title: Effect of pH on the stability and molecular structure of nitrosyl hemochromogen.
abstract: This study explored the effect of pH on the stability and molecular structure of nitrosyl hemochromogen (NO-Heme) using ultraviolet (UV), electron paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) spectroscopy. The NO-Heme was extracted from pre-cooked cured beef and was dissolved in an 80% acetone solution pre-adjusted to different pH values with 2 mol/L HCl and 2 mol/L NaOH. The results show that pH significantly influences the optical properties and stability of NO-Heme. Strong acidic and weak basic conditions favor the red stability of NO-Heme. The conjugate structure of NO-Heme changed under strong basic conditions, as the NO(-) group was shown to be still associated with the iron porphyrin, but the color of NO-Heme changed from pink to yellow. NO-Heme is extremely unstable at weakly acidic pH, and this may be the why pH affects the apparent color of cured meat products during storage.
authors.affiliation: College of Life Science, Yangtze University, Jingzhou, Hubei 434023, China; Jingchu Food Research and Development Center, Yangtze University, Jingzhou, Hubei 434023, China.
authors.forename: Chensha
authors.initials: C
authors.lastname: Yu
authors.affiliation: College of Life Science, Yangtze University, Jingzhou, Hubei 434023, China.
authors.forename: Jingzhi
authors.initials: J
authors.lastname: Jiao
authors.affiliation: Department of Food Science, Tianjin Agricultural University, Tianjin 300384, China.
authors.forename: Lizhen
authors.initials: L
authors.lastname: Ma
authors.affiliation: College of Life Science, Yangtze University, Jingzhou, Hubei 434023, China; Jingchu Food Research and Development Center, Yangtze University, Jingzhou, Hubei 434023, China. Electronic address: sun_weiqing@163.com.
authors.forename: Weiqing
authors.initials: W
authors.lastname: Sun
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D061353:Food Storage; D006418:Heme / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008460:Meat; D015394:Molecular Structure; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: C007955:hemochromogen; D006418:Heme
keywords: EPR spectrum; FT-IR spectrum; Nitrosyl hemochromogen; Stability; pH