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Survival of Lactobacillus reuteri RC-14 and Lactobacillus rhamnosus GR-1 in milk

Authors

  • Sharareh Hekmat,

    Corresponding author
    1.  Department of Human Ecology, Brescia University College, The University of Western Ontario, London, ON, Canada N6G 1H2
    2.  Canadian Research and Development Centre for Probiotics, Lawson Health Research Institute, London, ON, Canada N6A 4V2
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  • Gregor Reid

    1.  Canadian Research and Development Centre for Probiotics, Lawson Health Research Institute, London, ON, Canada N6A 4V2
    2.  Departments of Microbiology and Immunology, and Surgery, The University of Western Ontario, London, ON, Canada N6G 1H2
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*Fax: +(519) 679 6489;
e-mail: hekmat@uwo.ca

Summary

Dairy products are suitable vehicles for delivering beneficial microorganisms to consumers. Both Lactobacillus reuteri RC-14 and Lactobacillus rhamnosus GR-1 are considered as probiotic agents with therapeutic properties. The objective of this study was to monitor growth and survival of these bacteria in milk during storage period. Four formulations of milk (1% fat) with 0.33% yeast extract (Y), 0.4% inulin (I), 0.33% yeast extract and 0.4% inulin (YI) and one with no additives (N) were prepared. The mixtures were autoclaved for 15 min, cooled to 37 °C and inoculated with 1% of starter culture. They were then incubated anaerobically at 37 °C overnight. Viable numbers of L. reuteri RC-14 and L. rhamnosus GR-1 were determined after 1, 7, 14, 21 and 28 days of storage at 4 °C. Both bacteria were able to grow and survive in all samples; however, they showed a higher survival rate (P < 0.05) in YI treatment. After 1 day of storage, the total colony counts of treatment YI for L. reuteri RC-14 and L. rhamnosus GR-1 were 2 × 108 and 1 × 109 CFU mL−1, respectively. The total colony counts for treatment YI decreased by 1 log cycle for both bacteria after 28 days of storage. The results of this study indicate that these bacteria can remain viable over the storage period, and there is potential for incorporating them into fermented dairy products.

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