New anti-fraud method: the proteomic technique applied to the identification of luxury animal fibers

Leading companies in the textile sector need objective and precise analytical methodologies able to univocally identify and quantify animal hair fibers present in textile articles, to guarantee that no falsification occurs, especially when cheaper fibers, like wool and yak, are blended with expensive fibers, like cashmere. Traditionally, the methods used for fibers identification are: light microscopy, that gives information on the internal and external structure of the fibers, reveals details of the shape, cuticle morphology, internal pigmentation and medullation; and scanning electron microscopy (SEM) that shows the fine structure of the cuticle cells at high resolution. Anyway, these methodologies are subjective, depending on the expertise of the operator, and often are affected by chemical treatments to which the fibers have been submitted during textile processing. Several methods have been developed in the past to remedy these problems, with poor results. CNR-ISMAC of Biella in collaboration with the Department of Food and Drug of the University of Parma developed a new method for qualitative and quantitative analysis of animal hair fibers. The method based on electrospray (ESI) mass spectrometry (MS) combined with liquid chromatography (LC) follows a proteomic approach to assess molecular markers for species identification [1-3]. In particular, the method focuses on the identification and quantification of wool, cashmere and yak fibers. Keratin from sheep, cashmere goat and yak are similar but not identical, because in some specific parts there are amino acidic variants resulting in specific peptide-markers which can be used to distinguish each animal fiber. The procedure includes an enzymatic digestion of the keratin after the protein extraction in order to obtain similar but not identical homologous peptides, which can be discriminated by LC/ESI-MS analysis. These markers have been successfully used not only for qualitative analysis of wool, cashmere and yak blends, but also for quantitative ones, with a limit of detection of 3%. Recently, this proteomic method has become international standard: "ISO 20418-1 Textiles - Qualitative and quantitative proteomic analysis of some animal hair fibres Part 1: Peptide detection using LC-ESI-MS with protein reduction". The standard method will be also adopted by CEN (European Committee for Standardization) and UNI (Ente Nazionale Italiano di Unificazione) soon. In the meantime, ISMAC Biella is continuing its research to verify the applicability of the proteomic method also to the South American camelids (lama, alpaca, vicuna and guanaco) and camel hairs, so that in the future it will be possible to extend the standard to these fibers as well.