Lysyl oxidase from jumbo squid (Dosidicus gigas) muscle: detection and partial purification

Lysyl oxidase (LOX) was detected and partially purified from jumbo squid (Dosidicus gigas) muscle, for the first time. A procedure for the purification of LOX from jumbo squid muscle which consisted of urea extraction, Sephadex G‐75 and anion exchange chromatography was developed. Activity of partially purified LOX was 390‐fold higher than the original extract. Two protein fractions with 32 and 24 kDa were detected by SDS‐PAGE. The enzyme was strongly inhibited by β‐aminopropionitrile fumarate, a specific LOX inhibitor. LOX was purified with 3.8% yield, showing a specific activity of 0.078 IU mg^?1 protein. This knowledge will help understand the behaviour of jumbo squid protein during cool storage or manufacture.     

Lysyl oxidase from jumbo squid (Dosidicus gigas) muscle: purification and partial characterization

Lysyl oxidase (LOX; E.C.1.4.3.13) was purified from jumbo squid muscle (Dosidicus gigas) with 1900‐fold and yield 1.9%, and characterized for the first time. The purification procedure consisted of fractionation with urea and a combination of size‐exclusion and anion‐exchange chromatography. The enzyme had a molecular weight of 32 kDa, as estimated by SDS‐PAGE. Using a specific LOX substrate (1,5‐diaminopentane), its optimum activity was determined at pH 8.2 and 65 °C. Activation energy (E_a) of the enzyme was 69.94 kJ K^?1 mol^?1. The enzyme was strongly inhibited by β‐aminopropionitrile fumarate (BAPN), a specific LOX inhibitor. Moreover, purified LOX was able to work at different temperatures (20–90 °C) at pH 8.2. Although further research is needed, the results from this work suggest that based on LOX activity, this enzyme may be of practical use in preventing textural changes in jumbo squid during storage or processing.     

Pink discoloration and quality changes of squid (Loligo formosana) during iced storage

Pink discoloration and quality changes of squid (6-10 squids/kg) with and without deskinning during iced storage at different squid/ice ratios (1:1 and 1:2, w/w) for 16 days were investigated. The increases in a* and b*-values of squid mantle were observed with increasing storage time (p < 0.05), indicating the formation of pink color on the mantle. The increase was more pronounced in squid without deskinning with a squid/ice ratio of 1:1 (p < 0.05). No changes in a*-value were observed in deskinned squid throughout the storage, regardless of squid/ice ratio (p > 0.05). However, the slight increase in b*-value was found in the squid with deskinning during the storage. Psychrophilic bacteria counts of squid increased continuously as the storage time increased. Coincidental increases in total volatile base (TVB), trimethylamine (TMA) and ammonia contents were observed during the storage. The rates of increase were greater in the samples with a squid/ice ratio of 1:1 than those found in the samples kept in ice with a squid/ice ratio of 1:2. Pink discoloration, psychrophilic bacteria count, TVB and TMA contents were much lowered when the squid without deskinning was treated with 0.1 g/100 mL sodium azide (NaN₃) prior to storage, suggesting that microbial growth was associated with those changes. Therefore, deskinning together with icing using a sufficient amount of ice as well as the use of safe antimicrobial agent could be a means to lower the pink discoloration and retard the losses in quality of squid stored in ice.     

Effect of dietary protein on muscle collagen,collagenase and shear force of farmed white shrimp (<Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>)

The effect of three protein sources (sardine-based diet, squid-based diet and commercial diet) in feed on white shrimp (Litopenaeus vannamei) growth, muscle collagen, collagenase activity and shear force was determined. Shrimp fed on diets with squid and sardine protein exhibited greater growth (p<0.05) than those fed with commercial feed. Shrimp muscle collagen obtained from each treatment group showed similar molecular weight to that of bovine collagen type I as determined by sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE). Denaturation thermograms by differential scanning calorimetry (DSC) for shrimp collagen showed a transition peak at 47 °C, whereas that for bovine collagen type I was 65 °C. The lowest enthalpy of transition was detected in collagen from shrimp fed on squid. The highest muscle collagenase activity was detected in shrimp fed with commercial feed. After 10-day ice storage, muscle from shrimp fed commercial feed required somewhat less shear force than those fed with sardine-based and squid-based meal. The results suggest that the source of protein influences the enthalpy of transition of collagen from shrimp muscle, collagenase activity, and texture in shrimp tail meat as well as growth rate.     

Proteomic identification and physicochemical characterisation of paramyosin and collagen from octopus (Octopus vulgaris) and jumbo squid (Dosidicus gigas)

To perform improvements in food science, it is fundamental to understand the physicochemical properties of proteins since their interaction with other macromolecules plays an essential role in food systems. Collagen and paramyosin help in the maintenance of the matrix structure cells, the textural behaviour and the technical functionality of the protein concentrates; because of this, their identification and characterisation are necessary. Cephalopods species have shown differences in the distribution of its muscle fibres. The amino acid profile of jumbo squid showed a high content of glycine and hydroxyproline, while octopus showed a high content of acidic amino acids. The thermal profile of jumbo squid showed an endothermic transition at 117 °C, which octopus did not present. Moreover, the proteomic identification confirms the identity of paramyosin with 33% coverage to paramyosin from Dosidicus gigas and a 4% coverage to collagen type II from Sepia pharaonis on octopus and jumbo squid, respectively.     

Chemical and microbial analyses of squid muscle (Loligo plei) during storage in ice

Chemical and microbial changes in squid muscle (Loligo plei) and the efficiency of chemical indices for freshness evaluation were investigated during storage in contact ice (CI) and non-contact ice (NC). Psychrotrophic bacterial counts and non-protein nitrogen, free amino acids, trimethylamine, volatile basic nitrogen (VBN), urea and free tryptophan contents were periodically determined in squid muscle. No difference (P < 0.05) was detected between treatments regarding the increase of psychrotrophic bacterial counts in squid muscle during storage. The leaching of soluble compounds in CI treatment drastically affected the efficiency of the chemical indices for freshness. Trimethylamine and VBN contents in squid muscle increased only after day 9 and no increase was observed in free tryptophan and urea contents in CI treatment. In the NC treatment the contents of VBN and trimethylamine slowly increased during the first days of storage whereas free tryptophan and urea contents markedly increased during the whole storage. Free tryptophan and urea can be useful freshness indices for L. plei in storage conditions wherein leaching have been minimized.     

Physicochemical and functional changes in jumbo squid (Dosidicus gigas) mantle muscle during ice storage

Physicochemical and functional changes of jumbo squid (Dosidicus gigas) mantle muscle stored in ice for 15 days were evaluated. Proximate analysis, pH, protein solubility (PS) and SDS-PAGE profile changes were monitored for muscle proteins, while texture profile analysis (TPA) (gel strength, elasticity and cohesiveness), water holding capacity (WHC) and colour changes were monitored for gels produced from this muscle. Fresh muscle chemical composition varied according to fishing season and/or physiological status presented by specimens. pH and PS were stable (p ? 0.05) throughout the study with a slight tendency to decrease towards the end of study. SDS-PAGE revealed no drastic changes in proteins influencing gelation (i.e., myosin). TPA and WHC of gels decreased towards the end of experiment; however, due to sampling variability, no significant differences (p ? 0.05) were found over storage time. Changes in gel colour were observed with hue angle decreasing towards yellow hues. Improved post-capture management of mantle muscle preserved its integrity and functionality for up to two weeks.     

The impact of collagen on softening of grass carp (Ctenopharyngodon idella) fillets stored under superchilled and ice storage

The objective of this work was to study the impact of collagen on softening of grass carp (Ctenopharyngodon idella) fillets during chilled storage. The fillets were stored under superchilling (?1.5 ± 0.2 °C) and with ice (0.2 ± 0.1 °C) for 21 days, and texture properties, collagen and the related enzyme activities were measured. Results showed that firmness and collagen content were strongly influenced by storage temperature and time. Fillet firmness decreased by 32.3% (superchilling) and 49.6% (ice stored) of the initial values after 3 days of storage, respectively. Total collagen content decreased with time, but different collagen fractions showed variations. Collagen degraded to different extents depending on storage conditions as indicated by SDS‐PAGE and amino acid analysis. In addition, collagenase activity declined significantly during the first 3 days, followed by a slow increase. This study demonstrated that collagen degradation was involved in grass carp fillet softening and provided useful information for fillet quality improvement.     

Physicochemical changes of pepsin-solubilized and insoluble collagen in jumbo squid (Dosidicus gigas) muscle after cooking process

Collagen is the major connective tissue (CT) protein and one of the main constituents of the jumbo squid (Dosidicus gigas). Therefore, physicochemical changes of pepsin-solubilized collagen (PSC) and insoluble collagen (IC) were studied after cooking (100°C/30 min) of muscle (mantle, fins, and arms). Different pyridinoline (Pyr) contents (the major cross-linking molecule in collagen fibers) were found in the fresh muscle of the three anatomical regions. After the cooking process, a decrease from 10 to 30% in the thermal resistance of collagen was observed, depending on the anatomical region and fraction evaluated. Furthermore, the electrophoretic profile, Fourier transform infrared (FTIR) spectroscopy, and the amino-acid profile revealed that structural changes occurred in the two different collagen fractions caused by the thermal process, and the changes were greater in the mantle. Under the conditions applied in this study, collagen fractions from the squid arms showed more stability during the cooking process due to the high cross-linking degree of their fibers.     

The role of lipid oxidation on biscuit texture during storage

The role of lipid oxidation and humidity absorption on the shelf life of biscuits was analysed. Biscuits with low lipid and sugar content were prepared employing different oils, and texture changes that biscuits experience during storage were studied. Water activity, peroxide value, malonaldehyde content and colour were also determined at different storage times. The maximum peroxide level was between 1 and 1.5 mmol kg^?1 of oil, at 166 days of storage. Values of malonaldehyde were between 5.2 and 15.8 nmol g^?1 of dry sample. Water activity and peroxide value influence the biscuit texture (P ≤ 0.05). To study the effects of both factors simultaneously, a mathematical model was adjusted to the data. Results indicate that an increase in the peroxide level, even at low level of lipid oxidation, increases Young's modulus and leads to a harder biscuit, while the humidity absorption lowers the fracture stress and Young's modulus.     

Jumbo squid (Dosidicus gigas) mantle muscle gelled-emulsified type product: formulation, processing and physicochemical characteristics

Jumbo squid ( Dosidicus gigas ), an abundant species in the Gulf of California, can have a great potential for production of gelled-emulsified type products. Thus, formulation, processing and physicochemical characteristics of frankfurter-type product from jumbo squid mantle muscle (JSF) was achieved. JSF were vacuum-packed and stored at 2–4 °C. Samples were analysed for physicochemical (colour, texture, TBARS, peroxide value, folding test, pH, and water content and holding capacity) and microbial changes at regular intervals during storage for up to 27 days. The sensory quality of the product was also evaluated. Shear force, cohesiveness and colour (hue angle and total colour difference) were the most affected ( P  <   0.05) parameters at day 27, changes most probably because of microbial growth as total aerobic counts increased to >2.7 × 10⁵ CFU g⁻¹ (day 21). Product showed acceptability. Results suggest a stable gelled-emulsified type product can be developed from jumbo squid mantle muscle opening a range of possibilities for product development.     

Effects of thermal processing and various chemical substances on formaldehyde and dimethylamine formation in squid Dosidicus gigas

BACKGROUND: Trimethylamine oxide (TMAO) in squid is demethylated to dimethylamine (DMA) and formaldehyde (FA) during storage and processing. This study examined the effects of thermal processing and various chemical substances on FA and DMA formation in squid. RESULTS: The thermal conversion of TMAO was assessed by analysing four squid and four gadoid fish species, which revealed that FA, DMA and trimethylamine (TMA) were gradually produced in squid, whereas TMA increased and FA decreased in gadoid fish. A significant increase in both FA and DMA levels was observed in the supernatant of jumbo squid with increased heating temperature and extended heating time at pH 6–7. Ferrous chloride combined with cysteine and/or ascorbate had a significantly positive effect on FA formation in the heated supernatant of jumbo squid. No significant difference was observed in the levels of Cu and Fe in squid and gadoid fish. The capability of Fe²⁺ to promote the formation of FA and DMA was not completely attributable to its reducing power in squid. CONCLUSION: Non‐enzymatic decomposition of TMAO was a key pathway during the thermal processing of jumbo squid, and Fe²⁺ was a crucial activator in the formation of FA and DMA. Copyright © 2012 Society of Chemical Industry     

Mass Transfer Modelling During Osmotic Dehydration of Jumbo Squid (Dosidicus gigas): Influence of Temperature on Diffusion Coefficients and Kinetic Parameters

Mathematical modelling was used to study the effect of process temperature on moisture and salt mass transfer during osmotic dehydration (OD) of jumbo squid with 6% (w v ⁻¹) NaCl at 75, 85 and 95 °C. The diffusion coefficients for moisture and salt increased with temperature. Based on an Arrhenius-type equation, activation energy values of 62.45 kJ mol⁻¹ and 52.14 kJ mol⁻¹ for moisture and salt, respectively, were estimated. Simulations of mass transfer for both components were performed according to Newton, Henderson and Pabis, Page, Weibull and logarithmic mathematical expressions. The influence of drying temperature on the kinetic parameters was also studied. Based on statistical tests, the Weibull and logarithmic models were the most suitable to describe the mass transfer phenomena during OD of jumbo squid.     

Muscle lysyl oxidase activity and structural/thermal properties of highly cross-linked collagen in jumbo squid (<Emphasis Type="Italic">Dosidicus gigas</Emphasis>) mantle,fins and arms

Muscle from mantle, fins and arms of squid (Dosidicus gigas) were compared based on lysyl oxidase activity (LOX), chemical/structural and thermodynamic properties of highly cross-linked collagen. The arms collagen presented the highest temperature (Tp) and enthalpy of transition. The arms collagen thermic properties may be explained by the higher imino amino acid content, proline and lysine hydroxylation degrees. Moreover, among the regions, the collagen from the arms had a more intense β band chain, hydroxymerodesmosine peak in the resonance magnetic nuclear spectra and pyridinoline peak in the Raman spectra. Fins showed the highest LOX activity. The LOX activity was associated with the Tp, proline and lysine hydroxylation degrees. These results implied that the collagen in the arms was more intermolecularly ordered than the mantle and fins, and may provide a theoretical basis for a better understanding of the thermal behaviour of squid tissues during management and processing.     

Effect of storage at 0 °C on mantle proteins and functional properties of jumbo squid

Effect of iced storage of jumbo squid mantle with fin on gelling capacity and changes in protein fractions and functional properties of jumbo squid mantle protein during storage at 0 °C were assessed. Most values of texture variables in gels did not significantly change during storage. On average, they were: strength 65.07 ± 4.71 N; elasticity 68.14 ± 5.3%, fracturability 52.97 ± 1.28 N and cohesiveness 36.6 ± 0.1%. Protein solubility increased more than 40%. Whippability increased during storage for 16 days at 0 °C (81–162%), as did foam stability (73–94%). Results suggest that iced squid mantle protein is a suitable ingredient for food products where these functional properties are desirable. Muscle fibres of squid mantle undergo various changes during storage. At 0 °C, they are disrupted, whereas at −20 °C, they aggregate and develop empty spaces in the tissue.     

Effect of air temperature on drying kinetics and quality characteristics of osmo-treated jumbo squid (Dosidicus gigas)

The present study investigated the influence of air temperature on the drying kinetics, color, rehydration, total volatile basic nitrogen (TVBN), antioxidant capacity and texture of osmosed jumbo squid fillets during convective dehydration at 50, 60, 70, 80 and 90 °C. The Logarithmic and Two-term models could be used to describe the squid experimental drying curves. Discoloration of product was more noticeable at high drying temperatures where combined effects of non-enzymatic browning as well as protein denaturation modified the original color of the squid samples. Rehydration indexes showed a decrease while texture presented an increase with increasing air-drying temperature probably due to changes in food protein matrix. Total volatile basic nitrogen increased with process temperature. Antioxidant activity presented a decrease with temperature, especially at high drying temperatures. Results of this study demonstrated that the drying kinetics together with the reported quality attributes of the dried squid can be used to improve the final characteristics of the product.     

Structural changes in squid (Loligo japonica) collagen after modification by formaldehyde

BACKGROUND: Formaldehyde (FA) has been suggested to cause changes in texture and functional properties in some marine species. It was therefore hypothesised that FA may affect collagen, a fundamental constituent of the extracellular matrix in squid. RESULTS: Two types of collagen, I and V, were isolated by pepsin digestion and differential salt precipitation. Type V collagen contained higher proportions of isoleucine, leucine, and lysine and lower proportions of alanine and hydroxyproline. The effects of FA on pepsin‐solubilised squid collagen were examined by differential scanning calorimetry and Raman spectroscopy. The squid collagen showed a transition temperature (T_m1) of 37.2 ± 0.2 °C, which was significantly reduced in the presence of 2 and 10 mmol L^?1 FA. In the presence of 1, 2 and 10 mmol L^?1 FA an additional peak (T_m2) was also observed at 77.7 ± 0.1, 78.4 ± 0.1 and 62.7 ± 0.2 °C respectively, suggesting FA–collagen interactions. Treatment with 2 mmol L^?1 FA increased the I₉₄₀/I₁₀₀₅ ratio from 1.09 to 1.66 and shifted the 990 and 1245 cm^?1 bands. The tyrosine doublet ratio (I₈₅₀/I₈₃₀) was also increased about threefold, suggesting that α helix, β sheet type and random coil structures were changed by FA. CONCLUSION: The secondary structure of squid collagen can be affected by FA through hydrophobic interactions. Copyright © 2008 Society of Chemical Industry     

Preparation of alcalase hydrolysed rice bran protein concentrate and its inhibitory effect on soybean lipoxygenase activity

Rice bran protein concentrate (RBPC) was prepared from defatted rice bran and hydrolysed by alcalase at different hydrolysis times. As the hydrolysis times increased, the degree of hydrolysis (DHs) increased. RBPC hydrolysate obtained at 50 min (RBPCH‐50) had the highest inhibitory efficiency on soybean lipoxygenase (LOX) activity (66%). The inhibition kinetics of the reaction analysed by Lineweaver–Burk plots indicates that RBPCH‐50 is a competitive inhibitor. RBPCH‐50 inhibited soybean LOX with an IC₅₀ of 11.73 μg μL^?1 RBPCH‐50, and the obtained K_I was 4.59 μg μL^?1 RBPCH‐50. LOX inhibitory activity of RBPCH‐50 was significantly higher than that of 50 and 100 ppm butylated hydroxyanisole (BHA) and 50, 100, and 200 ppm butylated hydroxytoluene (BHT) (P ≤ 0.05); however, LOX inhibitory activity of RBPCH‐50 was similar to that of 200 ppm BHA (P > 0.05). Therefore, RBPCH might potentially be used as a natural LOX inhibitor.     

Chymotrypsin isolation from jumbo squid (<Emphasis Type="Italic">Dosidicus gigas</Emphasis>) hepatopancreas: Partial characterization and effect on muscle collagen

Chymotrypsin was purified from jumbo squid hepatopancreas (HP) with 2.4-fold and yield 1.9%, and characterized with a molecular weight of 31 kDa, as estimated by sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE). Chymotrypsin effect over collagen extracted from the mantle, fins and arms of the jumbo squid was evaluated. The enzyme exhibited the maximum activity at pH 7 and 65°C using Suc-Ala-Ala-Pro-Phe-p-nitroanilide (SAAPNA) as a substrate and it was identified using the specific inhibitors N-tosyl-L-phenylalaninechloromethyl ketone (TPCK) and phenyl methyl sulfonyl fluoride (PMSF), showing residual activities of 6% and 0%, respectively. Furthermore, high activity was observed in the pH range of 4.0 to 8.0. Purified enzyme showed a moderate in vitro activity using muscle collagen as a substrate. Although further research is needed, the results suggest that the enzyme has a potential application where acidic or slightly alkaline conditions are needed.     

Biochemical,physical and sensory quality of ice-stored Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) as affected by pre-slaughter stress,percussion stunning and AQUI-S<Superscript>™</Superscript> anaesthesia

Biochemical, physical and sensory quality of farmed Atlantic cod subjected to percussion stunning (control), anaesthesia (AQUI-S^™) and excessive exercise (30 min chasing before slaughter, ‘stressed’) were analysed after 7 days of ice storage. The white muscle energy status (initial pH, muscle twitches and high-energy phosphates) revealed that the fish were truly representatives of rested (percussion stunned and anaesthetised) and stressed cod. Sensory evaluation showed that the fillets of cod exposed to percussion stunning and AQUI-S^™ anaesthesia prior slaughter had slightly higher whiteness scores, and that the fillets of AQUI-S^™ anaesthetised cod had slightly shinier surfaces than the fillets of cod exposed to pre-slaughter stress. Furthermore, fillets of anaesthetised (AQUI-S^™) cod had significantly higher inosine monophosphate (IMP) contents and lower K-values than fillets of cod exposed to pre-slaughter stress, after 7 days of ice storage. Pre-slaughter stress did to some extent affect fillet colour immediately after killing and after ice storage. Otherwise, no significant effects of stress were observed with regard to biochemical, physical or sensory quality (ultimate pH, water content, drip loss, water holding capacity, texture and gaping) of farmed Atlantic cod.