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The cutting and packaging of beef at retail has undergone many changes, from whole carcasses fabricated in retail backrooms, to tray-ready and now to case-ready beef. Currently, the majority of beef sold at retail is centrally packaged into primal and subprimal cuts, vacuum packaged and shipped as “boxed beef.” Retailers can purchase beef based on local preferences and buy a mix of cuts that fit specific consumer buying habits by store. Case-ready beef takes this one step further by packaging specific grinds of hamburger, steak and roast cuts at a central location ready for sale at the retail level. There are many options available for case-ready packaging systems; from over-wrapped trays that mimic in-store packaging to modified atmosphere sealed trays that contain differing levels of oxygen and/or nitrogen.
Modified atmosphere packaging (MAP) has been around for a long time. Recent innovations in packaging films and equipment technology have expanded packaging options for whole muscles. Each system has its own advantages and disadvantages which necessitates careful consideration of all features when a packaging option is selected for a given beef product.
Recently, there has been a strong interest in the marketplace for enhanced beef products. In most cases, beef is pumped with a variety of compounds designed to enhance shelf life, texture, flavor, and consistency. The ingredients typically include salt, phosphate, sodium lactate, antioxidants/seasonings that protect both color and flavor stability. In turn, performance of enhanced products in modified atmosphere packages should be evaluated.
The objectives of this study were to: (1) Accelerate the postmortem chill rate of beef round muscles by hot boning the knuckle (quadriceps) early postmortem; (2) evaluate the effects of hot boning the knuckle on color, color stability, color uniformity, and other chemical, physical, and sensory attributes of enhanced steaks from the round; (3) determine the effects of high- and ultra-low oxygen modified atmosphere packaging on chemical, physical, and sensory properties of enhanced steaks from the beef round; (4) make directional comparisons between 6 and 10% enhancement levels; and (5) determine the effects of MAP on premature browning in enhanced beef round steaks when cooked to a medium degree of doneness.
Fourteen beef carcasses (steers; A-maturity; quality grades Select to Choice; yield grades 2 and 3; weighing 750 to 850 pounds) were selected randomly from a commercial slaughter plant. Carcass sides were electrically stimulated and one side from each carcass was assigned randomly to a hot boning technique performed 60 to 90 min after stunning, and the other side remained intact until 48 hours postmortem. Postmortem temperature decline was monitored for 24 hours at various locations in each carcass.
Fabrication and Processing
At 48-h postmortem, the semimembranosus (SM), biceps femoris (BF), and the whole knuckle were removed from both intact and hot-boned (HB) sides, trimmed to 0.1 inch of fat, weighed, and vacuum packaged. Muscles were injected (approximately 5 days postmortem) using a multi-needle injector with a solution containing water, salt, phosphate, and natural flavorings containing rosemary. Sets of muscles (SM, BF, and knuckles) representing paired carcass sides (HB and chilled intact) were injected at 6% (n=7) in experiment 1 or 10% (n=7) of injected weight in experiment 2. Enhanced muscles were sliced into 1-inch thick steaks. Six knuckle steaks, consisting of both the vastus lateralis (VL) and RF muscles, were collected for packaging. Five steaks from sliced BF and SM were collected for packaging. Steaks from each muscle were assigned randomly for packaging in either high-oxygen modified atmosphere packaging (HiOx MAP, 80% O2 / 20% CO2), ultra-low oxygen modified atmosphere packaging (LoOx MAP, 80% N2 / 20% CO2), or vacuum packaging.
Steaks were packaged for use as follows: (1) Vacuum packaged and aged for 14 days and used for shear force testing; (2) vacuum packaged and stored for 1 day and used for chemical analysis; (3) packaged in HiOx MAP or LoOx MAP and used for chemical analysis, color analysis and odor analysis; and (4) packaged in HiOx MAP or LoOx MAP and used for trained sensory panel evaluation.
Steaks packaged in HiOx and LoOx MAP were displayed under simulated retail conditions. Steaks were evaluated for color at the beginning, middle and end of display and for odor at the end of display. Steaks packaged in HiOx MAP were displayed 5 days, and those used for sensory panel were displayed 2 days. Steaks packaged in LoOx MAP were displayed 3 d, and those used for sensory panel were displayed 1 day.
Sensory panel evaluations
After 2 days (HiOx MAP) or 1 day (LoOx MAP) of display, all steaks assigned for sensory panel evaluation were vacuum packaged, frozen, and stored at –4°F until evaluated. Steaks were thawed and cooked to an internal temperature of 160°F. A trained sensory panel (n=7) evaluated steaks on an 8-pont scale for tenderness, juiciness, beef flavor intensity, connective tissue amount, overall tenderness, and off-flavor. Panelists described off-flavors, if present, using either a provided list of potential descriptors or their own descriptors.