Journal of Dairy Research

Interactions between EPS-producing Streptococcus thermophilus strains in mixed yoghurt cultures

Ditte M Folkenberg a1a2c1, Petr Dejmek a3, Anne Skriver a2 and Richard Ipsen a1
a1 Dairy Technology, Agricultural University of Denmark, Rolighedsvej 30, 1958 Frederiksberg C, Denmark
a2 Chr. Hansen A/S, Bøge Allé 10-12, 2970 Hørsholm, Denmark
a3 Food Engineering, University of Lund, Box 124, 22100 Lund, Sweden

Article author query
folkenberg dm   [PubMed][Google Scholar] 
dejmek p   [PubMed][Google Scholar] 
skriver a   [PubMed][Google Scholar] 
ipsen r   [PubMed][Google Scholar] 


Mixed cultures of different EPS-producing Streptococcus thermophilus strains in combination with a Lactobacillus delbrueckii subsp. bulgaricus strain with negligible EPS-production were used for yoghurt production. The yoghurt texture was characterised with respect to sensory, rheological and microstructural properties and the EPS-concentrations were determined. The cultures resulted in yoghurts with highly different texture properties, and positive interactions between certain Streptococcus thermophilus strains were observed. The underlying properties of yoghurt texture are multidimensional, but a number of microstructural characteristics were apparent in the yoghurts with the highest mouth thickness, creaminess and viscosity. A strong protein network, not too dense and with medium size pores containing EPS, seems associated with these properties. The presence of capsular polysaccharides (CPS) also appeared to be beneficial as did a combination of EPS types, which were distributed differently in the protein network (in serum pores, respectively in association with protein). Obviously, a certain concentration of EPS must be present to provide for these effects on yoghurt texture, but other factors than concentration per se seem more important.

(Received July 6 2005)
(Accepted January 29 2006)

Key Words: exopolysaccharides; yoghurt texture; sensory profile; ropiness; confocal laser scanning microscopy; microstructure.

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