Tender and juicy is the expectation when people bite into chicken breast. Tough and chewy is the experience in a growing number of meals, and the blame lies with woody breast syndrome.
Also known as wooden breast disease (WBD), woody breast describes myopathy of the muscle in a broiler chicken’s chest, the most in-demand and valuable portion of the bird. Recently concluded research at the University of Delaware suggests it’s the result of damaged veins, which impairs lipid metabolism and leads to hardening of muscle tissue. The vein damage occurs in the first days of the chicken’s life and is barely detectable in live birds. There’s no human health risk, just a tough eating experience.
Half a dozen WBD research projects have been funded by the U.S. Poultry & Egg Assn., the industry group that underwrites research to solve problems plaguing poultry processors and growers. WBD is one of the top research focuses currently, according to John Glisson, vice president of research programs at the Tucker, Ga., association (www.uspoultry.org).
Old is a relative term, and some poultry professionals attribute WBD to older, heavier chickens. While the severity and frequency of the disease is more prevalent in eight-week-old chickens than those slaughtered at five or six weeks of age, “We know now that it’s occurring at a very early age” and is most likely a genetic trait, Glisson explains. That suggests the solution resides with breeder stock providers, and with two companies accounting for more than four-fifths of broilers worldwide, breeders are both the source and solution to the problem.
Some scientists theorize the condition was an unintended side effect of breeding projects that created positive attributes. Others have isolated a virus that may be involved, while still others think a change in diet is the solution. “When you’re grasping at straws,” says Glisson, “grab a handful.”
The immediate issue is detecting the presence and severity of WBD during processing. Much of the breast meet is bound for foodservice, and chains like KFC and Chick-fil-A have very exacting quality standards. Currently, human inspectors pick fillets off a belt and press them with their thumbs to make a judgment on the presence of WBD and the degree of severity.
It’s a subjective, laborious approach, and some of the current research aims to automate inspections. A solution based on visual and near-infrared (Vis-NIR) imaging already exists, though it has yet to be deployed in North America. Several European poultry companies are using it, according to Thorsten Niermeyer, business unit manager-process analytics at Tomra Sorting Ltd. (www.tomra.com) in Asker, Norway.
The in-line analysis is done by Tomra’s QVision analyzer, which uses multispectral light to determine the fat, protein, moisture and collagen levels in protein foods. Using laboratory measurements as a reference, the system grades up to four fillets a second as mild, medium, severe or WBD-free. “We get better than 0.3 percent accuracy, compared to the laboratory measurements,” says Niermeyer.
Multiple wavelengths of light penetrate up to 20mm (three-quarters inch) into the muscle to determine the chemical composition in the top cranial region. Software then calculates the severity of any myopathy.
Similar Vis-NIR imaging was used in a research project funded by U.S. Poultry & Egg and completed last year. “Using Vis-NIR hyperspectral imaging and experimentally developed classification models, breast fillets in this study could be categorized according to the wooden breast condition with greater than 95 percent accuracy,” summarized Brian Bowker, a protein chemist with USDA’s Agricultural Research Center in Athens, Ga. “This study also demonstrated that 3D imaging can be utilized to extract geometric and shape attributes of fillets which can subsequently be modeled to categorize wooden breast fillets with 90-95 percent accuracy.”
Bowker’s use of optical coherence tomography relies on surface images, which he maintains could distinguish between fat, muscle and connective tissue for quality assessments. Niermeyer takes exception, maintaining chemical changes in the meat may not manifest themselves on the surface. Light absorption is needed, and that’s the approach with Tomra’s “interactance spectroscopy” technology.
Detection systems using other technologies are being developed at the University of Delaware, Auburn University and other centers of poultry research. Regardless of which system wins favor with poultry processors, the work has broad implications in food processing. “Attempting to use vision technology to assess quality in chicken parts is something that hasn’t been done before and has wide applications,” notes Glissen. Non-invasive tests of fruits, vegetables and other foods might follow. “This is going to be a proof of concept thing,” he adds.