Meat and Livestock Commission
Identifying needs in meat quality research
(Defra Reference FO0310)
Report 1.2a
Review of recent UK research of meat quality (Objective 1.2): Red Meat
Contents
Introduction and Scope
Historical perspective on meat quality research in the UK
MLC Blueprints
Why is tough meat tough?
Nutritional quality
Beef quality research
Appearance
Defra funded
Other relevant research
Nutritional properties/Carcase composition
Defra funded
Other relevant research
Eating quality - flavour
Defra funded
Other relevant research
Beef Eating quality - texture
Defra funded
Other relevant research
Main recommendations to the beef industry
Research needs
Eating quality of beef - on line assessment
Other relevant research
Lamb quality research
Nutritional properties / carcase composition
Defra funded
Other relevant research
Eating quality
Defra funded
Other relevant research
Eating quality - on line assessment
Defra funded
Pigmeat quality research
Nutritional properties / carcase composition
Defra funded
Other relevant research
Eating quality
Other relevant research
Drip loss
Other relevant research
Multi-species / generic research
Flavour
Research on meat quality and genetics
Generic
Cattle
Defra funded
Other relevant research
Sheep
Defra funded
Other relevant research
Pigs
Defra funded
Other relevant research
Conclusions - Genetics of meat quality
Conclusions
Next steps
References
Meat and Livestock Commission
Identifying needs in meat quality research
(Defra Reference FO0310)
Report 1.2a
Review of recent UK research of meat quality: Red Meat (Objective 1.2)
Introduction and Scope
The purpose of this review is to summarise recent Defra funded research, together with other key UK research, on meat quality. Recent research on factors influencing meat quality and its measurement have been identified by searching the literature published over the last three years. This covers visual quality (colour), eating quality parameters (such as tenderness, juiciness and flavour) and nutritional characteristics (eg fatty acid composition). The review includes factors throughout the chain.
This literature search has been supplemented with reports on Defra funded projects, knowledge of levy-funded research and knowledge of other research being undertaken in UK research institutes. Whilst the focus is on UK research, major developments in the field internationally have been considered. An introductory section giving a historical perspective in meat quality research has been included as this is considered important background in understanding industry activity on meat quality improvement.
Report 1.1a of this project concluded:
A wide range of factors influence consumer acceptability of red meat. Many of these are perception issues which are addressed either by changes to the production system or communication activity. The important quality attributes that result from changes to meat’s physical or biochemical properties are appearance (colour and fat content), nutritional properties (primarily fat content and type) and eating quality (texture and flavour).
The review has therefore focused on research that has been aimed at improvements in colour, fat content, nutritional properties (fat type) and eating quality (texture and flavour). Each species is examined individually although the research on genetics has been grouped in a separate chapter as many of the issues are common across species.
Consideration has been given to the resource efficiency implications of implementing research results (qualitatively) and possibilities for future research. These are those obvious research avenues arising from the reviewed research. These are not necessarily those research needs identified by industry which have been identified through stakeholder interviews (see separate report).
Historical perspective on meat quality research in the UK
MLC Blueprints
In the late 1980s the Meat and Livestock Commission initiated a large programme aimed at developing guidelines for better meat quality in beef and pork. The programme included a thorough review of the literature and commercial knowledge. Where gaps in knowledge were identified research was either undertaken in-house or commissioned to address those areas. Specifications (the “Blueprints”) were drawn up from the accumulated knowledge and these were tested against retail product. These were aimed primarily at improving meat tenderness, but also included recommendations to address other attributes to some extent. Following this the Blueprints were launched in 1990 for beef and 1992 for pigs (MLC, 1990, 1992a). The Blueprint approach is described in more detail by Warkup (1993).
In lamb, there was not initially perceived to be an eating quality problem to address through the Blueprint approach. Research undertaken for MLC at the University of Newcastle (Webster et al., 1994), however, showed that older lambs have tougher meat. A Blueprint was therefore developed for lamb to specifically address the toughness problem in older lambs (MLC, 1994).
The Blueprint specifications were based on the available knowledge at the time. It was recognised that the approach was rather empirical and the specifications were therefore likely to include unknown interactions, and duplication. It was considered, therefore that further research to understand the underlying mechanisms determining meat quality would be necessary.
In addition, the Blueprint specifications focussed predominantly on post-slaughter factors. This was partly because these have been found to have larger effects on meat tenderness than pre-slaughter factors, and partly because the effects are clearer and easier to apply. Research in the last few years, therefore, has focussed more on pre-slaughter factors influencing quality traits.
Why is tough meat tough?
Despite the increased understanding and control of meat eating quality through the development of the Blueprints, there remained a proportion of carcases which produced unacceptably tough meat . A number of strategic research projects jointly funded by MLC and MAFF under the Agro-Food Quality LINK programme were established in the early 1990s to attempt to identify the underlying causes of this toughness variation, particularly in pigs. These projects are summarised below:
Investigation of pig muscle fibre characteristics as a source of variation in eating quality (AFQ12)
This project identified genetic variation in muscle fibre types as a source of variation in eating quality and lead to further research to identify this effect. Some aspects of the project were followed up in a subsequent LINK project (LK0626) which examined the genetic control of meat quality. Unfortunately, the results from this research project did not provide convincing support for the hypothesis that there is a major gene for muscle fibre composition related to meat quality. A number of Quantitative Trait Loci (QTL) for tenderness were discovered.
Collagen cross linking and meat texture (AFQ23)
This project eliminated collagen cross linking as a possible factor in meat eating quality variation between pigs of normal slaughter weight and thus enabled research funding to be channelled into other areas of interest.
Structural changes contributing to cooked meat toughness of muscle fibres and fibre bundles (AFQ24)
This project was the most “fundamental” of the suite of projects and developed some novel techniques for the study of individual muscle fibres. These contributed to an increased understanding of the relative roles of myofibrillar versus connective tissue contributions to toughness. The work showed that changes seen at the whole muscle level due to cooking, cold shortening, conditioning etc are reflected at the single muscle fibre level. This indicated that future research should be focussed on factors affecting muscle fibres and, in particular, the proteolytic events of conditioning.
Biochemical origins of variable rates of conditioning porcine muscle (AFQ33)
Interest in muscle growth in the late 1980s through work on beta-agonists and their link with calpastatin expression and toughness lead to research at the University of Nottingham on the effect of stress on the calpain enzyme system and meat toughness, including this project. Variation in proteolysis post-mortem was identified as a key factor in tenderness, in particular through the calpain enzyme system. It was found the you could not ethically stress animals enough to induce a measurable effect but adrenalin infusion was used as an experimental tool. This demonstrated that adrenalin did induce toughness through increased calpastatin. Tracing back animals from the abattoir identified a clear producer effect related to calpastatin expression but this was a multi-factorial effect. Early post slaughter measurement of calpastatin was also found to be related to later tenderness. The variability in tenderness with slaughter day and lack of consistent presentation of extremes of toughness/tenderness at slaughter gives rise to experimental difficulties. Work in this area has been pursued largely with BBSRC funding.
Post-mortem proteolytic events (AFQ34)
It is clear that proteolysis post-mortem is an important component of variation in meat tenderness. In this work the protein profile following proteolysis was examined in order to understand which proteins were the targets for the important proteolytic enzymes. This led to an increased understanding of events post-slaughter.
Taken as a group these projects showed that post-mortem proteolysis is the key factor in the variation of meat quality. Muscle fibre type has some relationship with eating quality and may explain some elements of genetic effects. At normal slaughter weight, differences in collagen cross-linking are unimportant in explaining variation in texture in the same muscle from different animals.
Subsequent to this set of projects, levy-funding for eating quality research became focussed on more near-market research. Some of this has been jointly funded with Defra and will be discussed below. Defra-funded research has tended to focus on production system effects on quality.
Nutritional quality
Meat has been a long standing component of the human diet. The main health benefits of eating red meat relate to its nutritional composition. Red meat contains high biological value protein and important micronutrients and most healthy balanced diets will include lean meat in moderate amounts (Williamson et al., 2005). Nevertheless meat and meat products form an important source of fat in the diet and there has been particular concern about the saturated fat intake from meat and meat products. Efforts have therefore been made over the last few decades to reduce or modify the fat content of red meat carcases and cuts.
Recent research of relevance to this has been in the area of measuring carcase fat content and modifying the fatty acid composition of meat (through dietary means).
Beef quality research
Appearance
Defra funded
Colour (and fat) stability of beef can be enhanced by the use of vitamin E supplementation. A joint-funded Defra research project at the University of Bristol (LS1801, concluded in 1999), indicated that 1000IU/head for 100 days would deliver a benefit in terms of shelf life. In mince this could increase by 4 days.
Work aimed at evaluating the effect of diet (forage versus concentrates) on the fatty acid composition and flavour of beef is described below. This also demonstrated that the antioxidants found in grass could improve colour stability compared with concentrate-fed animals.
Other relevant research
The benefit of conserved grass (silage and dried grass) on the oxidative stability of beef steaks during retail packaging was shown by O’Sullivan et al(O'Sullivan et al., 2003, 2004). This work also showed that type of forage conservation influenced meat colour. A large number of papers support the use of vitamin E in this respect for beef (Gatellier et al., 2001).
In a review of the literature, Liu et al(1995) concluded that 500IU vitamin E/head for 126 days prior to slaughter would assure benefits in increased shelf life and suggest a return of 10:1 for investment in vitamin E supplementation in terms of reduced wastage at retail. MLC estimates of the value to the British industry suggest a return of at least 3:1.
Main Knowledge gained (of benefit to beef industry)
- vitamin E can be used to improve colour shelf life in beef, particularly where concentrates are fed.
Nutritional properties/Carcase composition
Defra funded
Project LS1804 (1998-2001) examined the “deposition of n-3 polyunsaturated fatty acids in cattle and sheep and the effects on meat quality.” The use of linseed in the diet of cattle was shown to increase the muscle levels of 18:2 and 18:3. Use of a protected lipid supplement increased the level of 18:2 still further but this appeared to block the uptake of 18:3, suggesting that there is competition in the uptake of the two major unsaturated fatty acids. The use of a protected lipid supplement also resulted in an increase in lipid oxidation and abnormal flavour and a reduction in colour shelf life.
Building on from this, project LS3515 (2001-2006) was aimed at “optimising the eating quality of beef produced on sustainable forage systems.” This found that use of red clover could increase the content of PUFA (18:2 and 18:3) in beef (through reduced lipolysis in the rumen) but due to the low vitamin E content, colour shelf life is reduced. It was found that silage management strategies influence fatty acid composition, in particular extended wilting reduces the content of beneficial fatty acids. The work also increased understanding of rumen function and breakdown of fatty acids - showing that fish oil and red clover both reduce biohydrogenation in the rumen. This results in more unsaturated fatty acids being absorbed by the animal rather than being converted to saturated fatty acids by rumen microorganisms.
Parallel work (LS3511, Producing low-fat healthy ruminant products), unsurprisingly, concluded that producing leaner animals produces a better P:S ratio. Again protected lipid supplements were found to be effective in modifying fatty acid composition, and in this case the lipids used retained the favourable 18:2 to 18:3 ratio, but also increased the need for antioxidants.
Other Defra LINK research (LK0644 described below) aimed at improving the flavour of beef showed that use of grass silage resulted in a marked reduction in the n-6:n-3 ratio compared with concentrate feeding.
Work is being continued through the project FO0303 (Plant-based strategies to improve the nutritional value of beef for the consumer, ProBeef) which is linked to the large EU funded Integrated Project on beef safety and quality (ProSafeBeef). The overall objective of the project is to investigate key factors influencing the delivery of beneficial lipids from plants through to beef muscle. The project will investigate the potential for breeding perennial ryegrass varieties with a higher content of n-3 PUFA. Beef production experiments will then investigate the effect of increasing the levels of n-3 PUFAs in the cattle’s diet on the fatty acid composition of beef, shelf life and sensory attributes of the meat.
The role of unimproved biodiverse pastures and traditional breeds in achieving high levels of healthiness and quality in beef is being examined in project LS3523 (Healthiness and quality of beef produced from traditional and modern breeds reared in species-rich, unimproved grasslands). This will run from 2004 To 2008 at the University of Bristol.
Other relevant research
Irish work has shown a clear effect of the duration of grazing on the fatty acid composition, with increases in CLA, trans-vaccenic acid, the P:S ratio and the n-3 fatty acid content (Noci et al., 2005). The latter was primarily alpha-linolenic acid but with small increases in some long chain n-3 fatty acids. The general benefit of pasture on n-3 fatty acid levels has been found by a number of authors (Nuernburg et al., 2005; O'Sullivan et al., 2003; Steen et al., 2003).
Other work shows benefits of linseed feeding on the α-linolenic acid and CLA content of beef (Aharoni et al., 2004; Nuernburg et al., 2005; Raes et al., 2004). Dietary effects on fatty acid composition are reported by a number of other researchers (Basarab et al., 2007b; Duynisveld et al., 2006; French et al., 2003; Noci et al., 2007).
Diet choice (forage versus concentrate rations) is largely determined by the production system and changes to the diet can be costly. Use of protected lipids would certainly carry additional cost.
Beef Nutritional Properties
Main Knowledge gained (of benefit to industry)
- red clover can enhance the PUFA content of beef but at the expense of colour stability
- forage based diets result in a more favourable n-6:n-3 ratio.
- linseed can be used to enhance the n-3 content of concentrate-fed beef
Research needs
- means of delivering better n-3 uptake without use of lipid supplements
- research on the genetic variability of PUFA concentrations in muscle and fat tissues
- understanding of the mechanisms of the reduction in rumen biohydrogenation by use of clover or fish oils may help achieve these benefits without the associated disadvantages.
- alternative means of achieving protection from rumen biohydrogenation (without use of formaldehyde).
Eating quality - flavour
Defra funded
The Defra project LS1511 (1998-2003, Development of efficient, biologically sustainable and economically viable upland beef systems) included an evaluation of meat quality from Welsh Black and Charolais cross cattle finished on semi-natural rough grazing or permanent pasture (mainly perennial ryegrass/white clover). There were breed differences for carcase quality (Welsh Black being fatter). The grazing type influenced carcase quality with the improved pasture giving heavier, fatter carcases with higher killing out percentage, but lower ultimate pH and conformation scores. There were no differences in fatty acid composition or eating quality parameters.
The Defra LINK project LK0644 (2000-2003) was specifically aimed at (i) understanding the effect of diet on flavour and (ii) improving the flavour of beef when fed concentrates. This particular study did not show a large effect of forage based diets on flavour at 14 or 24 months of age, but at 19 months of age animals fed grass or grass silage had higher beef flavour and lower abnormal flavour than those fed concentrates (Richardson et al., 2004). In the second part of the study a protected lipid supplement was fed to modify the fatty acid composition of the beef. The original plan was to try to increase the n-3 level in order to emulate the effect of fatty acids on flavour in grass-fed animals. Unfortunately the researchers opted for a protected lipid supplement to increase overall polyunsaturated fatty acid levels and these did not sufficiently increase n-3 levels. The resulting flavour was indicative of concentrate feeding. The work also further demonstrated the need for higher antioxidant intakes for animals fed unsaturated fatty acids.