The objective was to determine the effect of electromagnetic field (EM) assisted freezing on thawing yield, shelf-life, and tenderness of beef striploins. Both striploins were collected from 12 USDA Choice carcasses, halved (N=48), weighed, and probed. Striploin halves were randomly assigned to 0, 2, 4, or 8kV EM and frozen under designated treatments in a walk-in freezer (-20°C) for 24h. Following freezing, frozen cores were taken for ice crystal size analysis, and halves were thawed, weighed, fabricated into steaks, and subjected to 10-day display. Swabs and purge were collected for aerobic plate count. Representative steaks were analyzed for instrumental and descriptive color measurements, muscle fiber spacing, Warner-Bratzler Shear Force (WBSF), purge and cooking loss, proximate analysis, lipid oxidation, antioxidant capacity, proteolysis, pH, and free calcium concentration. The 4 and 8kV samples took longer to reach the targeted temperature than those from lower voltage and control (P<0.05), but only 8kV samples had lower purge loss (P<0.01). The 4kV samples showed the least discoloration and highest a*, b*, and hydrophilic antioxidant capacity (P<0.01). Proteolysis was lower in higher voltage treatments, and EM-treated samples showed higher free calcium concentration compared to control (P<0.01). No differences were observed in other measurements mentioned above (P>0.05). Although the improvements in reducing post-thaw purge loss at 8kV and enhancing color stability at 4kV are statistically significant but numerically small, the overall potential impact may be substantial when considered for commercial applications.

Eighty-one young Swiss cross-bred bulls, half of which were disbudded at 7weeks of age, were reared in 6 rearing groups. Using a balanced design, these groups contained only horned, or only disbudded bulls (unmixed groups), or both (mixed groups), with only half of the bulls disbudded. They were slaughtered using two protocols, one with limited, the other with supplementary stress. Longissimus thoracis (LT) muscle samples were collected 48h after slaughter and subjected to individual shotgun proteomic analysis. Results show that horn status and slaughter conditions influenced only 16 (6.2%) and 8 (3.1%) proteins, respectively, which is not more than expected by random error. By contrast, rearing conditions influenced 40 (15.5%) of the identified proteins, which is significantly more than expected by random error. Eighteen of these differentially abundant proteins were involved in energy metabolism, and 9 in muscle structure and contraction. Overall, these proteins indicated greater glycolytic capacity and greater proportions of fast twitch fibres in the LT of bulls in mixed groups. These results are coherent with the lower physical activity and different physiological stress reactivity of these same mixed groups of bulls as reported in previous companion studies.