In taberna quando sumus: A Drunkard’s Cakewalk Through Wine Proteomics

Analysis of white and red wine trace proteomes via capture with combinatorial peptide ligand libraries (CPLL) is reported here. Most of the alcoholic beverages tested (all of Italian origin) were found to contain only traces of casein (on average from 20 to 60 mg/L, with a detectability of as low as 1 mg/L) and not any grape protein any longer, as they had been fined with bovine casein (surprisingly also red wines for which the typical fining agent is egg albumin). However, analysis of untreated white wine (Recioto, from Garganega grapes in the Veneto region) via CPLL capture indeed permitted to detect close to 100 unique gene products from the grapes, suggesting the possibility of proteotyping grand crus, i.e. those aged, high quality wines that should not be treated with fining agents. Thus the CPLL technique could become a formidable tool for traceability of beverages in particular and of foodstuff in general. For trace protein analysis, a new, most powerful CPLL methodology emerges: capture at pH=2.2 in 0.1 % trifluoroacetic acid (TFA) under the conditions mimicking reversed-phase mechanisms of adsorption.