A novel preparation technique of red (sparkling) wine for protein analysis

Despite their low concentration, proteins can influence several key enological parameters such as foam stability or haze formation in (sparkling) wine. Most studies focus on white (sparkling) wine since the higher content of phenolic compounds in red wines impairs proteomic research. The aim of the study was the development of a method for the preparation of red (sparkling) wine proteins for proteomic analysis. Three methods of sample preparation were assessed on silver stained SDS-PAGE gels and with MALDI-TOF MS. Our new method was highly suitable for the preparation of proteins for the aforementioned applications. The results showed a substantial increase in signal intensity with a simultaneous decrease in background noise. The preparation protocol consists of (i) dialysis and freeze drying of the sample, (ii) removal of phenolic compounds by water-saturated phenol and (iii) protein precipitation by addition of ammonium acetate. Employment of this method followed by SDS-PAGE analysis allowed for silver stained gels with diminished background or streaking and clearly resolved protein bands. Analysis of spectra obtained from samples prepared according to the proposed protocol showed increased intensity and signal-to-noise ratio in MALDI-TOF MS. Furthermore it was demonstrated that this method can be applied to various kinds of grape products.