This study evaluated four lactic streptococcal pairs which had been used routinely in cheese plants to determine (1) if strain growth interactions would produce stimulated growth and acid production; (2) final percent strain ratios and generation times after 1/1 initial inocula volumes and (3) whether final strain ratios could be controlled through adjustment of initial inocula volumes. Strains were propagated in fortified and unmodified whey substrate under pH control at 27C for 12 hours. Cell number and acid activity were evaluated on single and paired strains. Phage typing was used to determine generation times and the percent of each strain in a pair.
Cell number increase was found in two of the four pairs grown in the unmodified whey substrate but in only one of the four pairs grown in the fortified medium. Acid production increase was observed in one pair when grown in the unmodified whey substrate, and in one other pair when grown in the fortified medium. Final strain percent ratios of the two of the four pairs (with initial inocula of a 1/1, v/v, ratio), demonstrated unbalanced growth, with one strain accounting for 76 to 92% of the final flora. Generation times of the dominant strain varied significantly with incocula ratios. Increasing the inocula volume ratio of the dominated strain of one pair from 1/1 to 19/1 dropped the final percent of the dominant strain from an average value of 83 to 66%. The dominant organism of this pair increased its doubling time when the inocula ratio was varied from 3/1 to 19/1 (dominated/dominant).
| Identifer | oai:union.ndltd.org:UTAHS/oai:digitalcommons.usu.edu:etd-6300 |
| Date | 01 May 1982 |
| Creators | Hansen, Carol Lee |
| Publisher | DigitalCommons@USU |
| Source Sets | Utah State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | All Graduate Theses and Dissertations |
| Rights | Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact Andrew Wesolek (andrew.wesolek@usu.edu). |
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