Correlations of flavor score with volatiles of vegetable oils

A simple, direct, gas chromatograph (GC) technique is described for eluting flavor-related volatile components from commercially produced vegetable oils. A sample of oil was placed onto glass wool contained in a GC liner, and the liner was inserted in the heated inlet of the GC. Volatiles from the oils were rapidly eluted by heat and carrier gas onto the GC column. Profiles of the volatiles were obtained by temperature-programmed gas chromatography. Flavor score was highly correlated with individual volatile components considered separately, and very highly correlated with multiple volatile components considered together, indicating that reliable flavor characteristics of vegetable oils may be obtained rapidly and efficiently by instrumentation. Presented at the AOCS Spring Meeting, Mexico City, April 1974.     

Analysis of neutral volatiles of mayonnaise by direct gas chromatography and mass spectrometry

Simple procedures have been developed for analyzing neutral volatiles from mayonnaise by direct gas chromatography and combined direct gas chromatography-mass spectrometry. For gas Chromatographic analysis, a glass liner containing glass wool coated with alkali in the lower quarter and plain glass wool in the remaining space is placed in the heated inlet of a gas Chromatograph, and mayonnaise and water are injected onto the plain packing. Neutral volatiles eluted from the mayonnaise by the combined action of water, carrier gas, and heat collect on the cool column of the gas Chromatograph, but acetic acid is trapped by the alkaline glass wool and thus does not interfere with the analysis. After removal of the liner with the spent sample, the temperature of the column oven is programmed to resolve the volatiles. For mass spectrometric analysis, neutral volatiles are passed directly from a Chromatograph inlet to a second inlet liner containing a porous polymer that traps most organic compounds but has low affinity for water. These neutral organic volatiles are desorbed from the porous polymer in the inlet of a Chromatograph interfaced with a mass spectrometer for analysis. This procedure allows components resolved by the gas Chromatograph to be identified by mass spectrometry without interference from either water or acetic acid. A total of 21 neutral volatile compounds was identified in mayonnaise. Presented at the AOCS Meeting, Chicago, September 1976.     

Oilseed volatile analysis by supercritical fluid and thermal desorption methods

A knowledge of the volatile components present in an oil sample can provide important information relative to supercritical fluid extraction (SFE) process design, the current oxidative state of the oil, as well as the concentration and presence of important flavor volatiles in the oil. Volatile compounds from supercritical fluid-extracted oils were analyzed by headspace gas chromatography (GC) methods to determine if there were differences in the volatile profiles when two different methods of desorption were used. Canola, corn, soybean and sunflower seeds were extracted with supercritical carbon dioxide at 8000 psi and 50°C. Tenax porous polymer traps, attached at the exhaust port of the SFE apparatus, were utilized to collect the volatile components during the extractions. The volatile compounds on the Tenax trap were desorbed onto a GC column by both thermal and supercritical fluid techniques. Desorption temperature for the thermal method was 150°C, while conditions for the SFE technique were 50°C and 2000 psi. The lower-boiling volatiles from each oilseed were greater when desorbed by thermal means from the Tenax than by SFE; however, SFE desorbed the highermolecular weight compounds that were not removed by the thermal desorption method. Hexanal tended to be desorbed in comparable amounts by both methods. The SFE-based desorption technique provides a unique analysis method for the determination of both volatile and semivolatile compounds, as well as executing desorption under nonoxidative, low-temperature conditions that do not contribute to the degradation of lipid components.     

Dynamic headspace capillary gas chromatographic analysis of soybean oil volatiles

To develop new knowledge on preventing or eliminating the formation of undesirable flavors in soybean oil, we analyzed quantitatively the major volatile products in samples that were oxidized during storage in the dark at ambient conditions. The volatiles formed were recovered and separated by dynamic headspace capillary gas chromatography. The effect of sampling temperatures was investigated by heating the sample, sweeping the volatiles with helium and trapping and desorbing them from a porous polymer Tenax trap. The volatiles were flushed from the trap onto a fused silica capillary column with a bonded mixed dimethyldiphenyl siloxane phase. At peroxide values between 2 and 13, the major volatile products found were acrolein, pentene, pentane, 1-penten-3-ol, pentanal, hexanal, 2-hexenal, 2-heptenal, 2,4-heptadienal, 2-octenal and 2,4-decadienal. The profile of volatiles was significantly affected by the sampling temperature used and by the presence or absence of citric acid in the oils before storage. The relative amounts of volatile thermal decomposition products of linolenate and linoleate hydroperoxides, such as 2,4-heptadienal and 2,4-decadienal, increased significantly when samples were heated above 90 C. Dynamic headspace gas chromatography made it possible to analyze the volatiles in samples heated to 60 and 90 C. These volatiles may be representative of those present in oils at time of tasting.     

Novel technique for the analysis of volatiles in aqueous and nonaqueous systems

A simple, efficient, external inlet assembly is described for analyzing volatile components in raw and processed foods by direct gas chromatography and mass spectrometry. The device comprises three sections: a sample inlet, a condenser, and a six-port rotary valve. The versatility and effectiveness of this assembly is demonstrated by the analysis and identification of volatiles from diverse food products as salad oils, vinegar, and corn-soy food blends. The procedure is rapid, efficient, and offers the following desirable features: it is compatible with all commonly used chromatographs and can accomodate samples of different size; sample volatiles are obtained without use of prior enrichment techniques, at ambient or elevated temperatures; uniform heating enhances volatiles elution, thereby improving sensitivity; moisture and air are removed to facilitate mass spectral analysis; the closed nature of the system minimizes loss of low molecular weight volatiles during elution, thus producing a highly reliable pro-file of volatiles. 1Presented at the AOCS meeting in St. Louis, May, 1978.     

Direct gas chromatographic examination of volatiles in salad oils and shortenings

A simple, rapid and direct gas chromatographic technique was developed for the examination of volatiles in salad oils and shortenings at the 10 ppb level without prior enrichment. The liner of the inlet of the gas chromatograph is carefully packed with volatile-free glass wool to allow slow diffusion of the sample on the glass wool, but to prevent seepage onto the gas chromatographic column. The liner with sample is inserted in the heated inlet, and the volatiles are eluted rapidly from the samples as the carrier gas flows through the linear and sweeps the volatiles onto the column, which is temperature-programed between 55 and 190C to resolve the volatiles. Numerous samples of salad oils and shortenings were examined, and the better quality oils had only small amounts of volatiles. Presented at the JOCS-AOCS Joint Meeting, Los Angeles, April 1972. ARS, USDA.     

MAE-SPME联合提取GC-MS检测草莓果实中的香气成分

分别采用溶剂萃取法(SE)、固相微萃取法(SPME)和微波辅助-固相微萃取(MAE-SPME)联用技术等前处理方法提取草莓果实中香气物质,通过气相色谱-质谱(GC-MS)联用仪对挥发性成分进行了分离鉴定。结果表明,不同的前处理方法所得结果相差甚远,MAE-SPME联用技术前处理方法提取后,可鉴定到85种化合物,其中酯类53种,其他依次是醛类、酮类、醇类、酸类、醚类、烯烃、芳香烃和杂环化合物等;而用SE法、SPME法提取,分别仅鉴定到26种和16种香气物质。说明微波辅助-固相微萃取两种技术联用,是一种能较好地提取果蔬中香气物质的样品前处理技术。     

A Versatile and Quantitative Volatile-Delivery System for Laboratory Bioassays

A versatile moving-air system is described for delivering volatiles into a wind tunnel or other bioassay device. The system controls up to four volatile sources at one time. There is a calibrated, adjustable splitter for each source so that any percentage of a source's airstream, or none of it, can be directed to the system outlet at any moment. Thus, the system allows the sample volatiles to be bioassayed in any order and at any level or in mixtures of any desired proportions. Volatile sources of many types can be used, including single chemicals in slow-release formulations, mixtures of chemicals, or volatiles from living organisms. The volatile stream can be sampled by solid-phase microextraction (SPME) just before it enters the wind tunnel. Analysis of the SPME sample by gas chromatography allows absolute delivery rates of volatile components to be calculated. System performance was characterized with physical measurements and with bioassay experiments involving Carpophilus humeralis (F.) (Coleoptera: Nitidulidae). One bioassay experiment demonstrated how volatiles from a microbial culture (fermenting bread dough) and a synthetic counterpart (an aqueous solution of acetaldehyde, ethanol, 1-propanol, isobutanol, 3-methyl-1-butanol, 2-methyl-1-butanol, and ethyl acetate) could be compared at a range of dose levels, with just one sample of each type. These natural and synthetic volatile sources delivered very similar amounts of the above compounds and produced nearly identical dose–response curves. In another experiment, three bread dough volatiles (ethanol, acetaldehyde, and ethyl acetate) were tested in mixtures. Each component was used at four different levels (giving a total of 64 experimental treatments), but just one physical sample was needed for each chemical. The experiment provided clear information about response thresholds and interactions among these host volatiles. The volatile delivery system is versatile, easy to operate, and can be constructed from inexpensive materials.     

A preconcentration and subsequent gas liquid chromatographic analysis method for trace volatiles

A glass column containing a porous polymer was used to concen-trate headspace volatiles from enzymatically mediated reactions and inserted directly into the injection port of a gas liquid chromatog-raphy (GLC) for elution and separation of adsorbed volatiles. The polymer column was placed in an entrainment system attached to a water aspirator at 30 psi to collect volatiles produced by the en-zymatic reaction. A useful chromatogram was obtained from 1 g of raw material by this method. Volatiles collected in this manner could be stored on the polymer matrix at ambient temperatures without deleterious effects for subsequent GLC analysis. Multiple columns of the same or different trapping material could also be used in the entrainment system. Paper Number 5523 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, North Carolina 27650.     

Capillary gas chromatographic analyses of headspace volatiles from vegetable oils

Eight different vegetable oils obtained commercially were analyzed for volatiles by capillary gas chromatography (GC). Volatiles generated in a GC static headspace sampler at 180 C were injected automatically onto a chemically bonded capillary column. Only a small number of GC peaks of low intensity were observed in the fresh samples, which varied in peroxide values from 0.2 to 3. Several major peaks were evident in the oils aged eight and 16 days at 60 C with peroxide values ranging from 16 to 65. Thirty-four GC peaks were identified on the basis of relative retention time of reference compounds and on the basis of gas chromatography-mass spectrometry (GC-MS). Volatile compounds identified were those expected from the autoxidation of principal unsaturated fatty acid components of each vegetable oil tested. The relative concentrations of volatile components increased with the level of oxidation as determined by peroxide value. Presented at the AOCS Meeting in Chicago, May 1983.     

Elution and analysis of volatiles in vegetable oils by gas chromatography

A simple and very sensitive technique was devised to analyze volatiles in vegetable oils by direct gas chromatography. A large sample of oil is diffused on glass wool in an injection port liner. After the liner is inserted in the injection port, the volatiles are rapidly swept into the column of the gas chromatograph for analysis. Southern Marketing and Nutrition Research Division, ARS, USDA.     

Analysis of vegetable oil volatiles by multiple headspace extraction

Quantitative determination of the volatiles produced from oxidized vegetable oils is an important indicator of oil quality. Five vegetable oils, low-erucic acid rapeseed, corn, soybean, sunflower and high oleic sunflower, were stored at 60°C for four and eight days to yield oils with several levels of oxidation. Peroxide values of the fresh oils ranged from 0.6 to 1.8 while those of the oxidized oils were from 1.6 to 42. Volatile analysis by the multiple headspace extraction (MHE) technique, which includes a pressure and time controlled injection onto the gas chromatography (GC) column (a chemically bonded capillary column), was compared with that obtained by static headspace gas chromatography (SHS-GC). Several volatile compounds indicative of the oxidation of polyunsaturated fatty acids from the vegetable oils were identified and measured by MHE; pure compounds of twelve major volatiles also were measured by MHE, and peak area was determined. Multiple extractions of the oil headspace provided a more reproducible measure of volatile compounds than was obtained by SHS-GC. Concentration of all volatiles increased with increased oxidation as measured by peroxide value of the oil. Presented at the Annual American Oil Chemists' Society Meeting, May 8–12, 1988, Phoenix, AZ.     

Thermal decomposition processes in aromatic amine-based polybenzoxazines investigated by TGA and GC-MS

Three different aromatic amine-based polybenzoxazines are subjected to thermal decomposition in a thermogravimetric analyzer. The degradation products, which are volatile compounds evaporating out of the furnace as gases, are trapped and analyzed further by a gas chromatograph which is coupled with a mass selective detector (GC-MS). All the degradation products are separated by GC and come out at different retention times, as seen in the total ion chromatogram. All the compound's mass are selectively identified by MS. The chromatograms are divided into two regions; the low column temperature region containing low molecular weight and highly volatile compounds, and the high column temperature region containing higher molecular weight and less volatile compounds. The evolved gas analysis performed by GC-MS allows us to identify the molecular weight and also the structure of the volatiles. This information is then used to illustrate the processes occurring during the thermal decomposition of aromatic amine-based polybenzoxazines.     

Analysis of volatiles evolved during high-temperature treatment of thermally stable polymers. II. Polybutadiyne

Polybutadiyne samples were heated at 20°C/min up to 1200°C in a pyroprobe attached to a gas chromatograph/mass spectrometer (GC/MS). Analysis of the volatiles evolved during heating identified carbon dioxide (adsorbed on polymer surface), methane, ethylene, benzene, toluene, and traces of higher aromatics. Correlations have been made between sample temperature and evolution (onset, maximum, and end temperatures) of each of the five listed volatiles. Average polybutadiyne weight loss at 1200°C was 14 ± 2%. Two cure studies were performed in the pyroprobe, and it was shown that both weight loss and volatile evolution were affected. The results were consistent with a higher degree of polymer cross-linking as cure time and temperature increased. © 1996 John Wiley & Sons, Inc.     

A Versatile Method for On-Line Analysis of Volatile Compounds from Living Samples

A system especially designed for the on-line analysis of volatiles emitted by living aerobic organisms is described. The instrument consists of a modified thermal desorber and utilizes the purge and cold trap (PCT) technique coupled with gas chromatography–mass spectrometry. The system enables the use of a variety of sample vessels especially adapted to individual test organisms. Quantitative analyses of some volatile semiochemicals revealed that when only nanogram amounts of these compounds are evaporated at room temperature for a period of 10 min, they may be trapped and detected by this device. Emission of volatiles from two insect species and a plant species have been studied in detail by using this system.     

Determination of mesityl oxide and diacetone alcohol in oilseed meals and flours

Two methods were compared for quantitative determination of trace amounts of mesityl oxide and diacetone alcohol in acetone-extracted oilseed meals and flours. In the first, a simple, rapid and direct gas chromatographic procedure, a 0.04 g sample of oilseed meal or flour was placed between 2 small glass wool plugs in a liner of the injection port of a gas chromatograph. Water-saturated molecular sieve 5A (1.1 g) was added over the glass wool sandwich, and the liner was placed in the heated injection port and firmly secured. Mesityl oxide and diacetone alcohol, and other volatiles, were eluted rapidly from the sample onto the column by the combined action of heat, moisture, and carrier gas. The components then were resolved readily by temperature-programed gas chromatography on a 2 ft × 1/4 in. Porapak P column. The second method, which is time consuming and tedious, is a modification of the Todd azeotropic distillation procedure and was included, for comparison, as a conventional measure of the concentrations of mesityl oxide and diacetone alcohol. Samples of oilseed meals and flours were analyzed by both methods. The results are compared, and the relative merits of the two procedures are discussed.     

同时蒸馏萃取/气-质联用分析黑龙江香菇香味成分

在3个萃取时间下(2、4、6 h),用极性色谱柱DB-WAX,同时蒸馏萃取/气-质联用分析了黑龙江产香菇的香味成分,鉴定出137种成分,包括含氧杂环、含硫类、含氮杂环、苯酚类、醛类、酮类、醇类等。对比萃取率、萃取物气味特征及气-质联用分析结果,确定最佳萃取时间为6 h,此时萃取率0.51%,鉴定出相对质量分数较高的香味成分为3,5-二甲基-1,2,4-三硫杂环戊烷(4.20%)、二甲基二硫醚(3.07%),1,2,4,6-四硫杂环庚烷(3.33%)、甲基(甲硫基)甲基二硫醚(2.34%)、1,3,5-三硫杂环己烷(2.22%)、1-(2-噻吩基)乙酮(2.21%)、1-辛烯-3-醇(2.03%)。     

Rapid procedure for the determination of residual acetone and 2-propanol in oilseed meals and flours

A simple, rapid elution gas chromatographic method was used for quantitative determination of acetone or 2-propanol in finely ground, extracted oilseed meals and flours. In the procedure, a 0.05 g sample of oilseed meal or flour was placed between 2 small glass wool plugs in a liner of the injection port of a gas chromatograph. Water (250 μl) was added over the glass wool sandwich, and the liner was placed in the heated injection port and firmly secured. Acetone or 2-propanol and other volatiles were rapidly eluted from the sample onto the column by the combined action of heat, moisture, and carrier gas. The components then were resolved by temperature programmed gas chromatography (GC) on a 1 ft x 1/4 in. Porapak Q column. A second gas chromatographic method, a volatilization procedure, was included in the study for comparison as a measure of the concentrations of acetone or 2-propanol. Samples of oilseed meals and flours were analyzed by both methods. The rapid elution procedure proved to be a simple and effective means of detecting residual acetone or 2-propanol in the samples. The values were very similar to those obtained by the volatilization procedure.     

Biology of pheromone release by male caribbean fruit flies,Anastrepha suspensa (Diptera: Tephritidae)

Males of the Caribbean fruit fly,Anastrepha suspensa (Loew), typically form leks and attract females by releasing a multicomponent volatile pheromone. Previous reports have identified two nine-carbon alcohols, three lactones, a sesquiterpene, and a monoterpene in the volatiles. The present report is a study of the physiology of male pheromone release and of ecological and social interactions that influence pheromone release by laboratoryreared flies. Volatiles released by males were trapped on Tenax, eluted, separated, and quantitatively measured by gas chromatography. Experiments showed that the volatiles were primarily released from mouth and anus. Sealing the anal opening or the mouth with melted beeswax resulted in up to 40% or greater reduction in most components, and sealing both mouth and anus further reduced release of volatiles, but some volatiles are possibly still released directly from the cuticle. An anal pouch of everted tissue played a major role as a large evaporative surface for release of some of the volatile components. Male flies entrained to a 1410 light-dark cycle showed a peak release of volatiles at 11–12 hr into the photophase, but smaller quantities of the same volatiles were released over a broad period during the daylight hours. Laboratory-reared males peaked in pheromone release at 7–10 days and production and release continued through 35 days of age. Single males released significantly more of all components measured than did groups of males. The reduction by aggregations of males may be related to lekking behavior in this fruit fly. The pheromone probably serves to attract females to a lek site, but additional parameters are likely to enter into the choice of male made by the arriving female.This is University of Florida Agricultural Experiment Station Journal Series No. 9589.     

固始鸡/A-A鸡鸡汤中香味物质的比较

河南固始鸡 /华都肉鸡 (A A鸡 )分别经过同时蒸馏提取及高压蒸煮—常压蒸馏—溶剂萃取 ,香气提取物用Vigreux柱浓缩 ,然后用气 质联用仪对其进行分析。结果表明 ,重要的鸡肉味香味化合物反 ,顺 2 ,4 癸二烯醛、反 ,反 2 ,4 癸二烯醛还有反 2 辛烯醛、壬醛、反 2 壬烯醛、顺 2 癸烯醛、反 2 十一烯醛均从本实验的两种方法中分离鉴定出 ;而在高压蒸煮—常压蒸馏—溶剂萃取法中 ,固始鸡含有华都肉鸡所没有的重要香味物质如壬醛、1 甲氧基 4 ( 1 丙烯基 )苯 (反式茴香醚 )、十六醛、9 十八烯醛、1 十八醇等 ;反 ,反 2 ,4 癸二烯醛的含量固始鸡是A A鸡的 7倍还多