Headspace fingerprinting approach to identify the major pathway influencing volatile patterns of vinasse-cured duck processed by high pressure,as well as its impact on physicochemical and sensory attributes

As a decisive attribute, flavour could be influenced by HP treatments through multiple physical and chemical pathways within the high pressure (HP)-assisted meat curing process. This investigation aimed to identify the major pathway influencing volatile flavour patterns of two representative vinasse-cured duck (VCD) products with HP treatments (150–300 MPa/15 min), including wet and dry types, by employing headspace fingerprinting as an untargeted approach. Results suggested that HP treatments greatly lowered moisture contents and increased Warner-Bratzler shear force and thiobarbituric acid reactive substances of the cured samples. According to multivariate models, the volatile flavour patterns of the HP-processed VCD could be clearly separated from the unprocessed samples, but the VCD pressurised at different intensities represented similar volatile fingerprinting, which was validated by e-nose analysis. The discriminant analysis (OPLS-DA) model outlined vinasse-derived ethanol, acetic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, phenethyl alcohol and 2-methyl-3-octanone as the major discriminant aromas across the unpressurised and pressurised samples.     

正交偏最小二乘判别法对青蒿素拉曼光谱的研究

为了鉴别不同纯度的青蒿素样品,本文运用正交偏最小二乘法判别分析方法（OPLS-DA）研究了不同纯度青蒿素样品的拉曼光谱。研究表明,对青蒿素拉曼光谱进行OPLS-DA建模分析可以鉴别不同纯度的样品,从而用于青蒿素样品的质量评估。另外,青蒿素拉曼光谱OPLS-DA建模分析表明,青蒿素拉曼光谱中与生物活性官能团相关的724 cm^-1处的特征振动模式与青蒿素的纯度紧密相关:在不同纯度青蒿素样品中,该特征振动模式与其他振动模式的相对强度比具有统计学差异（单向方差分析,F=7.39,P<0.01）。     

基于电子鼻、HS-GC-IMS、HS-SPME-GC-MS技术联用分析不同发酵年份老香黄挥发性成分差异

基于电子鼻、顶空气相离子迁移谱（HS-GC-IMS）和顶空固相微萃取-气相色谱-质谱技术联用（HS-SPME-GC-MS）分析不同发酵年份老香黄挥发性成分变化,并结合正交偏最小二乘判别分析（OPLS-DA）法区分不同发酵年份老香黄。电子鼻主成分分析能明显区分发酵与未发酵的老香黄,两者风味差异较大,老香黄发酵3年和4年的风味成分最为相似,而其余发酵年份风味存在较大差异。HS-GC-IMS定性检测出39种挥发性成分,包括萜烯类、醇类、醛类、酯类、酮类、酚类、酸类、杂环化合物和其它共9类。HS-SPME-GC-MS则一共鉴别出50种挥发性成分,包括萜烯类、醇类、醛类、酚类、酯类、醚类、杂环化合物和其它共8类。α-蒎烯、β-蒎烯、月桂烯、萜品油烯、柠檬烯、异松油烯、1-石竹烯、巴伦西亚橘烯、芳樟醇、α-松油醇、糠醛、麦芽酚、茴香脑、2,4-二甲基苯乙烯为14种共有挥发性成分,经OPLS-DA模型筛选出8种标志性挥发性化合物（VIP>1)。综上,未发酵和发酵1~5年的老香黄风味存在较大差异,筛选出的8种挥发性成分为区别不同年份老香黄提供一定依据。     

基于GC-MS和快速气相电子鼻对我国东北地区代表性粳米香气组分分析

为探究我国东北地区4种代表性粳米（香米五优稻4号、绥粳18和非香米龙粳31、盐丰47）香气组分差异,通过顶空-固相微萃取-气相色谱-质谱联用（Headspace-solid phase microextraction-gas chromatography-mass spectrometry,HS-SPME-GC-MS）和快速气相电子鼻（Flash gas chromatography electronic nose,Flash GC e-nose）技术对粳米香气组分进行鉴定。本研究采用正交偏最小二乘法-判别分析（Orthogonal partial least squares-discriminant analysis,OPLS-DA）和层次聚类分析（Hierarchical clustering analysis,HCA）等方法对4种粳米香气组分进行分析,结果表明,4种粳米的主要香气组分构成类似,以己醛、壬醛等醛类为主;五优稻4号主要香气成分含量显著（p≤0.05）高于其它3个品种粳米,使得其香气更加浓郁;关于粳米香气组分鉴定技术,GC-MS技术的准确度和检测范围优于电子鼻技术,而检测效率低于电子鼻技术。     

低聚糖和多酚结合偏最小二乘判别分析鉴别油菜蜜产地

采用气相色谱-串联质谱技术测定油菜蜜中6 种低聚糖成分,高效液相色谱-串联质谱技术测定油菜蜜中18 种酚酸物质,并结合偏最小二乘判别分析（partial least square-discrimination analysis,PLS-DA）对来自湖北钟祥市、江苏盐城市、青海刚察县3 个具有显著地理、气候、环境差异的51 个油菜蜜样本进行产地鉴别。方差分析结果显示：3 个产地油菜蜜中松二糖含量具有显著性差异,且青海刚察油菜蜜低聚糖含量相对偏高;油菜蜜的18 种多酚类物质中大多数具有显著的地理差异性且湖北钟祥的油菜蜜中多酚含量相对偏高。多元统计分析结果显示多酚具有显著的地理特征性。油菜蜜中低聚糖和多酚的含量结合PLS-DA产地鉴别的预测精度可达到97%。     

Multivariate analyses of the physicochemical properties of turnip (Brassica rapa L.) chips dried using different methods

Abstract

The turnip is a traditional “medicine food homology” vegetable in China, but the processing of it remains traditional and limited. To increase and diversify the consumption of turnips, freeze drying (FD), explosion puff drying (EPD), infrared drying (ID), and hot air drying (AD) were used to produce turnip chips. FD chips maintained most of the starch, total sugar, vitamin C, and volume ratio, followed by EPD chips, which exhibited better crisp values and rehydration rate. These results suggest EPD as a favorable method for turnip chip production. The physicochemical properties of turnip chips dried using different methods differed greatly from each other. Principal component analysis revealed that FD produced the best chips, followed by EPD. Hierarchical cluster analysis and orthogonal projection on latent structure-discriminant analysis identified the volume ratio as the characteristic property of FD chips and the contents of soluble dietary fiber and insoluble dietary fiber as the characteristic properties of ID chips, which indicated that multivariate analyses may be used to classify dried products and identify their characteristic properties.     

Global Metabolic Regulation of the Snow Alga Chlamydomonas nivalis in Response to Nitrate or Phosphate Deprivation by a Metabolome Profile Analysis

In the present work, Chlamydomonas nivalis, a model species of snow algae, was used to illustrate the metabolic regulation mechanism of microalgae under nutrient deprivation stress. The seed culture was inoculated into the medium without nitrate or phosphate to reveal the cell responses by a metabolome profile analysis using gas chromatography time-of-flight mass spectrometry (GC/TOF-MS). One hundred and seventy-one of the identified metabolites clustered into five groups by the orthogonal partial least squares discriminant analysis (OPLS-DA) model. Among them, thirty of the metabolites in the nitrate-deprived group and thirty-nine of the metabolites in the phosphate-deprived group were selected and identified as “responding biomarkers” by this metabolomic approach. A significant change in the abundance of biomarkers indicated that the enhanced biosynthesis of carbohydrates and fatty acids coupled with the decreased biosynthesis of amino acids, N-compounds and organic acids in all the stress groups. The up- or down-regulation of these biomarkers in the metabolic network provides new insights into the global metabolic regulation and internal relationships within amino acid and fatty acid synthesis, glycolysis, the tricarboxylic acid cycle (TCA) and the Calvin cycle in the snow alga under nitrate or phosphate deprivation stress.     

Metabolomic approach for the detection of mechanically recovered meat in food products

Mechanically recovered meat (MRM) is generated by mechanical treatment of remnants following hand deboning. EU regulations exclude MRM from the definition of meat; as a consequence there is a need for robust analytical procedures to differentiate MRM from hand-deboned meat (HDM) and desinewed meat. Present study represents the development of an analytical platform for the detection of adulteration of meat products with MRM. Small molecular weight compounds were extracted from meat samples and analysed using GC–MS. Obtained metabolite profiles were modelled with OPLS-DA for the accurate classification of MRM, HDM and desinewed pork and chicken samples. Separation of three classes of products for fresh chicken and pork meat samples was achieved. In addition, the procedure also enabled proper prediction of samples not included in the model as well as pork commercial meat products. Compounds that could be potential markers for MRM detection in commercial products were also selected.     

基于UPLC-Q-TOF MS分析加工炮制对玄参化学成分的影响

为了全面阐明玄参加工工艺对其化学成分的影响,采用UPLC-Q-TOF MS技术对烘干玄参和传统加工玄参的化学成分进行分析比较,并运用主成分分析法(PCA)和正交偏最小二乘辨别分析法(OPLS-DA)进行数据统计,寻找差异性成分,同时依据一级质谱精确质荷比和二级质谱碎片信息进行成分解析。结果表明:与烘干玄参相比,传统加工玄参中共有26种成分的含量变化显著,实验鉴定出了其中的15种成分,包括9种环烯醚萜类化合物和6种苯丙素类化合物;含量降低的成分有桃叶珊瑚苷、6-O-甲基梓醇、哈巴俄苷、8-O-香豆酰基哈巴俄苷、8-O-阿魏酰基哈巴俄苷、阿格托苷、异阿格托苷、安格洛苷C和scrophuloside B1,其中scrophuloside B1为玄参中首次发现的成分;含量增加的成分有哈巴苷、哈巴俄苷同分异构体、6″-O-α-D-半乳糖哈巴俄苷、6-O-α-D-半乳糖哈巴俄苷、斩龙剑苷A和肉桂酸。本工作对研究玄参加工炮制机制有重要意义,同时可为阐明玄参药效的物质基础提供依据。     

不同陈化时间老香黄的差异物质识别及变化研究

目的 研究对佛手老香黄的挥发性物质在不同陈化时间的演变及其差异特征物质进行研究 。方法 利用气相色谱-离子迁移谱（gas chromatography-ion mobility spectrometry, GC-IMS）对潮州老香黄在老化过程中的挥发性物质进行分析,并通过正交偏最小二乘法（Orthogonal partial least-squares discrimination analysis, OPLS-DA) 模型不同年份的样品的挥发性物质进行区分和鉴别。结果 共检测出70种挥发性化合物,包括酯类8种,萜烯类23种,醇类11种,酸类5种,酮类3种,吡嗪类1种,噻唑类1种,醛类18种,其中的酯类、醇类、酸类随时间显著增加。OPLS-DA通过变量投影重要性 (variable importance in projection value, VIP） ＞1的标准进行筛选,陈化的第二年和第三年分别有22和15个挥发性物质产生显著变化。结果表明,GC-IMS可以有效区分不同陈化时间老香黄的显著差异成分,陈化的第二年和第三年分别有22和15个个挥发性物质产生显著变化,其中苯基乙醇、Alpha -水芹烯-D、Alpha-松油醇-D、2-蒈烯、三环烯、丙醛、乙酸香叶酯共7个物质在陈化期间持续显著变化。结论 GC-IMS可以有效区分不同陈化时间老香黄的显著差异成分,陈化过程中共30种挥发性物质产生显著变化,其中苯基乙醇、α-水芹烯-D、α-松油醇-D、2-蒈烯、三环烯、丙醛、乙酸香叶酯共7个物质在陈化期间持续显著变化。本研究为佛手老香黄特征风味的标志成分定性定量研究提供参考,可达到质量监控的目的。