Pection in Stirred Yoghurt: Theory and Praxis

Studenteropgave: Speciale (inkl. HD afgangsprojekt)

  • Christian Fiil Nielsen
4. semester, Kemi, Kandidat (Scient) (Kandidatuddannelse)
The present project has focussed on the application of low methylated (LM) pectin as stabiliser in the production of stirred yoghurt. The production process of stirred yoghurt is described and combined with a review of recent literature on the subject of yoghurt stabilisation by pectin, this is used as the basis for a description of the interactions during fermentation and the stabilisation mechanism of LM pectin in stirred yoghurt. The quality parameters of stirred yoghurt are described with the purpose of identifying the functional concentration range of LM pectin, and the limiting mechanisms. These mechanisms are used as the background for selecting and testing experimental methods for their applicability in determining the functional range of pectin and the effect of milk properties on the functional range of pectin. The upper limit is due to depletion flocculation and is determined by analytical centrifugation. Determining the lower limit of the functional range of pectin requires a deeper understanding of the interactions between milk and pectin during acidification. To determine these, a line of experiments combining rheology and electrophoretic mobility have been carried out. These show that pectin adsorbs to the casein network after gelation without affecting the gelation process, and that the gelation depends strongly on heat treatment of the milk. Using this knowledge a method using electrophoretic mobility to determine the minimum in the functional range have been suggested. Dielectric spectroscopy has been tested as a tool of monitoring yoghurt fermentation including particle-particle interaction and adsorption of pectin. This has helped identify the challenges and potential of this method. Intrinsic viscosity as a tool of predicting depletion flocculation has also been evaluated, showing some weaknesses of the application.
SprogEngelsk
Udgivelsesdato2009
Antal sider100
Udgivende institutionAalborg University, Department of Biotechnology, Chemistry and Environmental Engineering

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