解冻方式和条件对南极磷虾品质的影响

以感官检验、出肉率和可溶性蛋白质含量为指标,分析自然解冻、微波解冻、静水解冻和流水解冻方式对南极磷虾品质的影响,并对静水结合流水的解冻方式进行探讨和优化。结果表明,自然解冻和静水解冻方式很难保证南极磷虾品质,微波解冻和流水解冻对南极磷虾品质较好,但各自仍存在缺点。采用静水结合搅拌解冻方式的L9(34)正交试验,确定南极磷虾解冻最佳工艺为静水温度为15℃,浸泡时间为7 min,搅拌速度为40 r/min。在此条件下南极磷虾感官评分为9.4,出肉率为40.5%,可溶性蛋白质含量为96.8 mg/10 g,解冻时间共为14 min。     

美拉德反应对南极磷虾酶解液中非挥发性物质的影响

以南极磷虾酶解液和木糖进行美拉德反应,研究美拉德反应后,酶解液和美拉德产物中游离氨基酸、肽分子量分布、无机离子含量等非挥发性物质的变化规律。结果表明,美拉德反应后,酶解液中多数游离氨基酸含量显著降低,其中亮氨酸、精氨酸、组氨酸、异亮氨酸、半胱氨酸损失率分别为34.18%、16.75%、16.67%、16.10%、12.37%;酶解液肽段中451 Da～1 450 Da组分具有较高的美拉德反应活性;无机离子含量以Na+含量最高;脂肪酸组成呈现减少趋势,减少组分以多不饱和脂肪酸为主。     

Compositions,flavour and antiradical properties of products from subcritical water treatment of raw Isada krill

Comparative analysis of subcritical water (SCW) treatment and ambient pressure boiling one of raw Isada krill was performed for the nutritive, flavour and antiradical properties of krill extracts and residues as well as the molecular mass and odour intensity of the extract. SCW treatment was performed for 10 min in a batch‐type vessel in the temperature range of 100–240 °C, using a 1:1 weight ratio of raw krill to water. Higher protein and lipid contents were obtained by SCW treatment relative to boiling. The lipid content of the SCW extracts increased with increasing treatment temperature. Protein was the main component in these extracts, and the highest protein content was achieved by SCW treatment at 200 °C. High‐molecular‐mass species decomposed under SCW treatment at high temperatures with consequent generation of smaller molecules. The antiradical activity of the SCW extract, determined by DPPH and ABTS assays, increased with increasing treatment temperature. The krill extracts and residues exhibited shrimp‐like flavour, and the most desirable flavour was obtained by SCW treatment at 140 °C or 160 °C for 10 min. The treatment would be applicable for the production of seasonings from Isada krill.     

不同遮荫条件下苦槠和木荷的叶绿素含量及光谱特性

研究了遮荫处理对苦槠、木荷的叶绿素(SPAD相对值)、高光谱特性的影响。结果表明:遮荫处理提高了这两种亚热带常绿阔叶植物的叶绿素含量,80%遮荫处理下的叶绿素含量最大;随遮荫度的提高红光位置则会相应出现"红移"现象;但过高的遮荫度会抑制其生长,表现出"蓝移"现象。对所研究的树种而言,红边位置处—窄波长范围内的平均光谱反射率与叶绿素总量间的相关性普遍较高,相关系数大于0.7。建立的有关红边位置处的光谱反射率与叶绿素总量间的回归模型普遍具有较高的拟合度,应用前景广泛。     

Isolation and Identification of Antihypertensive Peptides from Antarctic Krill Tail Meat Hydrolysate

ABSTRACT:  Antarctic krill ( Euphausia superba ) obtained from the huge biomass in Antarctic waters is an important food product in Japan. Antarctic krill peptide powder (AKPP) prepared from the tail meat by enzymatic hydrolysis significantly decreased the systolic blood pressure in spontaneously hypertensive rats by a single oral administration (1, 10, or 100 mg). Presumably, the effect of AKPP was through inhibition of the conversion of angiotensin, which mediates blood pressure elevation, from its inactive propeptide to the mature angiotensin. Two potent angiotensin I-converting enzyme (ACE) inhibitory peptides were isolated from AKPP by high-performance liquid chromatography (HPLC) and identified as Val-Trp (IC₅₀= 2.75 μg/mL; 12.9 μM) and Leu-Lys-Tyr (IC₅₀= 4.26 μg/mL; 10.1 μM). Val-Trp and Leu-Lys-Tyr comprised 0.025%± 0.0023% (w/w) and 0.018%± 0.0023% (w/w) of AKPP, respectively, as measured by electrospray ionization mass spectrometry (ESI-MS). The contributions of Val-Trp and Leu-Lys-Tyr to the ACE inhibitor activity of AKPP were 17.7%± 1.60% and 8.04%± 1.03%, respectively, suggesting that these 2 peptides constitute a substantial portion of the overall ACE inhibitor potential of AKPP.     

气相色谱法同时检测南极磷虾中2种ω-3脂肪酸含量

目的 建立使用甲酯化-气相色谱法同时检测南极磷虾中二十碳五烯酸(eicosapentaenoic acid, EPA)和二十二碳六烯酸(docosahexaenoic acid, DHA)含量的分析方法。方法 样品经二氯甲烷提取后,与0.5%硫酸-甲醇溶液在60 ℃条件下反应30 min,反应液使用硅酸镁柱层析净化。将洗脱液转移至15 mL离心管中,2000 r/min离心20 min,上清液氮吹浓缩后,用乙腈定容至1 mL,使用DB-1701色谱柱(30 m × 0.32 mm, 1.00 μm)分离,火焰离子化检测器检测,外标法定量。 结果 方法在0.02~2.00 mg/mL的线性范围内,相关系数大于0.9999。扣除水分的影响,同一部位的新鲜、干燥样品相对偏差小于10%;平行样品的相对标准偏差不超过6%（n = 3）,平均回收率大于82.6%。结论 该方法简便高效,检出限低、重现性好,可用于新鲜和冻干南极磷虾样品中EPA和DHA的检测。     

南极磷虾原肌球蛋白纯化鉴定、理化特性及模拟表位肽预测

对南极磷虾原肌球蛋白（tropomyosin,TM）进行提取纯化与质谱鉴定,并对其热稳定性、pH值稳定性及消化稳定性进行研究,同时利用生物信息学对其进行序列同源性分析、空间结构同源建模及过敏原模拟表位肽识别。十二烷基硫酸钠聚丙烯酰氨凝胶电泳结果显示,经蛋白粗提、热除杂、等电点沉淀、硫酸铵盐析等多步提纯,最终仅在32 kDa附近得到一条清晰条带。利用超高效液相色谱-质谱联用对其进行扫描,经UniProt数据库检索确定该目的蛋白为TM（Euphausia superba）,蛋白分子质量32.6 kDa,肽段覆盖率达97%。同源性分析结果表明南极磷虾TM是一种高度保守蛋白,与26 种甲壳动物的TM序列同源性在88%～98.2%之间。南极磷虾TM对热、酸碱及胃液消化均具有较强的稳定性,而对肠液消化稳定性较差,易被胰蛋白酶和糜蛋白酶降解生成低分子质量肽段。通过DNAStar Protean、AntheProt、BepiPred 1.0 server、ABCpred server、Immunomedicine Group 5 种生物信息学工具最终预测识别出8 条南极磷虾TM模拟表位肽（EAQNKETNAKADKADDEVH、DLERSEERLN、TKLAEASQAADESER、EADRKYDE、ERAEERAEAG、VSEEKANQREEAYKEQI、RSVQKLQKEVDR、VNEKEKYKGI）,并在其空间结构中进行一一映射。本研究为南极磷虾TM模拟表位肽的精准预测识别及其相关低致敏性产品的开发提供了科学依据。