采用气相色谱、高效液相色谱和化学滴定法等手段,对我国不同产地的7个市售稻米油的特征参数及脂肪酸组成进行了分析测定,并与青刺果油等14种同步测定的植物油的脂肪酸组成进行了全面的比较研究.结果表明:稻米油的折光指数为1.465 6～1.467 7;相对密度d2020为0.918 6～0.922 1;碘值为100.1～107.3 g/100 g;皂化值为184.7～188.7 mg/g;谷维素含量在2 516.80～21 833.32 mg/kg之间;脂肪酸组成以油酸C18:1(39.38％～42.26％)、亚油酸C18:2(36.23％～39.86％)、棕榈酸C16:0(15.22％～17.38％)为主,不饱和脂肪酸含量在79.66％～81.39％之间.与其他14种植物油的脂肪酸相比∶棕榈酸C16∶0以稻米油为最高(16.48％),油酸C18∶1含量以橄榄油为最高(77.18％),亚油酸C18∶2以火麻籽油为最高(55.27％),亚麻酸C18∶3以美藤果油为最高(49.02％),不饱和脂肪酸以杏仁油为最高(95.12％),稻米油的油酸与亚油酸比值为1.00∶1～1.16∶1,单不饱和脂肪酸与多不饱和脂肪酸的比值为0.98∶1～1.15∶1,与世卫组织推荐的黄金比例1∶1比较接近.此外,稻米油的碘值、皂化值等多项特征参数与青刺果油较为接近.研究结果表明稻米油具备良好的、平衡的脂肪酸组成比例和较高的营养价值,也为消费者选择适合自身所需的营养价值、保健功能的食用植物油提供了参考依据.

ABSTRACT Potato and its products have become indispensable foods and snacks for most people. Steroidal glycoalkaloids (SGAs) occur in all tissues of the potato, and consuming potatoes with a high SGA content harms human health. Therefore, the effects of different cooking methods on the SGA content in potato foods were investigated in this study. The results indicated that adding food-grade acetic acid during the manufacturing process did not affect the SGA content in stir-fried shredded potatoes or fresh mashed potatoes. However, the SGA content in potato food after peeling was significantly lower than that in non-peeled food, and the volume ratio of potato skin to flesh decreased with the increase of the potato tuber volume. Therefore, potato breeders and farmers should make the most hard to increase the proportion of commodity potato via corresponding science and technology. In addition, frying significantly reduced the SGA content in potato chips. Further research indicated that SGAs degraded slowly at 150°C, while they degraded rapidly at 190°C within 30 min. The temperature of rapeseed oil in the frying process can be as high above 200°C. Thus, frying significantly decreased the SGA content in potato chips, which could be attributed to temperature. These results will provide a theoretical basis and practical guidance for potato breeding and cooking.

Baking is the last, and yet most essential, step in the formation of the final distinct flavour of most black tea products. In this study, the influence of baking on the volatile components of Dianhong black tea, which is one of the most popular black teas in China, was investigated. As a very fast, effective, and simple method for collecting volatiles, headspace solid-phase microextraction (HS-SPME) with a 65 mu m PDMS/DVB fibre was used to extract the volatile compounds of Dianhong black tea, and the volatile components were further separated and identified by gas chromatography-mass spectrometry (GC-MS). The results showed that the peak areas of alcohols, aldehydes, esters, and ketones were increased, but that those of some alkanes, acids, and nitrogen compounds did not demonstrate an obvious increase after baking. The differences generated by baking process actually result in the distinct flavour of most black teas and can be used as a model for analysing the chemical composition of special flavours, and for quality improvement and process control.

Pu-erh ripe tea is one of the main tea products in China, which has a unique woody, chestnut fragrance flavour, distinct from other teas. Because of the largely excessive production capacity, it is now possible and necessary to utilise it to produce tea essential oil. In this study, the extraction efficiency of Soxhlet extraction (Soxhlet), ultrasonic-assisted extraction (UAE), simultaneous distillation extraction (SDE), and steam distillation extraction (SD) for extraction oil of Pu-erh ripe tea was investigated. GC-MS and HS-SPME/GC-MS were then applied to identify the volatile compounds in the essential oils and tea samples. The results showed that the extraction ratios of the essential oil were 0.81 +/- 0.01 g/kg (Soxhlet), 0.36 +/- 0.01 g/kg (UAE), 0.11 +/- 0.01 g/kg (SDE), and 0.59 +/- 0.01 g/kg (SD). GC-MS identified 40, 38, 35, and 47 volatile compounds in the essential oils extracted by the different methods, whereas 55 compounds were identified by HS-SPME/GC-MS. Therefore, when both the essential oil extraction rate and oil flavour are considered, the best method is SD.

Consistent aroma characteristics are important for tea products. However, understanding the formation of tea aroma flavor and correspondingly proposing applicable protocols to control tea quality and consistency remain major challenges. Oolong tea is one of the most popular teas with a distinct flavor. Generally, oolong tea is processed with the leaves of tea trees belonging to different subspecies and grown in significantly different regions. In this study, Yunnan and Fujian oolong teas, green tea, black tea, and Pu-erh tea were collected from major tea estates across China. Their sensory evaluation, main water-soluble and volatile compounds were identified and measured. The sensory evaluation, total polysaccharide, caffeine, and catechin content of Yunnan oolong tea was found to be different from that of Fujian oolong tea, a result suggesting that the kinds of tea leaves used in Yunnan and Fujian oolong teas were naturally different. However, according to their aroma compounds, principal component analysis (PCA) and cluster analysis (CA) of the volatile compounds showed that the two types of oolong teas were similar and cannot be clearly distinguished from each other; they are also different from green, black, and Pu-erh teas, a result indicating that the same oolong tea processing technology applied to different tea leaves results in consistent aroma characteristics. The PCA analysis results also indicated that benzylalcohol, indole, safranal, linalool oxides, β-ionone, and hexadecanoic acid methyl ester highly contributed to the distinct aroma of oolong tea compared with the other three types of teas. This study proved that the use of the same processing technology on two kinds of tea leaves resulted in a highly consistent tea aroma.

In this study, the aroma components of six Wujiatai green teas were extracted and identified using headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS), and principal component analysis (PCA) was further used to reveal possible differences in these teas based on their aroma components. The results showed that, although there are some similarities in the aroma composition and content between Wujiatai green tea and regular green and black teas, the former had its own unique aroma characteristics. We suggest that the 'baking' procedure of Wujiatai green tea possibly causes the formation and/or increase of some aroma components, thus resulting in a more durable and prominent aroma characteristic as well as superior quality compared with the other teas investigated in this paper.

BACKGROUND:Biluochun is a typical non-fermented tea and is also famous for its unique aroma in China. Few studies have been performed to evaluate the effect of the manufacturing process on the formation and content of its aroma. RESULTS:The volatile components were extracted at different manufacturing process steps of Biluochun green tea using fully automated headspace solid-phase microextraction (HS-SPME) and further characterised by gas chromatography-mass spectrometry (GC-MS). Among 67 volatile components collected, the fractions of linalool oxides, β-ionone, phenylacetaldehyde, aldehydes, ketones, and nitrogen compounds were increased while alcohols and hydrocarbons declined during the manufacturing process. The aroma compounds decreased the most during the drying steps. CONCLUSION:We identified a number of significantly changed components that can be used as markers and quality control during the producing process of Biluochun. The drying step played a major role in the aroma formation of green tea products and should be the most important step for quality control. © 2016 Society of Chemical Industry.

To evaluate the effect of the processing technology utilized on the quality of teas, the major water-soluble and volatile components of 24 Biluochun and regular green tea samples obtained in different production areas were determined using the sensory evaluation, Folin-Ciocalteu method, the phenol-sulfuric acid method, high-performance liquid chromatography, and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. There were small differences between the contents of the major water-soluble compounds identified in these samples. Sixty-five volatile compounds were identified in these teas. These molecules included 22 hydrocarbons, 18 alcohols, 8 ketones, 6 esters, 3 aldehydes, 3 heterocyclics, 2 nitrogens, 1 lactone, 1 acid, and 1 phenolic. Statistical analyses of these 65 compounds using principal component analysis and cluster analysis revealed that the contents of the Biluochun samples were highly similar and were different from those of the regular green teas. This study suggested that, although the geographical origin and cultivar influenced the aroma characteristics of tea products somewhat, processing technologies played an important role on tea aroma.

The aroma components of sun-dried and baked black teas, three replicates each, extracted with headspace solid-phase microextraction (HS-SPME) were identified by gas chromatography-mass spectrometry (GC-MS). Their similarities and differences were compared by using principal component analysis (PCA) and clustering analysis (CA). A total of 76 aroma components were identified in these two kinds of black tea, mainly including alcohols, ketones, and esters compounds. Among them, alcohol compounds were the most abundant components in sun-dried black tea (57.43%) and baked black tea (60.45%), mainly including linalool, linalool oxides, geraniol, nerolidol, etc. The aroma components of sun-dried and baked black teas were very similar and difficult to distinguish from each other. However, PCA and CA showed that sun-dried and baked black teas could be clearly distinguished according to their volatile characteristics, which illustrated that drying methods have influences on aroma components of black tea. Therefore, HS-SPME-GC-MS in combination with multivariate statistical methods could provide a feasible and rapid technique to differentiate between sun-dried and baked black teas based on their volatile components and relative contents.

BACKGROUND:Modern instrumental analysis technology can provide various chemical data and information on tea samples. Unfortunately, it remains difficult to extract the useful information. We describe the use of chemical fingerprint similarities, combined with principal component and cluster analyses, to distinguish and recognize Pu-erh green teas, which from two tea mountains, Wuliang and Jingmai, in the Pu-erh district of Yunnan province. The volatile components of all 20 Pu-erh green teas (10 Wuliang and 10 Jingmai teas) were extracted and identified by headspace solid-phase micro extraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS).RESULTS:Sixty-three volatiles (including alcohols, hydrocarbons, ketones, and aldehydes) were identified in the 20 Pu-erh green teas, and differences in compound compositions between them were also observed. Through fingerprint similarity, combined with principal component and cluster analyses, the 20 Pu-erh green teas were differentiated successfully based on their volatile characteristics.CONCLUSIONS:This study demonstrates that the GC-MS combined with chemical fingerprint and unsupervised pattern recognition method is suitable for the investigation of the volatile profiling and evaluating the quality and authenticity of teas related to the different origins.Graphical abstractDifferentiate Pu-erh green teas from different tea mountains by using chemical fingerprint similarity and multivariate statistical methods.

Based on the fully automatic headspace solid-phase microextraction (HS-SPME)/gas chromatography-mass spectrometry (GC-MS) and multivariate statistical methods, a novel model of identifying and evaluating the quality of Yunnan Pu-erh green tea was constructed for the first time in this work. Twelve Pu-erh green teas from 12 typical production sites of Pu-erh district in Yunnan Province and 6 regular green teas from Zhejiang, Sichuan, Anhui, Henan, Hubei, and Jiangsu provinces of China were used to construct the model. Data from 18 green tea samples by GC-MS were processed with fingerprint technology and chemometric methods. The GC-MS fingerprints from 12 Pu-erh green teas whose correlation coefficients and congruence coefficients were over 0.850 and demonstrated Pu-erh green tea samples from different production sites in Yunnan were consistent to some extent in spite of slightly different chemical indexes. A total of 77 volatile compounds were identified in 18 green teas, mainly including linalool, linalool oxides, phytol, caffeine, geraniol, and dihydroactinidiolide, and their chemical compositions were slightly similar. Cluster analysis (CA) and principal component analysis (PCA) demonstrated that 12 Pu-erh green teas could be clearly distinguished from other six regular green teas according to their chemical characteristics. Our results thus indicate that the chromatographic fingerprint combined with multivariate statistical techniques is useful for the identity and consistency evaluation of Pu-erh green teas. Such an approach is believed to be equally applicable to other green teas.

In order to explore the volatile components in four kinds of black tea from China, including Dianhong, Qihong, Zhengshanxiaozhong and Jinjunmei, their volatile components were extracted by fully automated headspace solid-phase microextraction (HS-SPME) and identified by gas chromatography-mass spectrometry (GC-MS). The resultsshowedthattotal90volatileconstituentswere identiifed from four kinds of black tea. The major volatile components in Dianhong tea were linalool, geraniol, linalool oxides, methyl salicylate, 2-pentylfuran, and nerolidol; which in Qihong tea were hexadecanoic acid, phytone, geraniol, linalool oxides, β-ionone, phytol, and anthracene; phytone, geraniol, β-ionone, dihydroactinidiolide, caffeine, and linalool oxides in Zhengshanxiaozhong black tea; and geraniol, caffeine, linalool oxides, β-ionone, phenethyl alcohol, nerolidol, and phytol in Jinjunmei black tea. The common volatiles included benzaldehyde, phenylacetaldehyde, linalool oxides, linalool, geraniol, α-ionone, β-ionone, phytol, etc. The volatile compositions and contents had great differences among four kinds of black tea, only 32 compounds were common. The relative content of alcohol compounds in four black teas was high, counting for 69.08% in Dianhong tea, while that of ketone compounds was high in Qihong, Zhengshanxiaozhong, and Jinjunmei. The differences in volatile compound proportion and threshold value formed the uniquearoma characteristics of these black teas.

The aroma components of Junshanyinzhen yellow tea and Huoshanhuangya yellow tea were extracted by fully automated headspace solid- phase microextraction( HS- SPME),and were identified by gas chromatography- mass spectrometry( GC- MS). Then comparison of aroma components and contents between the teas was made.Results showed that a total of 75 aroma constituents were identified,their aromatic components were very similar and 66 of them were identical.Hydrocarbon and alcohol compounds were the major aromatic components in Junshanyinzhen yellow tea and Huoshanhuangya yellow tea,among hydrocarbon compounds representing 50.95%and 40.75% of the total peak area respectively.The major aromatic compounds of Junshanyinzhen yellow tea were tridecane,δ- cadinene,linalool,dihydroactinidiolide,geraniol,2,6,10,14- tetramethyl pentadecane,dodecane,etc,while the major aromatic compounds of Huoshanhuangya yellow tea were geraniol,tridecane,linalool,caffeine,δ- cadinene,dodecane,β- ionone,and dihydroactinidiolide,etc.

A method was developed based on head-space solid phase microextraction/gas chromatography-mass spectrometry (HS-SPME/GC-MS) combined with multivariate statistical methods to assess volatile profiles in different types of Pu-erh teas.

The aroma components of three kinds of Taiwan oolong tea from different fermentation degree were extracted by fully automated headspace solid- phase microextraction( HS- SPME) and identified by gas chromatography- mass spectrometry( GC- MS). Comparison of the analytical results obtained was carried out on the composition and content of aroma compounds. Results showed that in total 72 aroma constituents were identified,among Pouchong tea and Dongding oolong tea had smaller difference,but there were many differences with oriental- beauty tea. The major aromatic components in Pouchong tea were nerolidol,α- farnesene,indole,jasmine lactone,cis- 3- hexenyl benzoate,caffeine,methyl jasmonate,and β- ionone; the major aromatic components in Dongding oolong tea were α- farnesene,nerolidol,indole,jasmine lactone,geraniol,2,6,10,14-tetramethyl- pentadecane,cis- 3- hexenyl benzoate,caffeine,β- ionone,methyl hexadecanoate and geranyl acetone; while the major aromatic components in Oriental- beauty tea were linalool oxides,nerolidol,hexadecylic acid,β- ionone,linalool,dihydroactinidiolide,caffeine,geraniol,hexanoic acid- 3- hexene ester,geranylacetone,phytone,cis- 3- hexenyl benzoate,etc. In comparison,the similarities and differences in aroma composition and content of three kinds of Taiwan oolong tea may be related to the different processing technologies and fermentation degree.

茶叶的水溶性成分和挥发性成分是决定茶叶品质的两大核心要素.随着现代仪器分析技术的不断发展,对于茶叶中的水溶性成分和挥发性成分的分析己见诸多报道,茶叶水溶性成分保健和药效功能也不断的被发现和鉴定,但是对挥发性成分的研究则相对缺乏.事实上,茶叶挥发性成分不仅主导着茶香感受,是决定茶叶品质的重要因素;而且这些有机小分子还具有各种功效,具有众多潜在的医用,药用和商业价值.为进一步挖掘茶叶挥发性成分的潜在疗效,对茶叶中挥发性成分及其香气和功效进行了综述.

The quality of tea is presently evaluated by the sensory assessment of professional tea tasters, however, this approach is both inconsistent and inaccurate. A more standardized and efficient method is urgently needed to objectively evaluate tea quality. In this study, the chemical fingerprint of 7 different Dayi Pu-erh tea brands and 3 different Ya'an tea brands on the market were analyzed using fully automatic headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). A total of 78 volatiles were separated, among 75 volatiles were identified by GC-MS in seven Dayi Pu-erh teas, and the major chemical components included methoxyphenolic compounds, hydrocarbons, and alcohol compounds, such as 1,2,3-trimethoxybenzene, 1,2,4-trimethoxybenzene, 2,6,10,14-tetramethyl-pentadecane, linalool and its oxides, α-terpineol, and phytol. The overlapping ratio of peaks (ORP) of the chromatogram in the seven Dayi Pu-erh tea samples was greater than 89.55%, whereas the ORP of Ya'an tea samples was less than 79.10%. The similarity and differences of the Dayi Pu-erh tea samples were also characterized using correlation coefficient similarity and principal component analysis (PCA). The results showed that the correlation coefficient of similarity of the seven Dayi Pu-erh tea samples was greater than 0.820 and was gathered in a specific area, which showed that samples from different brands were basically the same, despite have some slightly differences of chemical indexes was found. These results showed that the GC-MS fingerprint combined with the PCA approach can be used as an effective tool for the quality assessment and control of Pu-erh tea.

Thirteen Pu-erh teas and 13 Fuzhuan teas obtained from two different production areas in China were profiled using fully automatic headspace solid-phase microextraction (HS-SPME)/gas chromatography-mass spectrometry (GC-MS) coupled with chemometric methods. A total of 93 aroma components were identified in 26 dark teas; among them, methoxyphenolic compounds (31.77%) were the most abundant components in Pu-erh teas, whereas ketone compounds were the most abundant components (25.42%) in Fuzhuan teas. Cluster analysis (CA) and principal component analysis (PCA) showed that these two types of dark teas could be clearly distinguished according to their chemical characteristics. This study suggested that the proposed strategy could provide a feasible and rapid technique to differentiate dark teas with similar morphological characteristics from different production areas by their volatile composition and relative content.

With the aim to study the volatile aroma component of dark teas from five different production regions (Yunnan, Hunan, Sichuan, Guangxi, and Hubei) in China, the fully automatic headspace solid-phase microextraction (HS-SPME) method was constructed for extracting the volatiles and gas chromatography-mass spectrometry (GC-MS) coupled with retention index (RI) of the volatiles were used to determine the volatiles variety in dark tea samples. The result showed that 105 aroma constituents were determined in five dark teas, mainly including alcohols, ketones, hydrocarbons, and methoxy-phenolic compounds, etc. Among which the methoxy-phenolic compounds were the most abundant components in the Pu-erh ripe tea, mainly including 1,2,3-trimethoxybenzene, 1,2,3-trimethoxy-5-methylbenzene, and 1,2,4-trimethoxy benzene. Ketones were the most abundant components in the Heimao tea and Yaan dark tea, mainly including ��-ionone, geranyl acetone, and 6,10,14-trimethyl-2-pentadecanone. While the hydrocarbons were the most abundant components in the Liubao tea and Qingzhuan tea, mainly including 2,6,10,14-tetramethyl-pentadecane, 2,6,10,14-tetramethyl-hexadecane, and heptadecane, etc. In comparison, there were remarkable differences in flavor and aroma composition of the five types of dark tea, which may be related to the different species or subspecies, growing region and processing technology.