Squid Mantle Research Articles

Autolysis of Squid Mantle Muscle Protein as Affected by Storage Conditions and Inhibitors

ABSTRACTAutolysis of squid mantle muscle was investigated under various conditions using muscle homogenate as a model system. Cleavage of myosin into heavy and light meromyosin was prominent during autolysis. Storage conditions such as NaCl concentration and temperature affected not only the rate of autolysis but also the products formed. Conditions for maximal autolysis were: NaCl concentration 0.3M, pH 7 and temperature 40°C. Autolysis was well inhibited by ethylenediaminetetra acetic acid and Na‐pyrophosphate at <25°C and by phenyhnethylsulfonyl fluoride and chymotrypsin inhibitor extracted from potato tuber at >35°C suggesting two different types of proteinases were involved.

Rheological Properties of Dried Squid Mantle Change on Softening

ABSTRACTTO CLARIFY differences between raw squid and softened dried squid, dried squid mantle was softened under various conditions, degree of swelling and certain properties were measured, and the musculature was examined by electron microscopy. Swelling the dried squid to the original level of raw squid required softening in three steps: presoaking, alkali‐soaking, and post‐soaking. The alkali‐soaking was mainly responsible for the swelling effect. Resulting properties were largely changed from those of raw squid. Electron microscopy showed much water permeation throughout the muscle fibrils and fibers, while there was almost no permeation of water inside the individual fibrils.

Purification and characterization of two metalloproteinases from squid mantle muscle, myosinase I and myosinase II

Metailoproteinases, myosinase I and myosinase II, that hydrolyze the heavy chain of myosin, were purified from squid mantle muscle. Myosinase I does not hydrolyze other muscle proteins, casein, haemoglobin, or MCA-substrates, while II hydrolyzes tropomyosin. Both myosinase I and myosinase II gave a single protein band on SDS-PAGE with a molecular mass of 16 and 20 kDa, respectively. Their activities were inhibited by EDTA and 1,10-phenanthroline, and II was also inhibited by EGTA. They could be reactivated with some divalent cations, I was especially reactivated with Co 2+ and II especially with Zn 2+. The optimum pH of both activities was 7.0; the optimum temperature for both was 40°C. Myosinase I hydrolyzes myosin heavy chains to produce 130 and 90 kDa fragments. The N-terminal amino-acid sequence of the 90 kDa fragment indicates that myosinase I splits the myosin heavy chain between Ala-ll61 and Thr-l162 in subfragment 2. Myosinase II hydrolyzes myosin heavy chain to produce 158 and 65 kDa fragments, and it splits between Glu-1381 and Thr-1382 in LMM. Myosinases I and II are most likely related to the metabolism of myosin in vivo.

Effect of high hydrostatic pressure on the thermal gelation of squid mantle meat

High pressure treatment was applied to squid meat paste in order to improve its lower thermal gelation ability. The meat pastes were compressed at up to 1000 MPa for 20 min with hydrostatic pressure and then heated in two ways; heated at 90°C for 30 min (one-step heating); heated at 35°C for 30 min followed by 90°C for 30 min (two-step heating). The breaking strength value of the gel formed by the pressure (400 MPa)-one-step heating treatment was twice as high as that of thermal induced gel. On the other hand, the value for gel with two-step heating was considerably lower than that with one-step heating. The deterioration of gels with two-step heating was completely suppressed by pressurization at 800 MPa for 20 min prior to heating. Pressure treatment at more than 800 MPa could inactivate protease(s) involved in proteolysis of squid mantle muscle protein. These results indicate that high pressure treatment before heating was effective in inducing thermal gelation of squid meat.

Proteolysis Affects Thermal Gelation of Squid Mantle Muscle

ABSTRACTThermal gelation of squid mantle muscle was studied by means of gel strength measurement and SDS‐polyacrylamide gel electrophoresis. The gel strength of thermally induced squid meat gel decreased when squid meat paste was heated in two steps (35°C for 30 min followed by 90°C for 30 min). This decrease in gel strength was effectively depressed by the addition of protease inhibitors such as ethylenediaminetetraacetic acid (EDTA), phenylmethylsulfonyl fluoride (PMSF), and soybean trypsin inhibitor, indicating that me‐tallo‐ and/or serine‐proteases were mainly involved in the deterioration of squid meat gel prepared by two‐step heating. SDS‐PAGE analysis demonstrated that EDTA or PMSF suppressed the degradation of myosin heavy chain.

EFFECT OF SQUID LIVER EXTRACT ON PROTEINS AND ON THE TEXTURE OF COOKED SQUID MANTLE

ABSTRACT The liver extract of squid Illex argentinus has a proteolytic activity at pH 2–8, with optimum at pH 2.6–3.1. At pH 6 the enzymes retain about 30 and 55% of the maximum proteolytic activity towards hemoglobin and casein, respectively. In squid mantle meat treated with the extract 24 h at 4C and 20C, the sarcoplasmic and myofibrillar proteins were hydrolyzed to low molecular fractions, as was shown by SDS-PAGE. Soaking isolated collagen fibers in the liver extract resulted after 24 h in almost complete solubilization of the fibers in buffered SDS/urea solutions. The solubilized product contained only low molecular weight components. A significant hydrolysis of the proteins in the squid mantle, treated with the liver extract at 20 or 4C, was accompanied by a decrease in toughness of the cooked product by about 65 and 40%, respectively, as compared to the toughness of untreated cooked samples. Cooking of the mantle directly in the liver extract had practically no tenderizing effect.

Feeds and Feeding Schedules for Indoor Nursery Culture of Postlarval Freshwater Prawns Macrobrachium rosenbergii1

AbstractPotential feeds, feeding schedules, and feed supplements for growing M. rosenbergii postlarvae to a juvenile size of 0.5 g were evaluated. Postlarvae were grown in 69 L aquaria for 6 to 9 weeks at densities of 1.3 or 2.0/L at a water temperature of 28 C. An experimental diet (HFX‐EXD‐86X) and four commercially available feeds (Purina Trout Chow No. 2, Silver Cup Fish Feed—Salmon No. 3, Zeigler Shrimp Post Larval Granules No. 3, and MFC Clover Brand 38% Catfish Fingerling Crumbles) were tested. Prawns fed Purina Trout Chow No. 2 had the best survival and yield. Four feeding schedules were then evaluated with Purina Trout Chow No. 2 as the only food: once daily (at 1600 h), twice daily (at 0800 and 1600 h), twice daily (at 0800 and 2000 h), and three times daily (at 0800, 1600, and 2400 h). Prawns in the oncedaily treatment exhibited the best survival, final weight, yield, and food conversion ratio. A oncedaily frequency was then used to test the effects of supplementing the Purina diet with beef liver, squid mantle, codfish muscle, or cooked (scrambled) chicken egg, at 20% dry weight of the total diet. Prawns fed the beef liver supplement had the best final weight and yield.

Role of collagen and contractile elements in ultimate tensile strength of squid mantle

Squid mantle was treated with probes to establish the relative importance of collagen and contractile proteins in tensile strenght as a function of sample orientation. Collagenase was used to modify collagen, and NaCl and a crude trypsin preparation were used to modify the contractile elements. The results support the hypothesis that collagen is a primary determinant of raw mantle strenght in the longitudinal direction and that muscle fibers are relatively more important in the transverse

Complex Formation between Regulatory and Essential Light Chain on Squid Mantle Myosin Subfragment-1 Revealed by Thermal Denaturation Method

Thermal treatment of squid myosin subfragment-1 (S-1) in the presence of EDTA results in a rapid inactivation of ATPase, a marked turbidity increase, and a dissociation of light chains. These effects were suppressed by addition of calcium ion. Different light chain binding in EDTA-medium from that in Ca-medium was demonstrated by the tryptic digestion of native squid S-1; the two types of light chain are both resistant to trypsinolysis in Ca-medium, whereas they are readily degraded in EDTA-medium. S-1 heavy chain was converted into three fragments with sizes of 27, 47, and 22 kDa in both media. However, trypsinolysis of S-1 inactivated in Ca-medium generated no such heavy chain fragments that survived, while the two types of light chain survived. These light chains were isolated as a complex lacking any heavy chain fragments, and the complex formation was Ca-sensitive. It is concluded that regulatory and essential light chains are present on S-1 as a complex whose formation is mediated by calcium ion, and this binding might alter the S-1 conformation so as to confer resistance to thermal treatment.

EFFECTS of HEATING and POSTMORTEM AGING ON PHYSICAL PROPERTIES of SQUID MANTLE

Physical and tensile properties of Loligo and Illex squid mantles were evaluated during refrigerated storage and after various heat treatments. A major decrease in ultimate tensile strength of the mantle occurred between 50° and 60°C in a direction parallel to the longitudinal axis of the mantle. After storage for more than 4 days at 4°C, the ultimate tensile strength of the mantle decreased significantly in the longitudinal but not the transverse direction. In addition, heating of mantle (100°C for 2 min) stored for more than 4 days led to greater strength loss than observed in heated, nonstored mantle, indicating that refrigerated storage produces changes in collagen that make it more susceptible to the effects of high temperature. Strength loss in the transverse direction after heating was observed in mantle of Loligo but not Illex.

BROWNING BEHAVIOR OF TAURINE AND PROLINE IN MODEL AND DRIED SQUID SYSTEMS

Model systems containing taurine or proline mixed with glucose at pH 6.4 were adjusted for water activity (Aw) to 0.99, 0.90, 0.84, 0.75 and 0.60 with celite. The browning rates measured during 96 h at temperatures between 5° and 45°C increased with increased temperature and reduced water activity. The model system containing taurine had a higher browning rate than that with proline at the same Aw and temperature. The browning rate with taurine at Aw = 0.60 increased 34 times at 45°C and 7 times at 35°C compared to that at 25°C. Decreases in Aw from 0.90 to 0.60 resulted in increased browning rate, 4.1 times at 45°C and 1.3 times at 35°C. The browning rate in model systems with proline followed the same pattern. Temperature had a more pronounced effect on browning rate than Aw. Browning was very slow in model systems at temperatures below 25°C. Evidence is provided that the Maillard reaction occurred in the mantle of squid (Illex argentinus) during air drying at 35°C. Dehydration resulted in loss of 50% of the taurine (from 22.3 to 11.6 mmoles/100g dry mass) and more than 60% of the proline (from 23.4 to 8.9 mmoles/100g dry mass). Total free amino acids remained unchanged when the moisture level was above 50% or Aw = 0.95. The browning intensity of the squid mantle increased 5 fold during drying. Taurine and proline were digested most at water activity above 0.95, while other amino acids were lost at a greater rate in the intermediate water activity range.

Water Activity and Temperature Effects on Nonenzymic Browning of Amino Acids in Dried Squid and Simulated Model System

ABSTRACTAt constant temperatures (5 to 45°C) browning rate patterns of 22 amino acids, induced during dehydration in presence of glucose and celite, pH 6.4, Aw 0.60 to 0.85, were classified into three types: 1. (lysine, histidine, and glycine) showed high rates over a broad aw range. 2. (Cysteine and methionine) had intermediate browning rates and a pattern of multiple maxima. 3. Amino acids (glutamine, valine and tryptophan) had low browning rates and showed a single sharp browning maximum. Squid mantle had broad browning maxima over the intermediate a range resembling type 1, which comprised 75% of the total free amino acids in squid. Browning of squid was accelerated at ≥ 23°C, with aw 0.60 to 0.90. Activation energy of the model systems was 10 to 35 kcal/mole, and Q10 were 1 to 8.

Thermal Conductivity of Fresh and Dried Squid Meat by Line Source Thermal Conductivity Probe

Thermal conductivities (TC) of fresh and dried squid mantle meat determined using a line source probe method varied from 0.52 to 0.04 w/m°C at 30°C. TC decreased with decreasing moisture. TC data correlated with moisture content by an exponential form equation.

A Study of the Antioxidative Substance(s) in Squid Mantle Muscle.

The lipid peroxidation suppressing ability of whole lipid extracted from commercially purchased squid mantle muscle of three common squids, i.e., Japanese common squid (Todarodes pacificus), flying squid (Ommastrephes bartrami) and short-finned squid (Illex argentinus), was evaluated by the progress of peroxide value (PV) and carbonyl value (CV) of purified sardine oil with or without addition of whole lipid fraction at 10% level. Every whole lipid extracted from the three species of squid markedly suppressed the peroxidation of purified sardine oil. The whole lipid of I. argentinus showed the strongest suppressive activity of the three. Neither differences in compositions of lipid and fatty acids nor content and composition of tocopherols in the mantle muscle could sufficiently account for their antioxidative ability. The addition of purified phospholipid fraction, fractionated from the whole lipid of I. argentinus, to purified sardine oil at the concentration of 5% (w/w) markedly suppressed the peroxidation of sardine oil.

Thermal Denaturation of Squid Myofibrils: Effects of Calcium Ion and EDTA.

The effect of Ca2+ and EDTA on the thermal inactivation rate (KD) of squid mantle muscle myofibrils (Mf) ATPase was investigated, and squid Mf was found to be remarkably stabilized (roughly 100 times) in the presence of Ca2+ compared with in the presence of EDTA. The KD value of squid Mf was also affected by KCl concentration present, and increase in KCl from 0.1 M to 0.7 M enhanced the inactivation 500 fold. Therefore, it was concluded that squid myosin was stabilized significantly by actin in the presence of Ca2+ at a low-salt medium. It was also found that stabilizing effect of sorbitol was independent on the presence of Ca2+, and functioned additionally if both were present together.

Studies on Precursors of the Odor Evolved from Cooked Squid Mantle Flesh.

In order to elucidate a mechanism responsible for the development of the odor characteristic of cooked squid flesh, squid mantle flesh was extracted with various solvents and the resulting extracts were evaluated organoleptically after cooking. As a result, 80% aqueous methanol extract was found to produce a cooked squid-like odor. The extract was fractionated by means of ion exch-ange column chromatography and each of the fractions obtained was subjected to cooking, followed by organoleptic evaluation. However, any fraction did not produce a cooked squid-like odor. On the basis of the composition of 80% aqueous methanol extract, an artificial extract was prepared with reagents. The artificial extract thus obtained closely resembled 80% aqueous methanol extract in respect of the cooked odor. To elucidate the role of individual components, the artificial ex-tracts from which certain components alone or as group were omitted were subjected to organoleptic evaluation after cooking. All of the neutral, acidic, basic, and sulfur-containing amino acids were involved in the development of the cooked squid-like odor. The odor of artificial extract cooked without addition of either octopine or ribose was lacking in the characteristics of cooked squid odor. Zinc ion as well as phosphorus compound accelerated the development of the cooked squid-like odor.

Laboratory investigations of bait acceptance by the cod, Gadus morhua L.: identification of feeding stimulants

A comparison has been made of the feeding stimulant activity of squid ( Loligo forbesi Steenstrup) mantle ethanol extract (SEE), synthetic squid mixture (SSM) and components of that mixture for juvenile cod, Gadus morhua L. The SSM and SEE were equally effective as feeding stimulants, demonstrating that all the active compounds present in SEE had been identified. The complete l-amino acid mixture and the neutral l-amino acid mixture both acted as feeding stimulants, but neither was as effective as SSM, while the non-amino acid components were inactive. Addition of the non-amino acid components to the neutral l-amino acid did not raise the feeding stimulant activity to that of SSM, indicating synergistic interactions between the neutral l-amino acids, the aromatic, basic and/or acidic l-amino acids and the non-amino acid components.

Determination of intracellular buffer values after metabolic inhibition by fluoride and nitrilotriacetic acid

Non-bicarbonate buffer values have been analysed in homogenates of squid mantle muscle and toad gastronemius muscle using the P CO 2 equilibration technique. Homogenate metabolism was inhibited by the addition of potassium fluoride and nitrilotriacetic acid. After and initial change in the concentration of organic phosphates a new metabolic equilibrium was achieved which was insensitive to pH changes during P CO 2 variations. Inaccurate measurements of homogenate buffer values could, thereby, be prevented. The accumulation of inorganic phosphate during the initial metabolic shift caused an increase in homogenate buffer values. Levels of unbound inorganic phosphate, which are effective in buffering, were estimated by enzymatic analysis in homogenate ultrafiltrates. Based on the evaluation of apparent dissociation constants pK′, and buffer values for fluoride and inorganic phosphate, the non-bicarbonate, non-phosphate i, (i:inorganic) buffer value of the tissue was calculated. The level of free inorganic phosphate in the resting tissue was considered for an estimate of the intracellular non-bicarbonate buffer value under control conditions.

Purification of calmodulin from squid Todarodes pacificus and its distribution.

Calmodulin (CaM) was purified from squid mantle muscle using hydrophobic chromatography. Relative molecular mass of the purified CaM deduced form the SDS-PAGE was exactly the same as that of bovine brain. Comparison of bovine brain and squid CaM indicates that each activates phosphodiesterase identically and that their activation curves are superimposable. Distribution of CaM in the squid tissues was also examined by measuring the activation level of PDE activity. The content of squid CaM in generative organ and fin is relatively higher than in pancreas, liver, and mantle muscle.

Feed optimization in atlantic cod ( Gadus morhua): Fat versus protein content in the feed

Two feeding experiments were performed with cod. One involved 40-g fish fed for 26 days and the other 180-g fish fed for 60 days. Feeds based on squid mantle, capelin oil and dextrinized potato starch were made up to give from 75% to 27% of available protein energy, balanced with from 11% to 61% fat energy, all with 12–15% carbohydrate energy. In the second experiment, three groups of fish were fed each day, and three groups every third day, whereas in the first experiment all fish were fed five days a week. Relative growth, feed conversion, digestibilities and retentions of protein and fat were determined. Protein retentions were calculated as PER (live weight gain over protein intake) and PPV (protein gain over protein intake). The apparent digestibilities for protein and fat were above 90%, except for a diet with 61% available energy from fat. The protein-sparing effect of fat seemed to be low in cod, and 26% to 29% of protein was retained, as compared with 50% to 60% of fat, except for groups on a very low-fat diet or on reduced feeding frequency. Dietary lipid was deposited as liver fat, and a linear relation between the liver index and the fat intake was demonstrated. It was concluded that PPV is a more appropriate index for growth than PER in studies on a lean fish such as cod with a low-fat fillet and a fatty liver. A reduced feeding frequency had no effect on feed conversion and PER whereas the weight gain and PPV were reduced. Based on these experiments optimal growth for cod may be achieved with a feed giving available energy concentrations of 60%, 25% and 15% from protein, fat and carbohydrate, respectively, fed every day.