Addition of sardine to hake minces and subsequent effect on dimethylamine and formaldehyde formation

Formaldehyde formation and reaction with muscle proteins in lean fish species during frozen storage is considered to be a major factor affecting texture and functionality deterioration. Formaldehyde formation and reaction with muscle compounds was reduced in lean fish minces and model systems when lipids with different degrees of oxidation were added. In order to increase the lipid content and slow down functional and textural changes, hake (Merluccius merluccius) and sardine (Sardina pilchardus) minces mixed in the ratios 3:1; 1:1 and 1:3 (w/w) were stored at ?20 °C and studied for 1 year. Dimethylamine formation and, by deduction, formaldehyde formation increased. However, less free formaldehyde was detected, probably owing to reaction with muscle compounds in the mixed minces. Nevertheless, addition of sardine minces improved the texture, protein solubility and viscosity of the mixed minces compared with the hake minces. In the mixed lots, formation of large protein aggregates was delayed or prevented. This suggests that in the mixed minces formaldehyde reacted with proteins in a different way from that in lean fish or reacted with other muscle components not directly involved in textural changes. © 2002 Society of Chemical Industry     

Seasonal variation in the viscosity of the extracts of muscle proteins of hake (Merluccius hubbsi) stored on ice

Changes in viscosity of high-ionic-strength muscle extracts of hake stored on ice are subject to seasonal variation. A rapid fall in the viscosity occurs in extracts of fish caught during the summer. The viscosity declines at a slower rate after the sixth day of storage for those fish caught during the autumn. No change in the viscosity was observed in hake caught during the winter and spring.     

INTERACTION BETWEEN TRIOLEIN AND NATURAL HAKE ACTOMYOSIN DURING FROZEN STORAGE AT -18C

The interaction of hake muscle actomyosin with triolein in 0.6 M KCl, pH 7, during frozen storage has been investigated. ATPase activity, protein solubility and relative viscosity measurements were performed. No effect of triolein on these functional properties was observed during the storage period studied. Incorporation of l-14C triolein to the protein was found over the storage period, indicating that despite the lack of effect on functionality, lipid-protein interaction occurs. No differences were found in the electrophoretic patterns between control and neutral lipid added samples.     

Influence of frozen storage on aptitude of sardine and dolphinfish for cold-smoking process

Stability of dolphinfish (Coryphaena hippurus) and sardines (Sardina pilchardus) of different fat content (lean and fatty sardines) during frozen storage and its suitability for cold-smoking throughout storage were evaluated in order to overcome seasonal and excess catches of these species. Dolphinfish showed a relative stability regarding protein functionality (protein solubility, apparent viscosity, water and lipid holding capacity), lipid oxidation and total volatile basic nitrogen (TVBN) accumulation, which led to high acceptability ratings of the resulting smoked product throughout frozen storage (340 days). However, both lean and fatty sardines showed a marked loss of protein functionality, which coincided with the accumulation of oxidation products and TVBN. Freezing of raw muscle may become a valuable preservation method for the smoking industry to overcome the short caught period of dolphinfish in the Balearic Islands and to make use of excess catches of both, lean and fatty sardine. High quality smoked products may be obtained from the frozen muscle during approximately twelve, four and two months of frozen storage for Dolphinfish, lean and fatty sardine, respectively.     

Biochemical and Physicochemical Properties of Actomyosin from Pre- and Post-spawned Hake (Merluccius hubbsi) Stored on Ice

Biochemical and physicochemical properties of natural actomyosin (NAM) from pre- and post-spawned hake stored on ice were studied. At the beginning of storage both reduced viscosity and ATPases activities of NAM from post-spawned hake were about 3 times higher than those of the pre-spawned ones, except for the Mg²⁺-(Ca²⁺)-ATPase. Higher loss of functional components during pre-spawned hake NAM purification was found compared to NAM from post-spawned fish. Reduced viscosity and Mg²⁺-(EGTA)-ATPase activity of NAM from both pre- and post-spawned hake decreased following ice storage. SDS-PAGE patterns of NAM from pre-spawned hake showed an absence of the myosin heavy chain and the presence of a 160 kDa component at zero time of storage. No proteolysis occurred in ice-stored fish caught in both gonadal stages.     

LIPID CHANGES IN FROZEN STORED FILLETS FROM PRE- AND POSTSPAWNED HAKE (MERLUCCIUS HUBBSI MARINI)

The lipid composition of frozen stored fillets from pre‐ and postspawned hake was studied. The total lipid (TL) content in the chloroform/methanol extract from unfrozen postspawned hake was four times higher than that of prespawned fish. After freezing, the TL content of postspawning hake muscle remained unchanged whereas the TL extracted from prespawning fish muscle increased about 90%. The TL extractability of muscle from fish in both different gonadal conditions was not affected by frozen storage. Lipolysis in frozen stored fillets from prespawned hake occurs principally by hydrolytic action on phospholipids (PL), and phosphatidylcholine was the main PL hydrolyzed. Triacylglycerols were the main substrates hydrolyzed in frozen stored fillets from postspawned hake. Freezing and frozen storage affected polyenoics and n‐3 fatty acids (FA). The decrease in the contents of n‐3 FA in fillets from postspawned hake was lower than that observed in fillets from prespawned fish.     

Hake natural actomyosin interaction with free fatty acids during frozen storage

The interaction of hake muscle actomyosin with free fatty acids in 0.6 M KCl pH 7 during frozen storage has been studied up to 280 days. ATPase activity, protein solubility and relative viscosity measurements were performed. Oleic and myristic acid had a detrimental effect on these properties during frozen storage. Oleic acid was bound to the protein from the beginning, mainly to the insoluble fraction. The diminishment of functionality following addition of oleic acid is not due to aggregation caused by covalent-type bonds, since it occurs well before the electrophoretic change is appreciable.     

Freezing and frozen storage of actomyosin from different species

A comparative study was made of the influence of freezing (–24°C) and frozen storage (–12°C) on the functional properties (viscosity, solubility) and physico-chemical characteristics (aliphatic and aromatic hydrophobicity, ATPase activity) of actomyosin (AM) from myosystems (chicken and hake) of differing freezing and frozen stability. The difference in functional behaviour between chicken and hake AM as a consequence of freezing and frozen storage suggests that, for hake AM, denaturation and aggregation occur essentially through direct aggregation of AM molecules to produce AM aggregates, whereas in chicken proteins, AM first dissociates into myosin and actin to produce myosin and myosin-actin aggregates.     

A study of the effects of frozen storage on certain functional properties of meat and fish protein

This paper presents a study of the effects of frozen storage on certain functional properties, namely protein solubility, emulsifying capacity, and viscosity, both in meat and in fish.
Correlations between these three functional properties were examined in an attempt to find the easiest and most sensitive method of analysis.
High correlation among the different functional properties tested was found only in the case of fish. This, together with the significant variations in the viscosity values found during the storage period, suggests that the analysis of apparent viscosity is a valuable indicator method for determining alterations occurring in the functional characteristics of fish protein.     

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.     

Emulsifying capacity of fish mince from several species during frozen storage

Abstract : As a functional property of protein, emulsifying capacity (EC) is of great technological interest. This article examines EC in fish mince from three species differing in fat content and in the pattern of deterioration during frozen storage—blue whiting (Micromesistius poutassou R), horse mackerel (Trachurus trachurus L) and mackerel (Scomber scombrus L)—caught during two seasons of the year in which physiological behaviour is expected to be different (winter and summer). EC and protein solubility were determined periodically. The results indicate the existence of a direct relationship between the fat content of the species used and its EC. Furthermore, in the species studied EC was independent of protein solubility and the amount of protein in the medium, both of which decline as a result of the formation of aggregates during frozen storage. This is not therefore a suitable method for determining protein quality during frozen storage.     

Localization of formaldehyde production during frozen storage of European hake (Merluccius merluccius)

The formation of dimethylamine and formaldehyde from trimethylamine N-oxide by the enzyme trimethylamine N-oxide demethylase in whole hake during frozen storage was studied. The objective was to check if there were parts of the muscle with a higher production of dimethylamine and formaldehyde, and if the presence of kidney during frozen storage had any significant influence on the production. Three variables were examined through one year storage. The first was anatomical location, considering the red muscle and three zones of white muscle, one located right over the kidneys, the dorsal part over the viscera, and the tail. The second variable was the temperature of storage, -11 °C or -18 °C. Finally, the influence of kidneys during storage, comparing fish with and without kidneys, was also evaluated. No differences were found in dimethylamine and formaldehyde production between fish with and without kidneys stored at -18 °C. However at -11 °C the amounts of dimethylamine and formaldehyde detected in fish without kidneys were, in some cases, higher than in those with kidneys. Kidney removal does not have a statistically significant influence on DMA and FA production in frozen storage hake. Differences in dimethylamine and formaldehyde values among different anatomical locations were found, especially in those stored over one year. It was found that, in general, the white muscle located right over the kidneys produced more dimethylamine than other parts of the fish.     

Extractability and thermal stability of frozen hake (Merluccius merluccius) fillets stored at −10 and −30 °C

The relationship between thermal stability changes and functionality loss was monitored in hake muscle fillets stored for 40 weeks at ?10 and ?30 °C. The evolution of changes in apparent viscosity, dimethylamine formation and extractability of muscle proteins in NaCl, sodium dodecyl sulphate (SDS) or SDS plus mercaptoethanol showed drastic differences as a function of temperature. At the higher storage temperature, both myosin heavy chain and collagen were the most severely unextracted in salt and SDS solutions, with actin becoming unextractable at the end of storage. Differential scanning calorimetry showed differences with storage time and temperature in both onset temperature and thermal denaturation enthalpy, mostly affecting the myosin transitions. Some protein denaturation occurred with little or no functionality loss. A considerably high fraction of hake muscle proteins remained in the native‐like condition even at the higher frozen storage temperature. In these conditions both apparent viscosity and myosin and actin extractability in NaCl were very low. © 2002 Society of Chemical Industry     

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.

The effect of added cod liver oil and oxidized cod liver oil on the measurement of texture in minced hake (Merluccius merluccius L.), megrim (Lepidorhombus whiffiagonis W.) and sardine (Sardina pilchardus W.) has been measured during frozen storage (-18 degrees 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.     

Foaming capacity of fish minces during frozen storage

This work covers a year's study of the foaming capacity (FC) of minced muscle of three fish species—blue whiting (Micromesistius poutassou R). horse mackerel (Trachurus trachurus L), and mackerel (Scomber scombrus L)—caught in two different seasons (January and July) and stored at – 18°C. Periodic assays were performed to determine protein solubility, FC and dimethylamine formation. The results show that FC is initially inhibited by the presence of the species own lipids; however, during frozen storage this effect is attenuated and thus FC increases. The results corroborate the view that protein solubility is not an indispensible requisite for FC, and that mere dispersion of proteins is sufficient. However, FC is not diminished by changes in protein during frozen storage when this deficiency is offset by sufficient protein concentration. On the other hand, FC is clearly affected by the formaldehyde generated during frozen storage, so that beyond a certain level the aggregates formed as a result of formaldehyde formation are too large to disperse, and hence FC decreases drastically.     

Total volatile basic nitrogen and trimethylamine nitrogen levels during ice storage of European hake (Merluccius merluccius): A seasonal and size differentiation

Whole ungutted European hake (Merluccius merluccius) caught by trawling off the Central Tyrrhenian coast of Italy in winter and in summer were stored in ice. The dynamics of changes of total volatile basic nitrogen (TVB-N) and trimethylamine-nitrogen (TMA-N) levels during ice storage of small- (20 ± 3 cm length) and large-sized (37 ± 6 cm length) hake caught in either season were studied. The TVB-N and TMA-N levels of hake caught in winter remained low (below 20 mg and 3 mg/100 g, respectively) throughout the experiment regardless of the body size. In summer TVB-N and TMA-N levels increased sharply (P < 0.05) during ice storage and at a higher rate in small than in large fish, a fact ascribable to fish exposure to high temperatures first in the water, during trawling, and then in the fishing vessel before ice-boxing. On the basis of the results obtained in this work, it may be concluded that ungutted European hake show a clear seasonal and size differentiation of the evolution of TVB-N and TMA-N during ice storage.     

Effect of Calcium Salts on the Properties of Proteins from Oil Sardine (Sardinella longiceps) During Frozen Storage

ABSTRACT:  The effect of calcium sulfate and calcium chloride on the enzymatic and structural properties of actomyosin isolated from sardine was investigated. Mince was prepared from sardine and different concentrations of calcium chloride and calcium sulfate were added to the mince and kept in frozen condition at −20 °C. The physico-chemical and functional properties of proteins from mince were analyzed as a function of time. The solubility of proteins decreased during storage. The reduction in solubility was less for samples treated with calcium chloride. However, sardine mince showed better functionality during storage in the presence of calcium compounds. The ATPase enzyme activity of actomyosin increased with increase in concentration of calcium and decreased after reaching the maximum value. ATPase activity of proteins from mince decreased during storage at low temperature. The reduction in ATPase activity did not correlate with the loss of functionality of proteins. SDS-PAGE did not reveal any major changes in the protein profile during storage as well as in the presence of different concentration of calcium compounds. The secondary structural content of actomyosin was not altered in the presence of both calcium chloride and calcium sulfate as evident from circular dichroic measurements.     

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

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. ©     

INFLUENCE OF RAW MATERIAL QUALITY ON QUALITY OF ICED AND FROZEN WHITE FISH PRODUCTS

The effect of raw material quality on final product quality was assessed. Initial physical, biological, chemical and sensory quality characteristics (total volatile bases, raw organoleptic assessment, freshness flavor, pH, viscosity, solubility, enzymatic activity, Ca²⁺sensitivity) were analyzed from actual experience in fish processing plants as well as from data obtained in the literature. These characteristics were studied together on a dimensionless scale, when white fish species, such as hake (Merluccius hubbsi) and cod (Gadus morhua), are processed to obtain iced and frozen products. A linear correlation between raw material and product quality was found. This correlation can be used by the industry in production planning and quality management. It is useful to settle the quality of the raw material to be purchased in order to achieve a certain product quality. Additionally, it can be used to test and check the overall process efficiency.     

Influence of feeding state and frozen storage temperature on the lipid stability of Atlantic mackerel (Scomber scombrus)

Lipid deterioration of mackerel caught in Icelandic waters was studied, as affected by different frozen storage temperatures (?18 °C vs. ?25 °C) and seasonal variation (August vs. September). The lipid stability was investigated by analyses of hydroperoxide value (PV), thiobarbituric acid reactive substances (TBARS), free fatty acids, as well as changes in fatty acid composition. Results showed significant lipid deterioration with extended storage time, where the lower storage temperature showed significantly more protective effects. Furthermore, a higher lipid oxidation level was recorded for fish caught in September than in August, although lipid hydrolysis occurred to be greater for fish in August than in September. Moreover, results indicated a rather stable level of omega‐3 fatty acid during the whole frozen storage period. The analysis indicated that both lipid oxidation and hydrolysis were affected by the frozen storage temperature and the stability differed with regard to season of catch.