Effect of high pressure processing of Atlantic mackerel (Scomber scombrus) on biochemical changes during commercial frozen storage

This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Springer and can be found at: http://www.springer.com/food+science/journal/11947This research focuses on biochemical changes related to quality losses observed in Atlantic mackerel (Scomber scombrus) muscle stored under commercial frozen storage conditions (9 months, -18 ºC) when subjected to high-hydrostatic pressure (HHP) treatments (125, 150, 175 and 200 MPa for 0 min) before freezing. After freezing, free fatty acid (FFA) formation (lipid hydrolysis assessment) showed a marked inhibition in HHP-treated fish and during frozen storage of samples treated at 175 MPa. Fluorescence ratio (FR) assessment of tertiary lipid oxidation showed a partial inhibitory effect during the 0-9-month period for samples treated at 175 and 200 MPa. After 3 months storage of samples treated at these pressure levels, one-dimensional SDS-PAGE analysis of the sarcoplasmic protein fraction revealed the disappearance of a band; while samples treated at 150 MPa showed the same effect at month 9. After gel excision, trypsin digestion, tandem mass spectrometry (MS/MS) and sequence database analysis, the band was identified as phosphoglycerate mutase 2 (28.7 kDa). On the other hand, HHP processing did not show a significant effect on trimethylamine (TMA) values, primary and secondary lipid oxidation, PUFA levels, 1-D myofibril protein pattern and the activity of acid phosphatase and cathepsins B and D. Biochemical quality indices such as FFA, TMA, and FR, and the activity of acid phosphatase and cathepsin B showed a progressive increase throughout the frozen storage of all samples