Ultrastructural and rheological changes during the gelation of giant squid (Dosidicus gigas) muscle

The giant squid or dosidicus (Dosidicus gigas) is normally shipped frozen from the coasts of America. During the period prior to freezing-when conditions are not always optimum-and during frozen storage, the functional capacity of the muscle proteins declines, rendering the material useless for certain processes such as conversion to gel. This paper examines the reasons for the lack of a good gel-forming capacity as measured both rheologically (breaking force, breaking deformation and gel strength) and in terms of ultrastructure (scanning microscopy). The study was carried out at four different temperatures known to be critical for fish muscle protein gel formation, and at two salt concentrations. At 35°C the structure was spongier in gels made with 1.5% NaCl, although a true gel was still not formed, as shown by rheological measurements. Above 30°C, the ultrastructure became more cellular, particularly in samples made with 2.5% NaCl, at which concentration gel strength values were higher. However, at neither salt concentration nor at any of the experimental temperatures was the mesh as spongy as in other fish gels reported in the literature. The values of rheological analysis and folding test were correspondingly low.     

Improvement of giant squid (Dosidicus gigas) muscle gelation by using gelling ingredients

Muscle of the giant squid (Dosidicus gigas) has a very poor gel-forming capacity and, therefore, gelation-enhancing ingredients are essential for the production of a gel of acceptable quality. Some synergy between such ingredients was found, mainly when one or two hydrocolloids (í-carrageenan or í-carrageenan and starch) were added along with a non-muscle protein (egg-white, soy protein, casein or gluten). The strongest gels were found to be those made with 1.5% NaCl and 76% moisture containing í-carrageenan, starch and non-muscle protein.     

Effect of pH and chitosan concentration on gelation of protein concentrate from giant squid mantle (Dosidicus gigas)

Jumbo squid (Dosidicus gigas) is characterised by its low commercial value, lean and white meat without bones or scales and high muscular yield. Therefore, it is an attractive species for the production of protein concentrates. However, the gelling ability of squid proteins is low due to the inherent characteristics of the proteins. Different hydrocolloids can be used to improve the gelling ability, where pH and concentration of the hydrocolloids are very important to stablish. Therefore, this study aimed to obtain a protein concentrate from Dosidicus gigas and evaluate the effect of pH and chitosan concentration on its gelation and conformational changes. Treatment at pH 7.0 with 2% chitosan improved the water‐holding capacity, elasticity and agglomeration according to the Z potential; it also improved the thermal stability and gelling according to the dynamic oscillatory measurements and differential scanning calorimetry. This information demonstrates that chitosan incorporation plays an important role in gel formation and improves the gelling capacity of squid proteins without affecting the brightness and whiteness, important parameters for this product.     

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.     

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.     

秘鲁鱿鱼丝在加工过程中挥发性风味物质的变化规律

为研究秘鲁鱿鱼丝在加工过程中挥发性风味物质的变化规律,本文采用电子鼻和顶空固相微萃取-气质联用技术（HS-SPME-GC-MS）分析了鱿鱼丝在加工工艺中5个关键控制点（原料、蒸煮4min、40℃烘干、-18℃平衡水分7d、125℃焙烤后压延拉丝）的挥发性风味物质变化。研究表明不同关键控制点样品的电子鼻信号表现出很强的聚类特性,主成分分析（PCA）和载荷分析（LA）测试样品的识别贡献率均达99.8%以上;HS-SPME-GC-MS结果分析出119种物质,各个关键控制点的产品中挥发性风味物质分别是23、31、45、61、35种,并对其中主要的挥发性风味物质的相对含量、相对气味活度值（ROAV）、气味特征及来源进行了计算和分析,表明秘鲁鱿鱼在不同加工过程中挥发性风味物质变化较大,共16种挥发性风味物质对鱼肉气味有显著性贡献,且不同关键控制点的气味物质也不完全相同。      

Postmortem biochemical behavior of giant squid (Dosidicus gigas) mantle muscle stored in ice and its relation with quality parameters

ABSTRACT:  Several freshness and spoilage indicators were monitored to characterize the postmortem biochemistry of giant squid ( Dosidicus gigas ) mantle muscle. Squid samples were obtained directly from the sea and kept at 0 °C during a 15-d storage period. Data at zero time were obtained from cryogenically frozen samples at time of capture. The adenosine 5'-triphosphate (ATP) degradation followed a different pattern as compared with that from fish species. ATP was almost completely depleted at 24-h postcatch from 6.54 to <1 μmol/g, while at the same time Hx was the predominant catabolite with a concentration of 4 μmol/g, reaching 6.85 μmol/g at day 15. K -value data followed a logarithmic pattern with time instead of a linear one, with no change after day 3, thus reducing its suitability as a freshness index. The coefficient Hx/AMP seems to be an adequate alternative for this purpose due to its constant increment with time. The high NH₄Cl content in mantle muscle (461.3 ± 24.5 mg of NH₄⁺/100 g) derived from its physiological importance for the species compromises the use of the distillation step of the TVB-N analysis commonly used as a spoilage index. This fact explains why the initially high value of TVB-N detected in mantle muscle (243.7 mg N/100 g) did not correlate with the initial low TMA-N content (1.5 ± 0.1 mg/100 g of muscle). The results suggested that under the experimental conditions the shelf life of squid exceeds 15 d.     

Rheological study of giant squid surimi (Dosidicus gigas) made by two methods with different cryoprotectants added

Two new methods were designed for making surimi from giant squid (Dosidicus gigas) muscle. The first is based on protein precipitation at the isoelectric point (type A), and the second on washing with an acid solution (type B). Chemical analyses (e.g. protein solubility, electrophoretic profile), structural analyses (scanning electronic microscopy) and above all rheological analyses were carried out. Small amplitude oscillatory tests were performed to evaluate the influence of these two methods on the viscoelasticity and gel-forming ability of squid surimi. The results showed that method B preserves the functionality of the myofibrillar proteins better, thus making for a better gel structure than method A. Moreover, the addition of different cryoprotectants (sorbitol + sucrose, sorbitol + trehalose, trehalose alone), resulted in essential differences between the two kinds of surimi. In surimi A, trehalose favoured less initial protein aggregation and hence a thermorheologically stable structure, with a better gelation profile than sorbitol + sucrose or sorbitol + trehalose, in surimi, suwari-gels and definitive-gels alike. However, in B samples the influence of different cryoprotectants was not discernible.     

Relationship between lysyl oxidase activity,pyridinoline content and muscle texture during ice storage of jumbo squid (Dosidicus gigas)

Collagen fibres, stabilised by lysyl oxidase (LOX), play an important role in jumbo squid because they are responsible for the union between various cells; therefore, a close interdependence between their functions and muscle firmness during ice storage has been suggested. In this study, the relationship between LOX activity, pyridinoline (Pyr) content and muscle texture (SF) during ice storage of jumbo squid mantle was evaluated. LOX activity was confirmed within the range of 4.1–7.1 × 10^?3 U g^?1 of protein, leading to an increase in Pyr content, detected in the range of 0.85–1.32 mmol mol^?1 of collagen after 5–20 days. The SF of the muscle became harder during the ice storage time, increasing from 21.08 to 37.95 N. It was therefore possible to establish the relationship between LOX activity, collagen cross‐links (Pyr content) and texture patterns during ice storage of jumbo squid muscle, which increased after 20 days.     

Effect of laver powder on textual,rheological properties and water distribution of squid (Dosidicus gigas) surimi gel

In order to ameliorate the gel quality of Dosidicus gigas surimi, the effects of laver powder on gel properties, rheological properties, and water-holding capacity (WHC) were investigated. Results indicated that the addition of laver powder could significantly increase the hardness, chewiness, and breaking force of surimi gels. However, the texture indexes and gel strength began to decline when additional amount exceeded 0.6%. Rheological results demonstrated that the addition of laver powder increased the storage modulus (G′) and viscosity of surimi, prolonged protein denaturation temperature in surimi gels. Moreover, the WHC of surimi gel was improved with the increase of laver powder. Further analyses in low-field nuclear magnetic resonance revealed that laver powder could shorten the transverse relaxation time, enhanced the combination with water, and altered the distribution of different water categories. The proportion of bound water and immobilized water reached its maximum and minimum at 0.6% of laver powder, respectively. Correlation analyses showed that WHC of surimi gel was negatively correlated well with the proportion of loose-bound water, but positively correlated with the strong-bound water and free water. In conclusion, the results supported that 0.6% was the optimal additional amount of laver powder for the squid-based surimi production based on the current ingredients of surimi products.     

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.     

The effect of sodium tartrate and sodium citrate on quality changes of squid (Dosidicus gigas) surimi gel

The yield of squid has grown gradually; however, the lack of intensive processing has led to the slow development of the squid industry. In a previous study, some organic salts were found to improve the quality of squid surimi gel. Therefore, this research focused on the effects of sodium citrate (SC) and sodium tartrate (ST) on the quality of squid surimi gel. Physical measurements, such as gel texture, water-holding capacity, and color of squid surimi gel, were conducted. The addition of 2.5% SC and ST significantly improved the gel strength by 40.7, 57.0, 22.9, and 58.1%, respectively, of gel strength compared with the addition of: 1.5 SC, 3.5 SC, 1.5 ST, and 3.5% ST alone. Rheological measurements revealed that the addition of 2.5% SC or ST shortened the gel degradation temperature range (i.e., 2.5% SC or ST: 40–53°C; other treatments: 40–60°C) of the squid paste during heating. Results of chemical force analysis showed that the addition of a high quantity of salt accelerated protein aggregation and reduced hydrophobic interactions and disulfide bond formation. Finally, an increase in the number of β-sheets and a decrease in the bulk water content demonstrated that the addition of 2.5% organic salt could form squid gel with a better network structure. The findings provide a scientific basis for the development of high-quality squid surimi gel.     

Effect of ionic strength on soluble protein removal from giant squid mantle (Dosidicus gigas) and functional evaluation of protein recovery

Myofibrillar protein are the principally responsible of gelling properties in fishery resource, hence, during protein concentrate or isolated proteins preparation, sarcoplasmic protein are discarded; however, myofibrillar protein can support low levels of sarcoplasmic proteins without affecting the gelling property. Therefore, the aim of this study was to gradually remove sarcoplasmic proteins from giant squid mantle by means of different ionic strengths (I). Solutions of NaCl with different ionic strengths (I=0.0, 0.1, and 0.3) were used to obtain 3 protein concentrates. The electrophoretic profile in SDS-PAGE showed differences in protein removal with a high solubility of mantle proteins. The texture profile analysis showed that hardness increased in mantle protein washed with higher I. The total reactive sulfhydryls showed significant changes (p<0.05) detecting major formation of S-S bonds with protein removal at an I of 0.3. Differential scanning calorimetry showed a minor denaturation temperature of the actomyosin complex when protein removal was performed with an I of 0.3. The present study indicates that removal of sarcoplasmic protein as a function of I results in better quality gels.     

卡拉胶寡糖对秘鲁鱿鱼肌原纤维蛋白功能特性的影响

为探讨卡拉胶寡糖对冻藏鱿鱼肌肉品质特性的影响,以0、0.2%、0.4%和0.6%(w/v)卡拉胶寡糖与鱿鱼肌原纤维蛋白溶液进行混合,在120d冻藏过程中,分析测定肌原纤维蛋白浊度、乳化能力、Ca~(2+)-ATPase活性、羰基含量、总巯基含量及表面疏水性等变化情况。结果表明,经冻藏120d后,空白组鱿鱼肌原纤维蛋白浊度、羰基含量和表面疏水性显著增加至0.623m~2/g、6.47nmol/mg和38.12μg,而其乳化活性指数(EAI)、乳化稳定性(ESI)、Ca~(2+)-ATPase活性和总巯基含量则显著下降至8.31m~2/g、9.39%、0.131U/mg和16.46μmol/mg(P<0.05)。相比于空白组,0.6%卡拉胶寡糖处理鱿鱼肌原纤维蛋白的浊度、羰基含量和表面疏水性增加至0.562m~2/g、5.05nmol/mg和32.05μg,而其EAI、ESI、Ca~(2+)-ATPase活性和总巯基含量则维持在9.18m~2/g、10.18%、0.163U/mg和21.03μmol/mg,对鱿鱼肌原纤维蛋白功能特性的保护作用显著优于空白组(P<0.05)。由上,较高浓度的卡拉胶寡糖对冻藏鱿鱼肌原纤维蛋白冷冻氧化变性的抑制作用较好,其可为冻藏鱿鱼的品质保障技术提供一定的理论依据。     

Bioactive peptides from collagen hydrolysates from squid (Dosidicus gigas) by-products fractionated by ultrafiltration

The bioactive properties of peptide fractions obtained from the hydrolysis of squid (Dosidicus gigas) by-products collagen, using Protease type XIV and ultrafiltration (UFI), were studied. The basic objective was to improve the bioactivity of squid hydrolysates via the application of UFI. Peptide fractions obtained after UFI had higher antioxidant and antimutagenic activities, but the antiproliferative activity did not improve after UFI. Peptides <5 kDa (Fraction F3) showed higher antioxidant and antimutagenic activities, as well as lower antioxidant and antiproliferative activities than both, peptides >10 kDa (F1) and those within the range of >5 to <10 kDa (F2). Band at lower field observed in FT-IR spectra and proton-peaks observed at higher ¹H-NMR fields, both associated to aromatic amino acids, as well as to other antioxidant amino acids such as hydroxyproline, glycine, arginine and lysine, may explain F3 bioactivity. Ultrafiltration can, therefore, be used to improve some bioactivities of squid collagen hydrolysates.     

基于混料实验设计优化鱿鱼甲醛复合抑制剂

为了研发水产品内源性甲醛的控制新技术,本文利用SAS软件的单纯型格子混料设计进行秘鲁鱿鱼甲醛复合抑制剂的优化。确定了茶多酚、氯化钙和氯化镁三种甲醛抑制剂的最佳配比为0.026%、0.642mmol/L、0.332mmol/L。通过模型的建立得到响应值与三种物质配比之间的回归方程,其中茶多酚对鱿鱼甲醛的减少率影响最大,而氯化钙对二甲胺的减少率影响最大。方差分析和验证结果表明,该模型能够准确可靠的预测响应值,并且甲醛抑制剂在高温及pH6.0时能有效降低鱿鱼中甲醛和二甲胺含量。因此,该复合抑制剂可用于鱿鱼制品高温加工过程中内源性甲醛生成的控制。