我国不同产区羊肉中碳、氮同位素比值特征及溯源研究

目的 研究我国不同产区间羊肉组织中C、N稳定同位素比值(δ13C和δ15N)的差异及规律.方法 采集我国4个代表性产区的羊肉,分离提取其肉粉、脂肪、脱脂肉粉3种组织部位,采用元素分析仪-稳定同位素比值质谱法(element analyzer-isotope ratio mass spectrometry,EA-IRMS...     

Characterization and comparison of key aroma-active compounds of cocoa liquors from five different areas

The volatile constituents of cocoa liquor and the differences between cocoa liquors from different origins were studied. Direct solvent extraction-solvent assisted flavor evaporation and gas chromatography-olfactrometry-mass spectrometry in conjunction with aroma extract dilution analysis were used to identify the key flavor compounds in five cocoa liquors. There were significant differences of specific compounds between cocoa liquor from different areas of origins. Then, the purge and trap method was used to gathering the aroma-active components of five cocoa liquors from different origins, and one internal standard was used during this process for the further quantitative analysis by gas chromatography-olfactrometry-mass spectrometry. The results indicated that 3-methylbutanal, acetic acid, tetramethylpyrazine, and 3-methylbutanoic acid were the components with high concentrations. The contents of most compounds in the five kinds of cocoa liquor were dramatically different. The content of odorants of cocoa liquors from Papua New Guinea was higher than that of the others and that from Indonesia was the lowest. For sensory evaluation, the overall odor outlines of the five cocoa liquors were very similar, the Papua New Guinea cocoa liquor had higher preference than those of the other four samples. Principal component analysis showed that the characteristics of cocoa liquor from Papua New Guinea, Indonesia, and Ivory Coast were very significant.     

Multielement stable isotope ratios (H,C, N,S) of honey from different European regions

The aim of this study as a part of the food traceability project “TRACE” funded by the EU was to investigate if honeys produced in regions with different climatic and geological characteristics could be discriminated on the basis of the isotopic data. The hydrogen, carbon, nitrogen and sulphur stable isotope ratios of 516 authentic honeys from 20 European regions are presented and discussed. As honey contains only small quantities of nitrogen and sulphur, the honey protein was precipitated in order to obtain measurable amounts of these elements. The mean hydrogen isotopic ratios of the honey protein were found to be significantly correlated with the mean hydrogen isotopic ratios of precipitation and groundwater in the production regions. Carbon isotopic ratios were influenced by climate. The sulphur stable isotope composition is clearly influenced by geographical location (sea spray effect) and surface geology of the production regions. The results show that the stable isotope ratios of the four bio-elements carbon, nitrogen, hydrogen and sulphur in honey protein can be applied to verify the origin of honey. Carbon and sulphur were identified by canonical discriminant analysis as providing the maximum discrimination between honey samples. For seven regions the percentage of correct classified samples is greater than 70%. It was concluded that the methodology in its current state can be used to provide reliable origin information.     

Study on distribution pattern of stable carbon isotope ratio of Chinese honeys by isotope ratio mass spectrometry

The δ ¹³C values of 26 varieties of Chinese pure single‐flower honeys, 323 census samples of six varieties of single‐flower honeys and one multi‐flower honey as well as 20 888 commercial honey samples from 135 honey‐related enterprises in 25 provinces of China were analysed by stable carbon isotope ratio mass spectrometry between 1998 and 2004. It was found that the δ ¹³C values of different Chinese honeys fell within the ranges of values proposed by JW White. This shows that White's theory of the stable carbon isotope ratio of honeys is applicable to Chinese honeys and further demonstrates that the theory is universal to honeys from all over the world. The study also confirmed that the δ ¹³C values of honeys do not bear much relation to the environment in which the honey plants are grown, e.g. geographical area, water and soil, climate, etc., but do vary slightly with the honey plant species. Copyright © 2005 Society of Chemical Industry     

Trace element levels in honeys from different regions of Turkey

A survey of 25 honey samples from different botanical origin, collected all over the Turkey was conducted to assess their trace element contents. The aim of this study was to determine the levels of cadmium (Cd), lead (Pb), iron (Fe), manganese (Mn), copper (Cu), nickel (Ni), chromium (Cr), zinc (Zn), aluminium (Al) and selenium (Se) in honey samples from different regions of Turkey. Trace element contents were determined by a flame and graphite furnace atomic absorption spectrometry technique after dry-ashing, microwave digestion and wet-digestion. The accuracy of the method was corrected by the standard reference material, NIST-SRM 1515 Apple leaves. The contents of trace elements in honey samples were in the range of 0.23–2.41 μg g⁻¹, 0.32–4.56 μg g⁻¹, 1.1–12.7 μg g⁻¹, 1.8–10.2 μg g⁻¹, 8.4–105.8 μg kg⁻¹, 2.6–29.9 μg kg⁻¹, 2.4–37.9 μg kg⁻¹, 0.9–17.9 μg kg⁻¹, 83–325 μg kg⁻¹ and 38–113 μg kg⁻¹ for Cu, Mn, Zn, Fe, Pb, Ni, Cr, Cd, Al and Se, respectively. Iron was the most abundant element while cadmium was the lowest element in the Turkish honeys surveyed. The results showed that trace element concentrations in the honeys from different regions were generally correlated with the degree of trace element contamination of the environment.     

Characterization of microorganisms in Argentinean honeys from different sources

Seventy polyfloral honeys including commercial samples obtained from supermarkets, harvested from apiaries and purchased in bulk were initially examined for total antibacterial activity. From each sample, numbers of aerobic mesophilic bacteria, total coliforms, moulds and yeasts were determined and the presence of Salmonella spp., Shigella spp., Clostridium sulfite-reducers, Paenibacillus larvae and Bacillus spp. was investigated. Moisture content, pH and total acidity were also determined for all samples. Any honey diluted to concentrations from 75% to 1% (w/v) of full-strength honey showed total antibacterial activity. The numbers of aerobic mesophilic bacteria, moulds and yeasts were less than 10(3) cfu/g for all 70 samples. Faecal coliforms, Escherichia coli, Salmonella spp., Shigella spp. and Clostridium sulfite-reducers were not detected but P. larvae subspp. larvae, Bacillus cereus, Bacillus pumilus and Bacillus laterosporus were found among samples. For commercial, apiary and bulk honey the mean values for moisture content, pH and acidity, respectively, were 17.50%, 17.40% and 17.50%; 4.60, 4.10 and 4.20; and 18.30, 20.60 and 21 meq NaOH/kg. P. larvae was recovered from 35% of apiaries including hives in which the bees did not display symptoms of American foulbrood disease.     

酿酒专用粮基地酿酒玉米生长过程稳定同位素研究

该文为了研究酿酒玉米稳定同位素,利用稳定同位素质谱仪测定了来自酿酒专用粮基地不同地块不同生长阶段酿酒玉米各部位的C、N稳定同位素比值,结果表明,各生长阶段,~(15)N/~(14)N均最易在酿酒玉米茎部富集,在根部贫化,而~(13)C最易在酿酒玉米生长旺盛的部位富集;多施有机肥,有利于酿酒玉米富集~(15)N/~(14)N,使底茎、底叶、果实δ~(15)N偏高;多施非有机肥,会使底茎、底叶、果实δ~(15)N偏低;由于植物δ~(13)C受多种因素共同影响,海拔因素在该研究中未对酿酒玉米δ~(13)C产生显著影响。该文研究结果为监控酿酒玉米生长过程提供了初步理论数据。     

Intra-muscular and inter-muscular variation in carbon turnover of ovine muscles as recorded by stable isotope ratios

In the case of muscle-based foods, the incorporation of dietary isotopic signals into muscle tissue is a dynamic process and it is not known whether all muscles, or locations within a muscle, have the same isotopic composition. Therefore, an experiment was conducted in which 28 lambs were switched from a control diet to an isotopically distinct experimental diet offered at two different energy allowances (EA). Small, albeit significant, differences were detected in tissue carbon (C) turnover within the muscle Longissimus dorsi. Inter-muscular comparison showed similar C half-lives for four of the five analysed muscles. The results also clearly demonstrated that the EA had a significant impact on intra- and inter-muscular C turnover. The findings of similar tissue C turnover of several muscles sold as meats and the comparable tissue-diet fractionation of the analysed muscles (both within the same EA) will enable scientists to analyse different meat samples according to availability without introducing large biases. However, EA must be considered a factor of uncertainty.     

Characterization of the aroma-active compounds in Daqu: a tradition Chinese liquor starter

Daqu is a fermentation starter and substrate complex that is used to initiate the solid fermentations for the production of Chinese liquor. The aroma of Daqu is one of the most important factors that influence the flavor of Chinese liquor. The objective of this study was to evaluate the potent aroma-active compounds in Daqu. Odorants of Daqu extracted by solvent-assisted flavor evaporation (SAFE) were investigated by gas chromatography–olfactometry (GC–O) system with two olfactometric methods: detection frequency (DF) method and aroma extract dilution analysis (AEDA). A total of 43 compounds were identified in Daqu. Thirty-eight aroma-active components were further detected among which 33 were identified. Among these compounds, 4 odorants seem to contribute actively to the aroma of Daqu: hexanal (green grass), unknown (no.u2, nutty, roasted), phenylacetaldehyde (floral, rose) and 4-ethyl guaiacol (clove, spicy).     

Effect of different carbon substrates on nitrate stable isotope fractionation during microbial denitrification

In batch experiments, we studied the isotope fractionation in N and O of dissolved nitrate during dentrification. Denitrifying strains Thauera aromatica and "Aromatoleum aromaticum strain EbN1" were grown under strictly anaerobic conditions with acetate, benzoate, and toluene as carbon sources. (18)O-labeled water and (18)O-labeled nitrite were added to the microcosm experiments to study the effect of putative backward reactions of nitrite to nitrate on the stable isotope fractionation. We found no evidence for a reverse reaction. Significant variations of the stable isotope enrichment factor ε were observed depending on the type of carbon source used. For toluene (ε(15)N, -18.1 ± 0.6‰ to -7.3 ± 1.4‰; ε(18)O, -16.5 ± 0.6‰ to -16.1 ± 1.5‰) and benzoate (ε(15)N, -18.9 ± 1.3‰; ε(18)O, -15.9 ± 1.1‰) less negative isotope enrichment factors were calculated compared to those derived from acetate (ε(15)N, -23.5 ± 1.9‰ to -22.1 ± 0.8‰; ε(18)O, -23.7 ± 1.8‰ to -19.9 ± 0.8‰). The observed isotope effects did not depend on the growth kinetics which were similar for the three types of electron donors. We suggest that different carbon sources change the observed isotope enrichment factors by changing the relative kinetics of nitrate transport across the cell wall compared to the kinetics of the intracellular nitrate reduction step of microbial denitrification.     

Volatile compounds of olive oils from different geographic regions in Turkey

In this research, changes in volatile compounds of olive oil were investigated in terms of cultivar, harvest year, and geographic regions (Mediterranean, Aegean, Southeastern Anatolia, Marmara, and Black Sea) were investigated. Volatile compounds of olive oils were extracted by using solid-phase microextraction (SPME) method and were identified with gas chromatography–mass spectrometry. A total of 59 volatile compounds from seven different chemical groups including aldehydes, ketones, hydrocarbons, alcohols, esters, terpenes, and furans were identified. Aldehydes were detected as the major group in all geographic regions. Among aldehydes, trans-2-hexenal was found to be relatively higher. Alcohols and esters were determined as other important compounds. While many volatile compounds were affected by olive cultivar factor, this factor had no significant effect on esters. Principal component analysis showed that volatile compounds could play an important role in the separation of regions.     

Volatile composition and key flavour compounds of spirits from unifloral honeys

The volatile components of industrially produced spirits from three unifloral honeys of campanilla morada (Ipomoea crassicaulis [Benth.] B.L. Robinson), citrus (Citrus spp. L.) and romerillo de costa (Viguiera dentata [Cav.] Spreng.) were studied by combined sensory and instrumental techniques. GC and GC‐MS analyses of the isolated extracts led to the detection of 205 volatile compounds, 150 of them were positively identified. In general, the most abundant classes were saturated alcohols, ethyl esters of saturated fatty acids and terpenes in all samples. Relative aroma intensity of individual volatile components was evaluated by aroma extract dilution analysis of solvent extracts, by gas chromatography‐olfactometry and by odour activity values. Results indicated that 11 compounds: ethanol, ethyl esters of isopentanoic, hexanoic, octanoic and decanoic acids, 2‐phenylethyl acetate, (E)‐β‐damascenone, hotrienol, decanal, methyl anthranilate and ethyl (E)‐cinnamate were the most potent odorants in the honey spirits.     

不同工艺市售芝麻油的气味活性成分和感官品质差异分析

旨在为芝麻油企业提高其产品的香气品质提供参考,以我国市场上不同工艺的13个品牌畅销芝麻油产品为实验材料,利用溶剂辅助蒸发(SAFE)法萃取挥发性物质,气相色谱-嗅闻-质谱(GC-O-MS)法和感官评价比较其气味活性成分和感官品质差异。结果表明:低温压榨芝麻油的气味活性成分以醛类、烯烃和醇类为主,生芝麻味最强;石磨水代和高温压榨芝麻油的气味活性成分以美拉德反应杂环类产物为主,具有较强的炒芝麻味、炒坚果味和焦香味;石磨水代芝麻油的苯酚类物质含量最高,烟熏味最强;高温压榨芝麻油的苦味最强。综上,不同工艺的市售芝麻油气味活性成分和感官品质具有显著差异。     

不同产区赤霞珠葡萄酒酚类物质特征性分析

目的 探究赤霞珠葡萄酒酚类物质的产区差异性。方法 利用高效液相色谱,分析了新疆天山北麓产区、焉耆盆地产区与山东半岛产区赤霞珠葡萄酒中酚类物质组成与含量,结合多元统计方法进行评价。结果 新疆天山北麓产区、焉耆盆地产区与山东半岛产区赤霞珠葡萄酒的酚类物质含量差异较大,其中新疆两产区的原花青素B1、儿茶素、表儿茶素、对香豆酸、总黄烷醇类、总黄酮醇类、总类黄酮及总酚含量显着高于山东半岛产区(P<0.05),焉耆盆地产区芦丁、槲皮苷、白藜芦醇含量显着高于山东半岛产区(P<0.05)。基于酚类物质的聚类分析结果显示,当欧氏距离超过15时,山东半岛产区样品聚为一类,新疆两个产区葡萄酒样品聚在一起;基于酚类物质的Fisher判别分析能区分山东半岛产区样品,对新疆两个产区个别样品有误判,回代检验与交叉验证合计正确率分别为91.30%和86.96%。结论 新疆天山北麓、焉耆盆地与山东半岛产区赤霞珠葡萄酒酚类物质具有明显的产地差异性。     

稳定同位素碳、氮在冬虫夏草原产地鉴别中的应用

利用同位素比值质谱仪(IRMS)测定了来自我国青海省、云南省、四川省以及尼泊尔的12个不同产区冬虫夏草样品和来自贵州省、江西省、湖南省的3种亚香棒虫草的δ15N和δ13C值。统计分析结果表明:不同来源的冬虫夏草样品之间δ13C值相互重叠,差异不明显,而δ15N值波动范围较大,除来源于青海海南州的1个样品外,其他冬虫夏草样品均可按地理来源进行有效区分;其中来源于青海玉树、果洛的优质冬虫夏草样品δ15N值与其他产地冬虫夏草样品存在显著差异(P<0.009);冬虫夏草样品与亚香棒虫草样品之间的δ15N、δ13C值存在显著差异。     

基于稳定同位素比值的不同产地枸杞特征分析及判别

原产地差异导致枸杞价格悬殊,为促进国内枸杞市场健康有序发展,该文应用元素分析仪-稳定性同位素质谱（elemental analyzer-stable isotope mass spectrometry, EA-IRMS）测定了来自青海、宁夏和新疆3个地区共97份枸杞样品δ¹³C、δ¹⁵N、δ²H、δ¹⁸O和δ³⁴S 5种稳定同位素组成,结合箱线图、单因素方差分析以及主成分分析（principal component analysis, PCA）对不同产地枸杞中稳定同位素比值分布规律和相关性进行了讨论,应用线性判别分析（linear discriminant analysis, LDA）和支持向量机（support vector machine, SVM）2种算法建立不同产地枸杞判别模型。结果显示,枸杞样品中δ¹³C、δ¹⁵N、δ²H和δ¹⁸O 4种稳定同位素对产地判别贡献率较大,δ^...