Smart Stimulation System

March 2005

The basic carcass electrical stimulation regimes of the late 70s and 80s, developed to hasten rigor mortis, prevent cold-induced toughening and enhance meat tenderness, are still valuable for the frozen meat trade.  However, but they are one size fits all treatments that dont take into account the variability in carcass response or the requirements of the more sophisticated chilled/chilled meat markets. 

The responses of carcass muscles to different electrical parameters are now much better understood, and stimulation processes have been refined.  Lower cost and more flexible systems have been developed that allow processors to dial up the end-product quality requirements of particular markets and tailor electrical parameters to the stimulation needs of individual carcasses to meet those quality requirements.  Systems for lamb and beef are now being trialed commercially.  This is a significant advance on the original MIRINZ work, and in part incorporates research done in Australia. 

In the first few hours after slaughter, carcass muscles will contract in response to cold temperatures and in that contracted state they can be tough.  Chilling or freezing hot carcasses soon after slaughter is a great way of producing tough meat.  This was discovered at the Meat Industry Research Institute (MIRINZ) in the late 60s, and in the 70s several ways of avoiding cold-induced toughening and enhancing tenderness were developed.  The most spectacular was high voltage electrical stimulation of lamb carcasses straight after slaughter as they travelled down the dressing chain. The electrical impulses made the energy in the muscles unavailable for contraction, rigor mortis was achieved in a couple of hours, and ageing of the meat started early.

High voltage systems became standard for lamb, but for beef they were tricky and not popular.  Low voltage systems were developed, and many beef plants adopted them for high quality markets and the chilled trade.

The problem with these one size fits all stimulation systems is that they do not take into account variation between carcasses, and some chilled meat was ending up with problems of high pH, poor colour, unsightly drip loss accumulating in primal and retail packs, and mealyness rather than tenderness.

Work at MIRINZ in the past decade has documented the variability in end-product quality and refined knowledge of how muscles react to different electrical currents, waveforms and voltages.    Recently they have trialed new smart systems of stimulation that first measure the response of individual carcasses to a standard pulse, and then tailor stimulation parameters (strength and duration of the current) to the needs of that particular carcass.  For example, feedback from the initial pulse may cause the Smart Stimulation System to deliver 15 seconds of stimulation to one carcass but 60 seconds to another. 

Moreover, the end product quality setting can be varied by processors to suit the needs of particular packaging systems, cooling regimes, and markets.  They may decide they need a final pH of, say, 6.2 for a particular purpose they can dial that into the smart system, and meat should end up being within plus or minus 0.1 pH units of that figure.

The result is that variability is greatly reduced, and products consistently have the desired quality attributes.  The NZ industry is delighted at the prospects particularly for lamb.  The Aussies are also keen, especially for beef, so although much of the initial research was funded by Meat & Wool New Zealand, Meat & Livestock Australia (MLA) have more recently supplied matching funding.  The Smart Stimulation System also takes advantage of some sophisticated electronics from Australia incorporating results of their research into applying constant current and mid-range voltages to carcasses.  NZ meat companies have supplied commercial test facilities.

Initially MIRINZ meat scientists were just looking for ways of overcoming the variability in the end product, but what they found was that the response of a particular carcass to the test pulse could be used to predict the ultimate pH and shear force of cuts ie. colour stability, tenderness, and suitability for processed products.

The Smart Stimulation System has now gone through the experimental phase and is now undergoing commercial validation for both an automated lamb system at a commercial meat plant and a manual beef system at the Ruakura abattoir. 

When available it will give the industry:

Greater flexibility in processing carcasses, with the ability to tailor the end-point quality of an individual carcass to a particular market
Lower cost options for stimulation high voltage systems are expensive and there are safety problems
Existing stimulation facilities and rubbing electrodes can be used
An easier way of exploiting the science behind the processes to enhance meat quality