Effects of pH and heat treatments on the structure and solubility of potato proteins in different preparations

The soluble potato proteins are mainly composed of patatin and protease inh ibitors. Using DSC and both far-UV and near-UV CD spectroscopy, it was show n that potato proteins unfold between 55 and 75 degreesC. Increasing the io nic strength from 15 to 200 mM generally caused an increase in denaturation temperature. It was concluded that either the dimeric protein patatin unfo lds in its monomeric state or its monomers are loosely associated and unfol d independently. Thermal unfolding of the protease inhibitors was correlate d with a decrease in protease inhibitor activities and resulted in an ionic strength dependent loss of protein solubility. Potato proteins were solubl e at neutral and strongly acidic pH values. The tertiary structure of patat in was irreversibly altered by precipitation at pH 5. At mildly acidic pH t he overall potato protein solubility was dependent on ionic strength and th e presence of unfolded patatin.