Characterisation of the key aroma compounds in a freshly reconstituted orange juice from concentrate

Application of an aroma extract dilution analysis on the entire volatile fraction isolated from an orange juice freshly reconstituted from concentrate revealed 40 odour-active constituents in the flavour dilution (FD) factor range of 4–2,048. Among them, ethyl butanoate and linalool showed the highest FD factor of 2,048, followed by octanal with an FD factor of 512. Thirty-six of the 40 odour-active compounds detected could be identified, all of which have previously been reported as volatile constituents of various orange juices. Quantification of 17 key odorants by stable isotope dilution assays followed by a calculation of odour activity values (OAVs) on the basis of odour thresholds in water or citrate buffer (pH 3.8), respectively, revealed the following most important odorants in the overall aroma of the freshly reconstituted juice: (R/S)-linalool, (R)-limonene and (S)-ethyl 2-methylbutanoate with the highest OAVs (>1,000) followed by octanal, (R)-α-pinene, ethyl butanoate, myrcene, acetaldehyde, decanal and (E)-β-damascenone with OAVs > 100. A model mixture containing all 14 aroma compounds with OAVs > 1 in their actual concentrations in the juice showed a good similarity with the aroma of the original orange juice under investigation, thus corroborating that the key odorants of a freshly reconstituted orange juice were characterised for the first time.     

Odour-active compounds in banana fruit cv. Giant Cavendish

Application of solid-phase microextraction, simultaneous distillation–extraction and liquid–liquid extraction, combined with GC–FID, GC–MS, aroma extract dilution analysis, and odour activity value were used to analyse volatile compounds from banana fruit cv. Giant Cavendish and to estimate the most odour-active compounds. The analyses led to the identification of 146 compounds, 124 of them were positively identified. Thirty-one odourants were considered as odour-active compounds and contribute to the typical banana aroma, eleven of them are reported for the first time as odour-active compounds.     

Glycidyl esters in refined palm (Elaeis guineensis) oil and related fractions. Part I: Formation mechanism

Glycidyl esters (GE) are process contaminants generated during the deodorisation step of edible oil refining. In particular, GE are found in high abundance in refined palm oil. Palm oil is unique in that it contains a high amount of diacylglycerols (DAG, 4-12%). In the present study, a series of model reactions mimicking palm oil deodorisation has been conducted with pure tri-, di- and mono-acylglycerols (MAG). Results showed that GE are formed from DAG and MAG, but not from TAG, at temperatures (T) above 200 °C. Our observations suggest that GE are formed predominantly by intramolecular elimination of a fatty acid from DAG. In addition, isomers of GE, formed from DAG heated at T > 140 °C, were identified as oxopropyl esters. These new isomers were found to represent approximately 10% of GE levels in refined palm oil. Based on these considerations, the final GE content of palm oil could be limited by reducing DAG levels before oil processing and minimising deodorisation temperatures.     

Crude palm oil from interspecific hybrid Elaeis oleifera × Elaeis guineensis: Fatty acid regiodistribution and molecular species of glycerides

The composition and structure of triacylglycerols (TAGs) and partial glycerides of crude palm oil obtained from interspecific hybrid Elaeis oleifera × Elaeis guineensis, grown in Colombia, were fully characterised and compared to data obtained by analysing crude African palm oil. Hybridisation appears to substantially modify the biosynthesis of fatty acids (FAs) rather than their assembly in TAGs. In fact, total FAs analysis showed significant differences between these two types of oil, with hybrid palm oil having a higher percentage of oleic acid (54.6 ± 1.0 vs 41.4 ± 0.3), together with a lower saturated fatty acid content (33.5 ± 0.5 vs 47.3 ± 0.1), while the percentage of essential fatty acid, linoleic acid, does not undergo significant changes. Furthermore, 34 TAG types were identified, with no qualitative differences between African and E. guineensis × E. oleifera hybrid palm oil samples. Short and medium chain FAs (8:0, 10:0, 12:0, 14:0) were utilised, together, to build a restricted number of TAG molecular species. Oil samples from the E. guineensis × E. oleifera hybrid showed higher contents of monosaturated TAGs (47.5–51.0% vs 36.7–37.1%) and triunsaturated TAGs (15.5–15.6% vs 5.2–5.4%). The sn-2 position of TAGs in hybrid palm oil was shown to be predominantly esterified with oleic acid (64.7–66.0 mol% vs 55.1–58.2 mol% in African palm oil) with only 10–15% of total palmitic acid and 6–20% of stearic acid acylated in the secondary position. The total amount of diacylglycerols (DAGs) was in agreement with the values of free acidity; DAG types found were in agreement with the representativeness of different TAG species.     

GC–MS and GC–olfactometry analysis of aroma compounds in a representative organic aroma extract from cured vanilla (Vanilla planifolia G. Jackson) beans

Volatile compounds from cured vanilla beans were extracted using organic solvents. Sensory analysis showed that the aromatic extract obtained with a pentane/ether (1/1 v/v) solvent mixture provided the extract most representative of vanilla bean flavour. Sixty-five volatiles were identified in a pentane/ether extract by GC–MS analysis. Aromatic acids, aliphatic acids and phenolic compounds were the major volatiles. By GC–O analysis of the pentane/ether extract, 26 odour-active compounds were detected. The compounds guaiacol, 4-methylguaiacol, acetovanillone and vanillyl alcohol, found at much lower concentrations in vanilla beans than vanillin, proved to be as intense as vanillin.     

Volatile constituents of cooked bullfrog (Rana catesbeiana) legs

Volatile extracts obtained from pressure-cooked bullfrog legs by simultaneous steam distillation and solvent extraction were analyzed by gas chromatography–mass spectrometry. Although the raw bullfrog legs used in this study contained 0.6% fat only, the extracts were dominated (qualitatively and quantitatively) by lipid oxidation volatiles such as alkanals, alkenals, alkadienals, alkanols and alkenols. Few Maillard volatiles were found, amongst them 2-acetylthiazole, the only sulfur-containing compound found in the extract. This profile of volatiles may be explained by the high proportion of phospholipids and low concentration of sulfur amino acid cystine in raw bullfrog meat, as previously reported by other researchers. Odour activity values (OAV) of volatiles were also estimated and major OAV compounds were: (E,E)-2,4-decadienal, (E,Z)-2,4-decadienal, (E,Z)-2,6-nonadienal, 1-octanol, and (E)-2-nonenal. Some of these potent unsaturated aliphatic aldehydes have also been associated with chicken flavour. This may contribute to flavour resemblances between bullfrog and chicken meat.     

Analysis of free and glycosidically bound compounds of ash gourd (Benincasa hispida): Identification of key odorants

Free and glycosidically bound aroma compounds of ash gourd were investigated. Gas chromatography–mass spectrometry (GC/MS) analysis of the free aroma compounds isolated by both steam distillation and high vacuum distillation revealed the presence of acetoin as the major constituent in both the oils. Acetoin was also identified as the major constituent existing as glycosidic conjugate. GC–olfactometry (GC–O) of the volatile oil based on detection frequency (olfactometry global analysis) was further used to characterise odour active compounds of the vegetable. Based on odour activity value (OAV) measurements the potent odorant among these were identified as acetoin (9522.5), octanal (8571) and nonanal (24,000). The region corresponding to the characteristic ash gourd aroma when collected by cryotrapping from a packed GC column and subsequently analysed by GC/MS was found to be mainly comprising of acetoin suggesting the role of this compound as the key odour active compound of this vegetable.     

Characterisation of odour‐active compounds in papaya (Carica papaya L.) wine

The volatile compounds of papaya wine were isolated by continuous solvent extraction and analysed by gas chromatography‐flame ionization detector and gas chromatography‐mass spectrometry. A total of 118 volatile constituents were detected, and ninety‐seven were positively identified. The composition of papaya wine included fifty‐three esters, twenty‐two alcohols, nine acids, seven phenols and derivatives, seven sulphur compounds, five lactones, five terpenes, three ketones, two aldehydes and five miscellaneous compounds. The aroma‐active areas in the gas chromatogram were screened by application of the aroma extract dilution analysis and by odour activity values. Six odorants were considered as odour‐active volatiles: ethyl octanoate, (E)‐β‐damascenone, 3‐methylbutyl acetate, benzyl isohtiocyanate; ethyl hexanoate and ethyl butanoate.     

Changes in volatile compounds of palm sap (Arenga pinnata) during the heating process for production of palm sugar

This study was carried out to determine the changes of volatile compounds composition during palm sugar production. The samples were collected at every 30 min interval for 4 h of heating process at 150 °C from a local traditional manufacturer in Kuala Pilah, Malaysia. The analyses were performed by gas chromatography–mass spectrometry after headspace solid phase micro extraction. The results showed that N-heterocyclic chemical class possessed the highest relative percentage area (RPA) 83.69%, followed by O-heterocyclic group with RPA of 14.5%. Main volatile compounds the determined were 5-methyl-6,7-dihydro-5H-cyclopenta pyrazine and 4-hydroxy-2,5-dimethyl-3(2H) furanone which were responsible for roasty and sweet caramel-like aroma notes, respectively. The pyrazine compounds increase exponentially with heating time but furan derivatives compounds were formed at a later stage, i.e. at 180 min of heating time and above 105 °C.     

Glycidyl esters in refined palm (Elaeis guineensis) oil and related fractions. Part II: Practical recommendations for effective mitigation

In a previous work, it was shown that at high temperatures (up to 280 °C) glycidyl esters (GE) are formed from diacylglycerols (DAG) via elimination of free fatty acid (FFA). In the present study, the impact of DAG content and temperature on the formation of GE using a model vacuum system mimicking industrial edible oil deodorization is investigated. These deodorization experiments confirmed that the formation of GE from DAG is extensive at temperatures above 230-240 °C, and therefore, this value should be considered as an upper limit for refining operations. Furthermore, experimental data suggest that the formation of GE accelerates in particular when the DAG levels in refined oils exceed 3-4% of total lipids. Analysis of the lipid composition of crude palm oil (CPO) samples allowed the estimation that this critical DAG content corresponds to about 1.9-2.5% of FFA, which is the conventional quality marker of CPO. Moreover, high levels (>100 ppm) of GE were also found in palm fatty acid distillate samples, which may indicate that the level of GE in fully refined palm oils also depends on the elimination rate of GE into the fatty acid distillate.     

Isolation and identification of odorants generated in wine during its oxidation: a gas chromatography–olfactometric study

 The changes in the flavor profiles of several white wines undergoing oxidation were monitored through gas chromatography–olfactometry (GCO). The study showed that up to 19 odorants were generated during wine oxidation, and that several of the odorants originally present in the wine disappeared or decreased. An aroma extract dilution analysis revealed that 5 of these 19 odorants have maximum dilution factors, and that a second group of 7 may have some sensory significance as well. The isolation and identification of the different odorants was achieved via normal and reverse-phase high-performance liquid chromatography and high-resolution GCO. The impact odorants of oxidized wine were found to be 2, 4, 5-trimethyldioxolane, methional (methylthiopropanal), sotolon (4,5-dimethyl-3-hydroxy-2(5H)-furanone), eugenol (4-propenyl-2-methoxyphenol) and an unknown compound with mass spectrum similar to methylvanillate. Other odorants also formed during wine oxidation were 1-octen-3-ol, t-2-nonenal, furfural, benzaldehyde, 2-butoxyethanol, acetovanillone and a dioxolane isomer. Received: 2 August 1999 / Revised version: 23 September 1999     

Characterisation of odour active volatile compounds of New Zealand sea urchin (Evechinus chloroticus) roe using gas chromatography–olfactometry–finger span cross modality (GC–O–FSCM) method

Sea urchin roe is a high value product; however, previous attempts to market the roe from the New Zealand sea urchin (Evechinus chloroticus) have been unsuccessful due to its inconsistent sensory quality. The current study investigated the odour active volatile profiles of roe from male and female sea urchins, harvested from two locations in New Zealand, using solvent assisted flavour evaporation (SAFE) extracts and a gas chromatography–olfactometry–finger span cross modality (GC–O–FSCM) method. Panellists detected 81 odour active compounds, 18 of which were identified using GC–mass spectrometry (MS). Generalised procrustes analysis (GPA) of the data revealed that there were differences in the volatile profile that were location and gender specific. These differences may have contributed to the inconsistent sensory properties of sea urchin roe. The differences in volatile profiles between sea urchin populations and genders must be appreciated before developing effective strategies to produce consistent sea urchin roe quality.     

Study of the aroma compounds of rose apple (<Emphasis Type="Italic">Syzygium jambos</Emphasis> Alston) fruit from Brazil

Volatiles of the headspace and total aqueous extract from the rose apple fruit were investigated by gas chromatography (GC)–flame ionization detection, GC–mass spectrometry and GC–olfactometry/aroma extract dilution analysis O/AEDA). The headspace fraction was rich in low boiling compounds, while medium and high volatility components predominated in the total aqueous extract. GC–O/AEDA revealed that hexanal, 3-penten-2-one, hexanol, (Z)-3-hexen-1-ol, linalool, isovaleric acid, benzyl alcohol, 2-phenylethylalcohol and (E)-cinnamaldehyde were potent odorants contributing to the headspace aroma. Thus, they might be related to the first odour impression of the fruit. Other potent volatiles, such as caproic and phenylacetic acids, methyl-(E)-cinnamate and (E)-cinnamyl alcohol were identified in the total aqueous extract, only. These results indicated that some volatiles, with medium and high boiling points, might also contribute to the overall rose apple flavour. Besides them, volatiles with lower odour potency, such as 7-octen-4-ol, acetic acid, 2-octen-1-ol and cinnamic acid, could have some additional effect for the overall fruit aroma.     

Analysis of volatile compounds of Antrodia camphorata in submerged culture using headspace solid-phase microextraction

In this work a headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) and GC–olfactometry (GC–O) was developed to evaluate the profile of the volatile compounds that contribute to the aroma of Antrodia camphorata in submerged culture. For this purpose, the HS-SPME sampling method for the volatile compounds of A. camphorata in submerged culture was optimised by a D-optimal design. A HS extraction of the culture broth of A. camphorata followed by incubation on a carboxen/polydimethylsiloxane (CAR/PDMS) fibre during 31.8 min at 54.6 °C gave the most effective and accurate extraction of the volatile compounds. By the optimised method, a total of 49 volatile compounds were identified in culture broth of A. camphorata, while a total of 55 volatile compounds were identified in the mycelia. A series of C₈ aliphatic compounds (mushroom-like odour), several lactones (fruity odour) and l-linalool (citrus-like odour) were the most potent key odourant in both the mycelia and culture broth. This combined technique is fast, simple, sensitive, inexpensive and useful to monitor volatile compounds associated to A. camphorata.     

Application of gas chromatography–olfactometry (GC–O) in analysis and quality assessment of alcoholic beverages – A review

In recent years, intensive studies have been carried out regarding the sensory activity of the individual components of the odours of various alcoholic beverages and the dependence between the odour and the chemical composition of the volatile fraction of these products, using gas chromatography with olfactometric detection (GC–O). GC–O is a technique based on sensory evaluation of the eluate from the chromatographic column. Quantitative and qualitative odour evaluation is possible thanks to the presence of a specially constructed attachment, a so-called olfactometric port.     

Volatile components of Negroamaro red wines produced in Apulian Salento area

Volatile composition of monovarietal young red wines made from Negroamaro cultivar, an autochthonous grape variety of Vitis vinifera grown exclusively in Salento area (southeast of Italy in Apulia region), was investigated. Volatile compounds were extracted following a solid phase extraction (SPE) method, and then analysed by gas chromatography–mass spectrometry (GC/MS). Results showed a complex aroma profile rich in alcohols, esters and fatty acids, with a minor contribute from aldehydes, lactones, volatile phenols and sulphur compounds. For the first time, aromatic patterns that characterise wines produced from Negroamaro autochthonous grape variety were established, starting a fundamental register of typicity and geographical identity of Apulians wines. Statistical data analysis techniques (Principal component analysis (PCA) and ANOVA) showed the structure of the experimental data and the significant differences for each compound in the different wines.     

Study of volatile organic acids in freeze-dried Cheonggukjang formed during fermentation using SPME and stable-isotope dilution assay (SIDA)

Volatile organic acids in freeze-dried Cheonggukjang were quantified using a stable-isotope dilution assay (SIDA) according to the fermentation period. Five organic acids, acetic acid, propanoic acid, 2-methylpropanoic acid, butanoic acid, and 3-methylbutanoic acid, were identified using solid-phase microextraction (SPME) in conjunction with gas chromatography–mass spectrometry (GC–MS). The contents of volatile organic acids in Cheonggukjang were highly dependent on the fermentation period and they increased during fermentation. Moreover, the branched-chained organic acids (namely 2-methylpropanoic acid and 3-methylbutanoic acid) were formed earlier and were present at much higher contents than the corresponding straight-chained organic acids during Cheonggukjang fermentation.     

Influence of provenance and roast degree on the composition of potent odorants in Arabica coffees

 Twenty-eight potent odorants were quantified by stable isotope dilution assays of medium-roasted Arabica coffee blends from Colombia (Col), Brazil (Bra), El Salvador (El) and Kenya (Ken) as well as the varieties Tipica (Tip) from Colombia and Caturra from the regions Pinas (Cat-P) and Quevedo (Cat-Q) in Ecuador. The blends from Col and Bra were similar in their composition of odorants. Ken contained higher amounts of 3-mercapto-3-methylbutylformate than Col and Bra, while 2-furfurylthiol, guaiacol and 4-ethylguaiacol were present in lower concentrations. El contained less 4-vinylguaiacol and 2-furfurylthiol, but more 3-methyl-2-buten-1-thiol. Tip, Cat-P and Cat-Q differed from Col, Bra and Ken in having lower amounts of 2,3-butanedione, 2,3-pentanedione and 4-hydroxy-2,5-dimethyl-3(2H)-furanone and higher contents of guaiacol, 3-mercapto-3-methylbutylformate and 3-methyl-2-buten-1-thiol. The largest amount of 2-furfurylthiol was found in Tip and Cat-P. The blends from Col and Ken and the variety Tip showed a significant increase of guaiacol, 4-ethylguaiacol and 3-methyl-2-buten-1-thiol when the roast degree was raised. 2-Furfurylthiol and 2(5)-ethyl-4-hydroxy-5(2)-methyl-3(2H)furanone increased only in Col and Ken, while in Tip the amounts of carbonyl compounds, 4-hydroxy-2,5-dimethyl-3(2H)furanone, methional and (E)-β-damascenone decreased during roasting from medium to dark. Received: 29 December 1998