Proteolysis Affects Thermal Gelation of Squid Mantle Muscle

Thermal 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.     

Measuring miniature eye movements by means of a SQUID magnetometer

A new technique to measure small eye movements is reported. The precise recording of human eye movements is necessary for research on visual fatigue induced by visual display units.¹ So far all methods used have disadvantages: especially those which are sensitive or are rather painful.^2,3 Our method is based on a transformation of mechanical vibrations into magnetic flux variations. In order to do this a small magnet is embedded in a close-fitting soft contact lens. The magnetic flux variations caused by eyeball movements during fixation are measured by means of a SQUID magnetometer. The recordings show the typical fixation pattern of a human eye. This pattern is composed of three kinds of movements: saccades, drift and microtremor. The last-mentioned type of movements are displacements in the order of 2 μm. It is possible to distinguish between movements which are perpendicular to each other.     

海带、鱿鱼复合海鲜营养酱的研制

本文介绍了一种以海带、鱿鱼为原料的复合海鲜营养酱的加工工艺,并对其工艺条件和质量指标进行了探讨。     

Dimethylamine, trimethylamine, and biogenic amine formation in high-pressure processed semidried squid (Todarodes pacificius) during refrigerated storage

The quality properties of semidried squid treated with high-pressure processing (HPP) were investigated during refrigerated storage. The vacuum-packed semidried squid samples were subjected to 500 MPa for 0 min (HPP-0), 5 min (HPP-5), and 10 min (HPP-10) by using a custom-made high-pressure processor and stored at a refrigerated temperature for 28 d. The populations of indigenous psychrotrophic and mesophilic bacteria were effectively reduced by approximately 1 and 2 log CFU/g at the HPP-10 treatment, respectively. Compared to the control, the bacterial counts in HPP-treated semidried squid samples were maintained at low levels throughout the storage period. The increase in the amounts of dimethylamine (DMA) and trimethylamine (TMA) was more pronounced at the unpressurized control than at the HPP treatments. The production of biogenic amines (BAs) varied with HPP treatment during refrigerated storage. Therefore, the application of HPP may provide a significant improvement in the safety and quality of semidried squid.     

Utilization of oryzacystatin for regulating the ripening of squid shiokara, a traditional Japanese salted and fermented seafood

Shiokara is a fermented seafood composed of sliced squid mantle muscle ripened with fresh squid liver. Preliminary sensory evaluation by using the ranking test revealed that the hardness of squid muscle in shiokara was reduced within 7 d of ripening. During the process of ripening, muscle proteins were digested by proteinases present in squid liver. The degradation of paramyosin and myosin heavy chain was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The hardness of squid mantle muscle in shiokara was reduced with the degradation of paramyosin and myosin heavy chain. This degradation was mainly caused by E-64-sensitive cysteine proteinases. To control the hardness of shiokara, we used rice seed oryzacystatin, which suppresses proteolysis by papain-like cysteine proteinases. When oryzacystatin was added 4 d after the start of shiokara ripening, the muscle protein degradation stopped, without further muscle softening. These results show that oryzacystatin is useful to control the ripening of shiokara by regulating its hardness.     

微波能对杀虫效果及鱿鱼干品质的影响

通过不同的微波能量（微波功率与作用时间的调整）对苍蝇蛹、卵及幼虫、蝗虫卵进行处理,以研究微波对虫卵的杀灭效果及其对鱿鱼品质的影响。试验结果表明：在微波能量为110J／g以上时,苍蝇蛹、附着在鱿鱼表面的蝇卵及其幼虫、蝗虫卵的死亡率为100％,或当微波加热的温度超过500℃,虫卵的死亡率也达100％。研究同时表明：在同等能量输出的情况下,采用较小的输出功率和较长的作用时间其灭虫效果更好;对于温度的敏感性,幼虫最为敏感,其次是虫卵和蛹。比较微波处理之后的鱿鱼干品质,其感官特点、理化指标及贮藏性能未出现明显的变化或基本没有变化。     

鱿鱼内脏糖蛋白提取工艺及其免疫活性初步研究

本文分析了鱿鱼内脏的一般营养成分;探索了NaCl溶液提取鱿鱼内脏糖蛋白的工艺流程及工艺条件;并初步探讨了鱿鱼内脏糖蛋白对小鼠免疫功能的影响.结果表明:鱿鱼内脏中含有较高的蛋白质;提取的最佳工艺条件是:料液比为1:6、浸提时间为60 min、NaCl浓度为3%、浸提温度为80 ℃;该工艺所提取得糖蛋白具有一定的免疫活性.     

鱿鱼下脚料水解物的制备及降血压抑制肽研究

通过对鱿鱼肝脏蛋白水解液中抑制肽的研究,为鱿鱼及其下脚料水解物的高效利用奠定了理论基础。采用酶解技术和凝胶过滤分离等技术进行研究。实验得出:胃蛋白酶为鱿鱼肝脏蛋白水解的最佳酶类,同时以水解度和ACE抑制活性为指标,得出胃蛋白酶水解的最佳条件:在36℃条件下酶解22h,酶与底物的质量比2%,底物浓度2.5%。经过上述条件处理后的水解液经超滤处理(分子量为20ku)后,用Sephadex G-50进行分离,洗脱得到等5个峰值,其中组分B的ACE抑制活性最高,其半抑制浓度(IC50)达到1.80mg/mL。     

气相色谱内标法测定鱿鱼油中的胆固醇

目的:以正三十二烷为内标物,建立了鱿鱼油中胆固醇含量测定的气相色谱(GC)分析方法。方法:采用0.5mol/L的氢氧化钾乙醇溶液在65℃水浴锅中对油样皂化30min,乙醚萃取,毛细管气相色谱法测定鱿鱼油中胆固醇,讨论并确定了样品皂化的最佳条件。结果:利用该方法,胆固醇与杂质可以得到较好的分离和准确的定量。内标法制定标准曲线相关系数大于0.999,测得胆固醇含量为29.01±0.56mg/g。胆固醇的最低检出限为2.21ng,加标回收率在92.14%～102.45%之间,其RSD<5%(n=3)。结论:该法灵敏度高,分离效果好,定量准确,适用于鱿鱼油中胆固醇的含量测定。     

Effects of hydroxyl radical induced oxidation on water holding capacity and protein structure of jumbo squid (Dosidicus gigas) mantle

Protein oxidation is considered as an important issue in food preservation process. In the present study, the potential influence of protein oxidation on water holding capacity and protein structure of jumbo squid (Dosidicus gigas) mantle was investigated. After the hydroxyl radical oxidation, it was found that the carbonyl, surface hydrophobicity and dityrosine content of myofibrillar protein significantly increased (P < 0.05), while the content of total sulphydryl decreased significantly (P < 0.01). Meanwhile, the fluorescence intensity of squid was weakened, and the maximum absorption peak of fluorescence red shift as the H₂O₂ concentration increased. The sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed that not only the protein cross-linking but also degradation could have occurred. The content of α-helix decreased, the content of β-sheet, β-turn and the unordered structures increased after oxidation. In addition, oxidation resulted in a decrease in water holding capacity. Taken together, oxidation resulted in the damage of the myofibrillar structure, the increase in muscle loss rate and the decrease in water holding capacity.