The effects of diet and aging of Australian longissimus lumborum on beef flavor



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Descriptive sensory attributes, pH, color, proximate and volatile flavor compound data were collected to investigate the effects of diet and extended postmortem wet-aging time on Australian beef flavor. Beef strip loins were collected from grass- and grain-fed cattle (n = 50 total) at a commercial abattoir near Brisbane, Australia. Beef longissimus lumborum were portioned into sections and assigned randomly to 1 of 3 postmortem aging periods (45, 70 or 135 d). As the section reached its respective postmortem aging designation, each section was fabricated into 2.54-cm steaks, packaged individually under vacuum and frozen (-21°C) on their respective aging day. Prior to steak fabrication, pH was obtained in triplicate and averaged for analysis. Twenty minutes after fabrication, instrumental color was measures on the second steak. Electric clamshell grills were used to cook thawed steaks to a medium degree of doneness (71°C) for sensory and volatile flavor compound analyses. Diet and aging impacted (P < 0.05) color while only aging impacted pH (P < 0.05). Grain-fed samples (P < 0.05) possessed a greater L* and Hue value than grass-fed samples. Samples aged 70 d had a greater (P < 0.05) a* value than 45 d and 135 d, but a lower (P < 0.05) L* value than other aging treatments. Samples at 135 d had a lower (P < 0.05) pH than 45 d and 70 d, which did not differ from each other (P > 0.05). Diet and aging impacted (P < 0.05) several descriptive sensory attributes. Diet specifically impacted (P < 0.05) beef flavor id, fat-like, liver-like, green-hay, bitter, and sweet attributes. Grain-fed samples were rated more intense (P < 0.05) for beef flavor id, fat-like, liver-like, and sweet; while grass-fed samples were more intense (P < 0.05) for green-hay and bitter attributes. Aging also impacted (P < 0.05) several attributes: beef flavor id, liver-like, metallic, rancid, green-hay, umami, bitter, overall tenderness and overall juiciness. Beef flavor id was more intense (P < 0.05) in 45 d samples than 70 d and 135 d and umami was more intense (P < 0.05) in 45 d and 70 d than 135 d but 45 and 70 d did not differ (P > 0.05) from each other. For liver-like, metallic, green-hay and bitter 135 d samples were most intense (P < 0.05), 70 d samples were intermediate, and 45 d samples were least intense. Overall tenderness and rancid were greater (P < 0.05) in 135 d than 45 d and 70 d, which were similar (P > 0.05). Finally, overall juiciness was similar (P > 0.05) and greater (P < 0.05) in 135 d and 70 d samples than 45 d samples. Diet influenced (P < 0.05) quantities of multiple volatile flavor compounds including: heptanal, alpha-pinene, p-Xylene, octane, acetaldehyde, methional, and carbon disulfide. Grass-fed samples were greater (P < 0.05) for all compounds except octane when grain-fed were greater (P < 0.05). Aging also influenced (P < 0.05) several volatile flavor compounds including: ethanol, 1-hexanol, 1-octen-3-ol, p-xylene, decane, 2-heptanone, 2-propanone, along with methional, phenylacetaldehyde, carbon disulfide and dimethyl sulfide. The majority of the lipid derived volatile compounds were greater (P < 0.05) for 135 d except for decane, which was greater (P < 0.05) for 135 d than 70 d, but 45 d did not differ (P > 0.05) from 70 d or 135 d. Phenylacetaldehyde and carbon disulfide were greater in concentration at 135 d (P < 0.05), while 45 d and 70 d did not differ (P > 0.05) from each other. Methional showed lower (P < 0.05) concentrations in 70 d samples while 45 d and 135 d were greater (P < 0.05) but did not differ from each other. Dimethyl sulfide was greater (P < 0.05) in concentrations at 135 d than 70 d; 45 d did not differ from either 70 d or 135 d (P > 0.05). These results indicate diet in combination with an extended wet-aging period accentuated negative descriptive sensory attributes while lessening palatability in beef from both diets. Also, extended postmortem aging and diet play a role in the development of volatile flavor compounds in cooked products that add to undesirable flavors.