Deer Industry News - Deer Industry New Zealand

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Learning how venison holds its water
We all know that when it comes to tenderness and mouth watering juiciness, venison stands head and shoulders above
other meats. One of the most passionate believers in the qualities of venison is a scientist who knows more than most
about what makes our champion protein tick.
AgResearch MIRINZ’s Dr Eva Wiklund is
undertaking two projects that will throw
more light on what happens to venison after
slaughter, and possible ways to get it to
market in optimum condition.
One problem, well known in the venison
processing industry, is drip loss in chilled
product – the tendency for venison to exude
liquid. As a regular attendee at the DeerQA
Venison Processors’ Technical Committee, Eva
hears first hand feedback from processors and
their customers about quality issues, and drip
loss has been identified as a high priority.
It’s a natural process linked to one of
venison’s greatest strengths – its tenderness.
Enzymes in the muscle cells – calpains – are
Dr Eva Wiklund.
central to the story. In life, the calpains are
busy regulating the muscle protein turnover;
building muscle when animals are growing and breaking
down protein if extra energy is needed. In death, however,
the calpains start to break down cell structures in muscle
tissue. This is the secret to the tenderness of venison, a
process that occurs very quickly post slaughter compared
with beef, which benefits from ageing. While the animal is
still alive, calpain inhibitors regulate the enzyme’s activity
and prevent the cell structure from being degraded, but this
balance is lost after slaughter.
Drip loss, this unwelcome side effect of the rapid
‘tenderising’ process post slaughter, is becoming more
important as the proportion of venison exported in chilled
form grows. With chilled venison taking at least six weeks
to reach its markets, drip loss inside vacuum packaging can
be quite pronounced by the time the product reaches the
consumer, but the meat is also very tender. After a prolonged
period, the drip inside vacuum packaging can also discolour
the meat.
Drip loss is more pronounced in venison than other meats.
Further water loss happens during cooking, but this is a
result of heating and denaturation of the proteins rather than
enzyme activity.
Eva Wiklund says that although the phenomenon is well
known, the processes that cause the chilled meat to expel
moisture this way are not well understood. Research into
these fundamental processes is the first step towards finding
ways to manage them, she adds.
A related problem for the presentation of venison is poor
colour stability. Cut meat exposed to air will ‘bloom’ a nice
cherry red colour as myoglobin, the oxygen-transporting
protein in muscle tissue, quickly oxidises. (Myoglobin
contains iron and forms the pigments responsible for meat’s
colour.) Unfortunately this is a relatively fleeting stage, and
the meat will eventually take on a less appetising grey/
brown appearance as the myoglobin continues to change
on exposure to oxygen. There is a higher concentration of
myoglobin in venison than in beef, which is why the colour
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change is more pronounced in venison.
The two research projects being led by
Eva Wiklund are designed to increase
understanding of the processes that go
on in chilled venison following slaughter.
The work could eventually point the way
to processes for mitigating the unwanted
drip loss and colour instability without
compromising the wonderful tenderness of
venison.
The first programme, seasonal variation in
venison quality, is already well underway.
DEEResearch is contributing $20,000 to
the $80,000 project, with the balance
funded by AgResearch.
The study has sampled muscle from deer
slaughtered at four different times of
the year – December, March, June and
September – to assess the seasonal variation in drip loss,
colour, calpain activity and tenderness.
Eva says preliminary results show deer slaughtered in
December have yielded the most tender venison and, along
with the tenderness, the greatest water loss during chilled
storage. The March-slaughtered venison was noticeably less
tender, and this seems to be linked to greater presence of
calpain inhibitors in the muscle tissue at this time. The July
and September-slaughtered venison was intermediate in
tenderness between the March and December product. Water
loss during cooking did not seem to be linked to season,
however.
At press time, Eva was still awaiting results showing seasonal
Drip loss (purge) in a vacuum bag. Venison sample has been
chilled at –1.5 C for 9 weeks.
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