Characterizing Grass-Fed Ground Beef and Enhanced Steaks Using Modified Atmosphere Packaging

Abstract

Fall-born Angus x Continental crossbred steers (n = 18) were randomly assigned to six 1.4 ha paddocks with 3 head in each paddock. The paddocks had been randomly planted with Marshall Ryegrass (Lolium multiflorum L.), Wren’s Abruzzi Rye (Secale cereael L.) and Harrison Oats (Avena sativa L.). Boneless strip loins and ribeyes from the left side of the carcass were collected at 48 h postmortem, vacuumed-packaged and stored at 2°C until 14 d postmortem. On d 14 postmortem three 2.54-cm-thick steaks were cut from the anterior end of the left strip loin from all 18 carcasses. The strip loins and ribeyes were cut in half and the posterior and anterior ends were randomly assigned to an injection treatment resulting in 0.6% salt, 0.4% phosphate (BRIFISOL 85 Instant, BK Giulini Corporation, Simi Valley, CA), 2.5% potassium lactate (Ultra-Pure PL-85 (60%), Trumark Inc., Linden, NJ), and 0.055% beef stock (Proliant Meat Ingredients, Ankeny, IA). They were pumped to a 112% of their green weight and cut into four 2.54-cm-thick steaks. Packaging treatments used for this study were a high oxygen (HO; 80% O2/20% CO2), low oxygen (LO; 65% N2/35% CO2), carbon monoxide (CO; 65% N2/34.6% CO2/0.4% CO), and vacuum packaging (VAC). Results indicated that the pumped strip loin steaks showed higher sensory scores for initial and sustained juiciness, initial and sustained tenderness, flavor intensity, and off flavor (P < 0.05). The HO resulted with the lowest scores for the sensory characteristics (P < 0.05) except for initial juiciness. Retail visual and instrumental scores were the highest for the CO which produced and maintained a bright, cherry-red appearance (P < 0.05) for both the strip loins and ribeyes. TBARS was conducted only on the ribeye steaks which indicated that the pumped steaks resulted with the most oxidation and the LO had the least oxidation (P < 0.05).

Eighteen kilograms of grass-fed beef trim from fall-born Angus x Continental crossbred steers and eighteen kilograms of grain-fed beef trim were ground to achieve separate batches with approximately 20% fat. Six titrations were made from each of the ground trimmings containing: 0% grass/100% grain (0/100), 20% grass/80% grain (20/80), 40% grass/60% grain (40/60), 60% grass/40% grain (60/40), 80% grass/20% grain (80/20), and 100% grass/0% (100/0) grain. Each titration was packaged using a high oxygen (HO; 80% O2/20% CO2), low oxygen (LO; 65% N2/35% CO2), carbon monoxide (CO; 65% N2/34.6% CO2/0.4% CO) or OV (overwrap). Results showed that there was no difference in diet*modified atmosphere packaging (MAP; P > 0.05) for initial and sustained juiciness, cohesiveness, flavor intensity, off flavor, or cookloss. The 100/0 titration resulted in better (P < 0.05) instrumental (a*) and visual color scores. The CO package produced and maintained a bright, cherry-red color through out the retail display. TBARS values were the lowest for the titrations with the most grass percentage (P < 0.05).