香米特征香味成分2-乙酰基-1-吡咯啉提取及检测方法研究进展

2-乙酰基-1-吡咯啉（2-AP）是目前已经探明的香米特征性香味成分，其含量的高低直接影响香米的品质与价格，但由于该成分在天然香米中的含量通常低至微克每千克，在采用现代分析检测方法测定时，还可能受到样品基质干扰、色谱分离共流出等问题的影响，因此，如何从稻米样品中高效提取该化合物并结合适当的检测方法进行精确测定具有一定的挑战性。该文综述了对稻米中2-AP进行测定时常用的样品前处理方法及仪器分析方法。样品前处理方法主要有蒸馏法、萃取法及顶空富集法等；仪器分析方法主要包括气相色谱及气相色谱-质谱法、气相色谱-嗅觉测试法，以及最新被开发出来的衍生化-高效液相色谱-串联质谱法。该综述将为食品贸易领域香米中2-AP的测定、农业领域香米的遗传育种及水肥管理、食品加工领域米香类稳定风味成分的开发等提供参考依据。     

Method development for the determination of manganese, cobalt and copper in green coffee comparing direct solid sampling electrothermal atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry

A method has been developed for the determination of cobalt, copper and manganese in green coffee using direct solid sampling electrothermal atomic absorption spectrometry (SS-ET AAS). The motivation for the study was that only a few elements might be suitable to determine the origin of green coffee so that the multi-element techniques usually applied for this purpose might not be necessary. The three elements have been chosen as test elements as they were found to be significant in previous investigations. A number of botanical certified reference materials (CRM) and pre-analyzed samples of green coffee have been used for method validation, and inductively coupled plasma optical emission spectrometry (ICP OES) after microwave-assisted acid digestion of the samples as reference method. Calibration against aqueous standards could be used for the determination of Mn and Co by SS-ET AAS, but calibration against solid CRM was necessary for the determination of Cu. No significant difference was found between the results obtained with the proposed method and certified or independently determined values. The limits of detection for Mn, Cu and Co were 0.012, 0.006 and 0.004 μg g⁻¹ using SS-ET AAS and 0.015, 0.13 and 0.10 μg g⁻¹ using ICP OES. Seven samples of Brazilian green coffee have been analyzed, and there was no significant difference between the values obtained with SS-ET AAS and ICP OES for Mn and Cu. ICP OES could not be used as a reference method for Co, as essentially all values were below the limit of quantification of this technique.     

茶叶香味扫描和挥发性化学成分分析

为区分不同茶叶的香味，利用电子扫描仪对铁观音、兰贵人、玉针、碧螺春和云雾茶等5种茶叶进行了香味扫描，确定了电子鼻在茶叶香味辨别中的作用。采用固相微萃取．气相色谱／质谱联用法对这5种茶叶样品中的挥发性化学成分进行了定性和定量分析，分别鉴定出40、40、35、16和13种化合物。在鉴定出的化学成分中，乙酸、大茴香醚、十六烷、咖啡因、十六酸和双酚A是5种茶叶样品中所共有的化学成分，每种茶叶样品中又都含有一些特有的化学成分。最后对香味扫描结果和挥发性化学成分分析结果进行了分析，研究了挥发性化学成分组成和含量上的差别，对茶叶样品数据点在香味分析三维图中位置的影响。     

Solid-phase microextraction-gas chromatography mass spectrometry and multivariate analysis for the characterization of roasted coffees

HS-SPME-GC-MS in combination with PCA was employed to discriminate different arabica/robusta blends having different geographical origins. HS-SPME confirmed to be an effective and reproducible sampling technique for routine characterization of coffees. In addition, the chemometric approach permitted to find parameters suitable for the differentiation of the different blends and the determination of the real quality of the products. Finally, the proposed methods have been successfully applied to some commercial coffee blends.     

Ultra-fast synthesis of carbon dots using the wasted coffee residues for environmental remediation

Currently, the coffee residues are one of waste resources which become a problem because the coffee consumption has increased. This is a worldwide problem due to the increase in disposal costs and environmental problems. Therefore, we use the wasted coffee residue which contains caffeine as starting material of carbon dot for solving disposal costs and environmental problems. The carbon dots were synthesized from coffee residues with different firing times by a facile and fast method. The emission peak of carbon dot is about 445 nm (cyan color) under 360 nm. The transmittance of the prepared carbon dot film reaches 90% which is high transparency. These results represent that carbon dot and carbon dot film can be applied for flexible display and optical application through recycling waste coffee residues.     

The assessment of π-π selective stationary phases for two-dimensional HPLC analysis of foods: Application to the analysis of coffee

Differences between alkyl, dipole-dipole, hydrogen bonding, and π-π selective surfaces represented by non-resonance and resonance π-stationary phases have been assessed for the separation of ‘Ristretto’ café espresso by employing 2DHPLC techniques with C18 phase selectivity detection. Geometric approach to factor analysis (GAFA) was used to measure the detected peaks (N), spreading angle (β), correlation, practical peak capacity (n_p) and percentage usage of the separations space, as an assessment of selectivity differences between regional quadrants of the two-dimensional separation plane. Although all tested systems were correlated to some degree to the C18 dimension, regional measurement of separation divergence revealed that performance of specific systems was better for certain sample components. The results illustrate that because of the complexity of the ‘real’ sample obtaining a truly orthogonal two-dimensional system for complex samples of natural origin may be practically impossible.     

Analysis of acrylamide in coffee and cocoa by isotope dilution liquid chromatography–tandem mass spectrometry

An accurate and precise method for the quantification of acrylamide using stable isotope dilution liquid chromatography–tandem mass spectrometry was developed and used to measure acrylamide in coffee and cocoa samples. The sample preparation involved extraction of the analyte and its internal standard, ¹³C₃-acrylamide, into water and subsequent defatting of the aqueous extract with dichloromethane. An aliquot of the resulting aqueous extract was then azeotropically dried under reduced pressure and subsequently purified using an aminopropyl-bonded silica cartridge. The purified extracts were then chromatographed on a 5-μm 2.1×150 mm Hypercarb column, the effluent of which was monitored for the analyte and its internal standard using positive-ion APCI-selected reaction monitoring. The intra-laboratory reproducibility of the method, expressed as a relative coefficient of variation (%, n=5), was determined at four levels of concentration (12.3, 42.3, 139.3 and 464.8 μg kg⁻¹) and was found to vary between 0.6–2.5%. The accuracy of the method was assessed using a reference sample of coffee. The average result obtained using our method differed from the assigned value of the reference material by less than 1%. An analysis of a cocoa sample revealed that the method is capable of precisely estimating acrylamide in challenging matrices down to a level of at least 12.3 μg kg⁻¹.     

Activated carbons by pyrolysis of coffee bean husks in presence of phosphoric acid

Activated carbons (Acs) were prepared by pyrolysis of coffee bean husks in presence of phosphoric acid (chemical activities). Husks from Colombian coffee beans were impregnated with aqueous solutions of H₃PO₄ following a variant of the incipient wetness method. Diffenent concentrations were used to produce impregnation ratios of 30, 60, 100 and 150 wt.%. Activation was carried out under argon flow by heating to 723 K with 1 h soaking time. The porous texture of the obtained ACs was characterized by physical adsorptions of N₂ at 77 K and CO₂ at 273 K. The impregnation ration had a strong influence on the pore structure of these Acs, which could be easily controlled by simply varying the proportion of H₃PO₄ used in the activation. Thus, low impregnation ratio led to essentially microporous Acs. At intermediate impregnation ratios, ACs with wider pore size distribution (from micropores to mesopores) were obtained. Finally, high impregnation ratios yielded essentially mesoporous carbons with high surface area and pore volume.     

气相色谱-质谱联用法分析北大仓白酒香气成分

利用溶剂萃取法进行分离和富集,采用气相色谱-质谱联用技术对北大仓白酒香气成分进行分析。从北大仓白酒的二氯甲烷萃取物中分离并鉴定了30种物质,其中酯类22种,占所有香气物质的94.847%;酸类2种,占4.659%;烷烃类2种,占0.228%;醇类2种,占0.185%;酮类1种,占0.060%;酸酐类1种,占0.021%。所含主要化合物为己酸乙酯、2-羟基丙酸乙酯和己酸,合计占总香气成分的96.396%,构成了北大仓白酒香气成分的骨架。     

固相微萃取法和液液萃取K-D浓缩法对化妆品香气的分析

分别利用固相微萃取法和液液萃取K-D浓缩法对化妆品调理水中的香气提取物进行分析比较。用这两种方法从化妆品调理水中提取、鉴定出30个化合物,从固相微萃取法提取物中鉴定出23个化合物,液液萃取K-D浓缩法提取物中鉴定出16个化合物,其中相同的化合物有9个。结果表明,两种提取方法得到的香气成分有明显差异,其香气特征成分主要集中在固相微萃取法所富集部分,因此采用固相微萃取法能够快速、高效、全面地对香气的香型进行定性分析。