Gabriel Sampedro

Effect of modified atmosphere packaging on shelf-life of iced fresh hake slices

Shelf-life of hake slices (Merluccius merluccius) stored in the ice state (2 ± 1°C) under modified atmosphere packaging (MAP) conditions was determined by measurements of pH, total volatile bases (TVB) and trimethylamine (TMA) content, mesophilic and psychrophilic bacterial counts, malonaldehyde content, exudation, protein functionality and sensorial analyses (colour and odour). The effect of different gas mixtures were evaluated : (1) 40% CO 2 , 50% N 2 , 10% O 2 ; (2) 60% CO 2 , 30% N 2 , 10% O 2 ; (3) 40% CO 2 , 30% N 2 , 30% O 2 ; (4) 60% CO 2 , 10% N 2 , 30% O 2 and (5) air (control). Important differences were found between MAP-stored and air-stored hake slices. Shelf-life of hake stored under MAP conditions was two-fold extended. Bacterial growth was inhibited, increases of pH, TMA and TVB were reduced, and alterations in protein functionality were delayed, and off-odours were not noted in MAP-stored hake slices after 21 days storage. Significant correlations were found between TMA content and total viable count (TVC), as well as between apparent viscosity and exudation. Hake slices could be stored in the ice state under MAP conditions for about three weeks without an important loss of quality. Fish freshness, handling practices and initial bacterial load have an important influence of shelf-life of hake.

Effect of carbon dioxide atmosphere on microbial growth and quality of salmon slices

Salmon slices (Salmo salar) were packed under CO 2 and stored in a chill room at 2 ± 1°C for 3 weeks. A study was carried out on the effect of CO 2 atmosphere on bacterial growth as well as on chemical deterioration (pH, total volatile bases, (TVB), trimethylamine (TMA), lipid oxidation) and sensory features (exudation, raw fish odour, cooked fish flavour). Results were compared with a control stored in air. Salmon slices stored under CO 2 had a shelf-life of nearly twice as long as those in air, having lower bacterial counts, pH, TMA and TVB, as well as improved sensory features after 18 days at 2 ± 1°C. Exudation was not significantly different between control and CO 2 -stored samples after 10 days ice storage. Exudate values extended from 1 to 2% for CO 2 -stored samples after 10 and 20 days storage, respectively. Salmon slices can be stored under CO 2 at 2 ± 1°C for about 18 days, with no substantial loss of quality. Shelf-life can vary depending upon the state of fish, handling practices, initial bacterial load and storage temperature.

The use of water and ice with bactericide to prevent onboard and onshore spoilage of refrigerated megrim (Lepidorhombus whiffiagonis)

This study investigates the effectiveness of ozonated water and flake ice (combined Petfrost system) to increase the quality and stability of fresh megrim on fishing boats. The captured fish were washed, placed in plastic boxes, covered with flake ice and refrigerated at 2°C for up to 2-weeks onboard and, thereafter, for 11 days onshore. The experiments employed sterile, filtered and ozonated water at a concentration of 2ppm for washing the fish and making the flake ice. The results are compared with samples from a traditional treatment consisting of water and flake ice of marine origin. Fish were caught in four different hauls, which took 14, 12, 8 and 3 days in being landed. Subsequently, fish were stored for 1, 5, 7 and 11 days at 3°C. The different treatments were evaluated using sensory, microbiological and chemical techniques. Fish treated with ozone always showed the best quality. Megrim treated with ozone was still suitable for consumption after 14 days on board, and megrim stored for 12, 8 and 3 days on board could be stored for a further five days in the ice state once landed with an acceptable quality. In contrast, control fish were not suitable for consumption if stored for longer than three days on board.The results indicate that treatment with water and ice flakes made from sterile and ozonated water maintains the quality of fresh megrim onboard fishing boats and upon arrival onshore.

A DSC study on the effects of various maltodextrins and sucrose on protein changes in frozen-stored minced blue whiting muscle

A DSC heat denaturation study on the effects of various maltodextrins and sucrose on protein changes in minced blue whiting muscle during frozen storage at -10 and -20 degrees C was carried out. All maltodextrins slowed down the decreases in the denaturation enthalpies (deltaHd) ascribed to myosin and actin, making evident a noticeable effectiveness against protein denaturation, especially at -20 degrees C. Sucrose was as effective as maltodextrins at -20 degrees C, but was the least effective treatment at -10 degrees C. Significant correlations between both deltaHds and either protein solubility or formaldehyde production were found at each storage temperature. A low protein sensitivity to the small amounts of formaldehyde produced during the first weeks of storage and errors associated with the determination of enthalpies led to poorer correlations at -20 degrees C. Maximum denaturation temperatures (Tmax) correlated with protein solubility only at -20 degrees C. No clear relationship between either Tmax and the effectiveness of cryostabilisation was found, as Tmax also depends on the effectiveness of the treatments against the thermal denaturation of proteins.

Chemical composition of the muscle tissue of ray (Raja radiata) from Terranova

Abstract The proximate analysis, nitrogen compound content and lipid and fatty acid analysis of the muscle of frozen ray (Raja radiata) caught in Terranova have been studied. The proximate analyses of the muscle were: 15% real protein, 1% non-protein nitrogen, 78% humidity and a fatty acid content lower than 1%. The urea reaches values of 2%. In the lipid fraction 14 fatty acids were identified. Palmitic acid (16:0) and stearic acid (18:0) were the majority fatty acids and represent 61.55% and 33.86% of the total saturated fatty acids. Oleic acid (18:1) was the most abundant of the monounsaturated fatty acids and corresponds to 72.72% of the total of these. Arachidonic acid (20:4), eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6) were the most predominant polyunsaturated acids, forming 12.95, 57.22 and 23.67% of the total of polyunsaturated fatty acids respectively. The results show that the lipid fraction of the ray (Raja radiata) is an excellent source of polyunsaturated fatty acids with high levels of omega-3 (n-3) especially the eicosapentaenoic and docosahexaenoic acids.

Changes in lipids of whole and minced rayfish (Raja clavata) muscle during frozen storage

ZusammenfassungDer Einfluß der Gefriertemperatur (−18 °C und −40 °C) und der Zugabe von Butylhydroxytoluene (BHT) auf die verschiedenen Lipoid-Klassen (Phospholipoide, Triacylglyceride, freie Fettsäuren, Sterole und Sterolester bzw. Sterolwachse und die Zusammensetzung der Fettsäuren in ganzem und zerkleinertem (8 und 12 mm) Rochenmuskel wurden nach einem Jahr Gefrierlagerung untersucht. — Der Phospholipoid-Anteil sank deutlich und der Anteil an freien Fettsäuren nahm deutlich zu bei beiden Gefriertemperaturen, besonders bei −18 °C. Deutliche Unterschiede bei beiden Lipoid-Typen wurden zwischen den zerkleinerten und den ganzen Proben gefunden, wobei sich die größten Unterschiede bei −18 °C zeigten. Ein signifikanter Anstieg der häufigsten Fettsäuren (22:6n-3 und 16:0) wurde nach einem Jahr Gefrierhaltung festgestellt, je niedriger die Gefriertemperatur, desto höher ihr Anteil. Der Anteil an polyungesättigten Fettsäuren nahm bei allen Proben deutlich zu, je niedriger die Temperatur, desto höher ihr Anteil. Unerhebliche Unterschiede wurden zwischen den auf 8 mm und 12 mm zerkleinerten Proben gefunden. In keinem der untersuchten Parameter zeigten sich signifikante Unterschiede bei Vorhandensein oder Nicht-Vorhandensein von BHT. Die Zerkleinerung beschleunigte die hydrolytischen und oxidativen Prozesse, die bei niedrigerer Gefriertemperatur langsamer waren, trotzdem wurden keine signifikanten Unterschiede zwischen den beiden Partikel-Größen festgestellt.AbstractThe effects of the storage temperature (−18 °C and −40 °C) and the addition of butylhydroxytoluene (BHT) on the different classes of lipids (phospholipids, triacylglycerides, free fatty acids, sterols and sterol esters plus waxes) and the fatty acid composition of minced (8 and 12 mm) and whole rayfish wing muscle stored for 1 year in the frozen state were studied.The phospholipid content decreased significantly and the free fatty acid content increased significantly at both storage temperatures, but more pronounced, at −18 °C. Significant differences were found between phospholipid and free fatty acid contents of the minced and the whole samples, which again were more pronounced at −18 °C. A significant increase of the major fatty acids (22∶: 6n-3 and 16:0) was observed after 1 year in the frozen state. Significant differences were also obtained between the samples stored at −18 °C and at −40 °C; the lower the storage temperature, the higher their content. The polyunsaturated fatty acid (PUFA) content increased significantly in all the samples. Significant differences were found between the samples stored at −18°C and at −40°C. The lower the temperature, the higher the PUFA content. Nonsignificant differences were observed between the 8-mm and the 12-mm minced samples. Non-significant differences were found between the samples stored in the presence and in the absence of BHT. Mincing hastened hydrolytic and oxidative processes, which were slowed down at the lower storage temperature. Nonetheless, nonsignificant differences were found between both particle sizes.

Effects of processing and ice storage on lipid classes and fatty acids of ray muscle (Raja clavata)

The effect of ice storage on the lipid material (total lipids, lipid classes and fatty acids) of whole and minced ray muscle has been studied. Neither processing nor ice storage for seven days significantly changed (p > 0.05) the total lipid content. The main fatty acids were: 22:6n-3, 16:0, 18:1n-9, 18:0, 20:5n-3, 20:4n-6, and 22:5n-3 in both whole and minced ray muscle. The contents of these fatty acids increased significantly (p < 0.001) during seven days of storage in the ice state, except those of 20:4n-6 and 20:5n-3, which decreased significantly (p < 0.01). The contents of the different fatty acids (saturated, monoenes, and polyunsaturated) increased significantly (p < 0.001) owing to both mincing and storage in ice. Phospholipids, sterol esters + waxes, triacylglycerides, free fatty acids, and sterols were studied. Phospholipids were the main lipid group in ray muscle. No significant differences (p < 0.01) were found as a consequence of mincing and ice storage in the contents of phospholipids and sterols. However, significant differences (p < 0.01) appeared in the free-fatty-acid content after seven days of storage in ice, but mincing did not affect this.