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High pressure (HP) treatment often results in discoloration of beef, lamb, pork, and poultry. The degree of color changes depends on the physical and chemical state of the meat, especially myoglobin, and the atmospheric conditions during and after pressurization. A decreased redness is attributed to a large degree to the oxidation of the bright red oxymyoglobin or the purplish deoxymyoglobin into the brownish metmyoglobin, as well as to the denaturation of myoglobin. Surely, the high myoglobin content makes beef more exposed to this discoloration compared to the white chicken meat. In addition, HP treatment causes denaturation of myofibrillar proteins followed by aggregation, consequently, changing the surface reflectance and increasing lightness. Other intrinsic and extrinsic factors may affect the pressure-induced color changes positively or negatively. In this review, the pressure-induced color changes in meat are discussed in relation to modification of the myoglobin molecule, changes in the meat microstructure, and the impact of the presence of different chemical compounds and physical conditions during processing.

The effect of high pressure (HP) treatment (400 MPa, 10 min) of porcine longissimus dorsi was investigated using reflectance spectroscopy and by UV-vis and circular dichroism spectroscopy for the soluble protein fraction. The soluble protein content was expectedly lowered significantly by HP treatment, whereas the solid state fraction of the meat responded to HP by exhibition of characteristic spectral changes in the visible reflectance data with a temporal evolution over the course of 2 days. However, the soluble protein fraction did not exhibit the same altered spectral characteristics in the visible region as seen in the solid state following HP, and there were no indications of altered folding of the proteins that remain in solution., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Color changes of minced cured restructured ham was studied considering the effects of high pressure (HP) treatment (600MPa, 13°C, 5min), raw meat pH(24) (low, normal, high), salt content (15, 30g/kg), and drying (20%, 50% weight loss). Raw hams were selected based on pH(24) in Semimembranosus, mixed with additives, frozen, sliced, and dried using the Quick-Dry-Slice® process. Meat color (CIE 1976 L*a*b*) and reflectance spectra were measured before and after HP treatment. HP significantly increased L*, decreased a*, and decreased b* for restructured ham dried to 20% weight loss, regardless of salt content and pH(24). L* and a* were best preserved in high pH/high salt restructured ham. HP had no effect on the color of restructured ham dried to 50% weight loss. HP had no effect on the shape of reflectance curves, indicating that the pigment responsible for minced cured restructured ham color did not change due to HP., (Copyright © 2011 Elsevier Ltd. All rights reserved.)