Drs. G.A. van Koningsveld : Properties of potato proteins

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27 Jun 2001 16:00
Unit: Wageningen University
Promotor: prof.dr.ir. A.G.J. Voragen (Food Chemistry)
Co Promotor: dr.ir. M.A.J.S. van Boekel (productontwerpen en kwaliteitskunde) & dr.ir. H. Gruppen (levensmiddelenchemie)

 Potato proteins were isolated from potato fruit juice (PFJ) by different precipitation methods. The best results with respect to precipitation (91 %) and resolubility (91 %) were obtained using organic solvents. The monomers of dimeric patatin were shown to unfold independently at 60°C. Thermal unfolding of protease inhibitors, between 60°C and 70°C, resulted in a decrease in inhibitor activities and protein solubility. Potato protein solubility was highest at neutral and strongly acidic pH, while at mildly acidic pH it was dependent on ionic strength and the presence of unfolded patatin. The presence of ethanol significantly reduced the unfolding temperature of potato proteins. The different mechanisms by which phenolic compounds may affect potato protein solubility are discussed. The foam forming properties of patatin could be strongly improved by partial unfolding of the protein. Whipping tests indicated that foams made with an ethanol precipitated protein isolate (PPI) were more stable than those made with ?-casein and ?-lactoglobulin. The average droplet size of emulsions made with potato proteins was found to be presumably determined by the release, due to the lipolytic activity of patatin, of surface active components from the oil phase during
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