26The aim of this study was to detect reactive oxygen species and evaluate the quality 27 of carcasses and beef meat from cold storage slaughterhouses located in the Federal District 28 and Surroundings. Information was obtained on the gender, breed and age of each animal, 29 as well as the distance travelled (km) and time (h) from the property to the cold storage 30 slaughterhouse. Data and samples were obtained from a total of 33 animals and their 31 respective carcasses. Fragments of the extensor carpi radialis muscle were extracted from all 32 the carcasses to analyze the presence of reactive oxygen species (ROS), and samples of the 33 Longissimus dorsi muscle to perform the 24h post-mortem pH, colorimetric test, cooking 34 loss and drip loss assessment and to measure the shear force. The presence of hematomas 35 was detected in 28 carcasses, where the tail and croup (17/33) and flank (17/33) regions were 36 the most affected. The electron paramagnetic resonance indicated an average of 52.59 ROS/g 37 in the analyzed pieces. The meat quality tests indicated averages of: 5.8 for the 24h post-38 mortem pH, L*29.34, a* 2.52 and b* 1.31 in calorimetry, 2.30 kg/f for the shearing force, 39 11.75% of cooking losses and 1.88% of drip losses. The statistical analyses demonstrated a 40 tendency to positive correlation between the presence of hematomas with and the amount 41 of ROS, and between the presence of hematomas and pH value. Furthermore, statistically, 42 female gender was one of the influential factors on the tenderness value. According to the 43 results, it was concluded that the meat evaluated in this study meets the desirable quality 44 parameters and it was possible to detect reactive oxygen species in the samples of muscle 45 tissue. 3 46 Introduction 47 Brazil's livestock farming stands out as an important sector of the national economy 48 and in the year 2016 it represented approximately 24% of the Gross Domestic Product [1]. 49 In 2017 Brazil kept its spotlight in the international market as the world's greatest beef meat 50 exporter [1]. 51 To maintain its market competitiveness, the country has invested in the productivity 52 and quality of the final product offered to the consumer [2]. In beef , tenderness, flavor, 53 juiciness and color are desired as determining characteristics for the purchase decision, 54 which are susceptible to changes due to intrinsic factors such as the gender, age and breed, 55 and extrinsic factors such as nutrition and stress during handling [3]. 56 Studies on meat quality often correlate these parameters when evaluating the 57 characteristics of the meat produced by crossbreeding and the comparison of age and diet 58 types [4,5,6,7], where the main analyzed characteristics are the pH, colorimetry and shearing 59 force [8,9,10] as well as water retention capacity when measured by evaluating cooking and 60 drip losses [4]. 61 Still related to the meat quality is the pre-slaughter handling performed by the farms 62 and industries of meat, which can generate stress, contusio...