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Research article2021Peer reviewedOpen access

Understanding the fermentation factors affecting the separability of fermented milk: A model system study

Priyashantha, Hasitha; Buldo, Patrizia; Berg, Thilo; Gilleladen, Christian; Ipsen, Richard


The demand for high-protein fermented milk products is globally increasing. The effect of added starter culture, cutting pH and fermentation temperature on separability, i.e., how well curd and whey separate, were evaluated in a model system aiming to resemble Greek-style yoghurt. Skim milk was fermented with three commercial starter cultures at 39 degrees C or 43 degrees C to a pH of 4.45 or 4.60. Stirred fermented gels were concentrated to produce high-protein (similar to 10%) fermented milk. The starter culture influenced the microstructure as well as the association (interactions) between exopolysaccharides (EPS) with the surface of the protein aggregates. The high association of EPS increased the viscosity and gel strength of the fermented model gels and decreased the zeta potential, the amount of whey removed as well as the protein and total solids concentration in the white mass. Increased fermentation temperature (from 39 degrees C to 43 degrees C) resulted in increased particle size and zeta potential values when EPS-producing starter cultures were applied. Cutting pH did not influence the separability of fermented stirred gels. The presence of EPS and pronounced association with protein increased the particle size, negative surface charge and structural rigidity, establishing a more stable system with reduced separability.


Greek yoghurt; EPS-producing culture; stirred gel; microstructure; fermentation

Published in

Food Structure
2021, Volume: 30, article number: 100232
Publisher: ELSEVIER

    UKÄ Subject classification

    Food Science

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