Antioxidant status, colour stability and myoglobin resistance to oxidation of longissimus dorsi muscle from lambs fed a tannin-containing diet

Fourteen lambs were individually penned for 60 days. Seven lambs (C) were fed a barley-based concentrate, while 7 animals (T) received the same concentrate supplemented with 8.96% (dry matter basis) quebracho (Schinopsis lorentzii) extract. Tannin supplementation extended colour stability of fresh longissimus dorsi muscle (LM) over 7 days of aerobic storage with lower changes in hue angle over time in LM from T-fed animals compared to C-fed lambs (P = 0.032). Muscle from T-fed lambs had lower metmyoglobin percentages (MMb%) than that from C-fed animals after 3 days of storage (P = 0.05) and tended to have slower rates of change in (K/S)572 ÷ (K/S)525 values (P = 0.07). Compared to the C diet, tannin supplementation increased the concentration of total phenols in muscle (+31.29%, P = 0.001) and resulted in a higher muscle antioxidant capacity measured by FRAP (+16.81%, P = 0.026) and TEAC (+24.81%, P = 0.001) tests. Furthermore, feeding tannins resulted in lower MMb% after nitrite-induced oxidation measured both at the meat surface (−10%, P = 0.012) and in a meat extract (−8.22%, P = 0.004).