Sardine alterations during chilled storage (0ЊC) were investigated by measuring the fluorescence ratio between two excitation/emission maxima (393/463 nm, 327/415 nm) and compared with common quality indices. Sardines were also maintained at 15ЊC to accelerate all reactions occurring at 0ЊC. Other quality indices (total volatile base-nitrogen, free fatty acids, formation of conjugated dienes, and thiobarbituric acid values) were determined and the use of the fluorescence ratio (fluorescence shift, ␦F) was analyzed. A high correlation was found between the ␦F and the total volatile base-nitrogen (r ϭ 0.93, at 0ЊC; r ϭ 0.92, at 15ЊC).

Rancidity development during frozen storage of mackerel (Scomber scombrus): effect of catching season and commercial presentationHydrolytic and oxidative rancidity development and its effect on quality loss were studied in frozen mackerel (Scomber scombrus) by biochemical and sensory indices. The effect of the lipid content on fish damage at a commercial freezer temperature (220 7C) was studied for up to 12 months; thus, mackerel caught at two different times of the year (May and November) was checked, May being the period of minimum lipid content, while November is known to be the time of maximum lipid content. The study was also focused on two different kinds of fish products (whole fish and fillets). Increasing lipid hydrolysis was observed for all kinds of samples during the frozen storage; no differences (p .0.05) between whole fish and fillets were found for free fatty acid formation; however, mackerel from May showed a higher (p ,0.05) hydrolysis development than its counterpart from November. Increasing lipid oxidation (peroxide value and thiobarbituric acid index) was observed for all kinds of samples during the frozen storage. Fillet lipid oxidation was found to be higher (p ,0.05) than in whole fish. Fattier mackerel (November fish) showed a higher (p ,0.05) oxidation development than its counterpart from May in the case of fillet products. Results of fluorescence assessment, related to interaction compound formation, proved to be higher (p ,0.05) in fillets than in whole fish, although they were higher (p ,0.05) in May samples. Sensory analysis corroborated the biochemical analyses, so that fillets showed a shorter shelf life (1 and 3 months for November and May fish, respectively) than their whole fish counterparts (5 months for November and May mackerel).

Malonyldialdehyde (malondialdehyde, MDA) is one of the most significant of the wide range of metabolic or deteriorative products of lipid damage. Its formation during food processing and storage is widely used in quality control. Its ability to react with -NH2 groups is also of great carcinogenic or mutagenic interest because of its possible interaction with important constituents (e.g. free amino acids, proteins, nucleic acids, and amino phospholipids) of foods during and after processing. Special attention has been given to the role played by MDA in the formation of the age pigments, commonly named as 'lipofuscin'.The present review compiles the general characteristics that have made MDA the most widely studied lipid metabolite, and the progress achieved in knowledge of MDA reactivity with biological molecules. The special stress given to the structural elucidation of the structures of these products have led to a new perspective about the role played by MDA.

Slurry ice is a biphasic system consisting of small spherical ice crystals surrounded by seawater at subzero temperature. Its employment was evaluated in the present work as a new chilled storage method for whole European hake (Merluccius merluccius) and compared to traditional flake icing. Different chemical analyses (nucleotide degradation, formaldehyde formation, lipid hydrolysis and oxidation, interaction compounds formation and electrophoretic protein profiles) related to quality changes were analysed and compared to sensory evaluation. An inhibitory effect on quality loss mechanisms was observed for the slurry ice treatment, according to nucleotide degradation (K value), free formaldehyde content, browning development and sarcoplasmic protein profiles. No differences in lipid hydrolysis and oxidation could be outlined by comparison between both icing conditions. The sensory analysis showed a higher shelf-life time for slurry icing than flake icing (12 days and 5 days, respectively). Results confirm the practical advantages of using slurry ice as a chilling storage method.

Lipid and trace mineral composition were studied in different sites of the edible flesh of farmed and wild turbot (Psetta maxima). Lipid matter (total content, sterols, tocopherols) showed to accumulate in the edge zone, except for phospholipids (PL) that provided a distribution that was found to be independent from the kind of turbot and the zone considered. Fatty acid composition of total lipids showed a non-homogeneous distribution, since the edge zone exhibited a different fatty acid group composition (higher monounsaturated and lower polyunsaturated and ω3/ω6 ratio values) than the other zones considered; less differences were observed by considering the PL fatty acid composition.Most minerals (Ca, Cu, Fe, Mn and Se) studied showed to be homogeneously distributed along the muscle sites of the wild fish, while more differences were obtained when considering the farmed one. For both kinds of turbots, the most important difference was obtained in the case of Zn, since a largely higher content in the edge zone than in the other zones was detected. A close relationship between Zn and total lipid contents (r 2 =0.90 and r 2 =0.76 for farmed and wild turbots, respectively) was observed.