Further development of a method for visualisation of exopolysaccharides in yoghurt using fluorescent conjugates

Exopolysaccharides (EPS) play a central role in creating yoghurt with high sensory appeal. To understand more precisely how EPS affect the microstructure of yoghurt, it is crucial to be able to visualise how EPS is distributed in the protein gel. Hence, the present study used confocal laser scanning microscopy combined with multiple fluorescent lectin conjugates in a single sample to further develop a methodology for visualising different types of EPS in acidified milk. Use of phosphate-buffered saline supplemented with CaCl2 and MgCl2 in the working solution of lectin conjugates minimised the influence of pH on their binding affinity to EPS in yoghurt. EPS could be visualised simultaneously by using lectin conjugates of concanavalin A and wheat germ agglutinin together. The method was verified using yoghurt samples made with commercial starter culture and can aid in the choice of starter cultures and processing parameters for yoghurt production.