Elsevier

Meat Science

Volume 66, Issue 1, January 2004, Pages 21-32
Meat Science

Effects of fatty acids on meat quality: a review

https://doi.org/10.1016/S0309-1740(03)00022-6Get rights and content

Abstract

Interest in meat fatty acid composition stems mainly from the need to find ways to produce healthier meat, i.e. with a higher ratio of polyunsaturated (PUFA) to saturated fatty acids and a more favourable balance between n-6 and n-3 PUFA. In pigs, the drive has been to increase n-3 PUFA in meat and this can be achieved by feeding sources such as linseed in the diet. Only when concentrations of α-linolenic acid (18:3) approach 3% of neutral lipids or phospholipids are there any adverse effects on meat quality, defined in terms of shelf life (lipid and myoglobin oxidation) and flavour. Ruminant meats are a relatively good source of n-3 PUFA due to the presence of 18:3 in grass. Further increases can be achieved with animals fed grain-based diets by including whole linseed or linseed oil, especially if this is “protected” from rumen biohydrogenation. Long-chain (C20–C22) n-3 PUFA are synthesised from 18:3 in the animal although docosahexaenoic acid (DHA, 22:6) is not increased when diets are supplemented with 18:3. DHA can be increased by feeding sources such as fish oil although too-high levels cause adverse flavour and colour changes. Grass-fed beef and lamb have naturally high levels of 18:3 and long chain n-3 PUFA. These impact on flavour to produce a ‘grass fed’ taste in which other components of grass are also involved. Grazing also provides antioxidants including vitamin E which maintain PUFA levels in meat and prevent quality deterioration during processing and display. In pork, beef and lamb the melting point of lipid and the firmness/hardness of carcass fat is closely related to the concentration of stearic acid (18:0).

Introduction

There has been an increased interest in recent years in ways to manipulate the fatty acid composition of meat. This is because meat is seen to be a major source of fat in the diet and especially of saturated fatty acids, which have been implicated in diseases associated with modern life, especially in developed countries. These include various cancers and especially coronary heart disease. In the UK, the Department of Health (1994) recommended that fat intake be reduced to 30% of total energy intake (from about 40%) with a figure of 10% of energy intake for saturated fatty acids (from 15%). At the same time, the recommended ratio of polyunsaturated fatty acids (PUFA) to saturated fatty acids (P:S) should be increased to above 0.4. Since some meats naturally have a P:S ratio of around 0.1, meat has been implicated in causing the imbalanced fatty acid intake of today's consumers. For this reason, ways to improve the P:S ratio during meat production are required. More recently, nutritionists have focussed on the type of PUFA and the balance in the diet between n-3 PUFA formed from α-linolenic acid (18:3) and n-6 PUFA formed from linoleic acid (18:2) (Williams, 2000). The ratio of n-6:n-3 PUFA is also a risk factor in cancers and coronary heart disease, especially the formation of blood clots leading to a heart attack (Enser, 2001). The recommendation is for a ratio of less than 4 and again some meats are higher than this. As with the P:S ratio, meats can be manipulated towards a more favourable n-6:n-3 ratio.

The increasing awareness of the need for diets to contain higher levels of n-3 PUFA has focused on the importance of meat as a natural supplier of these to the diet. The ratio of n-6:n-3 PUFA is particularly beneficial (low) in ruminant meats, especially from animals that have consumed grass which contains high levels of 18:3. Ruminants also naturally produce conjugated linoleic acids (CLAs) which may have a range of nutritional benefits in the diet (Enser, 2001).

Fatty acids are involved in various “technological” aspects of meat quality. Because they have very different melting points, variation in fatty acid composition has an important effect on firmness or softness of the fat in meat, especially the subcutaneous and intermuscular (carcass fats) but also the intramuscular (marbling) fat. Groups of fat cells containing solidified fat with a high melting point appear whiter than when liquid fat with a lower melting point is present, so fat colour is another aspect of quality affected by fatty acids. The ability of unsaturated fatty acids, especially those with more than two double bonds, to rapidly oxidise, is important in regulating the shelf life of meat (rancidity and colour deterioration). However, this propensity to oxidise is important in flavour development during cooking.

The aim of this article is to summarise the main effects of fatty acid composition on meat quality and to review recent work showing the effects on meat quality of changes in fatty acid composition achieved during production.

Section snippets

Fatty acid composition of meat

A survey conducted by Enser, Hallett, Hewett, Fursey, and Wood (1996) illustrated the differences in fatty acid composition and content between beef, lamb and pork. Fifty loin steaks or chops from each species were purchased from four supermarkets to represent the meat on sale to the public (Table 1). The total fat content of the steaks (obtained by dissection) was highest in lamb, probably because of a lower level of fat trimming during butchery. The total fatty acid composition of the

Components of meat quality

The components of technological meat quality influenced by fatty acids are fat tissue firmness (hardness), shelf life (lipid and pigment oxidation) and flavour. Although there have been suggestions that dietary fatty acids influence tenderness and juiciness, these are more likely to be affected by the total amount of fatty acids rather than individual ones. The effect of fatty acids on firmness is due to the different melting points of the fatty acids in meat. In the 18C fatty acid series,

Acknowledgements

We are grateful to our collaborators in providing many of the results presented here, including Institute of Grassland and Environmental Research, Harper Adams University College and University of Reading. Funding was provided by Department for Environment, Food and Rural Affairs (DEFRA), Meat and Livestock Commission, ABN Ltd, JSR Farms Ltd, Tesco Stores Ltd, Roche Products Ltd, International Fishmeal and Oil Manufacturers Association and Southern Counties Fresh Foods Ltd. We gratefully

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