Effect of pH on the protein profile and heat stability of an Italian white wine.

A large amount of research is currently being conducted on wine pH because of its effect on the formation of turbidity in unfined white wines. The haze-forming tendency and the protein profile of an Italian white wine (Erbaluce di Caluso D.O.C.G.), as affected by pH ranging from 3.00 to 3.60, a common pH range in wine, were analysed. The results indicated increased heat stability of the wine at lower pH, which was revealed by a lack of haze formation even above 70 °C. The pH increase was accompanied by a progressive shift in the haze formation temperature from 50–60 °C to 70–80 °C. The electrophoretic protein pattern of the wine was characterised, and proteins derived fromboth yeast and grape tissueswere identified. The statistical analysis of band intensities revealed that the solubility of five yeast and grape protein bands was modified by the pH shift. Most of the proteins involved were determined to be glycosylated, a feature that has been speculated to have an influence on the differential solubility of wine proteins in response to pH.