Enhancing the content of beneficial fatty acids in beef and consequences for meat quality

Abstract

There is a demand for food which offers human nutritional benefits. This has increased interest in producing healthier beef characterised by a (1) higher ratio of polyunsaturated (PUFA) to saturated fatty acids (P:S ratio), (2) more favourable balance between n-6 and n-3 PUFA (lower n-6:n-3 ratio) and (3) higher content of conjugated linoleic acid (CLA). Beef can have a low intramuscular fat content ranging between 0.6 - 5%. Incorporating linseed (rich in -linolenic acid, 18:3n-3) in the diet increases the content of 18:3n-3 and eicosapentaenoic acid (EPA, 20:5n-3) but not docosahexaenoic acid (DHA, 22:6n-3) in beef muscle and adipose tissue, resulting in a lower n- 6:n-3 ratio. Protecting PUFA from ruminal biohydrogenation results in further enhancement of PUFA in the meat resulting in higher P:S ratios and lower n-6:n-3 ratios. Grass in comparison to concentrate-fed beef has naturally high levels of 18:3n-3 and its longer chain (C20-C22) derivatives contributing towards higher P:S ratios and lower n-6:n-3 ratios. The main CLA isomer in beef is CLA cis-9, trans-11 and it is mainly associated with the neutral lipid fraction and hence is positively correlated with degree of fatness. The majority of CLA cis-9, trans-11 in beef is synthesised in the tissue by delta-9 desaturase from ruminally produced trans-vaccenic acid. Feeding PUFA-rich diets increases the content of CLA cis-9, trans-11 in beef. Increasing the content of n-3 PUFA can influence colour shelf life and sensory attributes of the meat. As the content of n-3 PUFA increases then sensory attributes such as “greasy” and “fishy” score higher and colour shelf life may be reduced. Under these situations, high levels of dietary antioxidant are necessary to help stabilise the effects of incorporating high levels of long chain PUFA into meat. Grass provides natural antioxidants (vitamin E) which help to maintain high n-3 PUFA levels in the meat while decreasing deterioration in quality during processing and retail display.