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The Relative Importance of Production and Processing Factors on Beef Palatability

Index (click on the links below)

1. Introduction
2. Discussion

2.1 MSA minimum requirements and variable inputs

2.2 Production minimum requirements

2.2.1 Breed
2.2.2 Growth Path
2.2.3 Glycogen level
2.2.4 Fat

2.3 Processing minimum requirements

2.3.1 pH/Temperature window

2.4 Production variable inputs

2.4.1 Marbling
2.4.2 HGP Implants

2.5 Processing variable inputs

2.5.1 Carcase supension
2.5.2 Ageing

3. Conclusion

4. References

Beef palatability refers to the tenderness, juiciness and flavour of cooked meat. Meat Standards Australia (MSA) consumer research resulted in a palatability score (CMQ4) with weightings 0.4, 0.1, 0.2 and 0.3 for tenderness, juiciness, flavour and overall acceptability (Polkinghorne et al. 1999).

In Australia a wide range of production systems over many different environments means a large number of factors impact on beef palatability. Extensive consumer testing of beef samples by MSA has resulted in over 500,000 CMQ4 scores for multiple production, pre-slaughter, processing, cut and cooking method combinations (www.msagrading.com 2003). This paper discusses the relative effect of production (genetics, growth path, glycogen level, rib fat, marbling and HGP implants) and processing variables (pH/temperature window, carcase suspension and ageing) on beef palatability. It focuses on MSA Grading system minimum requirements and variable inputs and the database of CMQ4 scores that underlies this system.

2. Discussion..................................................................................................................go to Top

2.1 MSA minimum requirements and variable inputs.......go to Top

Matching CMQ4 scores to beef chain variables, MSA has identified Palatability Assurance Critical Control Points (PACCP). The relative importance of production and processing variables could be defined at the most basic level through MSA’s classification of them as a minimum requirement or variable input. Given that if minimum requirements are not met the meat cannot be sold as MSA product, they may be considered as most important. The variable inputs will then determine whether the beef grades as everyday, better than everyday or premium eating quality.

2.2 Production minimum requirements.................................go to Top

2.2.1 Breed
Minimum requirement: Producers must declare Bos indicus %.
MSA CMQ4 scores show that high Bos indicus content steaks are tougher, dryer, less flavoursome and less acceptable (Newsome et al. 1999). Declaring Bos indicus content is important because B.indicus derived cattle comprise almost 40% of the Australian cattle herd (Bindon and Jones 2001). The palatability failure rate (CMQ4 < 48) of commercial carcases, classed using the MSA carcase pathway approach as having greater than 75% Bos indicus content (based on phenotype) was 63%. For carcases classed as having intermediate Bos indicus content (25 to 75%) the palatability failure rate was 31%, whilst for low Bos indicus content (<25%) carcases the palatability failure rate dropped to 11% (Polkinghorne et al. 1999). However as suggested by Hearnshaw et al. (1998) the true breed effect could be confounded by environmental effects to some extent.

Breed differences are substantially reduced, however, when carcases are effectively electrically stimulated, tenderstretched and the meat aged. Cooperative Research Centre (CRC) results suggest that under carefully controlled conditions Bos indicus content up to 75% has little impact on palatability (Rymill 1997). Regression coefficients for the effect of Bos indicus content on CMQ4 score of different muscles demonstrate a B. indicus X muscle interaction, with increased B. indicus content most evident for the high value muscles surrounding the spinal column (Thompson et al. 1999). MSA model simulations for a range of ‘normal’ commercial beef pathways show that breed effect on CMQ4 score could typically be expected to result in 0-14 units of palatability variation (Thompson 2003) .

CRC/MSA research shows a large sire difference in palatability (8 CMQ4 units) for Bos indicus cattle (Thompson et al. 2003). Of all beef that the MSA model classifies ‘ungraded’ about 30% will be ‘3 star’ according to consumer panels. Perhaps in the future genetic information such as sire gene markers will be incorporated in the model to reflect scope for within breed genetic improvement of palatability and increase accuracy of the model? For example, calpastatin DNA tests could be incorporated?

2.2.2 Growth Path
Minimum requirement: Ossification score below 300.
As physiological maturity (measured by ossification) is increased, eating quality decreases (Chappell 2001a). According to MSA Producer Training notes (Chappell 2001) consistent growth (at least 0.65 kg/day) is important to ensure the carcase’s physiological maturity is kept within bounds. However there is no clear consensus in the literature about the effect of growth rate on palatability. A recent detailed analysis of the Beef CRC CMQ4 score database by Perry et al. 2002 concluded there was a small positive relationship between growth rate of individuals within a contempory group during finishing and palatability. The effect was curvilinear, plateauing by approximately 1.2 kg/day.

Figure 1. Relationship between average daily gain during finishing and CMQ4 for temperate and tropically adapted animals grown-out and finished in NE NSW (S) or Queensland (N).

The MSA model currently includes a palatability score adjustment based on carcase weight nested within ossification score. MSA model simulations for a range of ‘normal’ commercial beef pathways shows that growth rate and maturity effect on CMQ4 score could typically be expected to result in 0-4 units of palatability variation (Thompson 2003).

2.2.3 Glycogen Level
Minimum requirement: Ultimate pH below 5.7.
MSA research shows beef with pH levels above 5.70 has lower and more variable eating quality. If pH excedes 5.9, the meat is dark, firm, dry (DFD) and tougher (Pethick et al. 1999). Table 1 below summarises the impact of pH on palatability as shown by MSA research.

Table 1. The effect of pH on CMQ4 score (Knee 2003).

In addition to the effect of pH on palatability, the association between high pH and dark meat, decreased shelf life and unsuitability for vacuum packaging should be recognised as contributors to this minimum requirement.

Production considerations such as nutrition (Pethick et al. 1999), handling (Lahucky et al. 1998), and transport (Knee 2003) have an effect on ultimate pH through their impact on glycogen levels.

2.2.4 Fat
Minimum requirement: Ribfat above 3mm
Some external carcase fat has been shown necessary to protect the carcase against dehydration and cold shortening (Goodwin 2001). Within breed selection on ultrasonic data or feedback, breed/animal maturity pattern selection, nutrition, and changing slaughter age are ways to improve compliance and usually this requirement is met.

2.3 Processing minimum requirements.................................go to Top

2.3.1 Minimum requirement: pH/temperature window
The rate and extent of pH decline and the temperature at rigor interact to govern the magnitude of myofibrillar contraction (O’Halloran et al. 1997). Muscle toughness can be very significantly affected by the state of contraction when the carcase goes into rigor (Thompson et al. 2001). At low muscle temperatures extensive shortening occurs and the subsequent increase in toughness is termed ‘cold shortening’. At high muscle temperatures some shortening also occurs, sometimes leading to increased toughness (Hwang and Thompson 2001a; Simmons et al. 1997; Uruh et al. 1986). More importantly high muscle temperatures at rigor mean denaturation of proteolytic enzymes and therefore the muscle has a reduced potential to age. MSA has set pH/temperature boundaries based on literature estimates for heat and cold shortening (Thompson 2000).

Commercially the rate and extent of pH fall can be controlled by chilling and electrical inputs including stimulation, immobilization and use of a rigidity probe during hide removal. Electrical stimulation causes accelerated muscle metabolism and hastens the onset of rigor mortis (Thompson et al. 2001). It can elicit other tenderness benefits in addition to preventing cold shortening. Studies (e.g. Ducastaing et al. 1985 Dransfield et al. 1992 Uytterhaegen et al. 1992 Ferguson et al. 2000) demonstrate that electrical stimulation accelerates post mortem proteolysis. Thompson et al. (2001) state that by removing the possibility of cold shortening and accelerating ageing, electrical stimulation has made the biggest improvement to meat quality over the last decade.

Following the introduction of electrical stimulation, it was recognised that commercial electrical stimulation protocols, particularly for low voltage stimulation, were resulting in exceptionally fast rates of pH decline and therefore high rigor temperatures (Butchers et al. 1998, Hwang et al. 1998). In some cases increased rates were due to additional electrical inputs in abattoirs utilising immobilisers (Ferguson et al. 2001). In Hwang et al‘s study (2001b) a combination of stimulation and chilling treatments were used to cause independent variation in pH and temperature decline. Results showed that, in situ, the rate of pH decline had the largest effect on eating quality. The main penalty of a rapid pH fall was reduced ageing and increased drip loss. To address these issues MSA staff visit abattoirs and adjust their particular electrical inputs to match the window specifications.

2.4 Production variable inputs.........................................go to Top

2.4.1 Marbling
The relationship between ‘marbling’ and sensory traits was examined by Thompson (2001). He concluded that marbling has a low and variable relationship with tenderness and shows a curvilinear relationship with flavour and juiciness, which tends to plateau at 15-20% chemical fat (equivalent to an AUSMEAT marble score 4).

Figure 2. The relationship between flavour and juiciness scores as a function of chemical fat percentage.

Chappell (2001) explains there is a distinction between marbling and intramuscular fat. The latter does not accurately measure fat distribution through the muscle. The USDA marble score recognises consumers do not like unevenly distributed ‘islands’ of fat in the muscle. It would be interesting to look at the relationship after adjustment for fat distribution.

MSA model simulations for a range of ‘normal’ commercial beef pathways show that marbling effect on CMQ4 score could typically be expected to result in 0-4 units of palatability variation (Thompson 2003).

As commercial uptake of the science behind the MSA system increases it is thought likely that much of the variation in tenderness due to production and processing factors will be addressed. As marbling becomes a relatively more important determinant of eating quality it is likely that genetic differences (within and between breed) will receive increased focus. Progeny tests (e.g. those presented by Bindon 2001) have shown significant differences between and within a breed in marbling ability.

2.4.2 HGP Implants
A number of studies report that HGP implants are responsible for reductions in marbling scores and an increase in dark cutters and also a trend for HGP treatment to increase meat toughness, although results vary (Thompson 2002). Consumer testing as part of the Beef CRC/MSA research program (McIntyre unpublished data) showed the striploin had the largest effect, with HGP treated striploins having a 10 point lower palatability score than the controls after 5 days ageing. The larger HGP effect appears to be associated with muscles that have a higher ageing rate. The effect still showed at 21 days ageing, although the magnitude had decreased to about 5 CMQ4 units. HGPs will be incorporated into the MSA model.

2.5 Processing variable inputs................................................................go to Top

2.5.1 Carcase Suspension
A way to avoid cold and heat shortening is to “tenderstretch” . There is a highly significant hanging method X muscle interaction (Bouton et al. 1973 Ferguson et al. 1999). Tenderstretching minimises the need for ageing meat. In a CRC experiment (O’Halloran et al. 1998) striploin samples from tenderstretched carcases were as tender as samples from normally hung carcases aged for 14 days. MSA model simulations for a range of ‘normal’ commercial beef pathways show that hanging effect on CMQ4 score could typically be expected to result in 0-10 units of palatability variation (Thompson 2003). The effect of electrical stimulation and tenderstretching on beef palatability has found to be additive (Ferguson et al. 1999).

2.5.2 Ageing
Most product processed in abattoirs is vacuum packed. This allows extended ageing which has a marked effect on palatability (Thompson et al. 2001). Ageing rates are higher for low connective cuts than high connective cuts (Thompson 2000). MSA model simulations for a range of ‘normal’ commercial beef pathways show ageing effect on CMQ4 score could typically be expected to result in 0-7 units of palatability variation (Thompson 2003).

3. Conclusion..................................................................................................................go to Top

MSA has identified Critical Control Points for beef production and quantified their effect using a unique standard research procedure. Research has shown that palatability is a reflection of many production and processing events. However, of all the factors identified, carcase processing conditions during the first 24 hours after slaughter have greatest influence on palatability. MSA has made the most important factors such as pH/temperature window mandatory (minimum requirements). As commercial uptake of science behind the MSA system (e.g. tenderstretching or pH/temperature window) increases it is likely that much of the variation in tenderness associated with production and processing factors will be addressed. As this occurs it is likely that higher order variables (e.g. the effect of marbling) will become more important determinants of palatability.

4. References..................................................................................................................go to Top

Bindon BM (2001) Genetic and non-genetic opportunities for manipulation of marbling. In ‘Proceedings of the Beef Quality CRC marbling symposium’, p. 30. (Coffs Harbour, Australia).

Bindon BM, Jones NM (2001) Cattle supply, production systems and markets for Australian beef. Australian Journal of Experimental Agriculture. 41, 861-877.

Bouton PE, Fisher AL, Harris PV, Baxter RI (1973) A comparison of the effects of some post-slaughter treatments on the tenderness of beef. Journal of Beef Technology. 8, 39-49.

Chappell G (2001a) On farm strategies to meet MSA requirements. The Armidale Feeder Steer School.

Chappell G (2001b) The importance of marbling in the domestic market – what does it mean for consumers? In ‘Proceedings of the Beef Quality CRC marbling symposium’, p. 30. (Coffs Harbour, Australia).

Dransfield E, Etherington DJ, Taylore MAJ (1992) Modelling post-mortem tenderisation. II Enzyme changes during storage of electrically stimulated and non-stimulated beef. Meat Science 31, 75-84.

Ducastaing A, Valin C, Schollmeyer J, Cross R (1985) Effects of electrical stimulation on post-mortem changes in the activities of two Ca dependent neutral proteinases and their inhibitor in beef muscle. Meat Science 15, 193-202.

Ferguson DM, Thompson JM, Polkinghorne R (1999) Meat Standards Australia: a ‘PACCP’ based grading scheme for consumers. 3. PACCP requirements which apply to carcass processing. In ‘Proceedings of the 45th international congress of meat science and technology’. P.18 (Yokohama, Japan).

Ferguson DM, Jiang S, Hearnshaw H, Rymill SR, Thompson JM (2000) Effect of electrical stimulation on protease activity and tenderness of M. longissimus from cattle with different proportions of Bos Indicus content. Meat Science 55, 265-272.

Ferguson DM, Bruce HL, Thompson JM, Egan AF, Perry D, Shorthose WR (2001) Factors affecting beef palatability – farmgate to chilled carcass. Australian Journal of Experimental Agriculture 41, 879-891

Goodwin M (2001) Rib fat and fat distribution. In ‘How do I do it- MSA Information Workshop Participant Manual’ P.13.

Hearnshaw H, Gursansky BG, Gogel B, Thompson JM, Fell LR, Stephenson PD, Arthur PF, Egan AF, Hoffman WD, and Perry D. (1998) Meat quality in cattle of varying Brahman content: the effect of post-slaughter processing, growth rate and animal behaviour on tenderness. Presented at the 44th international congress of meat science and technology. 44, p.1048 (Barcelona, Spain).

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Hwang IH, Hearnshaw H, ShawFD, Thompson JM (1998) The interaction between type (high or low voltage) and time (3 or 40 minutes post-stunning) of electrical stimulation on beef. In ‘Proceedings of the 44th international congress of meat science and technology’ p.1052. (Barcelona, Spain)

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