Beef contains an array of conjugated linoleic acid (CLA) isomers for which positive effects have been reported in animal models of human disease. The objectives were to develop a CLA-enriched beef production system and to assess its quality. Sixty Spring-born heifers were housed in Autumn and offered unwilted grass silage and a barley/soyabean concentrate or wilted grass silage and a concentrate containing sunflower oil and fish oil. In May, both groups were offered either pasture for 22 weeks, restricted pasture and sunflower oil and fish oil for 22 weeks, or pasture for 11 weeks and restricted pasture and sunflower oil and fish oil for the final 11 weeks. The predominant CLA isomer in beef was cis9, trans11 representing on average, 80% total CLA. The modified winter diet followed by supplementation for 22 weeks resulted in beef that had a CLA concentration that was higher, at a comparable intramuscular fatty acid concentration, than previously reported. The lipid and colour stability (over 10 days in modified atmosphere packaging) and sensory characteristics were generally not negatively affected. There were minor effects on the expression of candidate genes involved in lipid metabolism. Consumption of this beef would make a substantial contribution to the quantity of CLA suggested to have a positive effect on consumer health.

The volatile profiles of beef steaks (Longissimus lumborum) were analysed both raw and grilled to five different internal temperatures, 55 °C, 60 °C, 71 °C, 77 °C, and 85 °C, representing very-rare, rare, medium rare, well-done, and very well-done, respectively. Volatile organic compounds (VOCs) were extracted using direct immersion high-capacity sorptive extraction (DI-HiSorb) and analysed by gas chromatography–mass spectrometry (GC–MS). A total of ninety-one VOCs were detected with forty-two significantly impacted by the degree of doneness, thirty of which had Variable in Projection score > 1. Principal Component Analysis produced three distinct clusters, (i) raw, (ii) very-rare, rare, and medium-rare, (iii) and well-done and very well-done. Direct immersion high-capacity sorptive extraction (DI-HiSorb) provided a comprehensive volatile profile of grilled beef steak across different degrees of doneness and revealed that the abundance of methyl esters. The main findings were that in relation to the degree of doneness methyl esters were significantly reduced, with both aldehydes and pyrazines increasing due to thermal lipid oxidation, Strecker degradation, and Maillard reaction, highlighting the significance of internal temperature on the volatile profile of steak during grilling.