Materials Fabrication from Native and Recombinant Thermoplastic Squid Proteins

Natural elastomers made from protein extracts have received significant interest as eco‐friendly functional materials due to their unique mechanical and optical properties emanating from secondary structures. The next generation sequencing approach is used to identify protein sequences in a squid ring teeth complex extracted from Loligo vulgaris and the use of recombinant expression is demonstrated in the fabrication of a new generation of thermoplastic materials. Native and recombinant thermoplastic squid proteins exhibit reversible solid to melt phase transition, enabling them to be thermally shaped into 3D geometries such as fibers, colloids, and thin films. Direct extraction or recombinant expression of protein based thermoplastics opens up new avenues for materials fabrication and synthesis, which will eventually be competitive with the high‐end synthetic oil based plastics.     

Influence of Some Protease Inhibitors on Gelation of Squid Muscle

ABSTRACT: The effect of 4 food-grade protease inhibitors–bovine plasma, potato powder, ethylenediamine-tetraacetic acid, and sodium pyrophosphate–on heat gelation of squid (Todaropsis eblanae) muscle was studied. The action of these ingredients was characterized by determining the proteolytic activity in batters containing them and the rheological properties of gels made with them. The gelation profile showed that the setting effect was greatest with pyrophosphate (PPI) and that gel rigidity was highest with bovine plasma (BP). All 4 inhibited proteolytic activity to some extent at 65 °C. BP was the most effective. At 40 °C, only EDTA and PPI were active. Rheologically, the most effective combination was PPI plus bovine plasma in that this combined inhibition of proteolytic activity with gel enhancement.     

Sensory, Colour and Psychrotrophic Bacterial Analyses of Squids (Loligo plei) During Storage in Ice

The after catch quality decrease of squid, Loligo plei, was evaluated, comparing two storage treatments: contact and non-contact with ice. The squids were evaluated for their sensory, instrumental colour and psychrotrophic bacterial count changes. A principal component analysis of the sensory data indicated that the squid quality markedly decreased after 7 days of storage, in both treatments. The instrumental colour analysis showed that the red and yellow colours of the squid skin increased with time in both treatments, while in the muscle, the intensity of the red and yellow colours increased more in the non-contact than in the contact with ice treatment. The results of the sensory and instrumental colour analyses were highly correlated, both being adequate for squid quality evaluation. The storage methods did not affect the development of bacterial counts, which in both treatments were below 106 cfu/g of muscle after 16 days of storage. The results showed that in both treatments the end of the shelf-life of L. plei squid was determined by the loss of its sensory quality. The packaging of the squids resulted in more intense changes in the characteristic colour of the squid muscle, and did not promote a significant reduction in microbial growth. Thus the non-contact ice storage method presented no advantages when compared with the contact ice storage method with respect to the quality preservation of L. plei under laboratory conditions.     

Microencapsulation of Squid Oil with Hydrophilic Macromolecules for Oxidative and Thermal Stabilization

The oxidative and thermal stabilities of unencapsulated and encapsulated squid oils were compared by polyene ratio, DSC-FTIR and pressure DSC. Wall material containing gelatin, caseinate and maltodextrin provided optima1 protection against oxidation. Stability was improved when lecithin and Avicel were part of the wall material. The synergistic effects of lecithin with naturally occurring α-tocopherol and the compact structures of microcapsules enhanced stability. Stability of squid oil microcapsules decreased when α-tocopherdl was removed by alumina chromatography. Both DSC-FTIR and pressure DSC were suitable for evaluating oxidative and thermal stability of encapsulated oil products.     

Effect of solvent polarity and fractionation temperature on the physicochemical properties of squid viscera stearin

Complete utilization of squid viscera oil was found to be feasible by solvent fractionation. The effects of solvent polarity and temperature on yield, soft melting point, fatty acid composition and solid fat content of the stearin were studied. Although yield increased with increasing solvent polarity and with decreasing fractionation temperature, the stearin obtained has a lower soft melting point. This makes it unsuitable as a table margarine. Operation at lower temperature also increased the operating cost. Solid fat content of the stearins fractionated at-1°C was 10% higher than of those at -5 or -9°C for all solvent polarities studied. Solid fat content of stearin increased with the decrease of solvent polarity at every tested temperature. The combined effects of polarity and fractionation temperature affect the soft melting point and solid fat content, which determine the commercial application of the stearin. The percentage of saturated fatty acids of stearin decreased with increasing solvent polarity, and the percentage of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) increased with solvent polarity and fractionation temperature. The percentage of EPA + DHA in stearin decreased with temperature, except for those from 5.1 p′ solvent. The practical fractionation condition is at -1 or -5°C with a solvent polarity of 5.1 p′. The stearin fraction can be made into a series of products, such as high EPA- and DHA-containing table margarine.     

Contact chemosensory cues in egg bundles elicit male-male agonistic conflicts in the squid Loligo pealeii

Male Loligo pealeii engage in frequent agonistic bouts to gain access to female mates while aggregated at communal egg beds. Male squids are attracted to eggs in the field and in the laboratory. It was recently demonstrated that visual detection followed by physical contact with egg capsules elicited male–male aggression. We tested specific physical and chemical features of the egg capsules that may cause this strong behavioral reaction. Male squids were presented with either natural or artificial egg stimuli and scored for four selected behaviors (egg touch, egg blowing, forward-lunge grab, and fin-beating), the last two of which are highly aggressive behaviors. First, squids were presented with natural eggs versus eggs sealed in agarose-coated tubes (ESACT), which eliminated both tactile and chemical stimuli. Second, males were presented with natural eggs versus eggs sealed in agarose coated tubes containing C₁₈ Sep-Pak-purified extracts (TCPE) from squid egg capsules, which provided chemical cues from natural eggs without the physical stimulus of the egg capsules. Third, natural eggs versus heat-denatured eggs were tested to determine whether the active factor in natural eggs is heat-labile. Squids responded aggressively when contacting natural eggs and TCPE, whereas squids did not respond after touching ESACT or denatured eggs. These results suggest that aggressive behavior is elicited by a heat-labile factor that is embedded within squid egg capsules. This chemosensory cue appears to be a contact pheromone that stimulates the agonistic interactions that characterize the mating behavior of migratory squids on inshore spawning grounds.     

形状记忆合金丝驱动的仿生喷射推进器

为了给水下机器人提供一种高速、高效、高机动性、高隐蔽性的推进器,研制了一种采用形状记忆合金丝驱动的模仿乌贼喷射推进原理的仿生喷射推进器.对乌贼的喷射推进机理和乌贼外套膜肌肉结构进行了分析.在适当简化的基础上,模仿乌贼外套膜的肌肉结构设计了记忆合金丝驱动的仿生喷射推进器结构,建立了推进器的几何模型.对推进器样机进行了初步...     

乌贼喷射过程的数值模拟

为了研究乌贼喷水过程中的流场状态,为仿生乌贼机器人的研究提供理论基础,用CFD软件对乌贼的喷水过程进行了数值模拟.建立了简化的乌贼身体模型,用动网格技术模拟外套膜的收缩动作,对其二维轴对称、不可压缩、层流时的瞬态Navier-Stokes方程进行数值求解,仿真不同的外套膜收缩速度及不同直径喷嘴喷射后涡流环的形成发展过程...     

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.     

Stability of the physical properties of plasticized edible films from squid (Todarodes pacificus) mantle muscle during storage

Edible films from squid mantle muscle plasticized with different plasticizers were stored at 25 °C, 50% RH before the determination of physical properties. The results showed that tensile strength significantly increased (P < 0.05) upon the storage time, especially for the film plasticized with glucose, while there was no significant change (P ≥ 0.05) in elongation at break of all plasticized films. Water vapor permeability of glucose-plasticized film significantly decreased (P < 0.05) during storage, while there was only a slight change in those with glycerol, sorbitol, and fructose. Redness and yellowness of the films became significantly higher (P < 0.05) during storage, especially for the films plasticized with fructose and glucose. SDS-PAGE and protein solubility in SDS solution showed a possibility of protein aggregation throughout the storage. From these results, it is suggested that the changes in physical properties of the films were caused by the progress of Maillard reaction. PRACTICAL APPLICATION: In this study, squid mantle muscle was used as an edible film-forming material. By mixing with Na-citrate, squid mantle muscle possessed the ability to form transparent films with an excellent UV barrier property. Glycerol was found to be the most effective and stable plasticizer for the films. Edible films represent an option for the utilization of discarded squid during the fishing process.