Blind samples investigated and general experimental and analytical approach. (A) shows the subdivision of the blind samples and their investigation in a stepwise approach within a refining strategy validated through a final subset of 13 blind samples. Analyses were performed by MALDI MS with some selected samples submitted to MALDI MS/MS and/or LC MS/MS for protein identification/identity confirmation. (B) shows the five levels of identification theoretically permitted by the data. Of these levels, this study pursued the first three (continuous line) and generated some knowledge towards levels 4 and 5 (dotted line).