Enzymatic Activity During Frozen Storage of Atlantic Horse Mackerel (Trachurus trachurus) Pre-treated by High-Pressure Processing

10 pages, 2 tables, 9 figuresThe assessment of enzymatic activity on Atlantic horse mackerel (Trachurus trachurus) during frozen storage was carried out in samples pre-treated by high-pressure processing (HPP) combinations of 150, 300 and 450 MPa with 0-, 2.5- and 5-min holding time (untreated samples were used as controls). The activities of four enzymes (acid phosphatase, cathepsins B and D, and lipase) in fish muscle were quantified during accelerated storage conditions (up to 3 months at −10 °C). The experimental data were fitted to second-order polynomial models to determine the effect of pressure level, holding time and frozen storage time on these enzyme activities and to identify conditions of maximum/minimal enzyme inactivation. Acid phosphatase and cathepsin (B and D) activities were significantly (p < 0.05) influenced by HPP, showing behaviours during frozen storage different from control samples. Acid phosphatase and cathepsin B activities decreased (p < 0.05) with HPP treatments, being this effect more intense for cathepsin B, particularly at 450 MPa. Regarding cathepsin D, the activity increased (p < 0.05) at intermediate pressure (300 MPa) and decreased (p < 0.05) at higher pressure (450 MPa). During frozen storage, cathepsin D enzymatic activity tended to increase over time indicating activity recovery of these enzymes. Although a predictive model for its activity was not acceptable, the increase in lipase activity during storage was the most pronounced trend observed.We thank the financial support of the Xunta de Galicia (Spain; Project 10TAL402001PR, 2010–2012) and Fundação para a Ciência e a Tecnologia (FCT, Portugal), European Union, Quadro de Referência Estratégia Nacional (QREN), Fundo Europeu de Desenvolvimento Regional (FEDER) and Programa Operacional Factores de Competetividade (COMPETE) for funding the Organic Chemistry Research Unit (QOPNA) (project PEst-C/QUI/UI0062/2013; FCOMP-01-0124-FEDER-037296). This work was supported also by Formula Grants no. 2011-31200-06041 and 2012-31200-06041 from the USDA National Institute of Food and AgriculturePeer reviewe

Estimation of quality in frozen fish by low field NMR

This chapter addresses the potential of LF 1H NMR relaxometry to estimate the quality of fish products during freezing and frozen storage. This technique has shown to be, at least for some fish species, sensitive to changes occurring at subzero temperatures and the variation in the relaxation times kept a relationship with documented effects on the morphological and biochemical alterations of fish muscle. Moreover, the dependency of the relaxometry data on the freezing time and temperature has allowed the identification of indicators suitable for the estimation of shelf life, thus contributing to the increasing range of applications of the T2 decay signals.This work has been partly financed by Spanish ANIRISK (AGL2015–68248-C1) MINECO/FEDERPeer Reviewe