The aim of this study was to evaluate aging effects on tenderness and Heat Shock Proteins activity of beef muscle.

Were evaluated 303 F1 immunocastrated steers cross cattle (Nellore × South African Simmental), aged 18.0 ± 2.0 mo and live weights at slaughter of 500 kg. After 24 h post mortem, two 2.5 cm steaks were collected at the 12th and 13th ribs of the Longissimus muscle. The steaks were individually identified, vaccum packaged and aged for 1 and 14 d. Also, in each aging time, 1 piece of meat was cut and immediately frozen in liquid nitrogen for further Heat Shock Protein (HSP) analysis. The meat samples were analyzed for Warner Bratzler Shear Force (WBSF) according American Meat Science Association (1995) and the HSP quantification were determined by Bovine HSP 27 and HSP 70 ELISA kits (Mybiosource). The total of protein content was calculated by Bradford method. Beef samples were classified into 2 groups according WBSF values at 14 aging days: Tender (< 4.0 kg) and Tough (> 5.2 kg) and after then, were selected 20 samples from each group for HSP quantifications. Data were analyzed using GLM procedures of SAS (SAS Inst. Inc., Cary, NC), LS MEANS statement and the TUKEY adjustment were used for mean separation with an ɑ level of 0.05 (Version 9.2, SAS Inst. Inc., Cary, N.C.).

As expected, WBSF values (n = 300) at 14 aging days from Tender group were smaller (4.2 kg) than Tough group (5.3 kg; P < 0.05). The HSP 27 values decreased from 1 to 14 aging days inside the Tender and Tough groups, but no differences were detected between groups at the same aging day. Witch respect of the HSP 70 values, were observed differences only inside the Tender group and instead of HSP 27, the values increased from 1 to 14 aging days (Table 1).

In conclusion, there are no evidence of relationship between HSP 27 activity and meat tenderness but with respect to HSP 70 activity, more studies should be conduce for elucidate this question.