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Production of low browning Mozzarella cheese: Screening and characterization of wild galactose fermenting Streptococcus thermophilus strains

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Author(s): Anbukkarasi K | UmaMaheswari T | Hemalatha T | Dhiraj Kumar Nanda | Prashant Singh | Rashmi HM | Rameshwar Singh

Journal: International Journal of Advanced Research
ISSN 2320-5407

Volume: 1;
Issue: 5;
Start page: 83;
Date: 2013;
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Keywords: Galactose fermenting S. thermophilus | galactose stability | 16S rDNA sequencing | low browning Mozzarella cheese

ABSTRACT
Streptococcus thermophilus is a thermophilic lactic acid bacterium used for the manufacture of yoghurt and cheese. Most strains of S. thermophilus were galactose negative (Gal-) due to the weak induction of gal operon. Galactose positive (Gal+) strains can be exploited in reducing problems like browning of Mozzarella cheese. In this study, six galactose positive lactic Streptococcus spp. submitted to National Collection of Dairy Cultures (NCDC) were screened for galactose fermentation and characterized. Out of six isolates, four isolates namely NCDC 659, NCDC 660, NCDC 527, NCDC 661, were confirmed as S. thermophilus by phenetic and molecular methods. Galactose fermentation of these isolates in J8 broth containing 1% galactose revealed that NCDC 659 utilized 0.44% of galactose, followed by NCDC 661 (0.36%), and NCDC 660 (0.29%). In milk fermentation, NCDC 659 released less galactose (0.24%), followed by NCDC 661 (0.34%) and NCDC 660 (0.39%) after 8 h. Gal+ isolates exhibited enhanced stability in galactose broth than in milk after ten sub-cultures. During Mozzarella cheese preparation with Gal+ S. thermophilus strains and Gal+ Lactobacillus helveticus (NCDC 292), Gal+ S. thermophilus NCDC 659 expelled less galactose (0.15%) followed by NCDC 661 (0.3%) and NCDC 660 (0.33%), compared to the reference strain. Also, browning was less in Gal+ NCDC 659 and showed a hunterlab (L*) value (76.09±0.37) than control Gal- NCDC 218 (66.68±0.4). This study revealed that Gal+ S. thermophilus strains possessed more stability and it can be paired with Gal+ L. heveticus NCDC 292 for developing low browning Mozzarella.
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