Javier Borderías

Extension of the Shelf Life of Prawns (Penaeus japonicus) by Vacuum Packaging and High-Pressure Treatment

The present study has investigated the application of high pressures (200 and 400 MPa) in chilled prawn tails, both conventionally stored (air) and vacuum packaged. Vacuum packaging and high-pressure treatment did extend the shelf life of the prawn samples, although it did affect muscle color very slightly, giving it a whiter appearance. The viable shelf life of 1 week for the air-stored samples was extended to 21 days in the vacuum-packed samples, 28 days in the samples treated at 200 MPa, and 35 days in the samples pressurized at 400 MPa. Vacuum packaging checked the onset of blackening, whereas high-pressure treatment aggravated the problem. From a microbiological point of view, batches conventionally stored reached about 6 log CFU/g or even higher at 14 days. Similar figures were reached in total number of bacteria in vacuum-packed samples and in pressurized at 200-MPa samples at 21 days. When samples were pressurized at 400 MPa, total numbers of bacteria were below 5.5 log CFU/g at 35 days of storage. Consequently, a combination of vacuum packaging and high-pressure treatment would appear to be beneficial in prolonging freshness and preventing spotting.

Effect of heating temperature and sodium chloride concentration on ultrastructure and texture of gels made from giant squid (Dosidicus gigas) with addition of starch,l-carrageenan and egg white

This paper seeks to compare the ultrastructure of gels made from frozen muscle of giant squid (Dosidicus gigas) at various temperatures with a number of different rheological parameters, with reference to a variety of added ingredients (non-muscle proteins and hydrocolloids) and to NaCl concentration. Interesting data on gel rheological properties were found where formulae containedl-carrageenan, starch and egg white, with a low salt concentration (1.5%). This seems to be because carrageenan forms an independent network which supports the principal structure formed by the fish protein; starch is incorporated into the network and retains water; and egg white forms a supplementary network which helps to improve rheological properties.

Collagen characteristics of farmed Atlantic salmon with firm and soft fillet texture

The possible role of collagen in texture variations among Atlantic salmon (Salmo salar L.) grown under commercial conditions at a Norwegian farm was studied. The texture was determined instrumentally as the breaking strength, and collagen and its salt (SSC), acid (ASC), pepsin (PSC) and insoluble (IF) fractions were analysed in order to determine the collagen aggregation degree. The collagen solubility and its overall amino acid (AA) composition showed no correlation to the breaking strength, but a positive correlation was observed between the breaking strength and glycine (r=0.74) and alanine (r=0.87) contents of the PSC fraction. Salmon with high breaking strength had higher T(peak) (temperature of transition) and ΔH (enthalpy of transition), and the collagen seemed to have triple helix structures mainly stabilized by covalent associations as compared to salmon with low breaking strength. The glycosylation degree was also positively correlated to the breaking strength (r=0.88, p ≤ 0.05). It is concluded that firmness of salmon muscle was not related to the total amount of collagen in the muscle, but rather higher collagen stability.

Influencia de la subespecie, estacionalidad y procedimientos de estabilización en la aptitud gelificante del músculo de sardina (Sardina pilchardus) congelado/Influence of subspecies, season and stabilization procedures in gel-forming ability of frozen minced muscle of sardine (Sardina pilchardus)

This paper examines the gel-forming ability of minced muscle of sardine - caught from the Bay of Biscay and the Mediterranean at different seasons - kept in frozen storage for 150 days. The influence of atmospheric and vacuum packaging on the gel-forming capacity of minced muscle, and the addition of tocopherol as antyoxidant were also studied. From the outset of frozen storage, Mediterranean sardine muscle exhibited greater gel strength than that from the Bay of Biscay. Sardines from the Bay of Biscay caught in November produced the best gels from any area. Generally, when frozen muscle was vacuum-packed, rancidity was less and gel strength improved. Activity of tocopherol does not seem sufficiently clear. In nearly all cases, gel strength was greater the longer the muscle was kept in frozen storage, although in Bay of Biscay sardine muscle there was progressive myofibrillar protein aggregation throughout the storage.

Emulsifying capacity of collagenous material from the muscle and skin of hake (Merluccius merluccius L.) and trout (Salmo irideus Gibb): Effect of pH and NaCl concentration

Abstract The relationship between collagen concentration and emulsifying capacity as well as the effect of pH and sodium chloride concentration on the development of this functional property were studied. Due to what is known as the dilution effect, emulsifying capacity, when expressed in terms of the quantity of soluble protein, decreased as collagen concentration increased. When expressed in terms of total protein, emulsifying capacity decreased as the NaCl concentration increased and was highest at pH levels of between 1 and 3. A power function that described the behaviour of this functional property in terms of soluble protein independently of the factors considered, i.e., concentration, pH, and percentage sodium chloride, was found. Generally speaking, emulsifying capacity, expressed in terms of the quantity of soluble protein, can be regarded as higher in the collagenous material from the hake than in that from the trout, and higher in the muscle connective tissue than in the dermal connective tissue.

Distribution and hardness of muscle connective tissue in hake (Merluccius merluccius L.) and trout (Salmo irideus Gibb)

ZusammenfassungDie Menge des Bindegewebes und seiner Hauptproteine wurden auf dessen Schnittfestigkeit bezogen, um aus dieser Beziehung und den physikochemischen Daten bei Hecht und Forelle Schlüsse ziehen zu können. Weiterhin wird die Löslichkeit des Kollagens und das Verhältnis derα-, β- undγ-Komponenten bestimmt, um den Aggregationsgrad des Muskelkollagens zu ermitteln und auf diese Weise die oben erwähnten Zusammenhänge erklären zu können. Es wird festgestellt, daß das Bindegewebe über die Länge des Seehechtfilets unregelmäßiger verteilt ist als bei der Forelle, wobei ein höherer Anteil im Schwanz beobachtet wird. Der Grad der Kollagenaggregation ist im Bindegewebe an verschiedenen Stellen des Seehechtfilets gleich, jedoch nicht bei der Forelle, wo das näher am Schwanz liegende Gewebe einen höheren Aggregationsgrad aufweist. Das führt dazu, daß beim Seehecht eine signifikante Beziehung zwischen der Bindegewebsmenge und der Schnittfestigkeit besteht, bei der Forelle allerdings nicht.SummaryThe amount of connective tissue and its main protein, collagen, were related to connective tissue shear strength, in order to furnish data on the distribution and physiochemical characteristics of connective tissue in hake and trout. Collagen solubility and the proportions of the a,β, andγ components were also determined, in order to ascertain the degree of aggregation in the muscle collagen and to explain the above relationships. Connective tissue distribution along the length of the fillets was more uneven in the hake than in the trout, with higher levels in the tail. The degree of collagen aggregation was similar in the connective tissue taken from different locations in the hake fillets. However, in the trout fillets, aggregation was higher in the connective tissue taken from near the tail. As a consequence, the amount of connective tissue was significantly correlated to shear strength in the hake but not in the trout.

Behaviour of myofibrillar proteins and collagen in hake (Merluccius merluccius L.) muscle during frozen storage and its effect on texture

ZusammenfassungEs ist schwierig, die Texturveränderungen tiefgefrorener Fische nur mit der Anhäufung der myofibrillären Proteine zu erklären. Deswegen wird in diesem Aufsatz versucht, solche Texturveränderungen bei tiefgefrorenem Hechtmuskel mit der Veränderung, die das Kollagen während der Lagerungszeit erleidet, zu deuten. Gleichzeitig wird eine Beziehung für die Entstehung von Formaldehyd im Muskel und der Aggregation der Proteinmyofibrillaren und des Grundgewebes gesucht. Es wurde eine Wechselwirkung zwischen der Aggregation des Kollagens und der Zunahme der Härte im Bindegewebe des rohen Muskels, aber nicht des gekochten, gefunden. Es wurde eine mathematische Funktion, die eine Korrelation zwischen der Schnittfestigkeit des rohen Muskels und der Anhäufung der myofibrillären Proteine und des Kollagens darstellt, gefunden.SummaryIt is difficult to explain fully the changes in the texture of frozen fish muscle solely in terms of the aggregation of myofibrillar protein. Therefore this paper attempts to relate to such textural changes in frozen hake muscle and to the modification that collagen undergoes during frozen storage. A relationship is also sought between formaldehyde production in the muscle and the aggregation of myofibrillar protein and stroma. A correlation is found to exist between collagen aggregation and augmented hardness in the connective tissue of the raw muscle, but not in that of the cooked muscle. A function is proposed that relates the shear strength of the raw muscle to the aggregation of myofibrillar proteins and collagen.

Behavior of Octopus Muscle (Octopus vulgaris) under a Process of Pressure-Time-Temperature Combinations

Octopus muscle (Octopus vulgaris) of different sex was treated for various different simultaneous combinations of pressure (0.1 or 450 MPa), time (15 or 30 min) and temperature (7, 40, 75 or 100 °C). The sex of specimens was not a significant factor. High pressure was effective in reducing the microbial load and the intense autolytic activity in the octopus muscle. Pressurization time was found to be a significant factor for hardness, but neither hardness nor the exudates were reduced by pressurizing at 450 MPa. Progressive raising of the temperature increased the drip loss, while hardness was reduced only at high temperatures. Increasing temperature produced ultrastructural changes relating to softening, but nevertheless, the ultrastructural changes observed after pressurization did not correspond with modifications in shear strength.

Ultrastructural and rheological changes during the gelation of giant squid (Dosidicus gigas) muscle

The giant squid or dosidicus (Dosidicus gigas) is normally shipped frozen from the coasts of America. During the period prior to freezing-when conditions are not always optimum-and during frozen storage, the functional capacity of the muscle proteins declines, rendering the material useless for certain processes such as conversion to gel. This paper examines the reasons for the lack of a good gel-forming capacity as measured both rheologically (breaking force, breaking deformation and gel strength) and in terms of ultrastructure (scanning microscopy). The study was carried out at four different temperatures known to be critical for fish muscle protein gel formation, and at two salt concentrations. At 35°C the structure was spongier in gels made with 1.5% NaCl, although a true gel was still not formed, as shown by rheological measurements. Above 30°C, the ultrastructure became more cellular, particularly in samples made with 2.5% NaCl, at which concentration gel strength values were higher. However, at neither salt concentration nor at any of the experimental temperatures was the mesh as spongy as in other fish gels reported in the literature. The values of rheological analysis and folding test were correspondingly low.

Influence of collagenous material during frozen storage when added to minced cod (Gadus morhua)

ZusammenfassungEs wird der Einfluß von beigefügtem, gereinigtem, kollagenem Material der Haut in gehacktem Fisch während der Lagerung in gefrorenem Zustand untersucht, um die sensorischen Eigenschaften des gefrorenen Produktes zu verbessern. Als Grundmaterial wurden zerkleinerte, aufgetaute und frische Kabeljaumuskeln benutzt, denen kollagenes Material in unterschiedlichen Proportionen beigefügt wurde. Nach Reinigung wurde das kollagene Material auf vier verschiedene Weisen zur Stabilisierung vorbereitet (gefroren, vorgelöst/gefroren, durch Gefrierung dehydriert und vorgelöst/durch Gefrierung dehydriert), bevor es dem zerhackten Fisch beigefügt wurde. Es ergab sich, daß das kollagene Material eine positive Wirkung auf die Wasserhaltefähigkeit hatte und somit die sensorischen Eigenschaften von gehacktem Fisch während der Lagerung in gefrorenem Zustand verbesserte.AbstractThe influence of added purified collagenous material from skin on minced fish during frozen storage is studied with a view to improving the sensory quality of the frozen product. The base material used was minced cod muscle, thawed and fresh, to which collagenous material was added in varying proportions. Following purification, the collagenous material was prepared in four different ways (frozen, pre-solubilized/frozen, freeze-dried and pre-solubilized/freeze-dried) for stabilization before addition to the fish mince. This collagenous material was found to have a positive effect on water-holding ability and to improve the sensory properties of the fish mince during frozen storage.