冷藏鱼片中优势腐败菌的分离鉴定

为探讨冷藏7 d鮰鱼片中优势腐败菌的种类,将鮰鱼于4℃无菌冷库中取肉后真空包装放置于4℃冰箱中储藏7 d,从腐败鱼肉中分离出3株细菌,编号x1-1、y1-1、y2-1,进行细菌形态学观察、生理生化检测以及16S rDNA序列测定等研究。结果表明所有菌种均为革兰氏阴性短杆菌,且均为兼性厌氧菌,通过测序结果与系统进化树分析显示:x1-1与嗜水气单胞菌亲缘关系最近,达99.9%;y1-1与维氏气单胞菌亲缘关系最近,达99.79%;y2-1异嗜糖气单胞菌亲缘关系最近,达99.8%。以上各项研究结果表明:x1-1为嗜水气单胞菌;y1-1为维氏气单胞菌;y2-1为异嗜糖气单胞菌。综上所述,冷藏鮰鱼片中优势腐败菌为气单胞菌。     

不同蛋白添加剂对秘鲁鱿鱼鱼糜凝胶特性的影响

本文以不同比例柠檬酸钠（Sodium Citrate,SC）和酒石酸钠（Sodium Tartrate,ST）替代氯化钠（Sodium Chloride,NaCl）制备鱿鱼鱼糜凝胶,通过对其胶凝过程、感官特性、理化性质以及蛋白分子特性等分析,探索有机盐替代对鱿鱼鱼糜凝胶品质的影响。结果表明,当柠檬酸钠、酒石酸钠与NaCl的配比为2:1时,鱿鱼鱼糜凝胶强度、硬度、持水性均显著大于（P<0.05）其它复配组。两种有机盐（SC与ST）与NaCl配比结果表明,鱼糜凝胶的弹性和内聚性与鱼糜凝胶强度变化规律一致。盐复配添加使得鱼糜凝胶中疏水相互作用显著（P<0.05）低于对照组,并在SC、ST与NaCl配比为1:1时,疏水相互作用含量分别达至最低值（0.59、0.43 g/L）。流变学结果可以看出,有机盐添加显著缩短（40~57 ℃缩短至40~52 ℃）鱿鱼鱼糜热诱导过程中由于内源性蛋白酶导致的凝胶劣化。鱼糜凝胶的二级结构结果表明SC、ST与NaCl进行复配,α-螺旋和β-折叠含量呈现上升趋势,β-转角含量在复配比1:1时显著（P<0.05）高于对照组。低场核磁共振结果表明有机盐和NaCl的配比为2:1时,鱼糜凝胶相比其他配比组更容易固定水分,并且自由水含量更少。综上,有机盐和NaCl的配比为2:1时,可在一定程度上代替纯有机盐的添加。     

Drying and Quality Characteristics of Shredded Squid in an Infrared-Assisted Convective Dryer

Drying is one of the most common methods for processing and preserving squids. A novel forced convective dryer based on infrared heating was developed with an online temperature control. By setting the drying medium temperature of 50°C, we studied the effects of infrared wavelength and air velocity on drying characteristics of the shredded squid and qualities of dried squid products. We also compared it with the conventional hot-air drying (HAD) and advanced microwave vacuum drying (MVD). The infrared heating rate increase was faster than that of HAD. The heating and drying at the wavelength of 2.5–3.0 µm were more effective than those at the infrared wavelength of 5.0–6.0 µm. Specific energy consumption linearly increased with the air velocity. Microstructure observation showed that the infrared-dried rehydrated sample displayed a muscle fiber structure similar to the fresh sample. The infrared-dried squids had less drying shrinkage, brighter color, and better rehydration capacity than HAD products. Their sensory qualities were better than HAD and MVD products. Above all, infrared drying with wavelength of 2.5–3.0 µm and air velocity of 0.5 m/s was suggested as the best drying condition for squids in this study.     

Capabilities of a magnetic adiabatic calorimeter in measurement technology

The design of a magnetic calorimeter for the measurement of releases of energy that correspond to a number of rare events, for example, cosmic particles, particles of dark matter, isolated x-ray quanta, and so on, is proposed. The calorimeter is set into a working state by means of the method of adiabatic demagnetization and the response to energy release is measured by a quantum interferometer (squid). The action of the calorimeter in different practical problems is considered, and the sensitivity of the device and its measurement precision are estimated. Translated from Izmeritel'naya Tekhnika, No. 11, pp. 24–30, November, 2008.     

Identification of a cysteine proteinase from Jumbo squid (Dosidicus gigas) hepatopancreas as cathepsin L

A cysteine proteinase from Jumbo squid (Dosidicus gigas) hepatopancreas was partially purified by a two step procedure involving ammonium sulfate precipitation and gel filtration chromatography and further by SDS–PAGE. The molecular weight of the proteinase was 24 kDa determined by SDS–PAGE and 23.7 kDa with mass spectrometry. The activity had an optimum pH of 4.5 and optimum temperature of 55 °C under the assay for cathepsin L specific synthetic substrate Z-PAAFC. The cathepsin B and H specific synthetic substrates Z-AAAFC and H-AMC did not show any hydrolysis with the partially purified enzyme. Peptide mapping of trypsin digests of the 24 kDa band from SDS–PAGE showed the squid cysteine proteinase was homologous to cathepsin L from different animal sources. The activity of the partially purified fraction with the cathepsin L specific substrate Z-PAAFC was inhibited 75–89% by enzyme inhibitors specific for cysteine proteinases but was also significantly inhibited by serine and aspartate proteinase inhibitors.     

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.     

Effect of chitooligosaccharide from squid pen on gel properties of sardine surimi gel and its stability during refrigerated storage

Effect of chitooligosaccharide from squid pen prepared using lipase (COS-L) at various concentrations (0–30 g kg⁻¹) on gel properties of sardine surimi gel was investigated. Breaking force (BF) and deformation (DF) of gel were increased, when COS-L level was increased up to 10 g kg⁻¹ (P < 0.05). Water holding capacity and whiteness of gel were improved with the addition of COS-L than those of control. Gel added with 10 g kg⁻¹ COS-L had denser network with higher likeness score for all sensory attributes, compared to control. When gel incorporated with 10 g kg⁻¹ COS-L was stored at 4 °C, BF, DF and whiteness were maintained during 10 days of storage. Textural properties of surimi gel added with COS-L were higher than those of control throughout storage. Thus, incorporation of 10 g kg⁻¹ COS-L could improve gel properties of sardine surimi gel and retarded the deterioration of gel properties during refrigerated storage.     

Preparation and characterisation of selected physicochemical and functional properties of β‐chitosans from squid pen

Squid pen β‐chitosans prepared under various deacetylation conditions (30%, 35%, 40% and/or 45% NaOH for 15, 30 and/or 60 min) were characterised. β‐Chitosans (deacetylated with 35–45% NaOH for 15–60 min) had 87.1–96.2% degree of deacetylation (DD), 93.5–96.7% solubility and 120.5–654.9 mPa s viscosity. Treatment with 30% NaOH for 15–60 min yielded inadequately deacetylated β‐chitosans (DD = 51.9–80.2%). Two chitosans prepared under 35% NaOH for 15 min and 45% NaOH for 30 min (designated as 35%–15 and 45%–30, respectively) were further compared. Drying (sun‐drying vs. oven‐drying) methods did not affect DD. 35%–15 chitosan exhibited lower nitrogen, DD and bulk density, but higher viscosity compared with 45%–30 chitosan. Higher water‐ and fat‐binding capacity but lower DPPH radical scavenging activity were observed for 35%–15 chitosan compared with 45%–30 chitosan. Compared with 45%–30 chitosan, 35%–15 chitosan exhibited higher antibacterial activity against Salmonella Enteritidis and Listeria monocytogenes, but lower antibacterial activity against Escherichia coli.