negative impact of the less specialized field harvesting and processing conditions under which wild game meat is obtained and distributed. Here, two scenarios will be important, the first is the ethical procedures used during the harvesting and the second is the potential for microbiological contamination.

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