Effect of Diet and Essential Oils on the Fatty Acid Composition, Oxidative Stability and Microbiological Profile of Marchigiana Burgers

The objective of this study is to evaluate the effects of including linseed (L) or linseed plus vitamin E (LE) in the diet of Marchigiana young bulls on the oxidative stability, color measurements, microbiological profile and fatty acid composition (FA) of burgers treated with and without a blend of essential oils (Rosmarinus officinalis and Origanum vulgare var. hirtum) (EOs). For this aim, the burgers were analysed for pH, thiobarbituric-acid-reactive substance (TBARS) content, Ferric Reducing/Antioxidant Power Assay (FRAP), vitamin E and colour measurements (L, a*, b) at 3, 6, 9, 12 days of storage: the TBARs were the highest in group L compared to C and LE after 12 days of storage (0.98, 0.73, and 0.63 mg MDA/kg, respectively). The TBARS content was also influenced by the use of EO compared to burgers not treated with EO (p < 0.05). The vitamin E content was influenced by the diet (p < 0.01), but not by the EO. The meat of the L group showed the lowest value of redness (a*) compared to C and LE (p < 0.01), while the use of EO did not affect colour parameters. The microbiological profile of the burgers showed a lower Pseudomonas count for L and LE at T0 (2.82 ± 0.30 and 2.30 ± 0.52 Log CFU/g, respectively) compared to C (3.90 ± 0.38 Log CFU/g), while the EO did not influence the microbiological profile. The FA composition was analysed at 0 and 12 days. The burgers from the LE group showed the highest value of polyunsaturated FA compared to the L and C groups (p < 0.05). Our findings suggest that the inclusion of vitamin E in a concentrate rich in polyunsaturated fatty acids is useful to limit intramuscular fat oxidation and to preserve the colour stability of burgers from young Marchigiana bulls enriched with healthy fatty acids. Moreover, linseed and vitamin E had a positive effect on microbial loads and growth dynamics, containing microbial development through time.