How Crustastun works

The premise of Crustastun is straightforward. The lid of the unit contains an electrode and a damp electrode sponge. The base of the unit contains a tank of salt water, with another electrode.

The animal is placed belly down on a sprung tray in the unit. As the lid is closed, the shellfish and tray are pushed down by the electrode sponge into the saline solution. The operator then presses one of the stun buttons on the front of the machine and a current passes through the 13 brain centres of a lobster, or the two brain centres of a crab.

The stun current works by instantly interrupting the nerve function, so that the shellfish cannot receive stimuli and therefore cannot feel pain. This takes less than half a second. The prolonged application of the stun, for up to ten seconds, kills it. 

Using the freshwater drowning method, a crab can take 12 hours to die

This method has been researched by Dr David Robb of Bristol University, UK. Dr Robb has scientifically established that a current of 1–1.3 amps, applied for five to ten seconds, is required to stun and kill a shellfish. Crustastun uses a typical current of 4–6 amps to ensure that shellfish die quickly, with an absolute minimum of distress.
 
The electro-stunning technique is in stark contrast to killing methods such as freshwater drowning, where a crab can take 12 hours to die, depending on water temperature. During this time the animals produce stress hormones such as cortisol, which adversely affect meat quality. Crabs and lobsters dispatched using Crustastun produce meat of noticeably better taste and texture.

The key components of the Crustastun

The typical current profile when stunning
a crab during a 10 second stun cycle.
The current peaks at 8 amps, even
though a current of only 1.3 amps is
required to successfully stun the animal.