Kohonen Artificial Neural Network and Multivariate Analysis in the Identification of Proteome Changes during Early and Long Aging of Bovine <i>Longissimus dorsi</i> Muscle Using SWATH Mass Spectrometry

To study proteomic
changes involved in tenderization of Longissimus dorsi, Charolais heifers and bulls muscles were
sampled after early and long aging (12 or 26 days). Sensory evaluation
and instrumental tenderness measurement were performed. Proteins were
analyzed by gel-free proteomics. By pattern recognition (principal
component analysis and Kohonen’s self-organizing maps) and
classification (partial least squares-discriminant analysis) tools,
58 and 86 dysregulated proteins were detected after 12 and 26 days
of aging, respectively. Tenderness was positively correlated mainly
with metabolic enzymes (PYGM, PGAM2, TPI1, PGK1, and PFKM) and negatively
with keratins. Downregulation in hemoglobin subunits and carbonic
anhydrase 3 levels was relevant after 12 days of aging, while mimecan
and collagen chains levels were reduced after 26 days of aging. Bioinformatics
indicated that aging involves a prevalence of metabolic pathways after
late and long periods. These findings provide a deeper understanding
of changes involved in aging of beef and indicate a powerful method
for future proteomics studies.