17E-17 |
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S. MONY and H. G. Kristinsson. Dept. of Food Science & Human Nutrition, Univ. of Florida, 130-B Aquatic Foods Pilot Plant, PO Box 110370, Gainesville, FL 32611-0370 Hemoglobin (Hb) plays an important role in quality deterioration of fish muscle by promoting lipid oxidation, leading to color changes. The pro-oxidative activity of Hb increases when it auto-oxidizes into the brown met-Hb and/or becomes unfolded. Therefore to minimize lipid oxidation it is important to increase the oxidative and structural stability of hemoglobin. The objective of this study was to investigate whether binding of carbon monoxide (CO) to hemoglobin would increase its resistance to auto-oxidation and thermal denaturation. Oxy-Hb was isolated from tilapia blood. CO-Hb was prepared by treatment for 2 min with 100% CO. Met-Hb was prepared by treating Hb with ferricyanide. Auto-oxidation studies were performed by storing oxy-Hb and CO-Hb in sodium phosphate buffers at pH 6, 7 and 8 at -30, 4 and 20°C for a period of days. Degree of auto-oxidation was measured from the UV-visible spectra of Hb. Thermal denaturation experiments were performed on oxy-, CO- and met-Hb at pH 6-8 by following protein aggregation and heme group unfolding using UV-visible spectroscopy, and changes in protein structure investigated by circular dichroism spectroscopy (CD) and micro-differential scanning calorimetry (mDSC). CO-Hb was substantially more stable than oxy-Hb at all pH values and temperatures tested, as the CO molecule greatly stabilized the heme group from oxidation. As pH increased the stability towards autoxidation increased for both Hb types. Thermal-denaturation experiments revealed that CO-Hb was far by the most stable of the three types tested, followed by Oxy-Hb, with met-Hb being the least stable. Conformational results suggest that stabilization of the heme environment dictated the onset of overall protein unfolding and aggregation. These results suggest that CO binding stabilizes the heme group and thereby the whole protein molecule. This suggests that treatment with CO could be useful in prolonging shelf-life of fish muscle.
Session 17E, Food Chemistry: Proteins
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