Purpose: The aim of this study was to (i) use a metabolomics approach, in tandem with bioinformatics, to assess the microbiological quality of aerobically stored beef fillets and (ii) identify microbial biomarkers that are produced and metabolized during storage.
Methods: Naturally contaminated (NC) and sterile (S) beef fillets were stored, aerobically, at 2, 8, and 15οC. At appropriate time intervals beef samples were analyzed, microbiologically, for the determination of Total Viable Counts (TVC), while the biochemical changes (metabolomics) occurring in these samples were recorded using both GC/MS and HPLC-DAD-RI.
Results: Multivariate statistical models (PLS-R, PLS-DA) were developed for each instrumental, analytical technique, as well as in fusion to (i) predict TVC and (ii) classify the samples into quality classes (fresh, semi-fresh, spoiled). For TVC prediction, the mean values for bias and accuracy factors in both cases were close to 1 and 88% of the predictions were inside the relative error zone of 20%. Lastly, good prediction during classification, with an overall, correct classification rate close to 90% was achieved for the two methods.
Qualitatively, GC/MS analysis revealed that the compounds 2-butanone, 2-pentanone, 2-octanone, 2-nonanone, diacetyl, acetoin, 3- and 2-methyl-1-butanol and esters of acetic, isobutyric, and valeric acid were increased during storage and ,consequently, they could be characterized from microbial origin. The HPLC results showed that malic, lactic, propionic, glucose, and one unknown compound with retention time 29.2 min were correlated with fresh category; while acetic, citric and isobutyric acids were correlated with semi-fresh and spoiled samples, respectively.
Significance: Taking into account the above metabolomic approach, meat inspection could be determined through rapid, analytical techniques that give acceptable results within a few hours instead of 24-48hrs, as required by the conventional ISO method.