Effect of aging and frozen storage on palatability and chemical characteristics of grass-fed beef

The effect of aging and frozen storage on chemical composition of uncooked grass-fed beef, palatability, cooking losses and Warner- Bratzler shear value of cooked product, effect of aging time on carcass surface microbial population, and cooler shrinkage were studied. Twenty-four left sides weighing 155 to 180 kg (175 to 200 lbs.) from grass-fed steer carcasses were aged either 0, k, 8, or 12 days. Longissimus muscle samples of each side were assigned to 0, 30, and 60- day frozen storage periods. Neither aging or frozen storage affected protein, water or fat percentages of uncooked muscle. Sixty days frozen storage increased drip loss (P<.001) and total cooking loss (P<.01), but aging had no effect. Sensory panel evaluation showed eight days aging improved flavor (P<.05), juiciness (P<.01), tenderness (P<.001), and overall acceptability (P<.001). Thirty days frozen storage decreased juiciness (P<.05), tenderness (P<.01) and overall acceptability (P<.01), and 60 days frozen storage caused less desirable flavor (P<.05). Warner-Bratzler shear values increased (P<.01) with 60 days frozen storage but decreased (P<.001) with 8 days aging. Cooler shrinkage increased (P<.01) steadily up to 2.7 percent for sides aged 12 days. Microbial counts increased steadily during aging and highest counts were found on the flank followed by the neck, brisket, and outside round.