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Aging Big Game
Ray A. Field, and C. Colin Kaltenback
Hunters seldom agree as to the length of time a big game carcass should
be aged.
What is involved in the aging process? When is it beneficial to age game
meat? Under what conditions is it inadvisable to age game? This pamphlet
is concerned with answers to these questions.
Let's assume that the hunter has made his kill and properly dressed the
carcass. Now we want to know what he should do from the time the carcass
is eviscerated until it is ready to be cut into steaks and roasts.
What is Aging?
Aging of meat--also called seasoning, ripening or conditioning--is
defined as the practice of holding carcasses or cuts at temperatures of
from 34º to 37ºF. Thus enzymes (cateptic or proteolytic) function to
break down some of the complex proteins contained in the muscle.
Quick aging of beef is brought about commercially by holding beef at
temperatures of 62ºF to 65ºF for 2 or 3 days. High relative humidity is
maintained to prevent dehydration; ultraviolet lamps are used to prevent
microbial growth.
Some Meat Should not be Aged
Aging usually results in improvement of tenderness and flavor. However,
not all meat should be aged. Aging carcasses with little or no fat cover
is not recommended by meat specialists. These carcasses lose moisture
rapidly; excessive weight loss and surface discoloration of lean meat
result. In addition, lean meat is exposed and is susceptible to
deterioration through microbial growth. Slime formed by bacteria and mold
growth then must be trimmed.
Because grinding or chopping tenderizes meat, aging is not justified for
carcasses that are to be ground, or made into, bologna, frankfurters or
other sausages.
Pork never is aged because the animals are young when slaughtered and the
meat is naturally tender. Additionally, the unsaturated fats found in
pork fat oxidize during aging causing rancidity and off flavor.
Veal has very little protective fat covering and is high in moisture;
thus it does not lend itself to aging. Most markets require the "hog
style" veal carcass (skin on) because it prevents the outer surface of
the carcass from becoming dark and dry.
The above examples show that not all meat benefits from aging. Whether or
not game carcasses should be aged can be determined by first
understanding the changes which occur during aging.
Changes in Tenderness
Immediately after the animal's death all meat decreases in tenderness (
Figure 1). This is because muscle fibers shorten and harden as a result
of rigor mortis. The changes are similar to those which occur during
muscle contraction. The third day after slaughter, meat which has been
cooled at 34ºF has returned to its original tenderness level.
For example in Figure 1 : Immediately after death all meat decreases in
tenderness. From one to approximately 14 days, tenderness increases at a
constant rate. After 14 days aging, tenderness continues to increase,but
at a much slower rate.
If the carcass is to be made into chops, steaks and roasts, additional
aging at 34ºF is often recommended. At 34ºF and high relative humidity,
it usually takes 10 to 14 days for bacterial slime to develop on meat.
This, along with the fact that tenderization proceeds more slowly after
14 days aging than it does from 3 to 14 days, is the reason aging should
be limited to a maximum of 2 weeks.
Aging game that has been skinned often results in drying and high weight
loss. For this reason properly chilled game should be aged with the hide
on unless it is to be stored in a cooler where the humidity is high. Some
people think that leaving the hide on causes off flavor, especially in
antelope. However, research on factors affecting flavor of game has
failed to substantiate this claim.
Many meat processors do not recommend aging game. One reason for this is
that much of the game delivered to a meat processor has already been aged
long enough. Quick aging of the meat often occurs because the game
carcass could not be chilled at 34ºF after the kill.
Aging Game Shot in Warm Weather
A 65ºF temperature at the time of the kill will result in less toughening
and hardening of the muscles due to rigor mortis than will a temperature
of 34ºF. In addition, the action of natural enzymes which are responsible
for tenderness increases is much faster at 65ºF. Thus, aging at 65ºF for
3 days gives the same amount of tenderization as the more conventional
aging temperature of 34ºF for 2 weeks. Therefore, game which is killed
when the temperature is near 65ºF and held at this temperature should not
be aged.
Game slaughtered in the cold months of November and December should be
aged longer than game slaughtered in the warm months of September and
October. Alternating temperatures, such 65ºF days and 30 degree F nights
speeds up the aging process. Under these conditions aging game 1 week or
less is recommended.
During warm hunting seasons, special care should be taken to keep the
carcass cool. It should be kept in the shade and allowed as much air
circulation as possible. Transport the carcass to camp and skin it if the
temperature is expected to be above freezing the first night after the
kill. Cheese cloth or light cotton bags should be used to protect the
meat from insects and dirt. Because they hold in heat and cause meat to
spoil rapidly, airtight game bags or tarps should not be used.
Aging Game Shot in Cold Weather
Game carcasses under 100 pounds often chill rapidly if the temperature is
below freezing at the time of slaughter.
Muscle contraction or rigor mortis hardens the muscle to a greater extent
than if the temperature is above freezing. Very rapid chilling and
hardening causes meat to be tough. This condition is known as cold
shortening; it will occur if the internal muscle temperature drops to
32ºF within 12 hours after the kill. Leaving the hide on will help
prevent cold shortening and also help to keep the carcass from freezing.
Carcasses which undergo cold shortening should be aged at 34ºF. If the
carcass is frozen while hanging, little additional tenderization will
occur because enzyme action is very slow at freezing temperatures. Frozen
carcasses should be thawed and maintained at 34ºF. Alternate periods of
freezing and thawing should be avoided because these temperature
variations lower meat quality.
Recommended Aging Times
Antelope carcasses shold be cut and wrapped for the freezer within 3 days
after the kill. This short aging period helps prevent the "liver-like" or
"mushy" texture often found in antelope meat.
Deer, sheep, goat, cow elk and cow moose carcasses should be cut
approximately 7 days after the kill. If they have been held at higher
temperatures (above 40ºF) the meat should be cut before 7 days of aging
are completed.
Under ideal conditions bull elk and moose carcasses should be cut after a
14-day aging period at 34º to 37ºF. However, these carcasses are seldom
handled under ideal conditions. Slow chilled carcasses and carcasses that
have been in camp for a few days require less aging.
The preceeding recommended aging periods are sufficient for tenderness
and flavor development in most game carcasses. These aging periods are
not needed if game carcasses are to be ground, cured or made into
sausage. In addition, most meat recipes utilize moist heat cooking
methods which tenderize the meat and shorten the needed aging period.
Do not age any game carcass if it was shot during warm weather and not
chilled rapidly, if the animal was severly stressed prior to the kill, if
gunshot areas are extensive, or if the animal was under 1-year of age.
Aging has already occurred if the carcass has been in camp for 1-week in
relatively warm weather. No further aging is recommended.
Aging periods longer than those recommended are often accompanied by
extensive bacaterial growth on the game carcasses and by drying and
discoloration of the meat. Reducing the aging period reduces bacterial
growth on the carcass. At present there does not appear to be any
evidence that there is a helath risk in eating properly cooked game meat.
Nevertheless, adequate precautions with regard to aging time and aging
temperature should be followed.
Aging Carcass Parts
Individuals who cut and wrap their own game may want to process the
entire carcass--except the loin and rib cuts--three days after the kill.
This practice eliminates drying and spoilage on carcass parts other than
the loin and rib that are often ground or moist- heat cooked.
The loin and rib cuts, which usually have some fat cover to protect
against drying and are dry-heat cooked, could then be aged in a cool,
clean place up to 2 weeks or until deterioration due to drying or
microbial growth, indicated that aging should be discontinued. No
justification exists for the idea that fat should be trimmed from game
before meat is aged. The fat protects the meat during aging. However,
trimming fat after aging is recommended to avoid undersirable flavors
which are often associated with the fat.
Consideration for the Processor
Cooler space is a factor which often limits aging of meat in commercial
operations. Proper aging of meat and proper meat handling in general
could be facilitated for commercial processors if the game kill were
distributed over a wide period by staggering the opening dates of the
hunting season more than they are staggered at the present time.
Summary
Many practical considerations must ultimately determine whether to age or
not to age game meat. Among these are the temperature at the time of
kill, the chilling rate, the internal temperature of the muscle after
chilling, the youthfulness of the animal, the relative humidity, the
amount of weight loss the hunter is willing to sacrifice, the processing
procedure and the cooler space and labor available if the game is to be
processed commercially. Under ideal conditions, age antelope 3 days,
deer, sheep, goat, cow elk and cow moose 7 days and bull elk and bull
moose 14 days after the kill at 34ºF. If the temperature is higher, the
aging period should be shorter. Game which is killed when the temperature
is 65ºF or above and held at this temperature over 1 day should be cut
immediately. Game that is to be ground or chopped does not need to be
aged.
1.This document is Bulletin 513R, Agricultural Experiment Station,
University of Wyoming, Laramie, WY 82071. Publication date: October 1987.
2.Ray A. Field, Professor of Meat Science, Department of Animal
Science, and C. Colin Kaltenback, Director, Agricultural Experiment
Station, University of Wyoming, Laramie, WY 82071.
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