Electrical Stimulation of Chicken Breast Meat

Bioenergy Processing Articles >> Processing Technology

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.

The above is a summary of work reported by Alan Sams, Texas A & M University, in "Broiler Industry", December 1994 pp 18-22.

by John Summers - P.I.C. (Canada)

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