Abstract
In electrospray ionization (ESI) mode, peptides and proteins can be multiply charged ions; in this situation a doubly charged selected ion (DCSI) coupled with mass spectrometry (MS/MS) fragments monitoring (DCSI-MS/MS) method is the most suitable scanning mode to detect known peptides in complex samples when an ion-trap mass spectrometer is the instrument used for the analysis. In this mode, the MS detector is programmed to only select a doubly charged ion as a precursor and to perform continuous MS/MS on one or more of the selected precursors, either during a specific time interval or along the whole chromatographic run. Gelatin is a mixture of high molecular weight polypeptides from the hydrolysis of collagen. In this study, the DCSI-MS/MS monitoring mode was applied to the detection of previously characterized species-specific peptides from different gelatins. The proposed methodology makes use of tryptic digestion for sample preparation and peptide separation and identification by rapid resolution liquid chromatography coupled to an ion trap working in the DCSI-MS/MS mode for the analysis. This methodology was applied to the differential classification of five commercial, homological species of gelatins and proved to be an excellent tool for gelatin product authentication.
Highlights
The assessment of gelatin authentication and origin is of major concern for standards authorities, to assist in the prevention of commercial fraud in the food, cosmetic, and pharmaceutical industries [1, 2], and to help avoid the safety risks derived from diseases among livestock that might be harmful for human health
Polymerase chain reaction (PCR) method has been used in DNA analysis but again is not available for gelatin identification because of the heavy destruction of DNA in gelatin during processing, this method has been widely applied in collagen identification [3, 4]
As a result of the problems with the methods that we have outlined, proteomics methods have been proposed as alternative tools for the assessment of the authenticity and traceability of collagen species in gelatins [6], and mass spectrometry has been successfully applied to elucidate differences among homological gelatins [7]. In line with these results, we developed an analytical method based on proteomics to distinguish these gelatins effectively
Summary
The assessment of gelatin authentication and origin is of major concern for standards authorities, to assist in the prevention of commercial fraud in the food, cosmetic, and pharmaceutical industries [1, 2], and to help avoid the safety risks derived from diseases among livestock that might be harmful for human health. The correct identification of gelatin species becomes an issue of primary relevance for these industries. The characterization of external morphological features is a difficult method for gelatin species differentiation because of their apparent similarities and to the fact that they are frequently lost during the manufacturing process. Molecular method for gelatin species identification based on DNA or protein analysis is tedious and time consuming. Polymerase chain reaction (PCR) method has been used in DNA analysis but again is not available for gelatin identification because of the heavy destruction of DNA in gelatin during processing, this method has been widely applied in collagen identification [3, 4]. The immunochemical method has been used to identify collagen [5], but again the usefulness of this method might be influenced by the extent of the proline hydroxylation which plays an important role in determining
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