The following is a summary of work reported by Alan Sams, Texas A & M University,
in "Broiler Industry", December 1994 pp 18-22.
As the broiler industry moves further along the road of further processing
and ready-to-cook products, there is a continual search for ways to improve
product quality and reduce processing costs. The research of Dr. Sams has the
potential to do just that.
The common practice presently employed by those producing boneless chicken
breast meat is to hold processed carcasses, or breast halves, under refrigeration
for a period of 4 to 24 hours prior to deboning. After sufficient "Aging"
the breast fillets are removed. This process of storing product in coolers and
moving it about the plant, is time consuming and costly. It is estimated that
up to 50% of the energy costs of boneless meat production is involved in the
"Aging" procedures.
Meat aged on a skeleton leads to enhanced tenderness. The reason for this is
that when an animal is killed there is still a significant amount of chemical
energy in muscle cells. If the meat is immediately cut, as in the deboning process,
the muscles are stimulated and contract similar to what happens with a nerve
impulse.
If the skeleton is no longer present to limit the contraction, excessive muscle
shortening occurs and the meat is more dense and hence tougher.
Aging breast meat on the carcass for at least 4 hours allows time for the chemical
energy present in living cells to be degraded. This process of cell muscle energy
depletion, to the point where it is unresponsive to external stimuli, is known
as rigor mortis development.
Several decades ago scientists found that electrical pulses directed through
a beef carcass, immediately after death of the animal, acted like nerve impulses.
Thus, cell energy was depleted and the "Aging Process" shortened,
without resulting in tough meat. The process was quickly adopted by the beef
industry to shorten the aging period, thus increasing product quality while
at the same time reducing production costs.
Since chicken muscle is metabolically different from beef muscle, chicken breast
meat does not respond to electrical stimulation similar to that of beef. It
took many years for scientists to develop effective electrical stimulation for
poultry meat. There was a commercial application patented in the late 1980's
using electrical stimulation along with a steam chamber to help deplete cell
energy.
However, the process was not readily adopted as it required major changes in
processing procedures and slower line speed.
The method developed by the Texan scientists fits readily into existing processing
plants and requires a minimum of capital investment. The system uses much higher
voltage than the early system (400 compared to 100 V) and a shorter stimulation
period (15 seconds vs 24 minutes). The electricity (400 V, 320 mA) is pulsed
(2 seconds on, 1 second off) until the bird receives 5 pulses.
Recently the procedure has been scaled up to a commercial plant at commercial
line speeds. Basically, the stimulation consists of a pair of electrified rub
bars inside a protective tunnel. Positioning of the rub bars is adjustable to
accommodate variations in bird size.
The system allows meat to be deboned immediately after the carcass comes from
the chiller thus eliminating the refrigerated storage period. An added benefit
is that electrical stimulation markedly reduces the variation in tenderness
between fillets from different carcasses. This results in greater product uniformity
and thus better product acceptability.
A further benefit is that deboning yields are significantly improved (33.83
vs 32.82% for the reported test). When meat is aged normally, the muscle becomes
softer and tears easily when pulled. Meat that can be deboned immediately after
chilling is firmer, resists tearing and gives a cleaner separation from the
bone during deboning; hence, the reason for the increased yield with electrical
stimulation of the carcass.
While the above procedure is new and may have some start up problems to sort
out, it is quite likely to be readily adopted by the poultry industry as a means
of improving product quality while at the same time reducing product cost.