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Facts: Meat Science Aging of Beef
By F.C.Parrish, Jr., Ph.D.
Department of Animal Science
Iowa State University
, sometimes called
"conditioning" or "ripening," is a natural process which
improves the palatability attributes of meat, especially cuts from the rib and
loin. Commercially, postmortem aging is accomplished by subjecting carcasses,
primal or subprimal cuts to controlled, refrigerated (above freezing) storage
conditions. Of the palatability attributes of beef steaks, tenderness is the
attribute most demanded by consumers, and the improvement in tenderness is the
primary reason for postmortem aging. Postmortem aging, however, also improves
the palatability attribute of favor.
Primal or subprimal beef cuts from the loin and rib (middle
meats) are specifically aged post-mortem, since these serve as the source
desirable steaks (rib, T-bone, Porterhouse, top loin, sirloin and filet mignon
(While carcasses or cuts from any species could be aged,
postmortem aging is generally limited to beef, due to the relative youth of
pork, lamb and veal. Consequently, this discussion concentrates on the
postmortem aging of beef.)
Postmortem aging is a process that occurs naturally in all
muscle tissues, whether vacuum packaged or in the form of carcasses or wholesale
cuts. In the conversion of muscle to meat, natural enzymes (proteases) found in
muscles, breaks down specific proteins in muscle fibers (a process called
proteolysis). This breaking (or fragmentation) of these protein strands, called
myofibrils, by natural enzymes results in improved tenderness of the rib
Tenderization occurs o1 a relatively rapid rate until 3 to 7 days postmortem,
and then the rate of increased tenderness diminishes with time. Practically
speaking, the increase in tenderness of rib and loin muscles during postmortem
aging. Tenderization occurs at a relatively rapid rate until 3 to 7 days
postmortem, and then the rate of increased tenderness diminishes with time.
Practically speaking, the increase in tenderness of rib and loin cuts after 7 to
10 days is relatively small, compared with the increase during the first 7 to 10
Types of Aging
Two types of postmortem aging processes are practiced
commercially: "dry" and 'wet' aging.*
is the traditional process of placing an
entire carcass or wholesale cut (without covering or packaging) in a
refrigerated room for 21 to 28 days at 32-34 degrees F. and 100-85% relative
humidity, with an air velocity of 0.5 to 2.5 m/sec. All three conditions,
although varying widely in commercial practice, are extremely important in the
proper postmortem aging of carcasses, as well as beef ribs and loins.
A third method, accelerated aging uses a higher holding
temperature with ultraviolet light used to retard microbial grown which would
normally occur at higher temperatures. This method, however, has not been used
commercially to a significant degree in recent years, due to the extent that
vacuum packaged products are subjected to wet aging.
Too much humidity will allow excessive microbial growth,
whereas too little will cause excessive shrinkage. Eighty-five percent relative
humidity is a happy medium in slowing microbial growth and moisture loss.
Tenderness development can be accelerated by aging at a
higher temperature; however, increased microbial growth becomes a serious
problem at higher temperatures.
Air velocity is essential because it acts as a medium for
moisture removal from the refrigerated area. Insufficient air velocity will
allow excessive moisture to condense on the product, and as a result,
off-flavors and aromas, as well as spoilage, will occur. Too high an air
velocity, on the other hand, will result in excessive surface drying, with
resulting weight and trim losses. The main disadvantage of dry aging is the cost
associated with these weight and trim losses.
is the aging of meat in vacuum bags
(usually the middle meats) under refrigerated conditions of 32-34 F.
Obviously, humidity and air velocity are not necessary requirements for proper
wet aging. Because most beef is vacuum packaged at the site of carcass
fabrication (cutting), wet aging is the predominant method of postmortem aging
The aging process continues when a primal or subprimal cut
has been placed in a vacuum package. By the We the cut reaches the retail store,
at least 7-10 days have normally elapsed the following slaughter, due to holding
at packing plant for carcass chilling and fabrication, inventory storage,
shipping to the retail warehouse, and subsequent shipping to the retail store
level. Therefore, the time associated with the rapid tenderization (7-10 days)
and that associated with product movement to the retail store are similar.
However, additional aging time is generally beneficial.
Dry and wet aging both result in a similar degree of
palatability of rib and loin steaks; however, there can be distinct flavor
differences. meat from vacuum-aged cuts has a more bloody/serumy and metallic
flavor, whereas, meat from dry-aging has a more brown-roasted beefy flavor What
Factors Affect Aging?
Aging rate and time are postmortem variables affecting
tenderness. Different rates of aging means some carcasses and/or cuts tenderize
very early, while others tenderize gradually. In fact, some beef does not
tenderize appreciably, regardless of the aging time. Muscles that are moderately
high to high in connective tissue (e.g., muscles located in the round) generally
are not very tender after adequate aging because the connective tissue is not
fragmented sufficiently during aging.
Widely differing amounts of time for post-mortem aging
occur in commercial practice, due primarily to the time that vacuum packaged
cuts are held in inventory prior to being processed into retail cuts for sale.
The National Beef Tenderness Survey, conducted in 1991, indicated that beef was
held (and, in effect, aged) from 3 to 90 days (with an average of 17 days)
before retail sale. Aging beyond 28 days results in little benefit to enhanced
palatability, and may even be detrimental in terms of increased and unwanted
microbial growth and flavor changes.
Fortunately, most beef reaches some level of acceptable
tenderness during postmortem aging; even so, the National Beef Tenderness Survey
indicated that 15-20% of beef was undesirable in tenderness. Postmortem aging
optimizes tenderness, but does not insure totally and uniformly tender beef
Specific muscles and quality grades are also considered
important variables in postmortem aging. The tenderloin is the most tender
muscle in the beef carcass, and interestingly requires little postmortem aging.
The loin muscle, a relatively tender muscle, because of high fragmentation and
small quantities of connective tissue (Collagen), has a similar pattern of
postmortem aging as the eye of the round, a less tender muscle of low
fragmentation and more quantities of connective tissue (collagen). Steaks from
different USDA quality grades, although differing in tenderness within and
between grades, have a similar pattern of aging. That is, beef cuts from USDA
Choice will age very similarly to beef cuts from USDA Select.
While postmortem aging can have a profound effect on
improving palatability (especially tenderness), breeding, feeding, processing
and preparation all play an important role in final consumer satisfaction.
Indeed, cooking (preparation) often can be the most profound factor in
determining beef steak tenderness. For example, beef loin steaks broiled to a
rare degree of doneness will be more tender than steaks cooked medium or well
Postmortem aging of beef carcasses and cuts is a natural
process that usually improves tenderness under refrigerated conditions. Natural
enzymes act to break specific muscle protein strands into smaller pieces to
result in improved beef steak tenderness of rib and loin cuts. Most
tenderization Occurs early in the postmortem aging process, and by 10 days
postmortem, most tenderization has occurred in rib and loin cuts.
Although postmortem aging has a profound optimizing effect
on tenderness, it does not insure total and uniformly tender beef steaks because
several other ante- and postmortem factors impact tenderness.
Huff, E.J. and F.C. Parrish Jr. 1993. Bovine longissimus
muscle tenderness as affected by postmortem aging time, animal age and sex. J.
Food Sci. 58:713-716.
Huff-Lonergan, E.J., T. Mitsuhashi, D.D. Beekman, F.C.
Parrish, Jr., D. C. Olson and R.M. Robson, 1996. Proteolysis of specific muscle
structural proteins by u- Calpain at low pH and temperature is similar to
degradation in postmortem bovine muscle. J. Anim. Sci. 74(5):993-1008.
Miller, M.F., G.W. Davis and C.B. Ramsey, 1985. Effect of
subprimal fabrication and packaging methods on palatability and retail caselife
of loin steaks from lean beef. J. Food Sci. 1544-1546
Parrish, F.C., Jr., R.B. Young, B.E. Miner and L.D.
Anderson. 1971 Effect of postmortem conditions on certain chemical,
morphological and organoleptic properties of bovine muscle. J. Food Sci.
Parrish, F.C., Jr., J.A. Boles, R.E. Rust and D.G. Olson.
1991. Dry and wet aging effects on palatability attributes of beef loin and rib
steaks from three quality grades. J. Food Sci. 56W -603.
Warren, K.E. and (CL. Kastner. 1992. A comparison of dry
aged and vacuum-aged beef strip loins. J. Muscle Foods, 3:151.
M.E. Dikeman, Kansas State University
R.J. Epley, University of Minnesota
G.C. Smith, Colorado State University
This fact sheet was authored and reviewed by members of the American Meat ScienceAssociation.
For more information, contact:
Center for Quality
National Cattlemen's Beef Association
444 North Michigan Avenue Chicago, Illinois 60611
This fact sheet was developed by the Center for Quality
of the National Cattlemen's Beef Association as part of a coordinated
effort with State Beef Councils and the beef Board.