How pH causes paleness or darkness in chicken breast meat

Chicken breasts (Pectoralis) at a low-pH (5.91 +/- 0.12, n = 10) were compared wit h breasts at a high-pH (6.36 +/- 0.2 5, n = 10, P < 0.00 1). Low-pH breasts had the highest reflectance (P < 0.001 from 400 to 700 mn). High-pH breasts had the greatest transmittance into their depth and across individual muscle fibres (P < 0.001). The differences in refractive index between ordinary and extraordinary rays across individual muscle fibres were greater in low-pH than in high-pH breasts (P < 0.001). Light at low wavelengths had greater reflectance and lower transmittance than light at long wavelengths (P < 0.001). Myofibrillar refraction contributed to differences in light scattering between PSE (pale, soft, exudative) and DFD (dark, firm, dry) chicken meat, as it does in pork and beef. (C) 2008 Elsevier Ltd. All rights reserved.