The research team, led by Junjie Xu and colleagues at Yangzhou University, designed their experiment to eliminate every variable except marketable age. They raised 300 purebred B-line small white-feathered broilers and 300 purebred L-line yellow-feathered broilers from the same incubation batch under identical nutritional and environmental conditions. At 29 days of age, healthy birds with comparable body weights were transferred to individual cages with a floor area of 0.5 square meters each, a system that effectively removes fighting, feather pecking, and environmental heterogeneity as confounding factors. The white-feathered broilers were slaughtered at 56 days, their commercial marketing age, while the yellow-feathered broilers were raised to 112 days, reflecting their slower growth cycle and later market readiness. Twenty birds of each breed, with equal numbers of males and females, were randomly selected at each time point for comprehensive analysis.

The researchers measured conventional meat quality parameters including pH, color, shear force, and water-holding capacity using calibrated instruments. They found that increasing age significantly increased the redness (a* value) of muscles, with the most dramatic change in white-feathered broilers, whose leg muscle a* values rose from approximately 2.35 to 12.01 in males and from 2.89 to 14.74 in females. This shift reflects rising myoglobin content as muscles mature, a well-documented physiological process. Conversely, lightness (L) and yellowness (b) values decreased with age in most groups. The pH values at one hour postmortem dropped significantly in both breeds, falling from approximately 6.39 to 5.90 in white-feathered breast muscle and from 6.35 to 5.61 in yellow-feathered breast muscle. This decline suggests heightened glycolytic activity in older birds, pushing the postmortem pH further from the isoelectric point of muscle proteins and thereby improving water retention.

Shear force, the objective indicator of tenderness, increased with age across most muscle types, with yellow-feathered broilers showing significant increases in both breast and leg muscles while white-feathered broilers showed changes primarily in leg muscle. The breast muscle shear force of yellow-feathered males, for instance, rose from 15.26 to 28.16 newtons between 56 and 112 days. This trend is attributable to thickening muscle fibers, increased myofibrillar protein content, and collagen cross-linking within connective tissue, all hallmarks of muscle maturation. Water loss rate decreased with age in most groups while water-holding capacity increased, an inverse relationship explained by the pH moving away from the isoelectric point of muscle proteins, which strengthens their ability to bind water. Notably, yellow-feathered breast muscle showed the opposite pattern, with younger birds retaining more water, possibly because rapidly developing muscle with fine fibers and low collagen content has superior water retention.

Nutritional composition shifted meaningfully with age. Moisture content decreased across most muscle types, consistent with muscle maturation and reduced water-holding capacity. Crude protein increased significantly, particularly in the breast muscles of male white-feathered broilers and yellow-feathered broilers of both sexes, reflecting vigorous accumulation of structural proteins such as myosin and actin alongside connective tissue deposition. Intramuscular fat (IMF) displayed tissue-specific dynamics: leg muscle IMF rose with age in both breeds, while breast muscle IMF declined in yellow-feathered broilers. The researchers attribute this to reduced activity in older birds, which lowers energy expenditure and favors fat deposition in locomotive muscles with thicker fibers and more intermuscular adipocytes, while rapidly growing breast muscle prioritizes protein synthesis over fat storage.

The study then probed the flavor precursor landscape, measuring amino acids, fatty acids, and inosine monophosphate (IMP) content. IMP, the critical umami enhancer in chicken meat, decreased with age in leg muscles of both breeds and in the breast muscles of male white-feathered and female yellow-feathered broilers, likely due to increased phosphatase activity accelerating IMP degradation. Amino acid profiles remained largely stable in yellow-feathered broilers, consistent with their slow and steady muscle development, but the leg muscles of male white-feathered broilers showed broad increases in most amino acids at 112 days, suggesting that fast-growing breeds continue protein deposition even after reaching market age. Fatty acid remodeling was most pronounced in leg muscles, with polyunsaturated fatty acids (PUFAs) such as C20:4n-6 and C22:6n-3 increasing significantly with age in yellow-feathered males, while monounsaturated fatty acids (MUFAs) declined. These shifts matter because PUFAs are highly susceptible to thermal oxidation, generating aldehydes, ketones, and alcohols that impart desirable aromas to cooked meat.

Using two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC TOF MS), the team identified over 2000 volatile compounds in some samples, with the highest diversity in the breast muscle of 56-day-old yellow-feathered broilers. They screened for potential key flavor contributors using relative odor activity values (ROAV), where compounds with ROAV ≥ 1 are considered key contributors. Four compounds emerged as common to both breast and leg muscles of both breeds: (E)-2-nonenal, imparting fatty and cucumber notes; 2-methylbutanal, contributing cocoa and almond aromas; 2,3-butanedione, with its pronounced buttery character; and 2-pentylfuran, offering green bean and vegetable notes. Among these, 2,3-butanedione consistently achieved the highest ROAV, reaching 100 in multiple groups, making it the unambiguous flavor king of chicken meat. This ketone originates from amino acid catabolism and microbial oxidation of fatty acids, and its abundance of branched-chain amino acid precursors, particularly valine, provides direct substrate for its formation.

Pearson correlation analysis revealed that flavor precursor dynamics differ fundamentally between breast and leg muscle. In breast muscle, key volatile compounds relied more heavily on amino acid-mediated Maillard reactions and oxidative degradation of PUFAs, with naphthalene, ethyl 2-propenoate, and ethyl hexadecanoate positively modulated by multiple amino acids. In leg muscle, fatty acids predominantly positively regulated key volatile compounds, attributable to higher IMF content and more active lipid metabolism. Both tissues showed positive regulation by PUFAs and negative regulation by MUFAs, confirming that PUFAs undergo autoxidation while MUFAs remain relatively stable. Notably, IMP was significantly negatively correlated with several key volatile compounds in leg muscle, raising the possibility that IMP suppresses volatile accumulation through mechanisms that remain to be elucidated.

The study’s most striking finding is that yellow-feathered broilers accumulate flavor diversity from breast to leg muscle as they age, with the leg muscles of 112-day-old females exhibiting not only the greatest diversity of key volatile compounds but also a well-distributed ROAV profile. This suggests that slow-growing yellow-feathered breeds possess a breed-specific flavor advantage, with a longer window for flavor precursor accumulation, whereas fast-growing white-feathered broilers prioritize rapid protein deposition over flavor development. The findings provide scientific evidence for producers to select appropriate breeds and ages according to market positioning and consumer expectations, and offer valuable data for the meat processing industry to develop differentiated products. Future research should focus on the molecular basis of breed- and age-dependent flavor differences, including key enzymes and regulatory genes, alongside integrated sensory evaluations using gas chromatography-olfactometry and aroma recombination experiments to translate instrumental findings into quantitative relationships with human perception.

Subject of Research: Food science

Article Title: Characterization and comparison of meat quality and potential dominant volatile flavor compounds in yellow-feathered and white-feathered broilers under a cage rearing system: Effects of increasing marketable age

Article References: Xu, J., Gao, P., Ding, H., Liu, X., Chen, H., Sun, Y., Pang, M., Zhang, T., Zhang, G., Guo, X., Zhao, Z., Xie, X., & Xie, K. (2026). Characterization and comparison of meat quality and potential dominant volatile flavor compounds in yellow-feathered and white-feathered broilers under a cage rearing system: Effects of increasing marketable age. Food Chemistry: X, Article 104649. https://doi.org/10.1016/j.fochx.2026.104649

Image Credits: AI Generated

DOI: 10.1016/j.fochx.2026.104649

Keywords: Characterization, comparison, meat, quality, potential, dominant, volatile, flavor, compounds, yellow-feathered, white-feathered, broilers