Characterisation of volatile compounds of farmed soft‐shelled turtle (Pelodiscus sinensis) by solid‐phase microextraction and the influence of matrix pH on the release of volatiles

Although farming and consuming of soft‐shelled turtle has been practised for centuries, the aroma‐impact compounds in the meat have not been determined. Furthermore, matrix pH, usually changing during processing and storage stage, was rarely investigated for the influence on volatile profiles. To these aims, soft‐shelled turtle meat was subjected to different pH conditions and the potential volatile compounds were analysed under different extraction conditions by headspace solid‐phase microextraction (HS‐SPME). A total of forty‐three volatiles were identified; in which, nonanal, (E, E)‐2, 4‐heptadienal, octanal, decanal, hexanal, (E)‐2‐nonenal, heptanal, 1‐octen‐3‐ol and o‐xylene were assigned as aroma‐impact compounds by high relative odour activity value (ROAV). Overly basic or acidic pH significantly (P < 0.05) facilitated the release of volatiles under moderate extraction conditions. The total volatilisation increased by 30.1% to 298% in pH‐shifted samples, while the highest one was found in pH 2 or pH 11. However, the results of principal components analysis (PCA) demonstrated that increased extraction time or temperature hindered the pH enhancement.     

Characterization of Volatile Compounds in Microfiltered Pasteurized Milk Using Solid-Phase Microextraction and GC×GC-TOFMS

Volatiles of milk were characterized by solid-phase microextraction coupled with comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry. Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry two-dimensional gas chromatography with time-of-flight mass spectrometry not only separated the 52 compounds that co-elute in conventional gas chromatography-mass spectrometry, but also identified 107 compounds that were first reported in milk. These volatiles included aliphatic hydrocarbons (69), aromatic hydrocarbons (42), ketones (28), esters (16), aldehydes (14), alcohols (14), acids (14), nitrogenous compounds (9), ethers (8), and sulfo compounds (3). Five dominant volatiles were hexanoic acid (193.57 ng/mL milk), methoxy-phenyl-oxime (114.83 ng/mL milk), octanoic acid (109.38 ng/mL milk), 4,5-dimethyl-1-hexene (101.48 ng/mL milk), and 2-Pentanone (99.74 ng/mL milk). This proposes an improvement methodology for determining the volatiles of dairy products.     

Solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS) determination of volatile compounds in orujo spirits: Multivariate chemometric characterisation

A headspace solid-phase microextraction gas chromatography mass spectrometric procedure (HS-SPME-GC–MS) was developed and applied in order to determine 22 volatile compounds (including alcohols, esters, aldehydes and terpenes) in different orujo spirit samples from the Geographic Denomination “Orujo de Galicia/Augardente de Galicia”. The orujo samples considered in this study were elaborated from Albariño variety grapes grown in the Rías Baixas restricted geographical area, and Albariño variety grapes grown in other geographical areas of Galicia (NW Spain) using two of the traditional distillation techniques: alembic and steam distillation. HS-SPME adequate results were obtained using a 65 μm carbowax-divinylbencene fibre during a headspace extraction at 40 °C with constant magnetic stirring for 15 min, and after a 5 min period of pre-equilibrium time. Desorption was performed directly in the gas chromatograph injector port for 5 min at 250 °C using the splitless mode. The applied method was demonstrated to be sensible, accurate, precise, and linear over more than one order of magnitude. Multivariate chemometric techniques (such as cluster analysis, principal component analysis and linear discriminant analysis) were used to characterise the orujo samples according to the geographical origin of the grapes and the distillation system employed in their elaboration on the basis of the chemical information provided for their volatile composition data.     

啤酒中酒花香组分分析方法的研究及其在啤酒酒花香气质量评定中的应用

采用顶空固相微萃取-GC／MS技术，建立了啤酒中酒花香组分的分析方法，可以准确测定里哪醇、β-香茅醇、α-萜品醇、香叶醇、反式-橙花叔醇、乙酸香茅酯、香叶酸甲酯、乙酸香叶酯等8种酒花香组分。应用本方法测定了市售不同品牌啤酒的酒花香组分含量，通过统计分析并结合感官评定，评价了不同品牌啤酒的酒花香质量，本方法的建立有助于啤酒酒花香的量化评定。     

乙烯利在果蔬中残留量的快速分析方法

建立一种用顶空气相色谱快速测定植物生长调节剂乙烯利在果蔬中残留量化快速分析方法.在样品中添加碱液后恒温加热,吸取顶空瓶中的上层气体,采用GC-Q柱,GC-FID检测器进行测定.该方法的检测限为0.01 mg/kg,平均回收率为86.6%,相对标准偏差为2.1%～7.0%.     

白酒中香味物质的顶空一气相色谱／质谱联用分析

研究建立了一种快速简单的检测白酒中的香气成份的检测方法,即顶空一气相色谱／质谱联用分析方法,该方法采用静态顶空进样,GC-MS分离鉴定,总离子流色谱的峰面积归一化定量分析白酒中酯类和醇类等香气成份,方法操作简单,定性可靠准确。     

Multilayer emulsions as delivery systems for controlled release of volatile compounds using pH and salt triggers

Multilayer oil-in-water (M-O/W) emulsions were compared to primary oil-in-water (P-O/W) emulsions as carriers for volatile organic compounds (VOCs) under various environmental conditions (pH and salt). The M-O/W emulsion consisted of soy oil coated with β-lactoglobulin (βLG) and pectin layers. The release of VOCs with different physiochemical properties from aqueous solutions and emulsion systems was measured using static and dynamic headspace methods. The partition coefficients (K) calculated by the phase ratio variation (PRV) method, showed different volatile release profiles between the emulsion types. An increase in VOC release was found for the unstable P-O/W emulsion at pH 5, whereas M-O/W emulsions were stable at the same pH and retained the hydrophobic VOCs. Hydrophobic interactions and hydrogen bonds with the secondary dense layer of pectin may be responsible for the improved retention. Increasing pH and ionic strength acts as a VOC release trigger to detach the pectin from the interface. The release rates from initial dynamic curves support the results under equilibrium conditions. The results of this study demonstrate the capability of using M-O/W emulsions for controlled release of VOCs, as well as an alternative system to create stable emulsions with similar VOC release profiles.     

Headspace Volatile Oxylipins of Eastern Himalayan Moss Cyathophorella adiantum Extracted by Sample Enrichment Probe

Cyathophorella adiantum (Griff.) M. Fleisch. (Division-Bryophyta, Family-Daltoniaceae), an Eastern Himalayan moss was studied for the first time to identify the volatiles derived from cellular and membrane bound fatty acids. A high capacity sample enrichment probe (SEP) was used for extraction of headspace volatile (HSV) molecules followed by GC–MS analysis. Different short-chain oxylipins like alkenes, alkanes, saturated and unsaturated alcohols, saturated and unsaturated aldehydes, ketones were identified along with free and esterified fatty acids, cyclo compounds and some by-products of secondary metabolites. Fatty acid analysis of neutral lipids (NL) and phospholipids (PL) of this plant exhibits the predominance of C16 and C18 fatty acids. It also reveals some interesting information that might indicate the possible fatty acid precursors for volatile generation and their sources in this plant.     

The effects of roasting temperatures on the formation of headspace volatile compounds in perilla seed oil

Volatile compounds of perilla seed oils roasted at different temperatures (150–190°C) were analyzed by dynamic headspace gas chromatography-mass spectrometry. The headspace volatiles in roasted perilla seed oils (RPSO) were composed of thermally produced flavors and compounds originating from the raw perilla seeds. The roasting temperatures significantly affected the production of thermal reaction flavors. Oils from parilla seeds roasted below 170°C had relatively high concentrations of aldehydes, whereas pyrazines and furans were the predominant volatiles above 170°C. In all of the RPSO, the contents of both perilla aldehyde and perilla ketone remained almost constant and might be used to discriminate perilla seed oils from other roasted vegetable seed oils.     

Volatile fraction of DOP “Castelo Branco” cheese: Influence of breed

“Castelo Branco” cheese is a Portuguese DOP cheese made from raw ewe’s milk coagulated with Cynara cardunculus, ripened for at least 40 days. “Merino da Beira Baixa” pure race is frequently used to produce milk for this cheese, however, exotic races such as Assaf and crusade of these two races are also used. The aim of this work has been to compare the volatile profile and sensory characteristics of DOP “Castelo Branco” cheeses manufactured during winter season with milk of breeds from Merino, Assaf and crusade of these two races and identify volatile compounds that can distinguish these cheeses.