为什么鱼、肉的汤常温也会结冻

当温度低于0℃时,水会结冰。可是,为什么鱼、肉的汤不用到0℃也会结冻呢?A:鱼肉和猪肉是由很多蛋白质纤维束组成的,连接这些纤维束的物质叫做结缔组织。结缔组织主要是由韧带质和生胶质构成。当我们     

Analysis of volatile components in a Chinese fish sauce, Fuzhou Yulu, by gas chromatography-mass spectrometry

Volatile components of Fuzhou Yulu, a Chinese fish sauce, were analyzed by gas chromatography-mass spectrometry （GC-MS）, and two pretreatment methods, i.e., purge and trap （P＆T） GC-MS and ethyl acetate extraction followed by GC-MS, were compared. P＆T-GC-MS method determined 12 components, including sulfur-containing constituents （such as dimethyl disulfide）, nitrogen-containing constituents （such as pyrazine derivatives）, aldehydes and ketones. Ethyl acetate extraction fol- lowed by GC-MS method detected 10 components, which were mainly volatile organic acids （such as benzenepropanoic acid） and esters. Neither of the two methods detected alcohols or trimethylamine. This study offers an important reference to determine volatile flavor components of traditional fish sauce through modem analysis methods.     

气相色谱-质谱法测定鱼肉中丁香酚的残留

研究建立一种鱼肉中丁香酚(eugenol)残留量的固相萃取-气相色谱-质谱检测方法.样品采用正己烷提取,硅胶柱净化,乙酸乙酯洗脱,气相色谱-质谱测定,内标法定量.丁香酚的响应值与其质量浓度在0.005~0.5 mg·L-1范围内的线性关系良好,相关系数为0.999 8;10~200μg·kg-1添加浓度的日内和日间平均回收率为80.6%~93.2%,相对标准偏差为3.47%~8.47%;检出限为5μg·kg-1,最低定量限为10μg·kg-1.该方法适用于鱼肉中丁香酚残留的检测.     

气相色谱/质谱法同时检测鱼肉样品中三氯生及其甲基代谢产物

采用气相色谱/质谱(gas chromatography/mass spectrometry, GC/MS)法, 建立了可同时检测鱼肉样品中三氯生(triclosan, TCS)和甲基三氯生(methyl-triclosan, MTCS)的分析方法, 对比了不同衍生化试剂的衍生效果,考察了对鱼肉样品去脂净化过程有影响的相关因素, 最终确定鱼肉样品用正己烷-丙酮(体积比为1∶1) 提取, 凝胶色谱(gel permeation chromatography, GPC) 和复合硅胶柱净化, 乙酸乙酯衍生化, 气相色谱/质谱检测. 结果显示, 本方法对TCS 和MTCS 的线性范围分别为5~500和2~500 pg/μL, 相关系数均大于0.99, 检出限(limit of detection, LOD) 分别为1.3 和0.8 pg/μL. 在3 个空白加标实验中, TCS 和MTCS 的回收率分别为83%~89% 和
85%~98%. 最后, 应用此方法对鱼肉样品中两种化合物的浓度进行了定量分析.