JDS
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Journal of Dairy Science Vol. 73 No. 12 3357-3365
© 1990 by American Dairy Science Association ®
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Wenzel, J. M.
Right arrow Articles by Marth, E. H.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Wenzel, J. M.
Right arrow Articles by Marth, E. H.

Changes in Populations of Listeria monocytogenes in a Medium with Internal pH Control Containing Streptococcus cremoris

Jane M. Wenzel 1 and Elmer H. Marth 1

1 Department of Food Science and The Food Research Institute, University of Wisconsin-Madison, Madison 53706

Behavior of Listeria monocytogenes in a commercial starter culture medium with internal pH control was examined. The IPCM-1 medium was inoculated with L. Monocytogenes (strain V7, Scott A, or California) at ca. 103 cfu/ml and Streptococcus cremoris (.25%, 1.6 x 105 or 1.0%, 8.6 x 105 cfu/ml) and was incubated at 21 or 30°C for 30 h. The pH of the uninoculated medium and control (L. monocytogenes only) was between 6.8 and 7.0 before and after incubation. The area on a figure between control and treatment curves for numbers of L. monocytogenes was calculated, designated as area of inhibition, and used to quantitate inhibition of L. monocytogenes caused by S. cremoris. No significant difference was found in area of inhibition or pH values at 6, 24, and 30 h of incubation among the three strains of L. monocytogenes for a given set of conditions (percentage of S. cremoris added and temperature). Inhibition of the pathogen increase with an increase in amount of S. cremoris inoculum used and with higher rather than lower incubation temperature. Populations of L. monocytogenes in IPCM-1 medium without S. cremoris after 30 h of incubation were 106 to 107/ml at 21°C and 108/ml at 30°C. At 21°C inhibition of Listeria began after 18 and 24 h and at 30°C after 12 and 15 h of incubation in samples inoculated with 1.0 and .25% S. cremoris, respectively. In all trials with L. monocytogenes plus S. cremoris, populations of the pathogen increased to 104 to 105/ml before the start of inhibition; the pH of the medium at that time was approximately 5.5 (the value at which it is claimed to be ready for use). Complete inhibition of L. monocytogenes in IPCM-1 medium by S. cremoris was not seen when this pH was reached.

Key Words: Listeria monocytogenes • Streptococcus cremoris • starter culture medium

Submitted on April 16, 1990
Accepted on July 30, 1990






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1990 by the American Dairy Science Association ®.