Efficient synthesis of benzophenone derivatives in Lewis acid ionic liquids

Benzophenone and its derivatives were prepared via Friedel–Crafts acylation reactions using ionic liquids (ILs) of BmimCl–FeCl₃, BmimCl–AlCl₃ and BmimCl–ZnCl₂ as dual catalyst–solvent. Among them, BmimCl–FeCl₃ showed much higher catalytic activity than that observed for the other two ILs, and in conventional organic solvents. In these reaction systems, good to excellent yields (up to 97%) of acylation products were obtained in a short reaction time. This method features high yield, a simple product isolation procedure, ILs reusability and reduced waste discharge, thus rendering this catalytic system both efficient and environmentally friendly.     

不同种类淀粉对罗非鱼鱼糜凝胶品质的影响

为了改善淡水鱼鱼糜制品的品质,以冷冻罗非鱼鱼糜为原料,分别添加4%木薯原淀粉、3种木薯变性淀粉（磷酸酯淀粉、羟丙基淀粉和乙酰化二淀粉磷酸酯）及复配木薯变性淀粉（乙酰化二淀粉磷酸酯与羟丙基淀粉质量比为3∶2）,考察淀粉添加对鱼糜凝胶质构、流变学特性、持水性及水分分布和微观结构等的影响,探讨不同种类淀粉对鱼糜凝胶品质的改善。结果表明,与对照组相比,添加5种淀粉均会显著降低罗非鱼鱼糜凝胶的白度（P<0.05）,但其凝胶强度、硬度和咀嚼性显著增大,凝胶持水性显著提高（P<0.05）,蒸煮损失率显著下降（P<0.05）,结合水含量显著增加（P<0.05）,凝胶微观结构更加均匀致密,且添加了复配木薯变性淀粉的凝胶质构特性最好,持水性最高。低场核磁共振成像和光学显微镜观察结果显示,不同种类的淀粉均能有效锁住鱼糜凝胶基质中的水分;升温过程中淀粉吸水膨胀,在鱼糜凝胶网络结构中起浓缩和填充作用;添加了复配木薯变性淀粉的鱼糜凝胶结构最致密均匀。因此,添加复配木薯变性淀粉可以有效改善罗非鱼鱼糜制品的品质,为淡水鱼鱼糜制品的开发提供了理论支撑。     

可溶性褐藻膳食纤维对低盐鱼糜制品物理特性的影响

为考察可溶性褐藻膳食纤维(Soluble brown seaweed dietary fiber,SBF)应用于低盐鱼糜制品的适宜添加量,研究0%~1.5%浓度范围内,SBF对低盐鲢鱼(Hypophthalmichthys molitrix)制品蒸煮损失、凝胶持水力、质构特性(硬度、咀嚼性、内聚性、粘附性、胶黏性、弹性)和热物性(热扩散率、热阻率、热传导率、比热)的影响。结果显示:随着SBF浓度的增加,鱼糜制品的蒸煮损失显著下降(p<0.05),硬度、弹性、咀嚼性和粘附性表现出极显著增大(p<0.01);SBF浓度0.75%~1.5%范围内,凝胶持水力显著提高(p<0.05);添加SBF对鱼糜制品的内聚性、胶黏性和热阻率有不同程度的增大作用;对热扩散率、热传导率和比热有不同程度的降低。SBF可作为良好的膳食纤维来源添加到低盐鲢鱼鱼糜制品中,添加量<1%时,产品硬度在适宜的范围内。     

Shape control and stability of multicore millimetre-sized capsules using a combined monoaxial dispersion electrospraying–ionotropic gelation technique

Multicore millimetre-sized fish oil-loaded alginate capsules were developed using a combined monoaxial dispersion electrospraying–ionotropic gelation technique and their stability was explored. By adjusting the preparation parameters, the capsule shapes could be irregular, spherical with a short-tail, spherical, fusiform, and fusiform with a long-tail. The continuous phase of the millimetre-sized capsules consisted of hydrophilic alginate calcium and water. Moreover, the water content increased from 17% to 69% with increased alginate concentration (2.5–30 mg mL⁻¹). The capsules prepared with alginate concentration of 10 mg mL⁻¹ or 20 mg mL⁻¹ show a similar loading ratio (about 5–8%) of fish oil during storage. Headspace solid-phase microextraction–gas chromatography mass spectroscopy (HS-SPME-GC-MS) results confirmed the capsules masked the fishy odour of fish oil. Moreover, fish oil slowly migrated from the inside to the outside of the capsules. This work presented a simple method to prepare multicore millimetre-sized capsules with controlled shapes and a basic understanding of the effect of encapsulation using alginate to mask the fish oil odour.     

基于LC-MS/MS的酸乳肽谱及ACE抑制活性

利用液相色谱-串联质谱(liquid chromatography-tandem mass spectrometry,LC-MS/MS)的方法,对4种酸乳(优味舒风味发酵乳、风味发酵乳、初乳24+K风味发酵乳和十天风味发酵乳)的肽谱进行分析,分别鉴定到152、125、364条和274条肽段。利用血管紧张素转换酶(angiotensin converting enzyme,ACE)的抑制活性比较以上4种酸乳的生物活性,在相同质量浓度2.0 mg/L时,4种酸乳ACE抑制率分别为46.84%、42.75%、77.41%和63.84%。初乳24+K风味发酵乳含有肽的数量大、ACE抑制活性高可能与其独特的原料成分相关。对4种酸乳的肽谱及ACE抑制活性的考察,为进一步研究酸乳肽的功能特点和ACE抑制活性提供了理论依据。     

GC-MS鉴别保活流通过程中虾夷扇贝气味特征变化

在实验室模拟虾夷扇贝保活流通过程,采用气相色谱-质谱定量分析不同流通时间和阶段的活品虾夷扇贝挥发性成分,利用主成分分析和判别分析鉴别保活流通过程虾夷扇贝气味特征的变化。结果表明：在整个流通链中共分析出生鲜虾夷扇贝的57 种挥发性成分,可分为7 类,分别是含硫化合物、烷烃类、含氮化合物、杂环化合物、芳香族、醇类以及醛类,对每类化合物相对含量进行分析,发现含硫化合物、含氮化合物以及醛类的相对含量可以作为反映生鲜扇贝生理状态的参考;进一步做主成分分析,保活流通过程中8 个时间节点的样品可分为4 个阶段,其中第0天为阶段A、第1、2、3天为阶段B,第4、5、6天为阶段C,第7天为阶段D;通过判别分析得出,己烷、三氯甲烷、环己烯以及癸醛这4 种挥发性化合物是评判虾夷扇贝流通链不同阶段的最主要因素。     

去头/内脏处理对秋刀鱼冷藏特性的影响

为了探究去头/内脏处理对秋刀鱼冷藏货架期和腐败特征的影响,分析了不同形态秋刀鱼在4 ℃贮藏过程中感官评分、总挥发性盐基氮（total volatile basic nitrogen,TVB-N）值、硫代巴比妥酸反应物（thiobarbituric acid-reactive substance,TBARS）值、微生物指标（细菌总数）以及气味组成的变化规律。结果显示,随着贮藏时间的延长,2 组秋刀鱼样品的感官评分都呈下降趋势,去头/内脏处理组的下降趋势更为明显;处理组的TVB-N值在第8天时接近30 mg/100 g,而对照组在第12天时才达到该界限值,略滞后于感官评分指示的货架期终点;去头/内脏处理加速了鱼肉脂质的氧化速度,但2 组样品在货架期终点时TBARS均未超过5 mg/kg的限值;处理组的细菌总数初始值显著高于对照组（P＜0.05）,在第8天时超过7.0（lg（CFU/g））,对照组样品在贮藏第10天时接近该界限值。完整态秋刀鱼4 ℃贮藏的货架期为10～12 d,去头/内脏处理组的货架期约为8 d。货架期终点时2 组样品对应的电子鼻气味组成有显著性差异,表明腐败进程明显不同。     

耐高温α-淀粉酶高密度高表达发酵条件的优化

通过摇瓶实验对产耐高温α-淀粉酶的重组菌E.coli BL21的高密度高表达发酵条件进行研究。考察不同培养基和不同发酵条件对该菌株产耐高温α-淀粉酶的影响,并利用正交试验进行优化。结果表明:在葡萄糖0.5g/L,酵母粉15g/L,pH6.5,诱导时机为接种后发酵4h,诱导时间为6h,IPTG添加量为0.8mmol/L,接种量为体积分数3%的优化条件下,该重组菌发酵液菌体生物量为原来的1.29倍,酶活力达到8.754U/mL,是原来的1.55倍,目的蛋白的表达量也为原来的1.24倍。     

低磁场冷冻对鲢鱼肌原纤维蛋白的作用

采用2mT低磁场（low magnetic field,LMF）冷冻、0mT磁场（no magnetic field,NMF）冷冻和常规冷冻（conventional freezing,CF）技术对3 组鲢鱼肌原纤维蛋白进行为期28 d的冷冻实验。通过表面疏水性、巯基含量、溶解度、浊度、热稳定性、傅里叶变换红外光谱、内源性荧光光谱和紫外吸收光谱各项指标考察蛋白的结构和功能性质变化。结果表明：施加低磁场冷冻可以抑制蛋白聚集和内部疏水基团的暴露,且能抑制α-螺旋的展开,减弱α-螺旋向β-折叠转变的能力,并维持良好的二、三级结构稳定性;CF组的蛋白总巯基含量、溶解度和浊度与NMF组相比无显著差异,由于冷冻温度较低,对蛋白聚集和内部疏水基团的暴露有一定的抑制作用,同时也使得蛋白结构变得松散不稳定;与CF组相比,LMF组同样显示出对蛋白的结构和功能有较好的保护和改善作用。总体来说,低磁场冷冻可以抑制肌原纤维蛋白变性并维持良好的结构和功能,且与常规冷冻（－30 ℃）相比,低磁场冷冻（－20 ℃、2 mT）可以节约10 ℃的冷冻温差,预测其具有一定的节能潜力。     

Changes in appearance and natural microflora on iceberg lettuce treated in warm,chlorinated water and then stored at refrigeration temperature

The objective of this study was to determine the effect of warm, chlorinated water on the survival and subsequent growth of naturally occurring microorganisms and visual quality of fresh-cut iceberg lettuce. After dipping cut lettuce leaves in water containing 20 mg l⁻¹free chlorine for 90 s at 50°C, samples were stored at 5 or 15°C for up to 18 or 7 days, respectively. Populations of aerobic mesophiles, psychrotrophs, Enterobacteriaceae, lactic acid bacteria, and yeasts and molds were determined. The visual appearance and development of brown discoloration were monitored. Treatment of lettuce in warm (50°C) chlorinated water delayed browning of lettuce. Shelf life of lettuce stored at 5°C, as determined by subjective evaluation of color and general appearance, was about 5 days longer than that of lettuce stored at 15°C. Treatment in warm (50°) water, with or without 20 mg l⁻¹chlorine, and in chlorinated water at 20°C significantly (α= 0·05) reduced the initial population of mesophilic aerobic microflora by 1·73–1·96 log₁₀cfu g⁻¹. Populations increased, regardless of treatment, as storage time at 5°C and 15°C increased. The same trends were observed in populations of psychrotrophs and Enterobacteriaceae. Yeast populations increased slightly in lettuce stored at 5°C but were consistently about 3 logs lower than mesophilic aerobes. Populations of molds and lactic acid bacteria were less than 2 log₁₀cfu g⁻¹throughout storage at 5 or 15°C. Results suggest that heat (50°C) treatment may have delayed browning and reduced initial populations of some groups of micro-organisms naturally occurring on iceberg lettuce, but enhanced microbial growth during subsequent storage.