EVALUATION OF SPICES AND OLEORESINS VII. GAS CHROMATOGRAPHIC EXAMINATION OF GINGEROL, SHOGAOL AND RELATED COMPOUNDS IN GINGER

The products of thermal degradation of gingerols, the pungent component of the spice ginger under gas chromatographic conditions have been re-examined. Besides breakdown to zingerone and aldehydes, substantial dehydration of gingerols to shogaols has been established by improved gas chromatographic separation. The identity of the pungent and poorly pungent homologs have been clearly established as (6)- and (8)-, and (10)-gingerols/shogaols respectively. Programmed temperature gas chromatography combined with thin-layer chromatographic separation has provided a method for determining the ratio of the homologs and a possible method for estimation of gingerols and shogaols in ginger oleoresin.     

花椒中麻味物质的呈味机理及制备方法研究进展

不饱和烷基酰胺是花椒呈麻味的重要物质,从花椒中鉴定出的麻味物质主要成分有α-、β-、γ-、δ-山椒素 等及其衍生物。麻味物质通过激活瞬时受体电位（transient receptor potential,TRP）V1和TRPA1离子通道或抑制两 孔钾离子通道激发感觉神经元。麻味强度受麻味物质结构的影响,不同结构的麻味物质引起不同的受体激活,产生 不同程度的辛麻感。麻味物质的制备方法主要有两种：利用系列柱层析、制备色谱等进行纯化的常规方法和利用适 当化学反应进行制备的化学合成方法。本文对花椒中麻味物质的主要种类、麻味物质的呈味机理及麻味物质的制备 方法3 个方面的研究现状进行综述,为麻味物质进一步的系统化深入研究提供一定支持。     

Identification of the odour-active cyclic diketone cis-2,6-dimethyl-1,4-cyclohexanedione in roasted Arabica coffee brew

We investigated odour-active trace compounds in roasted Brazilian Arabica coffee. Aroma dilution extract analysis (AEDA) applied to the volatile oil extracted from roasted coffee brew revealed 34 odour-active compounds. Among these, a pungent-smelling unknown odour-active compound was determined. The volatile oil was fractioned by silica gel column chromatography. Gas chromatography–olfactometry (GC–O) and multidimensional gas chromatography–mass spectrometry (MDGC–MS) of the fraction which contained a significant amount of the target unknown compound revealed the cyclic 1,4-diketone, cis-2,6-dimethyl-1,4-cyclohexanedione, which had a pungent odour, and was thus first identified in roasted coffee. Model experiments revealed that cis-2,6-dimethyl-1,4-cyclohexanedione was formed via thermal degradation of sugars, especially monosaccharides, under alkaline conditions. Further, we demonstrated that 2-hydroxy-3-pentanone and 1-hydroxy-2-propanone, thermal degradation products of monosaccharides, were closely related to the formation of cis-2,6-dimethyl-1,4-cyclohexanedione.     

基于全二维气相色谱-飞行时间质谱法鉴定冷榨菜籽油的挥发性风味成分

以甘蓝型、白菜型和芥菜型3种不同基因型菜籽为原料,采用全二维气相色谱-飞行时间质谱法对冷榨菜籽油中挥发性风味成分进行鉴定,结合嗅觉检测器对其进行气味分析,并通过感官评定构建冷榨菜籽油风味轮廓图。研究表明:全二维气相色谱-飞行时间质谱法共分离共鉴定出156种挥发性成分,其中38种物质具有特征气味,主要包括异硫氰酸酯、含硫化合物、醇类、醛类、酸类、酮类、内酯和杂环类化合物;对于不同基因型原料而言,异硫氰酸酯和含硫化合物是冷榨菜籽油中风味差异的关键组分,甘蓝型、白菜型和芥菜型3种冷榨菜籽油的异硫氰酸酯总量分别为6. 94%、40. 86%和54. 94%,含硫化合物总量分别为2. 7%、0.44%、1.73%;通过感官评定,3种冷榨油中甘蓝型菜籽油中的辛辣味最弱,卷心菜味最强,白菜型菜籽油中青草味最明显,芥菜型中的酸味最明显;3个不同品种间种子味、坚果味、腐败味、发霉味、苦味差异不显著(P0.05)。     

Characterisation of cultivars of Jamaican ginger (Zingiber officinale Roscoe) by HPTLC and HPLC

In this study, a novel high performance thin layer chromatography (HPTLC) technique for fingerprinting of Jamaican ginger was developed and its application to the chemo-profiling of four cultivars of Jamaican ginger illustrated. Applications of the method to maturation and storage studies involving ginger oleoresins are also presented. The method showed good resolution of the pungent compounds characteristic of ginger: 6-gingerol, 8-gingerol, 10-gingerol and 6-shogaol, with five other discrete zones being described as additional references. HPTLC fingerprints of the ginger cultivars showed chemical homogeneity with small qualitatively observed differences in the intensities of the gingerol and shogaol zones. Quantification of these compounds by high-performance liquid chromatography (HPLC) revealed significant differences in total pungency among the cultivars. Essential oil yields from the cultivars also varied significantly. The described characterisations will prove useful in the authentication of Jamaican ginger.     

Volatile Components of Aqueous Liquid Smokes from Vitis viniferaL Shoots and Fagus sylvaticaL Wood

Vitis vinifera L shoots and Fagus sylvatica L wood were used to obtain aqueous smoke flavouring preparations. Both flavourings have a gold colour and pleasant odour. The flavour components of both samples are extracted with dichloromethane. The identification and quantitation of the components of the extracts are carried out by means of gas chromatography/mass spectrometry, and gas chromatography with flame ionisation detection. In both preparations carbonyl derivatives are in higher concentrations than phenol derivatives. Compounds that confer sweet, burnt and pungent flavours are in higher concentrations in the Vitis vinifera L shoots smoke flavouring, and compounds that give smoky flavours are in higher concentrations in the Fagus sylvatica L wood smoke flavouring. Ratios between the concentrations of the main components are proposed as parameters in order to characterise smoke and smoke flavourings, manufactured under specific conditions, from a specific wood. Finally, the yield of some components from a fixed amount of wood is also given.     

气相色谱-嗅闻-质谱联用分析牦牛肉的“膻味”成分

采用同时蒸馏提取制样,通过气相色谱-嗅闻-质谱联用对熟牦牛肉的挥发性风味物质进行分析,共检测出 72 种化合物,其中酯类4 种、羰基化合物31 种、醇类6 种、烃类13 种、醚类1 种,酚类2 种、杂环化合物7 种,含 硫化合物6 种、未知化合物2 种。通过嗅闻仪检测表明：异丁酸、丁酸、1-戊烯-3-酮、2,3-戊二酮4 种化合物具有强 烈的刺激性气味,对牦牛肉腥膻味的形成影响较大。     

Improvement of Coffee Aroma by Removal of Pungent Volatiles Using A-Type Zeolite

Experimental studies were conducted using molecular sieve zeolites to remove pungent smell components from a coffee aroma-containing gas evolved from roasted and ground coffee packed in a percolation vessel. The components such as methyl mercaptan or acetaldehyde were selectively adsorbed from coffee volatiles, and a decrease of pungent odor was recognized on sensory evaluation. The adsorption selectivity was based on pore sizes of adsorbents and molecular sizes of adsorbates. Zeolite 5Å was preferable to 4Å for separation efficiency of methyl mercaptan and recovery yield of residual volatile compounds.     

EVOLUTION OF VOLATILE COMPOUNDS DURING WORT-BOILING

Pilot scale trials have been carried out to determine the nature and patterns of evolution of compounds present in condensates obtained from boiling worts at atmospheric pressure. Analytical procedures involving gas chromatography and gas chromatography-mass spectrometry have been used to identify 70 compounds in condensates from unhopped ale worts. Over 30 of these volatile compounds have been classified according to one of three patterns of evolution. The rate of evolution for one class remained constant throughout the boiling period, for the second class decreased gradually towards the end of boiling, and for the third was sufficiently rapid to lead to the removal of most of a component during the early stages of boiling. Many of the compounds identified in the condensates are highly flavour-active.     

Characterization of fish sauce aroma-impact compounds using GC-MS, SPME-Osme-GCO, and Stevens' power law exponents

ABSTRACT:  The objectives of this study were to characterize volatile compounds and to determine the characteristic aromas associated with impact compounds in 4 fish sauces using solid-phase micro-extraction, gas chromatography-mass spectrometry, Osme, and gas chromatography olfactometry (SPME-Osme-GCO) coupled with Stevens' Power Law. Compounds were separated using GCMS and GCO and were identified with the mass spectral database, aroma perceived at the sniffing port, retention indices, and verification of compounds by authentic standards in the GCMS and GCO. Aromas that were isolated and present in all 4 fish sauce samples at all concentrations included fishy (trimethylamine), pungent and dirty socks (combination of butanoic, pentanoic, hexanoic, and heptanoic acids), cooked rice and buttery popcorn (2,6-dimethyl pyrazine), and sweet and cotton candy (benzaldehyde). All fish sauces contained the same aromas as determined by GCO and GCMS (verified using authentic standard compounds), but the odor intensity associated with each compound or group of compounds was variable for different fish sauce samples. Stevens' Power Law exponents were also determined using this analytical technique, but exponents were not consistent for the same compounds that were found in all fish sauces. Stevens' Power Law exponents ranged from 0.14 to 0.37, 0.24 to 0.34, 0.09 to 0.21, and 0.10 to 0.35 for dirty socks, fishy, buttery popcorn, and sweet aromas, respectively. This demonstrates that there is variability in Stevens' Power Law exponents for odorants within fish sauce samples.     

Aroma-Active Components of Lycii fructus (kukija)

ABSTRACT:  The fruit of Lycii fructus has been used as a tonic medicine and a long-term healthy food without side effect in Asia. An increase in the demand for natural healthy food, L. fructus has been thought as a source of healthy foods. For its value adding, its character impact aromas were isolated by using direct solvent extraction with vacuum transfer and identified by using gas chromatography olfactometry (GC-O) and GC-mass spectrometry (GC-MS). Thirty-three odor compounds were sniffed at GC-O, each trial equipped with DB-5MS and HP-WAX capillary column. The most contributing odor compounds in L. fructus were (E)-2-heptenal (green, mushroomy), 1-heptanol (planty, oily), hexanal (planty), 3-octanol (mushroomy, planty), 1-octen-3-ol (mushroomy), and 2-methyl-2-butenoic acid (pungent, planty), which might be produced by enzymatic oxidation and/or oxidation of lipids and carotenes, resulting in undesirable aromas.     

Effect of Pretreatment with Dehulling and Microwaving on the Flavor Characteristics of Cold‐Pressed Rapeseed Oil by GC‐MS‐PCA and Electronic Nose Discrimination

Raw and dehulled rapeseeds were treated with microwave energy (800 W) from 1 to 8 min with 1‐min intervals at a frequency of 2450 MHz to investigate the influence of microwaving and dehulling pretreatment on the flavor characteristics of rapeseed oil extracted by pressing. Headspace solid phase microextraction was used to isolate the volatile compounds of rapeseed oil, which were then identified by gas chromatography‐mass spectrometry analysis. The results indicated that microwave and dehulling pretreatment of rapeseed can significantly influence the kinds and content of volatile compounds. The key flavor compounds in rapeseed oil were oxidized volatiles, heterocyclic compounds, and degradation products of glucosinolates. A pungent compound, 4‐isothiocyanato‐1‐butene, was reduced by 97% in rapeseed treated for 3 min with microwaves energy when compared to the rapeseed oil without any treatment. The pyrazine compounds in the oil appeared after 6 min of microwave pretreatment and give a pleasant roasting flavor when compared to crude oils. Principal component analysis was able to differentiate between oils obtained using 4 pretreatment processes based on volatile compounds and electronic nose. The results showed that dehulling pretreatment could improve the flavor, yet microwaving had a greater effect on the flavor of rapeseed oils.     

High Performance Liquid Chromatographic Determination of Pungent Gingerol Compounds of Ginger (Zingiber officinale Roscoe)

The pungent gingerol compounds of green (4–5 months) and dry (8–9 months) ginger (Zingiber officinale Roscoe) were extracted by acetone and analyzed directly by high performance liquid chromatography (HPLC) on a reverse phase column (RP-18). The total gingerol content (6-, 8- and 10-gingerol) of green ginger ranged from 0.65–0.88% (w/w) while that of dry ginger varied from 1.10–1.56% (w/w).     

GAS CHROMATOGRAPHIC DETERMINATION OF TRIHYDROXYOCTADECENOIC ACIDS IN BEER

A rapid and quantitative method for measuring the content of trihydroxyoctadecenoic acids in beer is described. The acids are extracted from degassed beer with ethyl acetate and methylated with diazomethane. After washing, the methylated compounds are silylated and analysed by gas chromatography. The coefficient of variation of the method is 3·2%. The amounts of total trihydroxyoctadecenoic acids in commercial beer samples varied from 4 to 12 mg/litre. The effects of these acids on beer flavour and head retention are discussed.     

Distribution of glucosinolate and pungent odors in rapeseed oils from raw and microwaved seeds

The current study was aimed to investigate the effect of glucosinolate degradation on the flavor precursors and pungent odors in raw and microwaved rapeseeds. Five isothiocyanates and six sulfur compounds were identified using comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GC× GC-TOF/MS). Comprehensive analysis with headspace solid-phase microextraction (HS-SPME) and aroma extract dilution analysis (AEDA) with altering split ratio showed that 1-isothiocyanato butane, allyl isothiocyanate and 4-isothiocyanato-1-butene were responsible for the sulfur, pungent and green odors in rapeseed oils, due to their high flavor dilution factor. Dimethyl sulfide, dimethyl trisulfide and dimethyl sulfoxide, might be derived from methionine or isothiocyanate rearrangement reactions imparted onion-like, cabbage-like, garlic-like, and sulfurous-pungent odors. Rapeseed samples were heated in a microwave for seven minutes, and the total glucosinolate content decreased from 28.2 ± 0.8 μmol/g to 14.5 ± 0.6 μmol/g in Brassica napus, from 101.2±3.0 μmol/g to 42.2 ± 5.4 μmol/g in Brassica campestris, and from 132.02 ± 9.31 μmol/g to 52.50 ± 6.50 μmol/g in Brassica juncea, compared to untreated ones. Differences in the concentrations of six main odorants and the glucosinolate precursors from genetic types were responsible for the intensity of the pungent odors in raw and microwaved rapeseeds. The result can assist to determine the flavor of the commercial rapeseed oils.     

Volatile flavours in raw egg yolk of hens fed on different diets

BACKGROUND: Recent studies have suggested that the composition of lipophilic components of egg yolk is influenced by the feed. The aim of the present study was to isolate volatile flavours from egg yolk after different feeding trials using solvent extraction and thin layer high‐vacuum distillation. The resulting aroma extract was analysed by various gas chromatographic techniques. Chickens were either fed with laying meal, laying meal plus cabbage and onion or laying meal plus rapeseed oil or held in free‐range. RESULTS: The predominating odour impressions were described as onion‐like. Comparing all analytical and sensory data of the flavour extracts, there were minimal differences among the respective samples. Free‐range eggs contained fewer volatile compounds than the other samples, whereas rapeseed oil supplementation caused an enrichment of sulfur compounds. CONCLUSION: While data from gas chromatography/flame ionisation detection, gas chromatography/mass spectrometry and gas chromatography/olfactometry were less conclusive, the results from sulfur‐specific analysis using gas chromatography/flame photometric detection showed a considerable effect. However, because of the low abundance of sulfur compounds in the yolk, these differences are not expected to be perceivable by the consumer. Copyright © 2011 Society of Chemical Industry     

Investigation of aromatic compounds in roasted cocoa powder

Most of the volatile compounds identified are highly significant in determining cocoa powder flavour, and this paper demonstrates that basic sensory perceptions (undesirable, bitter pungent, repulsive, fruity, nutty, floral, vegetal, and sweet chocolate) can be totally explained by aroma compounds with R²-adjusted values of 0.85 and greater. Samples from five geographical origins of cocoa bean were characterized by chemical compounds and sensory attributes. The aroma extracts were obtained by a two-step procedure involving (1) preliminary steam distillation under reduced pressure to evaluate the methylpyrazines generated in roasted cocoa powder by spectrophotometry (flavour index), and (2) Likens-Nickersons simultaneous steam distillation and solvent extraction method with added NaCl. The distilled compounds were separated by adsorption chromatography in six fractions depending on the polarity. A combined total of 114 compounds were detected by gas chromatography/mass spectrometry, 110 of which were identified. About 15 components in the mean milligrams per kilogram range (1.09–4.67 mg kg^–1) and 95 components in the mean micrograms per kilogram range (12–980 µg kg^–1) were quantified. The major components of cocoa aroma were 2,3,5,6-tetramethylpyrazine, benzaldehyde, 2-phenylacetaldehyde, acetophenone, 3-methylbutyric acid, 5-methyl-2-phenyl-2-hexenal, ethyl phenylacetate, and 3-hydroxy-2-methyl-4-pyrone (mean greater than 1.30 mg kg^–1).     

Characteristic aroma compounds of cooked and fermented soybean (Chungkook‐Jang) inoculated with various Bacilli

BACKGROUND: For selecting Chungkook‐jang products with a less undesirable odour, the volatile compounds that affect the overall consumer acceptance of Chungkook‐jang products were analysed. The volatile compounds of Chungkook‐jang were extracted by using solid phase microextraction and direct solvent extraction and were detected by using gas chromatography‐olfactometry. The results were represented as the mean of the log₃ flavour dilution factors; principal component analysis was used to determine the effective components. RESULTS: Fifteen and 14 volatile compounds were detected in the extracts using solid phase microextraction and direct solvent extraction, respectively. The Bacillus species 2‐M1L, which has the most overall acceptance, might have a nutty initial top note and nutty and cheesy long‐lasting note aromas. In correlation analysis between the characteristic aromas and the overall acceptance, trimethyl pyrazine (nutty, pungent), butanoic acid (cheesy, butyric), and methyl pyrazine (burnt, roasted) were positively correlated with overall acceptance. In contrast, 3‐hydroxy‐2‐butanone (buttery, fatty) and 2,3‐butanediol (chemical, fatty) were negatively correlated with overall acceptance. CONCLUSION: Consumers might prefer Chungkook‐jang that has a more nutty and cheesy flavour and a less fatty one. Copyright © 2012 Society of Chemical Industry     

VARIETAL DEPENDENCE OF HOP FLAVOUR VOLATILES IN LAGER

A series of lagers brewed with single hop varieties was analysed via extraction and gas chromatography/mass spectrometry. Each hop variety contributed a small number of unique flavour compounds to the beers. Significant, reproducible differences were found between the concentrations of individual hop compounds and hop compound classes in the different beers.     

WORT COMPOSITION AND BEER FLAVOUR. II. THE INFLUENCE OF DIFFERENT CARBOHYDRATES ON THE FORMATION OF SOME FLAVOUR COMPONENTS DURING FERMENTATION

Wort, to which was added various amounts of solutions of glucose, fructose, sucrose or maltose, was fermented, and in the resulting beers the concentrations of the following flavour components were determined by gas chromatography: ethyl acetate, isobutyl acetate, iso-amyl acetate, 2-phenyl ethyl acetate, ethyl caproate, ethyl caprylate, n-propanol, isobutanol, amyl alcohols, 2-phenyl ethanol, caprylic acid and capric acid. The concentrations of these compounds were affected in different ways by the various amounts of sugar added, and some differences were observed etween the different carbohydrates.