Analysis Of Headspace Volatiles Research Articles

Headspace Analysis of Volatile Compounds in Leaves from the Juglandaceae (Walnut) Family

Headspace volatile analysis coupled with software extraction of overlapping GC-seperated components was employed for volatiles profiling in leaves of six Juglans and Carya species. Qualitative and quantitative differences were observed among species. Sesquiterpenes dominated the volatile blend of all species (J. nigra L. 70%, J. cineara L. 61%, J. regia L. 47%, C. cordiformis, (Wangh.) K. Koch, 50%, C. laciniosa (Michx.) Loud. 41%, and C. illinoinensis (Wangh.) K. Koch 24%) with germacrene D occurring in the largest amount. Higher levels of monoterpenes were found in the headspace of J. cineara, J. regia and C. laciniosa leaves (35%, 24% and 18%, respectively). Among the benzenoids, methyl salicylate was found as the major leaf headspace component (J. regia 17 %, C. cordiformis 15%, C. laciniosa and C. illinoinensis 10%,).

Sample preparation optimization in wine and grapes: Dilution and sample/headspace volume equilibrium theory for headspace solid-phase microextraction

Most headspace solid-phase microextraction (HS-SPME) volatile analysis methods have been developed for aqueous samples and have been either adapted or applied to complex matrices. This study examines sample/headspace equilibrium based on realistic (non-spiked) concentration levels in real complex sample matrices (grapes and wine) with a systematic multivariate statistical approach. The presence and absence of matrix effects are explained through exponential and linear relationships, respectively. The potential of over- and underestimating volatile compounds in a diluted sample is illustrated and the common dilution equation ( C 1 V 1 = C 2 V 2) is shown to not always apply to headspace volatile analysis. Additionally, sample dilution was shown to be more sensitive to matrix effects than sample/headspace volume variations with the latter showing analyte dependency. An optimum sample size of 6.9–8.6 g in a 20 mL vial without dilution was observed. This study shows that sensitivity and limit of detection (LOD) can be improved to a limit with a subsequent loss – an extension to existing theory. The study further illustrates that in trying to bring an analyte within linear range through sample dilution, sensitivity and LOD can be lost with a probable shift in optimum ranges and sample/headspace equilibrium.

Electronic Nose Evaluation of Cabernet Sauvignon Fruit Maturity

The ability of an electronic nose to classify cabernet sauvignon (Vitis vinifera L.) fruit based on maturity levels was investigated over two seasons. Maturity of samples collected 18, 19, and 20 weeks post-bloom was evaluated by measuring berry weight, pH, Brix, titratable acidity, total phenols, color intensity, hue, total anthocyanins, and total and phenol-free glycosides. Results were compared, using discriminant and canonical discriminant analysis, with analysis of headspace volatiles via a hand-held electronic nose. The electronic nose was able to determine differences among the three sample groups in both seasons. Additionally, in one season electronic nose measurements were compared to chemical analyses of samples collected from east and west sides of north – south oriented vineyard rows. Results demonstrated the ability of the electronic nose to distinguish fruit from vine canopy sides. Field measurements demonstrated the potential for the electronic nose as a rapid, non-destructive tool for evaluating grape maturity.

Headspace volatile markers for sensitivity of cocoa (Theobroma cacao L.) somatic embryos to cryopreservation

The mechanisms that reduce the viability of plant somatic embryos following cryopreservation are not known. The objective of the present study was to evaluate the sensitivity of cocoa (Theobroma cacao L.) somatic embryos at different stages of an encapsulation-dehydration protocol using stress-related volatile hydrocarbons as markers of injury and recovery. The plant stress hormone ethylene and volatile hydrocarbons derived from hydroxyl radicals (methane) and lipid peroxidation (ethane) were determined using gas chromatography headspace analysis. Ethylene and methane were the only volatiles detected, with both being produced after each step of the cryogenic protocol. Ethylene production was significantly reduced following exposure to liquid nitrogen, but then increased in parallel with embryo recovery. In contrast, the production of methane was cyclic during recovery, with the first cycle occurring earlier for embryos recovered from liquid nitrogen and desiccation than those recovered from earlier steps in the protocol. These results suggest that loss of somatic embryo viability during cryopreservation may be related to the oxidative status of the tissue, and its capacity to produce ethylene. This study has demonstrated that headspace volatile analysis provides a robust non-destructive analytical approach for assessing the survival and recovery of plant somatic embryos following cryopreservation.

MEASURING OXIDATIVE STABILITY OF STRUCTURED LIPIDS BY PROTON NUCLEAR MAGNETIC RESONANCE

ABSTRACT The oxidative stability of enzymatically modified oils (structured lipids) and their unmodified counterparts were assessed using proton nuclear magnetic resonance (1H NMR) spectroscopy. This methodology was used to monitor relative changes in the proton absorption pattern of the fatty acids of oils during storage at 60C. Relative changes of aliphatic to olefinic (Rao) and aliphatic to diallylmethylene (Rad) proton ratios during oil oxidation were determined by 1H NMR spectroscopy. An increase in Rao and Rad values was obtained over the entire storage period. The oxidative stability of oils was also evaluated using conjugated dienes (CD) determination, 2‐thiobarbituric acid reactive substances (TBARS) and headspace volatile analysis. A highly significant correlation (r = 0.930–0.992; P ≤ 0.005) existed between the CD values and changes in Rao and Rad during oxidation of all oils. The correlation coefficient between TBARS and changes in Rao and Rad values was in the range of 0.779–0.983 (P ≤ 0.05). A high correlation (r = 0.948–0.996; P ≤ 0.005) was found between hexanal content and Rao and Rad of oils. Propanal content was also highly correlated (r = 0.950–0.990; P ≤ 0.005) with Rao and Rad.PRACTICAL APPLICATIONSAssessment of the extent of lipid oxidation in food is of much interest to producers and scientists alike. Proton nuclear magnetic resonance spectroscopy provides a valuable tool for quantitation of oxidation of food lipids. This procedure was used for evaluating the oxidative state of structured lipids. The procedure is rapid and nondestructive, requires a small amount of material, and may be considered as “green” because it uses a very minimum amount of solvent and is readily applicable to edible oils and oils extracted from food and biological samples.

Influence of Starter Culture on Flavor and Headspace Volatile Profiles of Fermented Whey and Whey Produced from Fermented Milk

Rennet whey and skim milk were compared as media for fermentation by commercial cheese, yogurt, and probiotic starter cultures. Effect of culture, medium, and their interaction on flavor was assessed and compared by sensory descriptive analysis and headspace volatile analysis by proton transfer reaction-mass spectrometry. In general, the aroma of fermented whey was similar to that of whey separated from fermented milk, indicating a favorable possibility of substituting milk with whey in the manufacture of fermented milk-like beverages. Starter culture significantly affected most sensory characteristics of the products. Key volatile compounds for the characteristic flavor of yogurt, such as acetaldehyde and diacetyl, were not significantly affected by medium when fermented with the yogurt culture, and reached similar levels in both systems. Volatile analysis results were consistent with the results of the sensory evaluation, indicating the high reliability of proton transfer reaction-mass spectrometry in detecting important volatile compounds for aroma. Integration of this sensory and chemical information allows a better understanding of how flavor and related compounds are affected by ingredients or processing, which may be useful for the development of value-added whey products.

The Significance of Background Odour for an Egg Parasitoid to Detect Plants with Host Eggs

Scots pine has been shown to produce a volatile bouquet that attracts egg parasitoids in response to oviposition of the herbivorous sawfly Diprion pini. Previous analyses of headspace volatiles of oviposition-induced pine twigs revealed only quantitative changes; in particular, the sesquiterpene (E)-beta-farnesene was emitted in significantly higher quantities by oviposition-induced pine. Here we investigated whether (E)-beta-farnesene attracted the egg parasitoid Chrysonotomyia ruforum. We tested the behavioural response of C. ruforum females to different concentrations of (E)-beta-farnesene. Egg parasitoids did not respond to this sesquiterpene at either concentration tested. However, they did respond significantly to (E)-beta-farnesene when this compound was offered in combination with the volatile blend emitted from pine twigs without eggs. This response was dependent on the applied concentration of (E)-beta-farnesene. Further bioassays with other components [(E)-beta-caryophyllene, delta-cadinene] of the odour blend of pine were conducted in combination with the volatile blend from egg-free pine as background odour. None of the compounds tested against the background of odour from an egg-free pine twig were attractive to the egg parasitoid. These results suggest that the egg parasitoids responded specifically to (E)-beta-farnesene, but only when this compound was experienced in the 'right' context, i.e. when contrasted with a background odour of non-oviposition-induced pine volatiles.

Effects of storage conditions on oxidative stability of soybean oil

AbstractSoybean oil in the presence or absence of 200 µg g−1 tert‐butyl hydroquinone (TBHQ) was subjected to accelerated oxidative storage at 60 °C for 10 days or stored at room temperature for 12 months. Tocopherol contents of the oil decreased, whereas the headspace volatiles and peroxide values (PV) increased as the storage time increased. During accelerated storage, TBHQ was effective in retarding the formation of hydroperoxides and headspace volatiles in the oil. TBHQ also protected tocopherols, especially α‐tocopherol, from oxidation. During long‐term room‐temperature (LTRT) storage, the changes in PV between the oils with and without TBHQ were similar, but the oil with TBHQ had lower headspace volatile contents than that without TBHQ. Headspace volatile analysis was more suitable than PV measurement for predicting the oxidative stability of soybean oil during LTRT storage. The contents of hexanal or (E)‐2‐heptenal in the oil at 1–5 days of accelerated storage could be used to predict those of the corresponding compound in the oil at 0–4 weeks of LTRT storage. Copyright © 2005 Society of Chemical Industry

Behavioral Response of Lygus hesperus to Conspecifics and Headspace Volatiles of Alfalfa in a Y-Tube Olfactometer

The western tarnished plant bug, Lygus hesperus Knight, feeds and develops on a variety of weeds in the spring, with later generations moving to alfalfa and cotton where severe damage to reproductive structures can occur. A synthetic attractant for monitoring or mass-trapping L. hesperus, or the identification of potential attractants for natural enemies, would be useful tools for integrated pest management programs. Studies investigated the response of naive and experienced fifth-instar and adult L. hesperus to odors associated with conspecifics and alfalfa, Medicago sativa L. Fifth-instar L. hesperus responded to all plant/insect combinations, whereas female L. hesperus only responded preferentially to vegetative and flowering alfalfa where conspecifics had fed for 24-72 hr, and to vegetative alfalfa where conspecifics were added approximately 30 min before the test began. Males were not attracted to headspace volatiles from any of the alfalfa treatments. Analysis of headspace volatiles showed that (E)-2-hexanal, (Z)-3-hexen-l-ol, alpha-pinene, (Z)-3-hexenyl acetate, (E)-2-hexenyl acetate, limonene, (Z)-ocimene, (E)-beta-ocimene, linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, and (E, E)-alpha-farnesene are emitted from both vegetative and flowering alfalfa. Indole and (3E, 7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene were only detected in flowering alfalfa. Damage to alfalfa by L. hesperus increased emissions of (Z)-ocimene, (E)-beta-ocimene, (E)-beta-caryophyllene, and (E, E)-alpha-farnesene, while beta-pinene, myrcene, methyl salicylate, and (3E, 7E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene were only detected from damaged plants. Thus, individual or mixtures of these alfalfa volatiles may be useful as attractants for capturing nymphs and adult females of L. hesperus in the field.

AROMA VOLATILE DIFFERENCES IN COMMERCIAL ORANGE-FLESHED CANTALOUPES, THE INBRED PARENTAL LINES AND STORED FRESH-CUTS

ISHS XXVI International Horticultural Congress: Issues and Advances in Postharvest Horticulture AROMA VOLATILE DIFFERENCES IN COMMERCIAL ORANGE-FLESHED CANTALOUPES, THE INBRED PARENTAL LINES AND STORED FRESH-CUTS

Analysis of Headspace Volatiles of Corn Gluten Meal

ABSTRACTCorn gluten meal is the high‐protein fraction from wet milling of corn. Although protein, minerals, and fat compositions have been reported, minor components that cause unpleasant flavor and taste are not known. The objective of this study was to determine the compounds present in headspace of corn gluten meal and wet cake (dryer feed). A solid‐phase microextraction device with a polyacrylate coating was used to collect volatiles for 1 hr at 25 and 100°C above a stirred water slurry of corn gluten meal or wet cake. The absorbed compounds were desorbed onto the inlet injector of a gas chromatograph equipped with a mass selective detector. Compound identification was done using a Wiley library and confirmed by retention time of pure compounds in the gas chromatograph. Twenty‐nine compounds were identified. Knowledge concerning volatiles of corn gluten meal may lead to improvement of flavor and taste, and increased utilization of this material, produced over 1 million metric tons per year in the United States.

Chemical and Stability Characteristics of Structured Lipids from Borage (Borago officinalis L.) and Evening Primrose (Oenothera biennis L.) Oils

ABSTRACT: Structured lipids of borage and evening primrose oils containing n‐3 fatty acids were produced via acidolysis catalyzed by lipase from Pseudomonas sp. The structured lipids were characterized, and their oxidative stability evaluated under Schaal oven conditions at 60 °C by measuring conjugated dienes (CD), 2‐thiobarbituric acid reactive substances (TBARS) and headspace volatile analysis. Among the oils examined, enzymatically modified products gave rise to higher (p # 0.05) CD, TBARS, and headspace volatiles as compared to those of their unmodified counterparts. Introduction of highly unsaturated fatty acids and removal of endogenous antioxidants such as tocopherols might be responsible for this observation.

Effect of gallic acid on the aroma constituents of soymilk and soy protein isolates

AbstractVolatile compounds from soymilk were analyzed by gas chromatography/olfactometry/mass spectrometry (GCO/MS) with direct injection of various volumes of static headspaces. The most powerful odorants, determined by the minimum headspace volume required to detect by olfactometry, were (i) hexanal, (ii) acetaldehyde, (iii) methanethiol, (iv) dimethyl trisulfide (DMTS), and (v) 2‐pentyl furan. Analyses of soymilk prepared with the addition of 100 ppm gallic acid revealed that the only two detectable odorants were hexanal and acetaldehyde. Sensory analyses of the soymilk treated with 100 ppm gallic acid produced a significantly lower score (P=0.0006) for overall odor intensity compared with the control soymilk. Aqueous slurries of soy protein isolates (SPI) prepared with the addition of 100 ppm gallic acid also had lower odor intensities than the control SPI (P<0.0001). GCO/MS analyses of headspace volatiles revealed that the gallic acid treatment had removed all detectable levels of methanethiol and DMTS while having no significant effect on the level of hexanal (P=0.81).

Epicuticular Wax of Juvenile Eucalyptus Leaves and Headspace Analysis of Leaf Volatiles

This study was performed to determine the variation in leaf epicuticular wax composition and yield between 17 species of Eucalyptus with horticultural potential, and to identify a possible solvent for epicuticular wax using headspace volatile analysis. Variation in the amount and composition of leaf epicuticular wax among 17 species of Eucalyptus L'Héritier (Myrtaceae) with horticultural potential, was characterized by GC, TLC and GC/MS. Across species, wax yield ranged from 0.7 to 4.5 mg/cm2. The major wax constituents in all species except E. delegalensis R. Baker, were β-diketones (24.7–83.0%), followed by wax esters (6.4–26.5%), n-alkanes (3.5–26.5%), fatty acids (3–15.9%), n-alcohols (0.6–11.1%) and aldehydes (0–9.2%). In E. delegatensis the major wax constituents were wax esters (46.6%), β-diketones (24.7%), n-alkanes (11.5%), fatty acids (7.5%), n-alcohols (5.2%) and aldehydes (4.3%). Volatile organic compounds emitted from developing Eucalyptus leaves of six species were studied using solid phase microextraction (SPME), and were analyzed by GC and GC/MS. Leaf oils were extracted from four of the six species and the relative amounts of volatile compounds in the extract and headspace compared. The major volatile constituents were α-pinene (11.4–57.8%, headspace; 15.3–32.2%, oil extract) and 1,8-cineole (3.2–88.6%, headspace; 20.8–54.7%, oil extract). Other terpenoids present in the headspace in significant quantities were allo-aromadendrene, viridiflorene, α-thujene, α-phellandrene, γ-terpinene and limonene. In the oil extract, allo-aromadendrene, α-phellandrene, viridiflorene and limonene were present in significant quantities. Components of leaf oils are potential solvents involved in the transport of waxes from the epidermis to the cuticle, although this is not confirmed by the present study.

QUALITY EVALUATION OF QUICK COOKING BASMATI RICE

Basmati rice is valued for its flavour and long, bold grains. Traditionally this rice var. requires a special cooking method including pre-soaking, boiling in an optimum amount of water and spreading for cooling. Until recently, the technology to develop quick cooking rice (QCR) has only been available for nonscented rice; however, this has recently been extended to include basmati rice. In this study, effects of processing (cooking and drying) on cooking quality of basmati QCR were tested by descriptive sensory analysis and GC analysis of head-space volatiles to investigate release of basmati flavour during rehydration. Data indicated that some loss of basmati flavour and whiteness occurred during processing, while some breakage of dehydrated rice grains occurred due to handling. Extension of rehydration time from 6 to 8 min caused no substantial improvement; cooking for 6 min resulted in high stickiness and starchy texture, indicating that a 6 min rehydration time was sufficient. It is concluded that the QCR process may be confidently applied to aromatic and non-aromatic rice var. but with some sacrifice of sensory quality.

The Analysis of Essential Oil and Headspace Volatiles of the Flowers ofPelargonium endlicherianumused as an Anthelmintic in Folk Medicine

The Analysis of Essential Oil and Headspace Volatiles of the Flowers of<i>Pelargonium endlicherianum</i>used as an Anthelmintic in Folk Medicine

The evaluation of frying oils with the p‐Anisidine value

AbstractThis study was conducted to examine the relationship of p‐anisidine value with headspace volatiles, sensory evaluation, and polymers. Partially hydrogenated soybean frying oil was used to fry shoestring potatoes. The oil was evaluated by p‐anisidine value, headspace volatile analysis, sensory evaluation, and polymer analysis. p‐Anisidine value was found to be correlated with hexanal (r=0.81), heptanal (r=0.66), t‐2‐hexenal (r=0.81), t‐2‐heptenal (r=0.71), t‐2‐octenal (r=0.92), and t,t‐2,4‐decadienal (r=0.86) contents. p‐Anisidine value was correlated with overall odor intensity (r=0.82) and correlated with fried food odor (r=0.53) and burnt odor (r=0.43). p‐Anisidine value and polymers were also correlated (r=0.84).

Molecular characterization of an Arabidopsis gene encoding hydroperoxide lyase, a cytochrome P-450 that is wound inducible.

Hydroperoxide lyase (HPL) cleaves lipid hydroperoxides to produce volatile flavor molecules and also potential signal molecules. We have characterized a gene from Arabidopsis that is homologous to a recently cloned HPL from green pepper (Capsicum annuum). The deduced protein sequence indicates that this gene encodes a cytochrome P-450 with a structure similar to that of allene oxide synthase. The gene was cloned into an expression vector and expressed in Escherichia coli to demonstrate HPL activity. Significant HPL activity was evident when 13S-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid was used as the substrate, whereas activity with 13S-hydroperoxy-9(Z),11(E)-octadecadienoic acid was approximately 10-fold lower. Analysis of headspace volatiles by gas chromatography-mass spectrometry, after addition of the substrate to E. coli extracts expressing the protein, confirmed enzyme-activity data, since cis-3-hexenal was produced by the enzymatic activity of the encoded protein, whereas hexanal production was limited. Molecular characterization of this gene indicates that it is expressed at high levels in floral tissue and is wound inducible but, unlike allene oxide synthase, it is not induced by treatment with methyl jasmonate.

Volatile components associated with bacterial spoilage of tropical prawns

Analysis of headspace volatiles by gas chromatography/mass spectrometry from king ( Penaeus plebejus), banana ( P. merguiensis), tiger ( P. esculentus/semisulcatus) and greasy ( Metapenaeus bennettae) prawns stored in ice or ice slurry, which is effectively an environment of low oxygen tension, indicated the presence of amines at the early stages of storage (less than 8 days) irrespective of the nature of the storage media. Esters were more prevalent in prawns stored on ice (normal oxygen conditions) at the latter stages of storage (more than 8 days) and were only produced by Pseudomonas fragi, whereas sulphides and amines occurred whether the predominant spoilage organism was Ps.fragi or Shewanella putrefaciens. The free amino acid profiles of banana and king prawns were high in arginine (12–14%) and low in cysteine (0.1–0.17%) and methionine (0.1–0.2%). Filter sterilised raw banana prawn broth inoculated with a total of 15 cultures of Ps. fragi and S. putrefaciens and incubated for two weeks at 5°C, showed the presence of 17 major compounds in the headspace volatiles analysed using gas chromatography/mass spectrometry (GC/MS). These were mainly amines, sulphides, ketones and esters. Principal Component Analysis of the results for the comparative levels of the volatiles produced by pure cultures, inoculated into sterile prawn broth, indicated three subgroupings of the organisms; I, Ps. fragi from a particular geographic location; II, S. putrefaciens from another geographic location; and III, a mixture of Ps. fragi and S. putrefaciens from different geographic locations. The sensory impression created by the cultures was strongly related to the chemical profile as determined by GC/MS. Organisms, even within the same subgrouping classified as identical by the usual tests, produced a different range of volatiles in the same uniform substrate.

Antioxidant properties of myricetin and quercetin in oil and emulsions

AbstractThe effect of quercetin and myricetin on the stability of sunflower oil and oil‐in‐water emulsions was studied by storage experiments monitored by measurement of peroxide values, conjugated dienes, and headspace volatile analysis. Myricetin showed strong antioxidant activity in oils stored at 60 or 30°C and in oil‐in‐water emulsions stored at 30°C, whether tocopherols or citric acid were present or not; however, quercetin showed similar antioxidant activity in stripped sunflower oil but no activity in oils that contained tocopherols and citric acid. This showed that myricetin is effective owing to strong radical scavenging and metal‐chelating properties, whereas quercetin has weaker radical scavenging activity, although it is also active by metal‐chelation. The effects of copper and iron salts on the antioxidant activity of myricetin and quercetin were studied in sunflower oil and oil‐in‐water emulsions. Quercetin and myricetin enhanced the prooxidant effect of cupric chloride in oil‐in‐water emulsions (pH 7.4), but this effect was not observed with cupric stearate. The addition of myricetin to emulsions that contained ferric chloride at pH 5.4 also produced a strong prooxidant effect, and small prooxidant effects of flavonols were also detected in the presence of cupric chloride under these conditions. However, myricetin and quercetin reduced the prooxidant effect of ferric palmitate in oils. Myricetin also showed a strong antioxidant effect in oil that contained cupric stearate, although quercetin had no significant effect on the oxidative stability of this system. It therefore appears that flavonols may exert a prooxidant effect in the presence of metal salts, but the nature of the metal salt is important in determining whether a prooxidant effect occurs.