A.J. Borderías

Oyster Preservation by High-Pressure Treatment

The purpose of this study was to analyze the effect of 10-min continuous pressure and pulsed pressure in two 5-min steps (400 MPa at 7 degrees C) on the microbial flora, total volatile bases, pH, and texture of purified and unpurified oysters. High-pressure treatment reduced the number of all the target microorganisms (total viable count, H2S-producing microorganisms, lactic acid bacteria, Brochothrix thermosphacta, and coliforms), in some cases by around 5-log units. The difference between the counts in the control and the pressurized oysters remained stable throughout 41 days of storage at 2 degrees C. No Salmonella spp. were detected in either the control batch or the pressurized batches during this storage period. Deterioration of the oyster was accompanied by increased total volatile bases, mainly in the nonpressurized samples. The pH was practically constant in the pressurized oysters and fell slightly in unpressurized samples. As for mechanical properties, shear strength values were higher in pressurized than in unpressurized oysters. Step-pulse pressurizing (400 MPa at 7 degrees C in two 5-min pulses) produced no apparent advantages over continuous pressurizing based on any of the indices used.

Functional characterisation of muscle and skin collagenous material from hake (Merluccius merluccius L.)

Abstract The purpose of this paper was to examine the modifications occurring in certain functional hydration properties (protein solubility in 0.5 M acetic acid, apparent viscosity and water-binding capacity) of the collagenous material from skin and muscle of hake ( Merluccius merluccius L.) in relation to the pH and the ionic strength (expressed as variation in NaCl concentration) of the medium. At the same time, these modifications were compared with those reported for collagenous material from trout in a previous paper. Generally speaking, skin collagenous material showed higher functionality than muscle collagenous material. It was found that protein solubility, apparent viscosity and water-binding capacity presented maximum values at pH levels between 2 and 4, and at concentrations of less than 0.25 M NaCl. Finally, the functional values were found to be higher in collagenous material from hake than from trout, especially in the skin material. ©

First Processing Steps and the Quality of Wild and Farmed Fish

First processing steps of fish are species-dependent and have common practices for wild and for farmed fish. Fish farming does, however, have certain advantages over traditional fisheries in that the processor can influence postmortem biochemistry and various quality parameters. This review summarizes information about the primary processing of fish based on the influence of catching, slaughtering, bleeding, gutting, washing, and filleting. Recommendations are given for the correct primary processing of fish.

Emulsifying properties of an ultrafiltered protein from minced fish wash water

Centrifugation and ultrafiltration were used to concentrate soluble proteins in the water used to wash minced muscle of sardine caught at two different times of year. The proteins thus extracted were largely of less than 67 kDa molecular weight. Part of the resulting concentrate was frozen-stored and part freeze-dried. Irrespective of the season of capture, samples exhibited high emulsifying capacity and emulsion stability, values being higher in freeze-dried samples. Both properties were virtually unaffected by solutions, with NaCl concentrations ranging from 0 to 3%.

Frozen storage behaviour of squid (Loligo vulgaris)

Abstract Samples of squid were subjected to five different methods of preparation and were then kept at −20°C for 408 days. The texture, as measured by sensory, instrumental and chemical methods, was maintained for all samples and no rancid flavour or odour was found. No melanosis was detected, but if thawed material was held at a chill temperature for three days melanosis then appeared in all batches which were not skinned.

Changes in hake muscle collagen during frozen storage due to seasonal effects

Abstract The present study deals with alterations occurring in hake muscle collagen during frozen storage as a result of processing and seasonal influences. Salt and acid solubility and component distribution of collagen were measured to check the aggregation. The results indicate that aggregation is dependent on storage conditions but not on seasonal variations. Correlations between dimethylamine content and insoluble collagen fraction indicate that formaldehyde might be one of the causes of aggregation.

Frozen storage of dressed and pre-fried portions of minced sardine muscle.

ZusammenfassungDie Veränderung von zugerichteten und vorgebratenen Portionen aus zerkleinertem Fleisch von Sardinen (Sardina pilchardus) während der Tiefkühllagerung wurde untersucht. Die Einwirkung unterschiedlicher Vorbratzeiten, der Einfluß der Vakuumverpackung sowie von Antioxydationsmitteln sollte geprüft werden. Es zeigte sich, daß Tocopherole nicht die erwarteten Wirkungen hatten, sondern daß der während der Lagerung erreichte Ranzigkeitsgrad nur geringfügig verringert wurde, während die Konsistenz im Vergleich zur Kontrollprobe gleich blieb. Obwohl der gewaschene Muskel minimale Ranzigkeitswerte aufwies, ergaben die Geschmackproben die niedrigste Punktzahl für Akzeptanz. Im Gegensatz dazu wiesen die vakuumverpackten Proben weniger Härte und Ranzigkeit auf und wurden als annehmbarer betrachtet, weshalb dieses letztere Verfahren für die Tiefkühllagerung von vorgebratenen Sardinenportionen geeigneter erscheint.AbstractThe aim of this work was to study the modifications occurring during frozen storage (−18° C) of dressed and pre-fried portions of minced muscle of the sardine (Sardina pilchardus). Various samples were prepared in order to discover the effect on the samples of different preparatory frying times, the influence of vacuum-packing and the possible alterations in the state of preservation of the portions due to the presence of anti-oxidant agents. The results indicate that the presence of tocopherols did not have the expected effect on rancidity; it reduced the degree of rancidity reached during storage only slightly, while texture with respect to the control sample remained the same. Although the washed-muscle sample presented minimum rancidity values, the tasting panel awarded it the lowest score for acceptability. In contrast, the vacuum-packed sample presented less toughness and rancidity and was considered more acceptable, in the light of which this latter procedure would appear to be the best suited for frozen storage of pre-fried battered sardine portions.

Effect of different storage methods on some functional properties of sardine muscle

ZusammenfassungEs werden drei unterschiedliche Methoden zur Aufbewahrung des Sardinenfleisches untersucht: 1. Aufbewahrung in Salz nach dem Fang auf dem Schiff und dann in Eis nach der Landung; 2. Aufbewahung in Eis nach dem Fanz und 3. Einlagerung im Schiff bei Raumtemperatur und in Eis nach der Landung im Hafen. Der Salzzusatz veränderte drastisch den Muskel, der seine Fähigkeit, Gel zu bilden, verlor. Die Aufbewahrung in Eis unmittelbar nach dem Fang erlaubte eine längere Aufrechterhaltung der Gel-bildenden Fähigkeit als bei der Aufbewahrung in Eis nach der Landung. Die elektrophoretische Profile der myofibrillären Proteine, die aus dem in Salz aufbewahrten Muskel extrahiert worden waren, unterschieden sich sehr von denen der Proteine des durch die zwei anderen Methoden aufbewahrten Muskel; alle Profile aber änderten sich im Laufe der Aufbewahrungszeit.SummaryThree different storage methods for sardine muscle: (1) in salt on board the fishing vessel and in ice after off-loading, (2) in ice from capture, and (3) after storage at ambient temperature in ice from off-loading, were studied. Storage in salt drastically altered the muscle, which lost its gel-forming capacity. Storage in ice from the time of capture maintained the gel-forming capacity for a longer length of time than when the fish were stored in ice only after off-loading. The electrophoretic profiles of the myofibrillar proteins extracted from the muscle stored in salt were quite distinct from those for the proteins from muscle stored using the other two methods, but all underwent changes during the study period.

Effect of selective breeding on collagen properties of Atlantic salmon (Salmo salar L.)

Collagen content and properties of skeletal muscle were studied among selected (FP) and unselected (WP) Atlantic salmon lines that were reared together to avoid any environmental effects. The FP group had significantly higher body weight at harvesting, softer texture and lower connective tissue yield compared with the WP group. The relative collagen fractions (acid, pepsin, insoluble) were similar, but the FP group had a greater abundance of amino acids involved in collagen triple helix conformation and stabilisation (Gly, Pro, Hyp and Hyl), whilst the Lys content was greater for the WP group, indicating a more aggregated collagen. The connective tissue denaturation temperature was lower for the FP group, coinciding with a lower degree of collagen self-assembly and intermolecular-crosslinks. It is concluded that selective breeding has resulted in lower connective tissue stability of Atlantic salmon fillets.

Fibre-enriched seafood

The chapter reviews addition of soluble, semi- soluble and insoluble dietary fi bre (DF) of various origins to restructured seafood products. It pays particular attention to the effect of non- soluble or partially soluble ones, since soluble DF has been more extensively studied and more frequently used for many years in the processing industry. The main purpose of this addition is technological, but its presence may have a positive effect on health. A compromise needs to be found in order to meet functional and technological requirements while offering consumers healthy, tasty and attractive seafood products.