Erschienen in:
International Journal of Food Science & Technology, 49 (2014) 5, Seite 1254-1263
Sprache:
Englisch
DOI:
10.1111/ijfs.12505
ISSN:
0950-5423;
1365-2621
Entstehung:
Anmerkungen:
Beschreibung:
SummaryExopolysaccharides (EPS) excreted by lactic acid bacteria used in the dairy environment are either liberated into the medium (free EPS) or remain attached to the cells (capsular EPS). After batch fermentation of Streptococcus thermophilus ST‐143 at pH 6.0, three EPS fractions were isolated and purified: free EPS (EPSf), capsular‐derived EPS (EPScd) and the entire total EPS (EPStotal). EPSf and EPScd were uncharged, consisted of rhamnose, galactose, glucose and N‐glucosamine in different amounts and showed a molecular mass of 2.6 × 106 Da (EPSf) and, in case of EPScd, 7.4 × 103 Da and 1.4 × 105 Da in a ratio of 9: 1. Intrinsic viscosity of the polymers was 1.14 mL mg−1 (EPSf), 0.06 mL mg−1 (EPScd) but 1.23 mL mg−1 for EPStotal. The higher functionality of the entire EPS that was also observed in shear rheology measurements indicates that the presence of small capsular‐derived EPS facilitates the entanglement of the larger polymeric carbohydrates of the EPSf fraction.