Modiﬁcations of the 1 H NMR metabolite proﬁle of processed mullet (Mugil cephalus) roes under different storage conditions Paola Scano, a * Antonella Rosa, b Emanuela Locci, a Giorgia Manzo a and M. Assunta Dessì b 1 H NMR spectroscopy was employed to study the modiﬁcations over time of the water-soluble low molecular weight metabolites extracted from samples of salted and dried mullet (Mugil cephalus) roes (mullet bottarga) stored at different conditions. Samples of grated mullet bottarga were stored for 7 months at 20  C, at 3  C, and at room temperature in the presence and in the absence of light and then timely extracted and analyzed by NMR. Principal component multivariate data analysis applied to the spectral data indicated that samples stored at 20  C maintained similar features over time whereas, along PC1, samples stored at room temperature in the presence and in the absence of light showed, over time, marked metabolite modiﬁcations. The comparative analysis of the integrated areas of the selected regions of the 1 H NMR spectra indicated that the major compositional changes due to storage conditions were (i) the increase of the derivatives of the breakdown of phosphatidylcholine (choline, phosphorylcholine, and glycerol), (ii) the breakdown of nucleosides, (iii) the decrease of methionine, tryptophan, and tyrosine, and (iv) the cyclization of creatine. These changes were observed at different storage conditions, with more pronounced trends in the samples stored at room temperature. The role of metabolites in food aging is discussed. Copyright © 2012 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this article. Keywords: NMR; 1 H; food; metabolites; storage Introduction The salted and dried mullet (Mugil cephalus) roe product, manufactured in Italy under the name of bottarga, is gaining considerable interest in the international food market as a delicacy for appetizers or as a pasta seasoning. Mullet bottarga is highly appreciated for its organoleptic qualities: it has an amber color, it is ﬁrm and compact to the touch, and it has an intense, slightly bitter ﬂavor. Bottarga is sold as a whole ovary in baffe with the intact membranes, sealed under vacuum, or grated in glass jars or plastic bags. Although salting and drying are effective strategies for food preservation, known since ancient times, they cannot avoid the deterioration of food matrices. Therefore, a deeper knowledge of the chemical modiﬁcations that bottarga undergoes during shelf life could certainly improve production techniques and protocols for packaging and storage. In the study of the stability of ﬁsh products, many researches have been devoted to the study of the lipid fraction for its elevate content of health beneﬁcial n-3 fatty acids, which are highly susceptible to oxidation, having up to six double bonds. [1] In addi- tion to hydrolysis and oxidation of lipids, other important changes regarding different molecular components can take place during processing and during shelf life; these changes can affect not only the nutritional qualities but also the ﬂavor and the rheological characteristics of ﬁsh derivatives. In fact, bottarga during storage tends to assume a darker color, [2] combined with changes in texture and ﬂavor (empirical data), and these phenomena represent a big issue for producers and sellers of this product. The browning phenomenon of dried mullet roes was attributed to a series of reactions between amines, amino acids, peptides, and proteins with reducing sugars and oxidized lipids (Maillard reaction and lipid–protein interactions). [3] A very interesting molecular pool that can reﬂect modiﬁcations of the original matrix of this product is that composed by the water-soluble low molecular weight metabolites. This pool comprises free amino acids, organic acids, nucleotides and derivatives, sugars, volatile amines, and others. These are intermediates of metabolic pathways, products of oxidation and breakage of macromolecules such as triacylglycerols, phospholipids, nucleic acids, proteins, and polysaccharides. It is worth remembering that some of these metabolites are also involved in the deﬁnition of the ﬂavor, color, and smell of food. [4,5] Recent studies demonstrated that the aqueous extract of different food matrices, studied by 1 H NMR spectroscopy, can give precious information on the metabolic changes over time due to packaging in cheese, and ripening and microbial spoilage of fruits. [6–8] Furthermore, the aqueous extracts of mullet * Correspondence to: Paola Scano, Dipartimento di Scienze Chimiche, Università di Cagliari, Cittadella Universitaria di Monserrato, SS 554 Bivio per Sestu, 09042 Cagliari, Italy. E-mail: scano@unica.it a Dipartimento di Scienze Chimiche, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, SS 554 Bivio per Sestu, 09042 Cagliari, Italy b Dipartimento di Biologia Sperimentale, Sezione di Patologia Sperimentale, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, SS 554 Bivio per Sestu, 09042 Cagliari, Italy Magn. Reson. Chem. (2012) Copyright © 2012 John Wiley & Sons, Ltd. Research Article Received: 29 November 2011 Revised: 18 February 2012 Accepted: 23 March 2012 Published online in Wiley Online Library (wileyonlinelibrary.com) DOI 10.1002/mrc.3819 1