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Examine roles of myoglobin, heme, iron in determining fresh meat color properties.

Fresh meat products, such as ground beef and sausages, are packaged for retail sale in oxygen-permeable films. Browning of the product due to the formation of metmyoglobin causes consumers to mistrust both the safety and quality of the product, potentially leading to a decrease in sales.

Carnobacterium maltaromaticum stabilizes the red color of refrigerated fresh meats stored under aerobic conditions. Research shows that C. maltaromaticum promotes the formation of oxymyoglobin, most likely through the reduction of ferric compounds to ferrous iron.

Scientists have investigated this reaction. Understanding the mechanism involved in the stabilization of red meat color will allow you to develop strategies that increase the retail storage life of meat products.

The mechanism of C. maltaromaticum involved in accessing iron in myoglobin was examined by evaluating the production of siderophores using a chrome azurol S (CAS) assay, and by examining the ability to bind heme, an iron compound, by growing the culture in a medium containing hematin.

Levels of hematin were measured in supernatant over time. The amount of hematin absorbed equaled the hematin concentration of the medium, less the hematin in the supernatant. The effect of heme on C. maltaromaticum was explored by the researchers, as the metabolic activity of some lactic acid bacteria can change from fermentation to respiration due to its presence.

Growth efficiency was measured by monitoring oxygen at 600 nm. NADH oxidase activity was measured by adding cell extract to a mixture containing NADH. Conversion to nicotinamide adenine dinucleotide was calculated by measuring oxygen at 340 nm for 10 minutes and comparing it to a standard curve.

The CAS assay did not detect any siderophores from C. maltaromaticum, nor was there any significant heme binding activity exhibited. Also, neither heme nor myoglobin had any significant effect on growth efficiency. The addition of heme during growth did not increase NADH oxidase activity of C. maltaromaticum, which would occur if metabolism had switched to a respiration process.

Further information. Emefa A. Monu, Department of Food Safety and Processing, 100 Food Safety and Processing Building, 2605 River Dr., University of Tennessee, Knoxville, TN 37996, phone: 865-200-4293; email: emonul@utk.edu.
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Publication:Emerging Food R&D Report
Date:Dec 1, 2012
Words:353
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