Pale, soft and exudative (PSE) meat – meat that is pale in colour, forms soft gels, and has decreased ability to hold water – is a problem often associated with pork. But according to researchers, it has increasingly become a challenge for some poultry producers as well, particularly in the turkey industry, according to the Poultry Science Association (PSA).

While researchers stress that PSE is not a problem with whole turkeys, it is impacting further processed products, such as sliced turkey deli meats, particularly whole-muscle deli rolls or loaves. In these whole muscle products, there is less opportunity for protein extraction due to decreased surface area compared to comminuted, i.e. chopped and formed, products. There is also decreased water-binding in these products due to protein damage caused by the development of PSE. Therefore, the damaged proteins in PSE meat have a reduced ability to bind, hold water, and maintain their texture.

According to researchers Dr Christine Alvarado, associate professor in the Animal & Food Sciences at Texas Tech University Department, and Dr Casey Owens, associate professor in the Department of Poultry Science at the University of Arkansas, a host of causes may play a role in the growing incidence of PSE meat in turkey plants. The two scientists have published extensively on the problem of PSE in Poultry Science, a scientific journal published by the PSA.

Finding an effective means to reduce levels of PSE turkey meat would have a significant economic impact for the typical turkey producer, who, according to Professors Alvarado and Owens, could be losing between $2 million and $4 million annually to the problem – a level which, if correct, puts annual turkey industry losses due to PSE meat at more than $200 million.

The Role – or Lack of One – of Genetics

"PSE meat results from an animal's inability to tolerate stress," said Professor Alvarado in a recent interview with PSA. "The root of stress intolerance may be genetic, as it is in swine, where the specific genetic mutation associated with stress-susceptibility is known. But to date, we lack sufficient evidence either to support or refute a similar genetic mutation as the underlying cause for the same condition in turkeys."

Reducing Pre- and Post-Mortem Stress Levels

* "Annual turkey industry losses due to PSE meat at more than $200 million"

Whether or not there is a genetic basis for increased stress intolerance, taking an active, holistic approach to reducing both pre- and post-mortem stress levels will be key to producers decreasing the level of PSE turkey meat in their plants.

"Turkeys and swine are both subjected to similar pre-mortem environmental stress such as heat stress, pre-slaughter handling practices and transportation. These can lead to a higher level of PSE in these animals. Therefore, finding ways to lower those stress levels will be critical to reducing PSE. For example, newer techniques in gas stunning methods where turkeys are stunned while on the truck after it arrives at the processing plant, rather than after they have been placed on the line, may help reduce PSE by decreasing the human-handling component," said Professor Owens.

Environmental factors in the post-mortem environment can also contribute to PSE, even in normal, non-stressed animals, according to Professors Alvarado and Owens. For example inadequate chilling, which turkeys are susceptible to given their relatively large body size and muscle mass, can contribute to PSE.

Possible Solutions

While current solutions are limited, researchers are looking for ways to reduce the prevalence of PSE meat. According to Professors Alvarado and Owens, one approach might involve developing a sorting process in which meat having a higher probability of developing PSE would be directed away from whole-muscle products or toward product formulations incorporating marinades containing functional ingredients such as salt, phosphates, starches or gums. This kind of sorting process might be based on characteristics such as meat colour and meat pH. Similar automated pH assessment systems are already in development in the pork and beef industries for the same purpose of sorting meat for optimum meat function. And equipment to assess color online is already available and could be used for sorting.

"What's critical in any approach to tackling the turkey industry's growing incidence rate of PSE is that it be holistic, taking steps to reduce the many pre- and post-mortem stresses associated with production," said Professor Alvarado.

May 2010