Analysis of odour‐active compounds of black mangrove (Avicennia germinans L.) honey by solid‐phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The volatile compounds of Cuban black mangrove (Avicennia germinans L.) honey were analysed by solid‐phase microextraction (SPME) followed by gas chromatography–mass spectrometry and gas chromatography–olfactometry. A total of 66 compounds were positively identified in this product for the first time. Application of the aroma extract dilution analysis in a novel approach, which consisted of carrying out successively dilutions of the honey sample with a synthetic honey before the SPME, revealed 17 odour‐active areas in the flavour dilution factor range of 32–1024. On the basis of the quantitative data and odour thresholds, odour activity values (OAV; ratio of concentration to odour threshold) were calculated. Sixteen compounds showed OAVs >1, among which dimethyl sulphide, 3‐methyl butanal, 2‐methylbutanal, heptanal, octanal, phenylacetaldehyde, (Z)‐linalool oxide, (E)‐linalool oxide, nonanal, hotrienol, isophorone, lilac aldehyde A, 1‐nonanol, decanal, 4‐vinyl‐2‐methoxyphenol and (E)‐β‐damascenone showed the highest values and should be considered as the most odour‐active compounds, particularly (E)‐β‐damascenone, nonanal and decanal.     

Headspace solid‐phase microextraction analysis of volatile compounds from spice essential oils in dry flavourings

The composition of volatile compounds in nine spices was analysed by means of headspace solid‐phase microextraction (HS‐SPME) from dry flavourings of the spice essential oils, to devise an effective method to determine the content of the essential oils. The HS‐SPME was combined with GC‐MS and GC‐FID for identification and quantification of the volatile compounds. The optimisation of the extraction conditions was carried out by response surface methodology. The evaluation of the analytical parameters indicated that the method had a high precision (coefficient of variations lower than 3%), it was linear (response factors were smaller than 5%) and recoveries were higher than 89%. In the ruggedness test, sample quantity and pre‐extraction time were the factors that stood out as the causing of the greater effects on the analytical results.     

固相微萃取-气相色谱-串联质谱法快速筛查葡萄酒中农药残留

目的建立固相微萃取-气相色谱-串联质谱法快速筛查检测葡萄酒中农药残留。方法葡萄酒样品稀释后进行固相微萃取,直接进行气相色谱-串联质谱检测。优化选择了萃取纤维类型、萃取方式、萃取时间等固相微萃取的实验条件,考察了方法性能(检出限、添加回收率和精密度等)。结果确定方法可检测目标农药为94种,其检出限10μg/L,平均回收率在60%~110%之间,且方法的重复性和再现性标准偏差分别在20%和30%之内。结论该检测方法操作简便、快速,单个样品分析时间不超过1 h,适用于葡萄酒中农药残留的快速筛查检测。     

Analysis of brandy aroma by solid‐phase microextraction and liquid–liquid extraction

Headspace solid‐phase microextraction (SPME) and continuous liquid–liquid extraction (LLX) with Freon were used to extract and analyse aroma volatiles in brandy. In general, SPME using a non‐polar polydimethylsiloxane coating was more selective for esters and acids than was LLX. LLX using Freon 11 extracted the higher alcohols more efficiently than SPME. Relative differences in volatiles between brandies made from Vitis vinifera L cv Colombard and Vitis vinifera L cv Ugni blanc were observed, particularly for hexanol, 3‐methylbutylacetate, 3‐methylbutanol and 3‐methylbutyloctanoate. In addition, a combination of SPME with GC–olfactometry was used to provide more detailed information on sensory characteristics of varietal brandies. © 2000 Society of Chemical Industry     

Assessment of the effect of the non-volatile wine matrix on the volatility of typical wine aroma compounds by headspace solid phase microextraction/gas chromatography analysis

BACKGROUND: The aim of this study was to evaluate the effect of the whole non‐volatile wine matrix composition on the volatility of typical wine aroma compounds by comparing the slopes of regression lines of five deodorised and reconstituted wines with the slopes calculated for the same compounds in a control wine with no matrix effect. RESULTS: The main effect observed was a reduction in the slopes, or a retention effect, that was largest for the reconstituted sparkling wine, which showed between 11 and 69% lower slopes than the control wine. In addition, an increase in the slopes, or a ‘salting‐out’ effect, in the most compositionally complex reconstituted aged‐red and sweet wines was also noticed for some volatiles with a very low boiling point or a low hydrophobic constant value. CONCLUSION: This study has shown that the non‐volatile composition of wines strongly affects the volatility of wine aroma compounds. In addition, the aroma chemical class, in particular its physicochemical properties (volatility and hydrophobicity), strongly influences this behaviour. On the basis of these results, many odour threshold values calculated in simple hydroalcoholic solutions and usually employed to evaluate the odour importance of specific volatile compounds may have been over‐ or underestimated. Copyright © 2011 Society of Chemical Industry     

Estimation of the honeydew ratio in honey samples from their physicochemical data and from their volatile composition obtained by SPME and GC‐MS

Differentiation of nectar and honeydew honeys is difficult, not only because of the wide variability in composition and organoleptic properties among samples from the same source, but also because of the frequent existence of honeys resulting from a blend of nectar and honeydew. A mathematical expression to evaluate the relative presence of honeydew in a honey sample (HD) has been developed from relevant physicochemical properties of honey samples selected as highly representative of both honey types on the basis of their physico‐chemical and melissopalynological analysis. As honey aroma depends on its volatiles composition, GC‐MS analysis of the volatile fraction obtained by SPME has been carried out in order to evaluate its usefulness in honey source differentiation. Stepwise regression from multicomponent volatiles data was used for the estimation of HD and for determining which volatile compounds were related to the different honey sources. Copyright © 2004 Society of Chemical Industry     

Determination of volatile compounds to characterize fish spoilage using headspace/mass spectrometry and solid‐phase microextraction/gas chromatography/mass spectrometry

Changes in volatile compounds were monitored in whiting (Merlangius merlangus), cod (Gadus morhua) and mackerel (Scomber scombrus) and related to spoilage. Data are presented from headspace/mass spectrometric (HS/MS) analysis and solid‐phase microextraction/gas chromatographic/mass spectrometric (SPME/GC/MS) analysis at two time points (day 0 and day 10) during storage at 4 °C. HS/MS revealed 24 ions that could be used as markers of spoilage. SPME/GC/MS identified 86 compounds, 20 of which could perhaps be used to characterize freshness: principally alcohols, ketones, aldehydes and C₂–C₁₁ esters. Compounds common to the three species studied appear to be generated by microbial degradation. Copyright © 2005 Society of Chemical Industry     

Determination of flavour compounds in beer using stir‐bar sorptive extraction and solid‐phase microextraction

The analysis of volatile compounds in beer is important for quality control in the brewing industry. In this study, stir‐bar sorptive extraction (SBSE) and solid‐phase microextraction (SPME), two solvent‐less enrichment techniques, were applied in combination with gas chromatography flame ionization detection (GC/FID) for the determination of four flavour compounds (isoamyl acetate, ethyl hexanoate, benzaldehyde, myrcene) in beer. Limits of detection, linearity and repeatability of both methods were determined using standard ethanol solutions, while accuracy was determined by conducting recovery tests on commercial beer samples. Both methods were characterized by high linearity (r > 0.996) and repeatability (RSD = 1.76–10.66%). When both methods were compared, higher recoveries were obtained by SBSE, with limits of detection 1.8–2.8 times lower compared with SPME. In the analysis of commercial beer samples using both methods, SBSE analysis resulted in higher recoveries, therefore demonstrating promise for the analysis of beer volatiles. Copyright © 2015 The Institute of Brewing & Distilling     

Application of the fast sensory method ‘Rate‐All‐That‐Apply’ in chocolate Quality Control compared with DHS‐GC‐MS

This paper studied the fast sensory Rate‐All‐That‐Apply (RATA) method as a contributor to existing quality control (QC) in chocolate production by comparing it with the outcome of dynamic headspace sampling combined with gas chromatography–mass spectrometry (DHS‐GC‐MS). Seven different chocolates were evaluated by a semi‐trained panel using RATA. RATA showed potential as a sensory evaluation tool which could be part of QC programmes in chocolate production as RATA was efficient to perform and captured important sensory deviations, herein addition of excess lecithin and prolonged roasting. However, product deviations caused by long conching were only detected by DHS‐GC‐MS. A more extreme conching process must occur before it can be perceived by humans. RATA and DHS‐GC‐MS should be used as complementary methods in detecting future important issues in chocolate production. DHS‐GC‐MS detects product deviation from chemical perspectives while sensory evaluation gives information on quality parameters from a perceivable perspective influencing consumer satisfaction.     

Analysis of volatile composition of toasted and non‐toasted commercial chips by GC‐MS after an accelerated solvent extraction method

The analysis of the volatile profile of different oak chips carried out by gas chromatography–mass spectrometry after their isolation by accelerated solvent extraction permitted faster and thorough extractions, while the appearance of artefacts was avoided. Statistical analysis revealed that toasting treatment is the main factor for the volatile compounds with a great sensorial impact. Indeed, toasting process overrode the differences between species. Furthermore, it was evidenced that the toasting treatment is not a homogeneity process. Concentrations of furaneol, 2,3‐dihydro‐3,5‐dihydroxy‐6‐methyl‐4H‐pyran‐4‐one and 5‐hydroxymethylfurfural could be used to monitor the intensity of the toasting process. Differences in the volatile composition with respect to species were also found, being the most remarkable the high concentration of trans and cis‐β‐methyl‐γ‐octanolactone in oak chips from Quercus alba and Quercus petraea species. The differences found in the volatile composition of different commercial oak chips evidenced the necessity to know their chemical composition previously to predict their aromatic potential.     

HS‐SPME/GC‐MS and chemometrics for volatile composition of Chinese traditional aromatic vinegar in the Zhenjiang region

The main purpose of this study was to determine the volatile composition of Zhenjiang aromatic vinegar, one of the four famous China‐style cereal vinegars, by using headspace solid‐phase microextraction (HS‐SPME)/gas chromatography‐mass spectrum (GC‐MS) and chemometrics. For this purpose, the HS‐SPME sampling method for the volatile compounds of Zhenjiang aromatic vinegar was optimized by a second‐order rotatable central composite experimental design (CCD). A HS extraction of the volatile compounds by incubation on a 65 µm thickness polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre during 44.2 min at 69.5°C with 1.9 g NaCl add gave the most effective and accurate extraction. By the optimized method, a total of 58 volatile compounds, including 9 alcohols, 13 acids, 16 esters, 5 aldehydes, 4 ketones and 8 heterocycle compounds, were identified from 13 aromatic vinegar samples manufactured in Zhenjiang region. By principal components analysis (PCA), the thirteen vinegar samples were classified into 3 groups, and 10 volatile compounds were chosen as characteristic compounds of Zhenjiang aromatic vinegars. Copyright © 2012 The Institute of Brewing & Distilling     

普洱熟茶香气成分的顶空固相微萃取条件优化

目的优化普洱熟茶香气成分顶空固相微萃取(headspace solid-phase microextraction,HS-SPME)-气质联用的萃取条件。方法利用Box-Benhnken的中心组合实验设计原理,以香气物质的质谱图峰面积为考察指标,对水/茶比、萃取温度、萃取时间进行3因素3水平响应面分析。结果萃取时间、萃取温度、萃取时间-萃取温度、水茶比的二次项和萃取温度的二次项对普洱茶中香气成分提取有显著影响(P0.05),而其他几项影响不显著。利用Design-Expert 8.0软件,对数据分析后,得到最优条件为水/茶比为9.76、萃取时间2.47 h、萃取温度76.64℃。结论在优化的条件下,香气物质峰面积可达到理论上的最大值是5.48×10~8。     

Simple determination of formaldehyde in fermented foods by HS‐SPME‐GC/MS

We describe an automatic method to detect formaldehyde (FA) in some fermented foods. This method is based on derivatisation with 2,2,2‐trifluoroethylhydrazine (TFEH) and consecutive headspace solid‐phase micro‐extraction and gas chromatography‐mass spectrometry. FA in food reacted for 30 min at 40 °C with 2,2,2‐TFEH in a headspace vial, and the formed FA‐TFEH derivative was simultaneously vaporised and adsorbed on 85‐μm carboxen–polydimethylsiloxane. Under the established condition, the limit of detection was 0.1 μg kg^?1 by using 1.0‐g solid food and 1.0‐mL liquid food, and the relative standard deviation was less than 10% at FA concentrations between 0.050 and 0.500 mg kg^?1. The concentrations of FA in several traditional Korean foods including gimchi, watery radish gimchi, soybean paste, red pepper paste, soy sauce and bean‐paste soup were measured. All food samples had detectable levels of FA (0.104–13.05 mg kg^?1).     

Rapid determination of ethyl carbamate in Chinese rice wine using headspace solid‐phase microextraction and gas chromatography–mass spectrometry

Ethyl carbamate (EC) is a naturally occurring toxic contaminant that may imply a risk to human health and is usually found in alcoholic beverages such as Chinese rice wine. An automated procedure for the rapid determination of EC in Chinese rice wine was developed by headspace solid‐phase microextraction (HS‐SPME) coupled to gas chromatography–mass spectrometry (GC‐MS). Using propyl carbamate as internal standard, the optimized HS‐SPME sampling with a polyacrylic fibre was 45 min at 70°C after applying 38.8% NaCl to saturate the sample. This method showed good linearity over a range of 25–600 µg L^?1 (R² = 0.997). The recovery, relative standard deviation and limit of detection were 90.21–97.35%, lower than 2.89% and 1.19 µg L^?1, respectively. Additionally, the ethanol concentration had no effect on the analysis of EC. The total analysis time of 57 min per sample in continuous determination was twice as fast as the widely used solid‐phase extraction–GC‐MS method. This solvent‐free HS‐SPME‐GC‐MS procedure is suitable for the rapid, automated, and therefore convenient, determination of EC in Chinese rice wine. Copyright © 2012 The Institute of Brewing & Distilling