指纹图谱异常指数法在烟气色谱数据处理中的应用

研究表明卷烟产品特有的感观特征不是任意一种或少数几种成分所起的作用,而是烟气中各种成分的综合反映。差谱法、因子分析、主成分模式识别法和聚类分析等数据处理方法都曾应用于卷烟烟气复杂的数据处理,但指纹图谱异常指数法在烟气分析中的应用未见报道。本文结合毛细管色谱分析方法,将指纹图谱间共有峰、缺失峰和额外峰的差异情况之和作为总异常指数表达两种卷烟烟气指纹图谱间的差异。该方法成功应用于烟气色谱数据分析:收集12个品牌的卷烟,包括烤烟型、英式烤烟型和混合型卷烟,将其中一个烤烟型卷烟作为标准,计算每个品牌指纹图谱异常指数值。结果表明指纹图谱异常指数法比主成分模式识别法和差谱法能从色谱数据中挖掘更多的质量信息。      

Pattern Recognition of GC Profiles for Classification of Cheese Variety

Volatile components in Cheddar, Gouda, Edam, Swiss, and Parmesan cheeses were concentrated with a modified Likens-Nickerson apparatus and analyzed with a fused silica capillary GC. Stepwise discriminant analysis was applied to the 118 peaks in the resulting gas chromatograms to classify objectively cheese varieties, and most of the cheese samples were successfully assigned to the correct varieties. Discrimination between Gouda and Edam was the most difficult among all combinations of two varieties within the five cheeses. Clusters corresponding to young, mild and old cheeses were observed in the canonical plot based on the GC data of Cheddar cheese samples.     

Classification of Whiskies by Principal Component Analysis

Trace components in forty-eight samples in five whiskey categories were extracted into methylene chloride, concentrated and separated by capillary column gas chromatography. The technique of principal component analysis was applied to the peaks in the resulting gas chromatograms and the samples formed clusters according to category. Further studies showed that variation in sample composition due to dilution, blending, or contamination using a model contaminant could be detected with good sensitivity.     

基于指纹图谱和化学计量学的浓香型白酒分类研究

该研究以市售畅销的7个品牌、不同等级的浓香型白酒为研究对象,利用气相色谱-质谱联用（GC-MS）技术建立了浓香型白酒中风味成分的指纹图谱,结合相似度分析、主成分分析（PCA）和判别分析（DA）对不同品牌的浓香型白酒样品进行了有效区分和鉴别。结果表明,不同品牌间样品的相似度存在一定差异;PCA表明前三个主成分累计方差贡献率达到89.71%,能对样品进行聚类和区分;利用判别分析可以将不同产地的酒样区分开,正确率为100%。综上,相同品牌不同等级的白酒具有明显的相关性,不同品牌白酒可以利用指纹图谱结合化学计量学方法进行鉴别和分类,为白酒质量控制及真伪鉴定提供了一种新方法。     

不同地区黄酒挥发性物质差异性分析

比较不同地区黄酒中主要挥发性物质种类及其含量的差异,采用顶空固相微萃取和气相色谱-质谱联用技术对不同地区的12 个品牌黄酒的挥发性物质进行测定,并分别对黄酒中的挥发性物质进行主成分分析、对不同地区黄酒进行聚类分析。结果表明：从不同地区的12 种黄酒中共检测出142 种挥发性物质,其中酯类、醇类、醛类、酮类、酸类、酚类、烃类占挥发性物质总量的比例分别为33.04%、39.26%、24.64%、0.37%、0.63%、0.28%、1.36%,其中13 种物质为12 种黄酒所共有;通过主成分分析发现黄酒中对整体风味以及口感的形成影响较大的挥发性物质为异丁醇、苯乙酸乙酯、乳酸乙酯、乙酸乙酯、苯乙醇和糠醛;此外,通过聚类分析可将所研究的不同地区12 种黄酒分为3 类,各类黄酒的挥发性物质均有其显著特征,客观地反映了样品的真实信息。     

Rapid Method for Small Grain and Corn Flour Authentication Using GC/EI–MS and Multivariate Analysis

The aim of this study was the application of the gas chromatography–mass spectrometry system (GC/EI–MS) system and multivariate data analysis to investigate the possibility of chemical differentiation between small grain flour (wheat, barley, oat, triticale, rye) and corn flour samples. All cereal flour samples were first defatted with hexane, after which the extraction with ethanol was performed. Extracted simple sugars (monosaccharides, disaccharides, trisaccharides, and sugar alcohols) were analyzed in the form of their corresponding trimethylsilyl oximes. Peaks of simple sugar derivatives were selected in total ion current (TIC) chromatograms by monitoring exclusively the following characteristic abundant ions: 204, 217, and 361?m/z. The total surface areas under the selected peaks were subjected to multivariate analysis. Applying principal coordinate analysis and hierarchical cluster analysis to obtained data, samples of corn flour could be very clearly distinguished from all samples of small grain flour, which presented a weaker separation among each other. This method circumvents common analytical procedures by excluding simple sugar identifications, quantitative analysis, the use of analytical standards, and calibration curves. Results are applicable in the quality assurance of mixed flour on the market, considering the increased popularity of their consumption in human nutrition.     

Improved methodology for the characterisation of transgenic Bt-11 maize cultivars using RP-HPLC profiles of albumin,globulin, prolamin,and glutelin protein fractions and chemometric analysis

A clear differentiation between Bt-11 transgenic and isogenic non-transgenic maize cultivars has successfully achieved analysing the perfusion and monolithic RP-HPLC profiles of the albumin, globulin, prolamin, and glutelin maize fractions together with a discriminant analysis. Significant differences between transgenic and isogenic non-transgenic cultivars were observed in the chromatograms obtained from any of the four protein fractions. The application of linear discriminant analysis to the area percentages corresponding to every peak detected in every protein fraction was successfully employed for the classification of transgenic Bt maize lines obtaining a global percentage of correct classification of 100%. For perfusion RP-HPLC, the variables with more discriminant power and prediction capability were the following peaks: peaks 1 and 3 for albumins, peak 2 for globulins, peaks 3 and 6 for prolamins, and peaks 7 and 8 for glutelins. In the case of monolithic RP-HPLC, the variables were peaks 2 and 3 for albumins, peak 5 for globulins, peaks 5, 6, and 7 of prolamins, and peak 10 for glutelins.     

基于多元统计学分析的市售甜面酱品质综合评价

该研究从市场上采集了隶属于18个品牌22个品名的甜面酱样品,并采用色度仪、质构仪、常规理化分析和多变量统计学方法相结合的手段对其品质进行了评价。研究表明甜面酱样品在红绿度（a*值）和黄蓝度（b*值）等指标上差异较大。通过聚类分析（CA）、多元方差分析（MANOVA）和典范对应分析（CCA）发现,市售甜面酱样品可以划分为3个聚类,经Kruskal-Wallis秩和检验发现隶属于不同聚类的样品其硬度、稠度、凝聚性和表观黏度等质构指标存在显著差异（P＜0.05）。     

南路边茶高效液相色谱指纹图谱的建立

应用高效液相色谱法初步建立了南路边茶的指纹图谱。采用线性梯度洗脱,乙腈和0．3％甲酸水溶液为流动相,柱温为30℃,检测波长为280nm,流速为1．0mL／min。根据平均相对保留时间、共有峰、平均相对峰面积等对色谱指纹图谱进行了分析。方法的精密度、重复性和稳定性良好。通过对48批不同生产企业、不同生产年限的南路边茶样品进行分析,以咖啡碱为参照峰,共确定了37个色谱峰作为南路边茶的特征指纹峰。运用相似度评价和聚类分析法对各批次南路边茶样品指纹图谱进行了化学模式识别研究。各批次南路边茶样品与对照指纹图谱共有模式的相似度均大于0．90;对相对峰面积的聚类分析结果表明,当临界值为15时,48批南路边茶样品可聚为2类。该研究为南路边茶的鉴别和质量控制提供了参考。     

Authenticity Control of Roasted Coffee Brands Using Near-Infrared Spectroscopy

In this work, a methodology based on near-infrared spectroscopy (NIRS) was exploited in order to discriminate between commercial coffee brands. The main advantages of this approach compared to other strategies (e.g., wet chemistry methods) are its lower cost, less labor, and lower time per analysis. Two commercial brands were discriminated among several others present in the Portuguese market. The chemometric method used to estimate discriminant models was partial least squares discriminant analysis (PLSDA). Results show that it is possible to discriminate coffee brands using this strategy with a correct classification of 100 %. The spectral region, more favorable to discrimination of roasted coffee brands, can be related with differences in the concentrations of compounds, such as, chlorogenic acid and sucrose, and also due to differences on lipid fraction. This methodology is adequate for field implementation, namely, adopting handheld NIRS instruments.     

Comparison of aroma characteristics of 16 fish species by sensory evaluation and gas chromatographic analysis

The aroma properties of fish broths prepared from 16 fish species (10 saltwater, three freshwater, two anadromous and one brackish water species) were described quantitatively by reference to 10 sensory attributes. Principal component analysis (PCA) and cluster analysis of sensory attributes classified the fish into four groups. Group 1, characterised by a strong ‘green’ odour, comprised all three freshwater species (loach, pond smelt and carp), two saltwater whitefish species (snapper and conger) and eel. Group 2 included migratory coastal species (sardine, banded blue‐sprat and mackerel) and was distinguished by strong ‘fish oil’ and ‘grilled fish’ notes. Group 3 consisted of swordfish, sablefish and salmon, which exhibited a strong ‘fried chicken’ note. Group 4 included flounder, cod, tuna and goby, which were scored high for ‘cooked fish’, ‘roasted soy sauce’, ‘canned tuna’ and ‘sweet’ aromas. Partial least squares regression (PLSR) models derived from selected influential peaks in the gas chromatograms of the volatile components in the broths for each attribute were highly predictive (R² ≥ 0.936). The selected peaks corresponded well to each sensory attribute. © 2003 Society of Chemical Industry     

不同类型食醋的香气特征及挥发性成分分析

使用超快速气相色谱电子鼻检测市售的香醋、米醋、陈醋3 类共25 个品牌发酵食醋,通过保留指数和外标法对3 类食醋的挥发性化合物进行定性和定量分析,结合气味活性值构建食醋风味轮,比较不同种类食醋挥发性香气差异与化合物含量间关系,并以线性判别分析和随机森林法研究食醋的挥发性化合物差异,进而实现对食醋的区分。从3 类食醋中共检测出44 种挥发性化合物,主要包括醇类、酯类、醛类、酮类、酸类、烷烃类和杂环类。酸类在食醋中含量最高,其次为醇类和醛类,而烷烃类含量最低。食醋样品的气味活性值和气味雷达图说明乙酸、3-甲基丁醛、苯乙醛、5-甲基糠醛、愈创木酚等对香气贡献较大。香醋的酸味、水果香和坚果可可香高于米醋和陈醋。但陈醋的花香高于其他两类。线性判别分析表明,不同品牌和不同种类的食醋均存在明显差异;随机森林通过机器学习对食醋样品的训练和测试,准确度最终达到100%,对不同种类的食醋区分显著,并筛选出3-甲基丁醇、愈创木酚、苯甲醛、丙酮可作为食醋种类鉴别的重要化合物。     

烟丝裂解产物指纹图谱及在卷烟品质评价中的应用

为考察卷烟烟丝裂解产物应用于卷烟品质评价的可能性,建立了获取卷烟烟丝指纹图谱的裂解-气相色谱/质谱(Py-GC/MS)方法,并对4个品牌共20个卷烟样品的烟丝进行了测定;基于烟丝的Py-GC/MS指纹图谱筛选共有峰,采用聚类分析和主成分分析法对数据进行分析评价,建立了卷烟评价模型,并进行了模型验证。结果表明:①利用Py-GC/MS可对卷烟烟丝进行表征,从烟丝的指纹图谱中共筛选出29个共有峰。②通过模式识别,实现了4个品牌的卷烟样品的较好区分。③建立的评价模型对15个建模样品和5个验证样品的正确判别率为100%。该方法简便、快速,可为卷烟品质评价提供参考。     

Trapping of soursop (Annona muricata) juice volatiles on porapak Q by suction

The trapping technique of Singleton and Pattee, in which the volatiles are swept to a Porapak Q trap by suction rather than by a sweeping gas, was modified and used to isolate soursop juice volatiles. Using fixed, low vacuum and operating conditions determined specifically for soursop volatiles, very high reproducibility was obtained. The majority of the peaks had a coefficient of variation less than 0.10. The relative amounts of the volatile components obtained by direct headspace sampling was fairly well maintained in the Porapak Q concentrate. The chromatograms showed distinct differences between two commercial brands or between lots of the same brand of soursop juice. The trapping technique appear to have wide applicability provided that the operating conditions are adapted to each product studied.     

Combining means-end chain analysis and the Portrait Value Questionnaire to research the influence of personal values on food choice

Personal values can be measured using quantitative or qualitative methods. This paper aims to investigate the attribute-consequence-value patterns collected from means-end chain analysis and to examine their relationship to personal value domains from Schwartz value theory measured through the use of the Portrait Value Questionnaire. The study was performed on two product categories, potato chips and orange juice, in which two value segments of opposing value domains were found, Conservatism and Openness to change clusters. There was consistency between means-end chain analysis results and the expected traits of the value domains. The Conservatism cluster embracing security, tradition, and conformity values sought financial security through saving money by paying more attention to price and selected familiar brands in order to avoid risks of spending extra money. The Openness to change cluster, which embraced hedonism and stimulation values, emphasized attaining pleasure and enjoyment in life through various consequences that branched out from a number of sensory product attributes. This study illustrates the compatibility between the two instruments. The use of means-end chain analysis confirmed Schwartz’s definition of values as guiding behavior, and that values are ordered by relative importance.     

Proteolysis on Reggianito Argentino cheeses manufactured with natural whey cultures and selected strains of Lactobacillus helveticus

Reggianito Argentino cheese is traditionally manufactured with whey starter cultures that provide typical and intense flavor but can cause poor quality standardization. In this study, the influence of natural and selected starters on Reggianito Argentino cheese proteolysis was investigated. Cheeses were manufactured with three strains of Lactobacillus helveticus (SF133, SF138 and SF209) cultured individually in sterile whey and used as single or mixed starters. Control cheeses were made with natural whey starter culture. Cheeses were analyzed to determine gross composition, as well as total thermophilic lactic flora. Proteolysis was assessed by N fractions, electrophoresis and liquid chromatography. Gross composition of the cheeses did not significantly differ, while viable starter cell counts were lower for cheeses made with strain SF209 alone or combined with other strains. Soluble N at pH 4.6 was the same for cheeses made with natural or selected starters, but soluble N in 12% trichloroacetic acid and 2.5% phosphotungstic acid was significantly higher in cheeses made with starters containing strain SF209. Nitrogen fractions results indicated that natural whey starter cultures could be replaced by several starters composed of the selected strains without significant changes to proteolysis patterns. Starter cultures prepared only with SF209 or with the three selected L. helveticus strains produced cheese products with significantly more proteolysis than control cheeses. Chromatographic profiles analyzed by principal components showed that three main peaks on chromatograms, presumptively identified as Tyr, Phe, and Trp, explained most of variability. Principal component scores indicated that cheese samples were grouped by ripening time, which was confirmed by linear discriminant analysis. On the contrary, samples did not cluster by Lactobacillus strain or type of starter.     

Headspace Adsorptive Microextraction Analysis of Oregano Fragrance Using Polyaniline-Nylon-6 Nanocomposite,GC-MS,and Multivariate Curve Resolution

Volatile components of oregano (Origanum vulgare L.) were extracted using headspace adsorptive microextraction and were analyzed by gas chromatography-mass spectrometry. Novel polyaniline-nylon-6 nanocomposite was used for headspace adsorptive microextraction due to its suitable characteristics. Multivariate curve resolution-alternating least square was applied for resolving the co-eluted gas chromatography-mass spectrometry peak clusters into pure chromatograms and mass spectra. Problems such as low signal-to-noise ratio of peaks and noisy data were handled with the aim of chemometrics. Chemicals of γ-terpinene, p-cymene, thymol, and carvacrol are the main components among 48 identified components of oregano fragrance. The volatile components of the fragrance and the essential oil of oregano were compared in term of chemical components and relative percentages points of view. The reproducibility in peak responses was investigated using three replicate experiments for the fragrance and the essential oil samples. The results proved that headspace adsorptive microextraction, gas chromatography-mass spectrometry, and multivariate curve resolution techniques could be useful to extract and analyze natural aromas and fragrances.     

基于气相离子迁移谱对葵花籽油精炼程度的检测

运用气相离子迁移谱（gas chromatography-ion mobility spectrometry,GC-IMS）对不同精炼程度的葵花籽油的挥发性有机成分进行分析,构建葵花籽油精炼程度的指纹图谱,并对葵花籽油的精炼程度进行判别和分类。采用二维差谱方法筛选出22?个有效特征峰作为表征精炼程度差异的变量,采用主成分分析和有监督模式识别方法（K最近邻、二次线性判别分析、Fisher线性判别分析）进行模式识别。结果表明,3?种有监督模式识别方法均可以有效地区分不同精炼程度的葵花籽油样,识别率高达97.30%。使用GC-IMS技术结合化学计量学方法能够准确直观地区分不同精炼程度的葵花籽油样品,便于企业对植物油进行质量控制,同时为质检技术人员提供了一种新的检测方法。