Drip, tenderness, electrical stimulation
and meat quality
by Carrick Devine
HortResearch/AgResearch, Hamilton
„ We will go over the role of water in meat and reveal
some surprising things
„ Water changes are central to tenderisation
„ This means old concepts need to be revised
http://www.hortresearch.co.nz
http://www/mirinz.co.nz
How do we measure drip ? You have got to get
this right - poor measurement poor results
1. Weigh blot and reweigh
2. Hang meat in a bag
3. Measure drip in a tray
4. Squash weighed meat and watch the spread
5. Centrifuge meat and weigh
6. When we do this over time we see how the
drip arises and increases
7. Visual estimate of drip are flawed
Water is scattered throughout the muscle in
between cells and various spaces – but it just
doesn’t leak out
In muscles
In muscle proteins
In muscle fibres
Note: It is titin breakdown that
is important for drip release as
meat tenderises
More later
Live muscle to meat
„ Live muscle does not drip - at rigor mortis energy runs out and
water “equilibrates”. Higher pH muscles have less drip.
„ At rigor mortis, there is no major drip unless protein
denatures.
„ Classically this is PSE pork - high pre rigor
temperatures, low pH denatures myosin (Modern pork
without the halothane gene and good processing has
this under control)
„ The PSE condition does not happen in beef and
lamb and venison under usual processing
conditions, so forget it!
„
Meat science text books, refer extensively to pork - we need
to update with new knowledge
„ Rigor mortis protects muscle from further changes
„ Water holding capacity (WHC) is the amount of added water.
„ By the way, according to Honikel, there is no relationship
between WHC and juiciness - surprising
New Information – drip and tenderisation
„ There is very little drip at rigor mortis in sheep cattle and
venison (unlike pork) - drip arises when the meat tenderises
„ If there is a lot of drip in a few hours after slaughter, it means
the meat has tenderised fast - electrical stimulation, because it
ensures early tenderisation, shows early drip
„ After rigor mortis muscle is protected from any temperature/pH
effects. This is not generally recognized
„ Electrical stimulation
does not and in fact
cannot cause extra drip in sheep and cattle
„ Unfortunately you cannot have tender meat and no drip
„ In the market place 6 weeks away the drip will reach the same
levels for the same tenderness
Electrical stimulation and drip
No stimulation - not good
„ High rigor mortis temperatures reduce tenderness
„ This is because the enzymes that tenderise meat are
inhibited at high rigor temperatures and this limits
tenderisation and limits drip
„ Stimulation - good
„ Causes rapid rigor mortis – this is good, not bad as some
think
„ Rigor protects meat from any pH/temperature effects,
therefore protects tenderising enzymes, enhances
tenderisation - has no effect on total drip
„ Warm meat tenderises fast, drip increases initially and meat
reaches a higher degree of tenderness than for non
stimulated meat
„ “Stimulation” is not an add-on to “no stimulation” – it really
is a completely different process
„ Thus stimulation ensures early rigor, protects the enzymes
that tenderise meat and does not affect total drip.
What is the background to these statements?
„ Several studies since 2001 for beef and lamb were
involved, some as part of the NIR project
„ We followed meat as it tenderised
„
„
„
„
With and without electrical stimulation
With wrapping (behaves like meat on a carcass) and
without wrapping
We controlled temperature and shortening - high
(35°C) and low (15°C, 7°C, 4°C)
We aged at a constant temperature
„ As the meat tenderised there was an increase in
drip over time - unrelated to temperature
„ This was initially surprising considering many earlier
reports (just incomplete)
„ We have published this for beef and lamb
Relationship between drip, shear and rigor
temperature in lamb while ageing
25
pre rigor 4°C
pre rigor 7°C
prerigor 15°C
pre rigor 35°C
„ There is no drip
increase at high
rigor temperatures
% cenrifuge drip
20
15
10
5
0
0
20
40
60
80
100
Shear force (N)
120
140
160
180
Changes in drip (free water), bound water,
dry matter and tenderisation in lamb
100
16
72
90
14
70
80
Drip
12
68
10
Bound water
8
66
64
6
25.2
Dry matter
25.0
24.8
Time vs shear force (N)
Time vs dry matter %
24.6
70
24.4
Shear force
60
24.2
50
24.0
62
40
4
60
2
58
80
23.8
30
0
10
20
30 40 50 60
Post-Rigor Age (h)
Drip and bound water
McGlone et al 2005
70
23.6
0
20
40
60
Ageing duration (h)
Dry matter and shear
80
Dry matter %
74
Shear force (N)
18
Bound Water (%)
Free water (%)
All from same muscles
Drip and tenderisation in beef
200
24
23
Electrically stimulated 15°C rigor
22
180
20
160
18
140
22
16
14
NES 35
ES 35
ES 15
NES 15
12
Drip
120
20
shear
100
19
80
18
60
10
17
40
8
0
20
40
60
Duration of ageing (h)
Drip with various pre rigor treatments
Sarcomere length may influence drip
and not important here
80
100
20
0
20
40
60
80
16
100
Duration of ageing (h)
This is an electrical stimulation treatment with a
fitted curve and including shear force
2
Drip (cm )
Shear force (N)
2 -1
Drip (cm g )
21
Where does the drip come from?
„ Drip is formed over time as the meat tenderises
„ It comes from a generally unrecognized protein called “titin” that is up to
10% in muscle
„
Titin is the largest protein in animal kingdom
Breaks down as meat tenderises.
„ When proteins degrade they release water.
„ Drip is inevitable if the meat tenderises - Pity.
„
Titin
Titin in living muscle has a role of energy
recovery – it isn’t just there to make meat tough
Other examples in the literature
Chilled beef -1.5°C
Payne et al, 1998
50+ muscles
Pork in tray
on display 4°C
Otto et al 2006 374 samples
What is the take home message?
„
„
„
„
Drip arises as meat tenderises. No tenderisation - no drip
Final drip will be the same for the same tenderness
High rigor temperatures in beef lamb and venison do not increase drip
Electrical stimulation
„ Does not increase drip - as meat tenderises faster it appears earlier
„ Enhances tenderisation as well as preventing cold shortening
„ We need to have the best stimulation – by the way don’t stimulate
twice
„ Some quarters suggest reduced stimulation – Wrong!
„ Give full stimulation not a tickle – you cannot over stimulate as the
responses are self limiting (exhaustion is exhaustion).
„ It can be good low voltage beef or high voltage lamb.
„ Processing variation explains why drip differs from plant to plant
„ This is serious stuff and needs more research – it
will explain some of the variation in meat quality in
New Zealand