thetuna, the better the meat. The best tuna I’ve ever
eatenwas a 100kg bluefin that I caught off Portland in
Victoria. I kept some of that fish in the fridge and each
daywe’d eat some, either raw as sashimi or as steaks
lightlyseared on the barbecue. Those enjoying it with
meallagreed that each day it got better and better.FAST TWITCH & SLOW TWITCH
MUSCLES
Beforegetting to the steps that will give you better
tastingtuna, first we need to understand a little about
their amazing muscle structure. In an upcoming
BlueWater article I’ll go into much more detail about
their fascinating design and how it enhances their
swimming and fighting abilities, but I’ll briefly explain
thekey points here.
There are two main types of skeletal muscle in
animals, including fish: ‘fast twitch’ and ‘slow twitch’
muscles. An Olympic runner like Usain Bolt has plenty
of fasttwitch fibres in his muscles!
Interrestrial animals such as pigs, cows and even
humans, these two types of muscle are mixed in
the one bundle. You can’t tell the difference with
thenaked eye. In fish, however, including tuna, the
two types of muscle are distinctly separate and are
easilydistinguishable as the fast twitch ‘white’ muscle
(whichis actually a pink colour in tuna) and the slow
twitch ‘red’ muscle – as seen in the nearby photo
showing the cross-section of a tuna.TUNA ARE DIFFERENT
The red muscle is the muscle that does most of the
day-to-day work when a tuna is swimming. This
muscle can go all day without getting tired. It is
located internally in tuna, close to the backbone.
This is different from most other fish, where the red
muscle is located laterally, closer to the skin. There
are a number of reasons for this and it has a lot to
do with the way tuna swim (see my next article for
more explanation on this). Importantly, having the
red muscle internally means it is insulated from the
outside by the large mass of white muscle around it.
The red muscle is generally a dark red as it has a
huge amount of oxygen-carrying pigment and blood
vessels running through it, which keep it well supplied
with blood and oxygen.
Any muscle that is working creates heat. That is why
you warm up when you start exercising. This is true
for muscles in fish as well. For most species of fish,
the heat created in their working muscles is lost when
the blood that has been warmed up while passing
through the working muscles then passes through the
gills, where it comes in close contact with the water.
How cold the water is will affect how quickly the blood
cools down, but any heat is usually quickly lost as gills
are a great heat exchange unit.
Tuna, though, are different. When the warmed blood
comes out of their working red muscle it doesn’t
directly go off to the gills. Instead, the blood vesselsTools for preparing
tuna like a pro,
including a hollow
coring tool, a brain
spike, a length of
flexible cable for
pithing the spine,
and a short-bladed
knife specially
designed for cutting
the shallow lateral
blood vessels for
bleeding the fish.“It astounds
me how few
tuna are
looked after
in a way that
maximises
their eating
qualities.”
74 facebook.com/BlueWatermagazine
From boatside to plate