Collagen, cooking losses and shear force of aged meat from Nellore steers fed protected or unprotected linseed oil

Abstract Text: This work assess the effects of aging times and the inclusion of protected or unprotected linseed oil of rumen degradation on the diet of 21 Nellore steers finished on feedlot on collagen (COL), cooking losses (CL) and shear farce (SF) of Longissimus muscle. At the beginning of the experiment, animals had 18 months of age and 397.74 ± 14.07 kg of BW, and they were kept in individual pens and adapted during 21 days. The diets were composed by 40% corn silage and with no oil addition (73% TDN and 2.9% EE), with in natura linseed oil or with protected linseed oil (76% TDN and 6.1% EE). After 105 days at feedlot, the animals were slaughtered with 522.72 ± 27.99 kg of BW and carcasses were chilled for 24 hours. After this period, a section of the Longissimus between 6^th and 13^th ribs was removed and separated in 2.54 cm steaks, which were individually vacuum packed and chilled to 2 °C for one, seven or 14 days. The amino acid hydroxyproline was quantified to measure the collagen content by spectrophotometer reading at 500 nm; for CL, the steaks were roasted in an electric woven up to 71 °C at its geometric center, and the weights before and after cooking were used for the calculation. After 24 hours of cooling, six cylinders of 1.27 cm diameter were removed from the steaks to determine the force required to cut across each cylinder using a texturometer, and the average were used to represent the SF. The results were submitted to analysis of variance using mixed models, considering a random block one, and a 3 x 3 factorial scheme. For COL (0.70 mg/100g muscle), no differences were found among treatments (P=0.5806), and for the aging times, a quadratic effect (P=0.0168) was observed. An interaction for CL was found (P=0.0433), and its evaluation showed a quadratic effect (P=0.0134) for unprotected linseed oil during aging periods, the remaining variables showed no differences (P>0.05). SF was not influenced by the treatments (P=0.2718) and aging times showed a quadratic effect (P<0.0001) (5.38; 3.35 and 3.34 kgf, for one, seven and 14 days, respectively). Meat tenderness is not affected by the addition of linseed oil on the bovine diet, but it is improved by aging up to 14 days. On the other hand, collagen content is increased by aging.

Keywords: Longissimus, tenderness, zebu