Antimicrobial activity and meat colour stabilizing properties of Carnobacterium maltaromaticum

  • Author / Creator
    Monu, Emefa A
  • Listeria monocytogenes is a foodborne pathogen of concern in meat products. Also, many fresh meat products packaged for retail sale with oxygen permeable films are prone to browning, leading to a decrease in sales. The first objective of this study was to investigate the inhibitory effect of C. maltaromaticum UAL307 against L. monocytogenes in fresh beef sausage with and without the supernatant extract of Enterococcus faecalis 710C or C. maltaromaticum UAL307. C. maltaromaticum significantly reduced counts of Listeria spp. in aerobic and modified atmosphere packaged products. The addition of cultures had no effect on pH or colour in sausages stored in a modified atmosphere; sausages stored aerobically with C. maltaromaticum UAL307 maintained a red colour during 10 d of storage. The mechanism behind this colour stabilization was investigated, particularly the effect of C. maltaromaticum on the state of myoglobin. Fe3+ exists in brown metmyoglobin and Fe2+ in red oxymyoglobin and purple deoxymyoglobin. C. maltaromaticum UAL307 and several other lactic acid bacteria were added to mMRS containing 0.3% myoglobin stored under aerobic and anaerobic conditions. Under aerobic conditions, only C. maltaromaticum promoted oxymyoglobin formation for a sustained length of time, which increased when samples were stored at 4°C. Under anaerobic conditions, metmyoglobin was converted to deoxymyoglobin by several organisms, but only C. maltaromaticum maintained the deoxymyoglobin at almost 100% for over 48 h. To evaluate iron reduction, cultures were inoculated into a medium containing Fe3+, and Fe2+ levels were determined using a modified ferrozine assay. C. maltaromaticum UAL307 was the only organism to significantly convert Fe3+ to Fe2+. The investigation of iron binding capacity did not detect the production of any siderophores. The effect of heme on C. maltaromaticum was investigated, as the metabolic activity of some lactic acid bacteria can change from fermentation to respiration in the presence of heme. The heme-binding ability of C. maltaromaticum was investigated, as well as the effect of both heme and myoglobin on growth efficiency, NADH oxidase and LDH activity and its ability to produce cytochrome oxidases through expression of cytochrome bd genes. Heme and myoglobin had no effect on any of these properties.

  • Subjects / Keywords
  • Graduation date
    Spring 2012
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.