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

The 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.     

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

The 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.

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Der Einfluß von kollagenem Material während der Lagerung in gefrorenem Zustand, wenn es gehacktem Kabeljau beigefügt wird (Gadus morhua)

Zusammenfassung Es 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.

     

Changes in lipids and proteins of marine catfish (Tachysurus dussumieri) during frozen storage

Changes in lipids and protein of marine catfish ( Tachysurus dussumieri ) were followed over a period of 300 days storage at –20°C. Phospholipids decreased and free fatty acids (FFA) and peroxide value (PV) increased. A linear relationship between the decrease in phospholipid and increase in FFA was observed, suggesting that FFA were formed by hydrolysis of phospholipid. Fatty acid analysis showed that polyunsaturated fatty acids (PUFA) increased in the neutral lipid fraction and decreased in the phospholipid fractions; this also suggests hydrolysis of the latter and release of free PUFA into the neutral fraction.
A decrease in water soluble protein (WSP) and salt soluble protein (SSP) indicated denaturation of proteins on prolonged frozen storage; both changes were strongly associated with the changes in peroxide value and free fatty acids.     

Aggregation of minced hake during frozen storage

 Aggregation in minced hake muscle (Merluccius merluccius) during storage at –20  °C was studied in conditions where there is progressive deterioration of functionality and texture as measured by apparent viscosity and shear resistance. Natural actomyosin was extracted with 0.6 M NaCl over a period of 49 weeks. Insoluble residue was extracted successively with 2% sodium dodecyl sulphate (SDS) and 2% SDS plus 5% β-mercaptoethanol (ME) solutions. SDS–polyacrylamide gel electrophoresis was performed on the extracted fractions. The results showed a 75% decrease in 0.6 M NaCl extractability by the end of the storage period. Initially the remaining precipitate was all extracted in 2% SDS and although the amount extracted in this solution increased as storage time progressed, its proportion decreased, accounting for as little as 40–50% of the protein aggregate by the end of storage. The proteins most involved in formation of the aggregate not extracted in 0.6 M NaCl were myosin and actin. Neither of these proteins was fully recovered in the fractions extracted with 0.6 M NaCl, 2% SDS, or 2% SDS plus 5% ME, and therefore it was inferred that they were forming part of the aggregates, bound by covalent bonds. Received: 17 November 1998     

Changes of lipids in sardine (Sardinella gibbosa) muscle during iced storage

Changes in lipids of sardine (Sardinella gibbosa) muscle during 15 days of iced storage were investigated. Lipid deterioration, lipolysis and lipid oxidation, occurred throughout the storage. The progressive peroxide formation was monitored by the increase in the absorbance band at 3600–3200 cm⁻¹ in Fourier transform infrared (FTIR) spectra and increased peroxide values were observed in sardine muscle up to 6 days of iced storage, followed by a continuous decrease from then for 9 days (P < 0.05). The increase in thiobarbituric acid reactive substances (TBARS) was noticeable throughout the iced storage (P < 0.05). However, no difference in conjugated diene (CD) of sardine muscle was found within the first 12 days of iced storage (P > 0.05). Marked decreases in unsaturated fatty acids, especially eicosapentaenoic acid (EPA; C20:5(n − 3)) and docosahexaenoic acid (DHA; C22:6(n − 3)) were observed as the storage time increased. Those changes indicated that lipid oxidation occurred in sardine muscle. A gradual increase in free fatty acid formation, with decreases in triglyceride and phospholipid contents, was found during iced storage (P < 0.05), suggesting hydrolysis induced by lipases and phospholipases.     

Effect of added lipids on the texture of minced hake (Merluccius merluccius L.), megrim (Lepidorhombus whiffiagonis W.) and sardine (Sardina pilchardus W.) during frozen storage

Summary The effect of added cod liver oil and oxidized cod liver oil on the measurement of texture in minced hake (Merlucdus merlucdus L.), megrim (Lepidorhombus whiffiagonis W.) and sardine (Sardina pilchardus W.) has been measured during frozen storage (–18° C). The results show that added neutral and oxidized lipids, even at high rancidity levels, do not affect shear resistances measured by the Kramer shear-compression cell in non-formaldehyde forming species such as megrim and sardine, over the frozen storage period. However, in a formaldehyde-forming species such as hake, in the presence of neutral and oxidized lipids at the end of the storage period, the values of shear resistances may be lower than in the absence of these lipids, probably owing to formation of less formaldehyde in these cases. Although it is very difficult to estimate the importance of a single compound or group of compounds on texture, these results seem to indicate that formaldehyde is a much more important factor than oxidized lipids in changes of texture in fish.

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Einfluß von zugesetzten Lipiden auf die Konsistenz von zerkleinertem Seehecht (Merlucdus merlucdus L.), Flügelbutt (Lepidorhombus whiffiagonis W.) und Sardinen (Sardina pilchardus W.) während der Gefrierlagerung

Zusammenfassung Der Einfluß von zugesetztem Kabeljauleberöl (CLO) und oxidiertem Kabeljauleberöl (OCLO) auf die Konsistenz von zerkleinertem Fischfleisch aus Seehecht (Merlucdus merlucdus L.), Flügelbutt (Lepidorhombus whiffiagonis W.) und Sardine (Sardina pilchardus W.) wurde während der Gefrierlagerung (bei–18 °C) gemessen. Die Ergebnisse zeigen, daß weder der Zusatz von neutralem noch der von oxidiertem Öl, selbst bei erheblicher Ranzigkeit, den Scherwiderstand im Fisch beeinflußt, wenn kein Formaldehyd gebildet wurde. Bei der Fischart aber, die während der Gefrierlagerung Formaldehyd bildet, wie z. B. Seehecht, können die Werte des Scherwiderstandes in Gegenwart von neutralen und oxidierten Lipiden gegen Ende der Lagerperiode niedriger sein als bei Abwesenheit der Lipide; wahrscheinlich wegen verminderter Formaldehydbildung. Obwohl es sehr schwierig ist, die Bedeutung einer einzelnen Verbindung zu bewerten, scheinen diese Ergebnisse zu zeigen, daß Formaldehyd für die Konsistenzveränderungen in tiefgefrorenem Fisch einen viel wichtigeren Faktor darstellt als oxidierte Lipide.

     

Effect of plant extracts on lipid oxidation during frozen storage of minced fish muscle

The aim of the study is to determine the effect of pomegranate seed extract (PSE) and grape seed extract (GSE) addition to chub mackerel minced muscle on lipid oxidation during frozen storage. Each extract was added to minced fish muscle at 2% concentration and then stored at ?18 °C for 3 months. The effect of plant dietary fibres to control lipid oxidation was compared with untreated samples (control). Formation of lipid hydroperoxides and thiobarbituric acid‐reactive substances (TBARS) was significantly inhibited by PSE and GSE addition when compared with control. Both extracts significantly retarded lipid oxidation according to the results of TBARS. A significant reduction of L* (lightness), a* (redness) and b* (yellowness) values was detected during frozen storage. GSE added samples had the highest redness and the lowest lightness and yellowness. However, samples with PSE showed the lowest redness and highest yellowness and h° (hue angle) values. The results from this study suggest GSE is a very effective inhibitor of primary and secondary oxidation products in minced fish muscle and have a potential as a natural antioxidant to control lipid oxidation during frozen storage of fatty fish.     

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

The 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.     

Changes in sugar phosphate and lactate concentration in trawled cod (Gadus callarias) muscle during frozen storage

The concentrations of glucose 1-phosphate, glucose 6-phosphate, fructose monophosphate, fructose 1,6-diphosphate, pentose phosphate and lactate have been measured in the muscle of trawled cod. The effects on these compounds of storage in ice during the immediate post mortem period, of freezing at different rates pre- and post-rigor and of storage at three sub-zero temperatures for over a year have been determined.     

Production and frozen storage of minced Baltic herring (Clupea harengus membras)

The production and storage of minced Baltic herring was investigated to develop a convenient semi-finished product which could be manufactured industrially and stored frozen as such or in the form of pre-manufactured convenience foods. Baltic herring has several disadvantages as a raw material for such use, namely small size, dark colour, strong odour, and soft texture. Dark colouring of the mince can be reduced considerably by skinning. The dark pigments of the belly lining are eliminated on filleting. The strong odour which evolves when Baltic herring is heated can be moderated by adding a small amount of suitable protein such as milk protein. This addition also has a positive influence on the water binding capacity and taste of the mince. The texture is improved by adding barley or wheat starch or possibly by pre-texturing part of the mince by heating to give a heterogeneous structure. Fish are skinned prior to mincing and 0.1–0.2% ascorbic acid or sodium erythorbate is added as antioxidant. The mince is vacuum packed in a gas-tight material such as polyethylene/polyamide laminate. In this way it is possible to store frozen minced Baltic herring at ?25 °C for at least one year. Even after such a period the mince is still quite acceptable and no rancidity or peroxides can be detected. Although it appears that certain adverse protein changes cannot be avoided during frozen storage, their effects can be masked in part by adding milk protein, starch and triphosphate to increase the water-binding capacity and generally improve the functional properties of the mince and mince-based products.     

Changes in lipids,proteins and kamaboko forming ability of silver carp (Hypophthalmichthys molitrix) mince during frozen storage

Frozen storage of mechanically deboned silver carp (Hypophthalmichthys molitrix) mince for 180 days resulted in a significant (P⩽0.05) decrease in myofibrillar proteins. In contrast, peroxide value (PV), free fatty acids (FFA) and total volatile base nitrogen (TVBN) contents increased significantly (P⩽ 0.05) throughout the storage period. The kamaboko forming ability and the sensory scores of the silver carp mince decreased significantly (P⩽0.05) during the storage period. Texture of the mince was significantly (P ⩽ 0.001) correlated with the decrease in the myofibrillar proteins (salt-soluble proteins), jelly strength and folding test grades; and increase in expressible water percentage, PV, FFA and TVBN content. Based on ‘texture’ of the mince, the product was acceptable for 180 days at −18°C.     

Changes in the lipids of turkey muscle during storage at chilling and freezing temperatures

Diced turkey leg and breast muscle stored for 22 days at 0° and —3°, and for up to one year at —10°, —20° and —60° was examined at intervals for lipid composition. Free fatty acids increased at all temperatures except —60°, with a Q₁₀ of 3-4 between 0° and —20° 90% of the fatty acids liberated were unsaturated, matching in composition the unsaturated acids of the muscle glycerophospholipids. Demonstration of linear relationships between increase in free fatty acids and decrease in phosphatidylethanolamine or increase in lysophosphatidylcholine confirmed phospholipase A₂ as the enzyme mainly responsible. The composition of the fatty acids liberated during storage at 0° and —3° showed that both lipase and phospholipase were active. A slight decrease in extractability, resulting in an apparent loss of phospholipid-P, was observed after storage at low temperatures.     

Vibrational spectroscopic analysis of hake (Merluccius merluccius L.) lipids during frozen storage

Vibrational spectroscopy (mid FTIR and FT-Raman) was used to monitor lipids extracted from hake fillets during frozen storage. Kramer shear resistance was used as a marker of texture changes and lipid damage was also investigated by following the development of conjugated dienes and free fatty acids by spectrophotometric methods. Results show that the intensity of the free fatty acid carboxylic ν(CO) band measured by ATR-FTIR spectroscopy can be used for monitoring the development of lipid hydrolysis in hake lipids. Changes in the Raman ν(CC) stretching region (1658 cm⁻¹ band), partially attributed to conjugated dienes development, were the only observed spectroscopic alterations related to lipid oxidation of hake lipids during frozen storage at −10 °C. The high correlation of free fatty acids with instrumental texture and the disappearance of the ν_as(PO₂⁻) band are consistent with membrane lipid hydrolysis being one of the factors directly related with toughening of lean fish flesh.     

Quality changes during the frozen storage of sea bass (Dicentrarchus labrax) muscle after pressure shift freezing and pressure assisted thawing

Quality of frozen sea bass muscle stored (1, 3 and 5 months) at two levels of temperature (−15 and −25 °C) after a pressure shift freezing process (200 MPa) — PSF — and/or a pressure assisted thawing process (200 MPa) — PAT — was evaluated in comparison with samples frozen and thawed using conventional methods (air-blast AF and AT, respectively). Frozen storage of high-pressure treated samples did not significantly affect initial quality of frozen muscle. Thus, parameters related to protein denaturation and extractability, water holding capacity and color presented similar values than those obtained for not stored samples. In addition, the improvement of the microstructure achieved by PSF application remains unchanged during frozen storage. On the other hand, conventional treated samples experienced significant changes during frozen storage, such as protein denaturation, and water holding capacity and color modifications. Storage temperatures did not have influence in the quality of PSF and PAT samples, but it showed some effects in AF muscle.Industrial relevance: This work demonstrates the potential application and benefits of high pressure (HP) in the freezing and thawing of fish meat in comparison to conventional methods, due to an improvement on the cellular integrity of the tissue. Although some negative effects are produced during processing with HP, no additional modifications occur during the frozen storage. The studied methodologies seemed to be very suitable for fish freezing and thawing, especially for products which will be frozen stored and/or cooked.     

Effect of frozen storage on lipids and functional properties of proteins of dressed Indian oil sardine (Sardinella longiceps)

Changes occuring in lipids and functional properties of dressed oil sardine during storage at −20°C (±2°C) were investigated for 12 weeks. Significant (P 0.05) changes were observed in the lipids and functional properties of frozen stored oil sardine meat. The extent of lipid oxidation and hydrolysis was strongly associated with decreased protein solubility (P0.01). Decrease in protein solubility (PS) positively correlated (P0.05) with the decrease in emulsifying capacity (EC), relative viscosity (RV) of soluble protein extracts, water binding capacity and negatively correlated with the cook loss. A positive correlation (P0.001) was established between the PS and the ability of soluble proteins to emulsify and stabilise an emulsion. High positive correlation between SSP & EC (P0.001) and PS & EC (P0.001) revealed that myofibrillar proteins are the main protein that decide the emulsion properties.     

Effectiveness of a natural Rosemary (Rosmarinus officinalis) extract on the stability of filleted and minced fish during frozen storage

 The objective of this study was to evaluate the effect of adding a natural Rosemary (Rosmarinus officinalis L.) extract to filleted and minced frozen fish and to compare the fat stability of the samples with that of the controls. Horse mackerel (Trachurus trachurus), a relatively fatty fish, and Mediterranean hake (Merluccius mediterraneus), a low-fat fish, were used. Fat stability evaluation was done by comparing the changes of the malondialdehyde (MDA) content and the percentage of polyunsaturated fatty acid (PUFAs) degradation that occurred during frozen storage at –18°C for 120 days. Total volatile bases-N (TVB-N) were also measured to assess for quality. The results showed that the natural antioxidant extract retarded the oxidation process throughout storage. The control samples of both filleted and minced frozen fish of both species showed a significant reduction (^* P <0.05) of PUFAs until day 50 of storage, while the oxidation was gradual but slower in the treated samples. Fillets and minced samples of both species treated with antioxidant contained significantly (^* P <0.05) less MDA compared with the controls during storage. Received: 2 December 1996     

Effectiveness of a natural Rosemary (Rosmarinus officinalis) extract on the stability of filleted and minced fish during frozen storage

 The objective of this study was to evaluate the effect of adding a natural Rosemary (Rosmarinus officinalis L.) extract to filleted and minced frozen fish and to compare the fat stability of the samples with that of the controls. Horse mackerel (Trachurus trachurus), a relatively fatty fish, and Mediterranean hake (Merluccius mediterraneus), a low-fat fish, were used. Fat stability evaluation was done by comparing the changes of the malondialdehyde (MDA) content and the percentage of polyunsaturated fatty acid (PUFAs) degradation that occurred during frozen storage at –18°C for 120 days. Total volatile bases-N (TVB-N) were also measured to assess for quality. The results showed that the natural antioxidant extract retarded the oxidation process throughout storage. The control samples of both filleted and minced frozen fish of both species showed a significant reduction (^* P <0.05) of PUFAs until day 50 of storage, while the oxidation was gradual but slower in the treated samples. Fillets and minced samples of both species treated with antioxidant contained significantly (^* P <0.05) less MDA compared with the controls during storage. Received: 2 December 1996