Improving the meat quality of venison and other exotic game

L.C. Hoffman , K.W. McMillin , in Improving the Sensory and Nutritional Quality of Fresh Meat, 2009

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 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.

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Nucleic Acids

G.D. Khedkar , ... B.A. Chopade , in Encyclopedia of Food and Health, 2016

Nucleic Acid–Rich Foods

Animal origin

•

Wild or farmed game meats: venison, pheasant, rabbit, hare, deer, and pork

•

Seafoods: sardines, sprats, herring, bloaters, anchovies, fish roe, caviar, taramasalata, trout or salmon, lobster, crab, and prawns

Plant origin

•

Vegetables: asparagus, avocado pears, peas, spinach, mushrooms, broad beans, cauliflower, and eggplant

•

Pulses and grains: legumes, pulses, and soya products such as bean curd, tofu, and Quorn

•

Cereals: all bran, oat, rye, or wheat cereals and products; whole meal, rye, and brown breads

•

Other: beer and yeast extracts/tablets; meat or vegetable extracts

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SPECIES OF MEAT ANIMALS | Game and Exotic Animals

L.C. Hoffman , D. Cawthorn , in Encyclopedia of Meat Sciences (Second Edition), 2014

Abstract

An overview is presented describing the characteristics of the meat (game and venison) obtained from various land animals and birds that are not conventionally considered domesticated. The species discussed include those derived from wild harvesting or farming, such as game birds, deer, antelope, kangaroos, rabbits, and wild Suid species, as well as camelids, buffalo, and bison. Physical and chemical meat quality attributes are considered, focusing on carcass characteristics, meat composition, and sensory aspects. Particular emphasis is placed on the meat's nutritional value, as well as its potential to contribute to food security and the health of a growing population.

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Measures of Food Quality

Sze Ying Leong , Indrawati Oey , in Reference Module in Food Science, 2017

Meat, Meat-Based Products and Seafood

Meat is the muscle tissue of animals. Pork, beef and veal, mutton and lamb, poultry (chicken, duck and turkey), venison, fish (lean and fatty fish) and shellfish (mollusc and crustacean) are the typical muscle-based foods consumed by human as an important source of protein in the daily diet. The chemical composition of meats vary due to differences in their genetics (breed/species), gender, age, their diet and nutritional status, the muscle type, the location and physiological function of the muscle in the animal and the physical exercise of the animal (related to the type of farming such as free-range, cage etc.). All these influence the muscle-to-bone ratio and fat-to-water-to-protein ratio, leading to consequences on meat quality. Some of the key quality traits for fresh meat cuts include muscle appearance, colour, texture, tenderness, juiciness, mouthfeel characteristics, fat content, connective tissue, and muscle fibre characteristics. These meat quality traits are further affected during slaughtering and post-rigor handling. The quality measures for fresh meat cuts and processed meats are summarised in Table 3.

Table 3. Common measures of quality-related changes in meat, meat-based products and seafood

Quality indicators Commonly-used measurement assays or techniques
Chemical composition Water content and water activity
Fat content (total level of free fatty acids, composition and the degree of saturation)
Protein content (amino acids, detection of protein oxidation products)
Minerals content (iron, zinc, magnesium, potassium, phosphorus, sodium, calcium)
Vitamin content (thiamine, riboflavin, niacin, pantothenic acid, folate, vitamins B6 and B12)
Nitrite level (especially for processed and cured meat products)
Water holding capacity (relate to the saleable weight and appearance of fresh meat and impact on meat tenderness after cooking) Drip/purge loss technique (press the animal muscle tissue under external mechanical force or centrifugation and compare the final weight to initial weight, weight loss is considered as the water that the tissue is unable to retain)
Cooking loss
Measurement of meat pH, glucose content and glycolytic potential (to obtain information on the post-mortem metabolism of muscle when converting to meat)
Mouthfeel (relate to muscle structure and eating quality - tenderness) Microscopy techniques to study meat microstructure
Texture profile analysis, shearing method, compression test, penetration test using texture analyser to define important texture parameters (cutting force, chewiness, hardness, springiness, cohesiveness, gumminess)
Sensory panel (assessment on meat tenderness, juiciness)
Collagen content (relate to meat toughness)
Colour and appearance (relate to chemical and biochemical changes of animal muscle tissues) Colorimeter or spectrophotometer or spectrocolorimeter, visible and near-infrared reflectance spectrophotometer and tristimulus colorimeter
Assessment of fat marbling using visual and image analysis
Colour chart or colour fan (e.g. salmon)
Pigments quantification
Sensory panel (assessment on colour and appearance)
Lipid oxidation (relate to off-flavour development) TBARS method
Flavour or volatiles identification and quantification
Sensory panel (assessment on acid and rancid flavour)
Meat flavour and aroma Flavour or volatiles identification and quantification of cooked meat (to distinguish species-specific flavours and to detect compounds developed as a result of thermal decomposition of amino acids and peptides, caramelisation of sugars, degradation of ribonucleotides, interaction of reducing sugars with amino acids or peptides (Maillard reaction) and thermal degradation of lipid), sensory panel (assessment on smell, aroma and flavour)
Detection of microbial flora, lactic acid bacteria, bacteriophages and early spoilage (determination of product shelf life) Microbiological assays (enumeration of microbial groups using selective growth media and conditions (total plate count), random isolation of colonies, splot/plaque assay, turbidity/growth test, impedance/conductivity measurement of the cultures, electron microscopy, flow cytometry, phenotypic methods)
Molecular methods (ELISA, PCR, sequencing of 16S rRNA genes)
Flavour or volatiles identification and quantification, sensory panel (detection of fishy or putrid odours in seafood)
Safety Using chromatography technique to detect toxicants, contaminants (chemical residues, heavy metals)
Quality indicators of fish and seafood Chemical and biochemical methods: determination of freshness and spoilage using k factor calculation (based on ATP and its breakdown products), analysis of biogenic amines (histamine or cadaverine), analysis of trimethyl amine, trimethyl amine oxide and formaldehyde, analysis of total volatile basic nitrogen
Physical methods: microscopy, pH measurement, texture and texture profile analysis, conductivity, colour measurement, image analysis
Microbiological methods: total viable count, determination of specific spoilage organisms, bacterial sensors, PCR-based methods
Species identification and authenticity: fish protein identification, DNA analysis
Differentiation between fresh and frozen-thawed products: examination of the opacity of the eye lens, measurement of the electrical resistance, determination of the red blood cells (erythrocytes), determination of specific enzymes (e.g. lactate dehydrogenase indicates cell membrane leakage due to mechanical damage cause by freeze-thawing)

Appearance (related to colour) and texture (related to tenderness and juiciness) are the most important quality traits in muscle-based foods since these two factors predominantly influence consumer choices at the point of purchase (Font-i-Furnols & Guerrero, 2014). Fresh red meat cuts such as beef are deemed as having a premium quality if the meat has a uniform appearance, is bright red in colour (related to freshness perception), has a moist surface (related to the perception of moisture level within the muscle), firm flesh texture, evenly marbled fat and reduced visibility of connective tissue (related to perception on meat tenderness). The general appearance of muscle-based foods usually reflects their price. For this reason, the meat industry maintains the uniformity of colour throughout the processing and handling of the muscle tissue. Measuring meat colour using an instrumental device such as a colorimeter is usually a good starting point to assess the state of myoglobin and to effectively sort or grade meat before displaying it for consumers.

Muscle foods, unlike other food systems, are not commonly eaten raw and hence the expectation of meat quality is mostly justified only when they are cooked and chewed. Textural properties of meat can physically affect the way consumers perceive the mouthfeel of meat. In this respect, tenderness and juiciness of (cooked) meat are considered the major textural quality attributes appealing to consumers that drive their willingness to pay high price for a particular meat cut. Meat tenderness is strongly influenced by the connective tissue and muscle fibre characteristics (Listrat et al., 2016). Connective tissue is a type of fibrous structure predominantly composed of cross-linking of collagen fibrils. Muscles from mature animals or muscles used in movement, which contain higher amounts of connective tissue and collagen cross-links, are generally tougher (or less tender) compared to muscles from younger animals or muscles that are used for structural support. Additionally, the amount of collagen and degree of their crosslinking in muscle tissue can have an implication on meat solubility during cooking.

Unpredictable changes in the characteristics of muscle fibres occurring during the post-mortem conversion of muscle to meat may bring consequences on meat tenderness (Soltanizadeh and Kadivar, 2014). As muscles enter rigor mortis, shortening or contraction of the myofibrils and muscle fibres takes place, causing muscle stiffness. The resolution of rigor will eventually take place and meat becomes tender. Therefore, meat ageing is necessary, allowing muscle fibres to become more relaxed and extensible. However, chilling the meats immediately after slaughter without allowing for the development of rigor mortis can produce extremely tough meat; the muscle remains contracted during the cold storage and the resolution of rigor mortis will not take place. In this respect, monitoring meat pH and the rate of pH decline at the first instance can provide an effective measure of the post-mortem status for muscle tissue. The addition of exogenous proteolytic enzymes of plant origin such as papain (EC 3.4.22.2) and actinidin (EC 3.4.22.14) have been introduced to tenderize meat at an industrial level (Ha et al., 2012). However, a careful control on the amount and the duration of enzymatic reaction is critical to avoid "over-tenderising" the meat that destroys the entire muscle fibre structure, resulting in a mushy, soft texture.

Muscle fibres also play an important role in the water immobilisation in meat, which contributes towards the perception of meat juiciness. Water accounts for about 70%–75% of meat's fresh weight, and the majority of water is confined via capillary in the spaces between myofilaments, between the myofibrils, and outside the fibres. Changes in the characteristics of muscle fibres can affect their water holding capacity (Huff-Lonergan and Lonergan, 2005). The biochemical reactions taking place during the conversion of muscle to meat can cause structural changes in the muscle fibres, either due to net charge effect between the fibres (i.e. excessive lactic acid production reduces meat pH leading to myofibril shrinkage) or stearic effect (i.e. muscle goes into rigor/contraction and reduces the space available for water within the myofibril) (Huff-Lonergan and Lonergan, 2005). These can critically influence the ability of muscle cells to retain water. Muscle water content or drip loss can be a good predictor of juiciness, albeit fatness or marbling in meat may also contribute towards juiciness perception.

In intact meat cuts, prediction of meat tenderness and juiciness can be performed using mechanical shearing probes or devices to mimic human mastication (see Table 3). However, in the case of processed-meat products, intact muscle tissue is usually comminuted (reduction of particle sizes) and then restructured through the gel-forming and emulsification properties of the muscle proteins. The rheological properties (hardness, deformability, elasticity, cohesiveness) of the meat particles are important quality measures to ensure homogeneity in quality and chemical composition of processed meat products.

With respect to seafood and seafood products, food safety of the raw material itself needs to be addressed before they are offered for consumption and processing. The recommended analytical methods to address them and to determine the seafood quality are summarised in Table 3. Compared to land animals, aquatic animals experience rigor mortis at a much faster rate due to a lower glycogen reserve. Aquatic animals are frequently contaminated with parasites and high amounts of viruses, microorganisms, toxins, harmful metal elements (e.g. mercury, cadmium), and environmental pollutants. Furthermore, residues of pharmaceuticals and hormones can accumulate in aquatic animals. All of these pose a risk to human health. Rapid formation of fish aroma after they are caught is due to autolytic activities (i.e. degradation of lipids and nucleotides and formation of biogenic amines). Thereafter, endogenous enzyme activity (lipoxygenase action on polyunsaturated fatty acids) and oxidation processes dominate within several hours. Finally, development of "fishy" odour (indicative of a loss of freshness and microbial spoilage) occurs. It has to be noted that the freezing-thawing process can alter the fish quality in several ways compared to freshly caught fish, including texture deterioration and development of rancid flavour.

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Volume 2

Alaa El-Din Ahmed Bekhit , ... Xu Zequan , in Encyclopedia of Food Chemistry, 2019

Myoglobin Content

The Mb content in meat varies with species, breed, individual animals, age, diet and muscle type. The highest Mb contents in commercial meats can be found horse meat and venison, but the exact values vary in literature depending on the study. Yasui (1956–1957) reported the average Mb contents in fresh pork, horse, sheep and cattle meats to be 1.9, 4.5, 2.1 and 3.3   mg/g fresh weight for deltoideus, 0.78, 4.4, 1.1, and 4.0 for longissimus dorsi, and 0.9, 3.3.2, 0.4 and 2.6 for semitendinosus, respectively. They found very high variation in Mb content among animals from the same species. McKenna et al. (2005) found Mb content in 19 beef muscles varies from 3.6 to 5.62   mg/g fresh weight. Wide range of Mb contents has been reported for different pork cuts that is likely to be due to breed and diet. For example, Topel et al. (1966) reported a range of 2.9–6.4   mg/g in various pig muscles, whereas Kim et al. (2010) found a range of 1.2–2.1   mg/g.

Among game meats, Zebra meat was reported to contain the highest Mb content (7.2   mg/g) (Onyango et al., 1998).

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Carcass interventions and meat tenderness

M.M. Farouk , ... K. Rosenvold , in Improving the Sensory and Nutritional Quality of Fresh Meat, 2009

24.6 Future trends

The following are some of the future directions for research based on the review of the literature used in writing this chapter and the authors' understanding of the current and future needs of the beef, lamb, venison and pork industries:

(i)

The current practice in the meat industry is to produce meat using accepted processing inputs, age the meat appropriately, then supply it to markets hoping that its eating quality meets the needs of the consumer with little measure of its attributes in the market place. The use of non-invasive methods such as NIR and NMR to predict tenderness of meat early post-mortem so that processors can guarantee the tenderness of meat sold to consumers would add a new dimension to meat retailing and should be encouraged.

(ii)

The current practice of applying various electrical stimulation waveforms and durations without determining the appropriateness for the markets needs to be evaluated. Over-stimulation has been raised as an issue but that is hardly likely to be important as the animals physiologically cannot respond past a certain point. Additionally, multiple electrical inputs separated by significant intervals appears to toughen meat whatever the duration. A system that will customise the electrical input to each carcass for maximum quality and consistency was developed at AgResearch MIRINZ and work is continuing in New Zealand. This system has not yet been sufficiently reported on in the public domain to speculate on its viability.

(iii)

Ageing is fine for table meats but is of less importance or even detrimental to the functionality of manufacturing meats (Farouk and Wieliczko, 2003). Thus selective stimulation of muscles could be beneficial. Individual muscle stimulation can be combined with hot-boning and immersion chilling to produce cuts that are optimised for table or manufacturing purposes.

(iv)

Maintenance of muscles at rest length or even slight stretching can be achieved if the muscles are removed from the carcass and wrapped or squeezed into a tube or mould. Thus, methods to simply achieve stretching that are commercially attractive should be developed. Whole carcass rather than individual muscle pre-rigor stretching through mechanical and electrical manipulation of the carcasses also offers a means of accelerating the ageing of meat and should be investigated.

(v)

While high pressure, ultrasound and hydrodyne technologies can improve tenderness, methods need to be developed to commercialisation.

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The eating quality of meat

R.A. Lawrie , in Lawrie's Meat Science (Seventh Edition), 2006

10.3.3.2 Conditioning (see also §§ 5.4 and 7.1.1.2)

That the tenderness of meat increases when it is conditioned (e.g. stored at chill temperatures for 10–14 days) has long been recognized (Lehmann, 1907 ); and, of course, such meat as venison is regularly aged for this purpose. The decrease in tenderness which is associated with the onset of rigor mortis (§ 10.3.3.1) is gradually reversed as the time of post-rigor conditioning increases. To reiterate the views in § 5.4.2, this is not due to the dissociation of the actomyosin formed during the onset of rigor mortis (Marsh, 1954), and the absence of any increase in end groups (Locker, 1960b) shows that the myofibrillar proteins are not appreciably proteolysed in these circumstances. Moreover, the absence of soluble hydroxyproline-containing substances in meat, even after one year at 37   °C, indicates there is no extensive proteolysis in connective tissue proteins (Sharp, 1959). Although there is little proteolysis of connective tissue proteins, certain cross-links in the telopeptide region of collagen molecules are apparently broken, possibly due to the action of lysosomal enzymes ( Etherington, 1971, 1972 Etherington, 1971 1972 ). In respect of the myofibrillar proteins, although no massive proteolysis occurs, it has already been indicated (§ 5.4.1) that a number of subtle alterations occur. Thus, the calcium-activated sarcoplasmic factor (calpains) attacks troponin T (above pH   6), the Z-lines (desmin), the M-line proteins, tropomyosin and the so-called gap filaments (connectin) ( Locker et al., 1977; Penny and Dransfield, 1979; Penny, 1980;Young et al., 1980 Locker et al., 1977 Penny and Dransfield, 1979 Penny, 1980 Young et al., 1980 ); and lysosomal enzymes attack troponin T (below pH   6) as well as the cross-links of the non-helical telopeptides of collagen and the ground substance. There is extensive proteolysis of the soluble sarcoplasmic proteins (Hoagland et al., 1917), and the cytoskeletal proteins (Kristensen and Purslow, 2001). These changes, together with a loss of calcium ions, and uptake of potassium ions, by the muscle proteins (Arnold et al., 1956), cause their water-holding capacity to increase during conditioning.

Proteomic techniques have revealed, in great detail, that changes in the patterns of proteins occur during post-mortem glycolysis and conditioning. It is envisaged that these changes in pattern will be related subsequently to a series of specific tenderness levels in meat (Lametsch et al., 2003).

Whatever the nature of the particular protein changes during conditioning which are significant in relation to the increased tenderness, it has long been clear that muscles contain proteolytic enzymes (§ 5.4.2) which operate much more readily at 37   °C than at 5   °C (Sharp, 1963), and that, in general, higher temperatures of conditioning produce a given degree of tenderizing in a considerably shorter time than do lower temperatures. This effect was studied by Bouton et al. (1958) and by Wilson et al. (1960). The former workers found that conditioning for 2 days at 20   °C gave the same degree of tenderizing as 14 days at 0   °C, and that the benefits of conditioning were more marked with beef of poor quality (cf. also Moran and Smith, 1929), which was initially tougher although the final degree of tenderness achieved was similar in beef of good and poor quality.

Wilson et al. (1960) employed antibiotics to control bacterial spoilage and were thus able to study temperatures as high as 49   °C. Semimembranosus muscles from the rounds of beef carcasses which had been infused with oxytetracycline (to a concentration of 30–50   ppm) were employed. The muscles were prepared as 3/4 inch steaks and vacuum sealed in plastic film. After appropriate conditioning periods at 2   °C, 38   °C, 43   °C and 49   °C, the meat was cooked and assessed for tenderness by a taste panel. Some of the results are given in Table 10.12.

Table 10.12. Mean tenderness values for beef steaks conditioned in various ways (after Wilson et al., 1960)

Time and temperature of conditioning Tenderness
Initial Residual
Non-conditioned controls 5.2 5.2
14   days at 2   °C 5.9 5.8
Non-conditioned controls a 5.3 5.5
2   days at 38   °C 6.0 6.1
Non-conditioned controls 5.1 5.2
1   day at 43   °C 6.3 6.2
Non-conditioned controls 5.2 5.4
1   day at 49   °C 7.4 7.2
a
Given 45,000   rad ionizing radiation.

As Table 10.12 shows, the tenderness score was increased by all conditioning procedures over that of controls. Moreover, the meat held for 2 days at 38   °C, or for 1 day at 43   °C or 49   °C, was more tender than that kept for 14 days at 2   °C. The tenderness increment was particularly high in the meat held at 49   °C, but the latter had a somewhat undesirable flavour. Conditioning at 38   °C was difficult to control, even with the dose of ionizing radiation given to steaks at this temperature (in addition to the antibiotics) because of the greater risk of bacterial growth. The optimum time and temperature required to have the same degree of tenderizing as that arising during 14 days at 0   °C was 1 day at 43   °C. Nevertheless, the rate of conditioning decreases gradually as holding temperatures rise from 40   °C to 60   °C. It then decreases sharply, ceasing altogether at 75   °C (Davey and Gilbert, 1976b). The observations of Penny and Dransfield (1979) are relevant in this context. Although proteolysis of troponin T correlated with increasing tenderness in beef muscles when conditioning took place at temperatures between 3 and 15   °C – and the rates of proteolysis increased with increasing temperature – the concomitant increase of tenderness was proportionately less at higher temperatures of ageing. This may reflect protein denaturation as an additional factor in the latter circumstances and recalls the observations of Sharp (1963) (§ 5.4.1), who found that muscles which had been stored at 37   °C homogenized less readily than those stored at 0   °C. However, it is known that CASF (calpains) (Dayton et al., 1976) and cathepsin B (Swanson et al., 1974) lose activity above 40   °C and 50   °C, respectively. At higher temperatures (ca. 60   °C) carboxyl proteases are active in proteolytic breakdown of muscle proteins (King and Harris, 1982); but, nevertheless, their capacity to break down connectin is less at 80   °C than at 60   °C.

Another interesting aspect of the large temperature coefficient of conditioning changes is the use of electrical stimulation to avoid cold-shortening in meat which is refrigerated swiftly post-mortem. As indicated in § 7.1.1.2, electrical stimulation produces a low pH rapidly in the musculature at a time when the temperature is still at in vivo levels. The combination of low pH and relatively high temperature activates lysosomal proteases, and, before the pH falls below 6, the temperature possibly activates calpains. Electrical stimulation promotes significant conditioning changes to occur during the short period when the meat is still at in vivo temperature (Devine and Graafhuis, 1995). If the meat is cooled too quickly after electrical stimulation, however, this advantage is lost and the tenderizing action does not operate, although the toughness due to cold-shortening can be avoided thereby.

Very fast chilling has been defined in the European Union as chilling to a temperature of −1   °C by 5   h post-mortem. As Joseph (1996) has pointed out, the very low temperatures required to achieve this in the refrigerating environment would cause much variation in the biochemical and biophysical status of muscles, especially in those nearest the source of the refrigeration. On one hand calcium ions, released by the cold shock, would tend to cause the toughening of cold-shortening; on the other hand they would tend to enhance tenderness either directly or by stimulating the action of proteolytic enzymes. In remote areas of developing countries there are considerable advantages in using solid CO2 as an alternative to mechanical chilling for hot, deboned meat (Gigiel, 1985). The procedure, however, promotes cold-shortening and toughness in the meat (Swain et al., 1999).

If high temperature conditioning is applied to meat immediately after slaughter, this can induce marked shortening of the muscles as they go into rigor mortis and subsequent toughness, an adverse effect long known in the laboratory and observed in practice in lamb carcasses (Davey and Curson, 1971). When, however, muscles are restrained from shortening, they are more tender if they undergo rigor mortis at 37   °C than at 15   °C (Locker and Daines, 1975). This may possibly be due to enhanced activity, at this temperature, of calpains (which operate optimally at near in vivo pH), since there is evidence that, in muscles held at 37   °C (but which were not free to shorten), tenderness was greatest in those wherein the pre-rigor pH, fortuitously, was slow to fall ( Marsh et al., 1981; Marsh, 1983 Marsh et al., 1981 Marsh, 1983 ). Harris and McFarlane (1971) found that beef l. dorsi muscle tenderized more rapidly than semimembranosus when aged at 0–1   °C for up to 6 weeks (cf. § 5.4.1). This was true whether or not the muscles were stretched by hanging the carcasses by the obturator foramen. Stretching was found to give a tenderizing effect equivalent to that obtained by ageing for 2 weeks at 0–1   °C when using the conventional method of suspension. Ouali and Talmant (1990) and Monin and Ouali (1991) have extensively reviewed the reasons for differentiation between muscles in the rates and extents of ageing which they undergo post-mortem (cf. § 5.4.2).

Further evidence for differences between muscles in their behaviour during conditioning has been provided by Bailey and Light (1989) based on the extractability of perimysial collagen (Table 10.13) and Stanton and Light (1990) have shown that although the extractability of endomysial collagen is much greater before conditioning in bovine psoas major and gastrocnemius than in extensor carpi radialis and supraspinatus, the subsequent increase in solubility of such collagen during conditioning is markedly more extensive in the latter two muscles. Simões et al. (2005) found that the tenderness of biceps femoris was the most accurate predictor for the overall carcass tenderness after ageing for 7 days at ca. 0   °C.

Table 10.13. Extraction of perimysial collagen from various bovine muscles before and after conditioning

Muscle Unconditioned Conditioned
Psoas major 0.8 10.5
Supraspinatus 0.4 4.6
Gluteus medius 0.6 2.3
Gastrocnemius 0.8 1.7
Pectoralis profundus 0.4 1.3

In general, endomysial collagen is much more labile during conditioning than that of the perimysium; and, within the endomysium, type III collagen is preferentially attacked in comparison with type I (Stanton and Light, 1990).

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Meat: Role in the Diet

S.H. McNeill , M.E. Van Elswyk , in Encyclopedia of Food and Health, 2016

Sources and Production

Meat sources vary throughout the world. Pork, beef including veal, poultry, lamb/mutton, and goat meats are the most commonly consumed; however, regional variations exist. According to availability or local custom, rabbit, deer (venison), horse, camel, and other mammals often serve as sources of meat. Currently, pig stocks lead the world's meat production with China and the United States producing more than half (55%) of the world's pork ( Tables 1 and 2 ). The United States is the largest producer of beef cattle, accounting for 19% of global production, followed by Brazil with 14% of global production. The United States, China, and Brazil are also the top producers of chicken, representing 19%, 14%, and 13% of global production, respectively. The United States is the largest producer of turkey, providing almost half (48%) the global production.

Table 1. Top meats produced worldwide (2011)

Meat source Production (metric tons)
Pig 108   055   178.57
Chicken 90   143   993.68
Cattle 62   941   735.68
Sheep 8   348   110.64
Turkey 5   462   721.70
Goat 5   262   747.23
Meat (total) 297   479   837.24

Source: FAO, Statistics Division (FAOSTAT), http://faostat.fao.org/

Table 2. Top meat-producing countries (2011)

Meat source Country Production (metric tons)
Cattle The United States 11   983   308.00
Brazil 9   030   000.00
China 6   182   155.00
Argentina 2   497   250.00
Chicken The United States 17   111   240.00
China 12   170   062.00
Brazil 11   421   730.00
Russian Federation 2   895   489.00
Goat China 1   889   602.00
India 596   600.00
Nigeria 292   100.00
Pakistan 285   000.00
Pig China 49   396   351.00
The United States 10   330   808.00
Germany 5   616   074.00
Spain 3   469   345.00
Sheep China 2   050   000.23
Australia 512   235.00
New Zealand 465   318.00
Sudan (former) 324   000.00
Turkey The United States 2   626   531.00
Brazil 489   000.00
Germany 467   354.00
France 398   082.00
Italy 309   483.00

Source: FAO, Statistics Division (FAOSTAT), http://faostat.fao.org/

The production of livestock for food is increasing driven by a shift toward the inclusion of more animal products in the diet. In Asia, where the bulk of increase in the world population has occurred over the last decade, consumption of meat has increased an estimated 3% annually. The rapid growth in meat production has been primarily the result of increased demand for poultry with beef, buffalo, and pork production remaining relatively stable as shown in Figure 1 . According to the Food and Agricultural Association (FAO) Statistical Yearbook 2013, a change in the composition of livestock production has been occurring since the 1960s. Growth of global beef production has gradually declined from almost 2% per year in the 1960s to <   1% per year in the early 2000s. Pig production has undergone a greater decline, from a growth rate of 4% per year to 0.8% per year during the same time period, while poultry stocks continue to grow at a rate of ~   3% per year. However, China and Oceania are exceptions to the trend in red meat production elsewhere. Pig stocks in China have shown a significant increase from 36.8 million tons in 2000 to 49.4 million tons in 2011, representing an increase of over 34% during the 11-year period. In Oceania countries, the percentage of total livestock produced – specifically cattle and buffalo – has increased from 11.8% in 2000 to 14.4% in 2011 ( Figure 2 ).

Figure 1. World meat production (2000–10).

Figure 2. Trend of cattle and buffaloes as percent of total livestock produced 1992–2011.

 FAO, Statistics Division (FAOSTAT), http://faostat.fao.org.

Several production systems contribute to the availability of meat around the world. No single production system best fits all livestock or the availability and security needs for food across different world regions and communities. Productions systems vary on a continuum from those that rely on livestock grazing and consumption of feed sources not readily consumed by humans to those occupying limited land, which rely, at least in part, on feed sources common to the human diet. Over 60% of the world's poultry meat and eggs are produced in so-called 'landless' production systems, which is not surprising, as poultry require limited space due to their size. As monogastric animals, poultry consume a diet containing food sources that also contribute nutrients to the human diet. In contrast, over 70% of the world's beef was produced using a mixed system including grazing and, as ruminant animals, consumption of crop residues and concentrates not otherwise edible for humans.

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Hepatitis E

Eyasu H. Teshale , in Foodborne Infections and Intoxications (Fourth Edition), 2013

Prevention and control

In hepatitis E outbreaks, as in other fecal-orally transmitted infection outbreaks, the provision of clean drinking water and improving the sanitary disposal of human waste are the two most important prevention approaches. Based on limited observations that consumption of undercooked pig and boar liver, undercooked meat, and undercooked venison is associated with hepatitis E, thorough cooking of such items is recommended. The incidence of foodborne hepatitis E is not well established and no specific interventions have been tested. As evidence for person-to-person transmission of HEV is increasing, it is prudent that strategies focused on reducing transmission from this route—such as soap and hand washing encouragement—be implemented in an effort to reduce transmission during outbreaks [35]. However, because the success of these interventions as assessed in outbreak situations is currently quite limited, the need to develop, test, and provide a reliable hepatitis E vaccine is imperative [38]. There are at least two hepatitis E vaccine candidates that have shown promise in clinical trials [39,40].

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NUCLEIC ACIDS | Physiology

H.A. Simmonds , in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003

Purine Content of Foods

A knowledge of the purine content of specific foods is essential if dietary effects are to be reduced to a minimum. Until recently, such data have been difficult to find but are now available on the web. Most tables give only purine nitrogen, which, as demonstrated by the purine loading studies mentioned earlier, is not always a good guide because of the variation in absorption. Pâté is a particular culprit, as is most offal and organ meat (liver, kidney, heart, brains, sweetbreads), game (venison, pheasant, partridge, grouse), and the nucleic-acid-rich fish and seafoods – herring, kippers, sardines, smelts, sprats, anchovies, salmon, trout, mackerel, crustaceans (crab, lobster, prawns), shellfish (scallops, mussels), and caviar or roe. Purine nitrogen varies and ranges from 50  mg per 100   g in beef steak to 234   mg per 100   g in sardines. Many fresh vegetables, e.g., spinach, peas, beans, lentils, mushrooms, asparagus, and cauliflower, also have a considerable purine content, as have soya and other pulses and grains (porridge and oats, wheat and rye cereals). All meat extracts (Bovril, Oxo) or yeast extracts (Barmene, Tastex) are very rich in purine.

However, many studies have established that humans addicted to diets rich in nucleic acids are generally very reluctant to alter their dietary habits despite the strongest advice to do so. Consequently, therapy to reduce the pathological effects of dietary nucleic acids, namely the elevated uric acid levels, becomes essential.

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