Volatile profile of yellow passion fruit juice by static headspace and solid phase microextraction techniques

Aroma is an important fruit sensory attributes that is influenced by the volatile compounds present in the fruit, and it determines whether a fruit is acceptable to consumers. The volatile compounds in 11 pear cultivars from different species were investigated by headspace solid phase microextraction and gas chromatography-mass spectrometry. In total, 70 volatile compounds, including three alcohols, six aldehydes, fifty-two esters, three acids, three terpenes and three ketones were identified and quantified. Ester was the dominant chemical class of which a total of 52 compounds were detected. Hexanal, hexyl acetate, ethyl hexanoate, ethyl 2-methylbutanoate and ethyl butanoate were the major volatile compounds. Pyrus ussuriensis Maxim showed a higher concentration of volatiles and higher ester content than in the other Asian pear species studied. Cultivars were clearly grouped into four clusters based on the concentration and number of different volatile compounds present in each cultivar. The clusters of different cultivars could be discriminated from each others using the first two principal components. The volatile profiles of the pears were qualitatively and quantitatively influenced by the cultivar. Key words: Pyrus, Asian pear, volatile compound, gas chromatography mass spectrometry (GC-MS), solid phase microextraction (SPME), multivariate analysis.

A method was developed for the analysis of volatile polar compounds in a water matrix using open cap vials Solid Phase Micro-Extraction (SPME) and Capillary Gas Chromatography (CGC). Both SPME techniques – direct sampling and headspace – were tested. Optimization of experimental conditions – exposure time, desorption time, with headspace SPME in addition the influence of the temperature and ionic strength of the sample solution on compound sorption, and finally GC response – were investigated. The analytes were extracted by directly immersing the 85 μm polyacrylate fiber in the aqueous sample or in the headspace. The linear range of the preconcentration process and the precision were examined. The amount of polar analytes sorbed on the fiber was determined and was found to be concentration dependent; it amounted to 0.014–0.64% in the concentration range of 0.00425–425 ppm studied in aqueous solution for direct sampling SPME and to 0.011–2.76% for solutions of concentration 0.0425–255 ppm for headspace SPME. The limits of determination were ascertained. Headspace SPME was applied to the analysis of real-life samples.

Changes in Hunter L, a and b values, glucose, fructose and sucrose contents, concentration of four volatile compounds (ethyl butirate, ethyl caproate, hexyl butirate and hexyl caproate) and furfural, were studied in yellow passion fruit juice (Passiflora edulis var. flavicarpa) pasteurized at 75ºC/60s, 80ºC/41s or 85ºC/27s, during storage at room temperature (25±5ºC) and refrigeration (5±1ºC) for 120 days. While the sucrose content decreased, the glucose and fructose contents increased significantly over storage time. The Hunter L and b values behaved similarly, with a tendency to decrease over time, inversely to Hunter a value. Volatile compound concentrations also decreased over time, inversely to the furfural content. Pasteurization at 85ºC/27s resulted minimum changes in the studied passion fruit characteristics, while that at 75ºC/60s was the most harmful. Storage under refrigeration tended to keep the best quality characteristics of the juice.

`Annapolis', `Cavendish', `Honeoye', `Kent', and `Micmac' strawberry fruit (Fragaria ×ananassa Duch.) were harvested underripe (75% to 90% red) or fully ripe. Fruit were stored at 0C for 5 days followed by 2 days at 15C. Volatiles were trapped onto Tenax-GR from the headspace over fruit before and after storage and analyzed using GC-MS. Volatile esters identified in headspace included methyl and ethyl butanoate, methyl and ethyl hexanoate, methyl and ethyl 3-methylbutanoate, 3-methylbutyl acetate, hexyl acetate, and methyl 2-methylbutanoate. Headspace concentrations of volatile esters over freshly harvested strawberries averaged 1.3 and 6.8 μmol·m–3 for underripe and ripe fruit, respectively. After 7 days of storage, volatile concentrations increased in both underripe and ripe fruit to 6.3 and 12.2 μmol·m–3, respectively. There were quantitative and qualitative differences between cultivars. Total volatile concentrations were 16.0, 8.1, 5.7, 2.4, and 0.9 μmol·m–3 in the headspace over `Annapolis', `Kent', `Micmac', `Cavendish', and `Honeoye', respectively. `Annapolis' had the highest concentrations of methyl and ethyl butanoate, while `Micmac' had the highest concentrations of methyl and ethyl hexanoate. Volatile concentrations at harvest increased 5.7, 1.9, 1.7, 1.4, and 1.3 times during storage in `Kent', `Annapolis', `Micmac', `Cavendish', and `Honeoye', respectively. Results indicate that strawberry fruit continue to produce aroma volatiles after harvest.

Changes on physiochemical properties and volatile compounds of Chinese kombucha during fermentation

Headspace solid phase microextraction (headspace SPME) has been demonstrated to be an excellent solvent‐free sampling method. One of the major factors contributing to the success of headspace SPME is the concentrating effect of the fiber coating toward organic compounds. The affinity of the fiber coating toward very volatile analytes, such as chloromethane, may, however, not be large enough for detection at the parts per trillion concentration level. Static headspace analysis, on the other hand, is very effective for these very volatile compounds. As analyte volatility decreases, the sensitivity of static headspace analysis drops. The complementary nature of these two sampling methods can be exploited by combining the SPME device with a gastight syringe. The sensitivity of the new sampling device is better than that of SPME for very volatile compounds or that of static headspace analysis for less volatile compounds. This new method can sample a wide range of compounds from chloromethane (b.p. −24°C) to bromoform (b.p. 149°C) with estimated limits of detection at the low parts per trillion level.

We obtained volatile aroma compounds from the juices extracted from three different Red Delicious apple (Malus domestica) varieties, which included esters, alcohols, and aldehydes. Among these compounds, ethyl 2-methylbutanoate, methyl 2-methylbutanoate, ethyl butanoate, ethyl hexanoate, hexanal, and butyl 2-methylbutanoate showed high odour active values in the juices. Four compounds (ethyl 2-methylbutanoate, ethyl octanoate, ethyl butanoate, and ethyl hexanoate) were selected to investigate possible interactions occurring in the apple juices. The results demonstrated that the additions of these four aroma volatile compounds could decrease the threshold and intensity of the sensory notes of the solutions compared to those without the addition of these compounds. Lastly, ethyl 2-methylbutanoate was added to the solutions to investigate interactions with σ–τ function. Here, σ represents the ratio of the aroma intensity of the mixed solution to the sum of aroma intensities of all compounds in the solution before blending. The τ represents the aroma of the mixture ratio between the mixture and the sum of aroma compounds before mixing. The results clearly indicated that additive or synergistic effects occurred among these volatiles at sub-threshold concentrations.

Solid phase microextraction and simultaneous distillation-extraction combined with GC-FID, GC/MS, aroma extract dilution analysis and odour activity values were used to analyse volatile compounds from guava (Psidium guajava L. cv. Red Suprema) and to estimate the most odour-active compounds. The analysis led to the detection of 141 compounds, 121 of which were positively identified. The composition of guava fruit volatiles included 43 esters, 37 terpenes, 18 aldehydes, 16 alcohols, ten acids, six ketones, four furans and seven miscellaneous compounds. Seventeen odorants were considered as odour-active compounds, with (E)-β-ionone, ethyl hexanoate, ethyl butanoate, hexanal, (Z)-3-hexenal, hexyl acetate, (E)-2-hexenal and limonene contributing most to the typical guava aroma of this cultivar.

Analysis of volatile compounds of pineapple wine using solid-phase microextraction techniques

Physicochemical measurements in ‘Mondial Gala ®’ apples stored at different atmospheres: Influence on consumer acceptability

The study aims to determine volatile compound profile of Kars Gruyere cheese, which was produced by the traditional method. The volatile components were extracted from samples obtained from 20 different sales points, by using the SPME (solid phase micro-extraction) technique and identified using Gas Chromatography/ Mass Spectrometer (GC/MS). In the samples, totally 40 compounds were identified including aldehydes, ketones, alcohols, acids, esters, terpenes, aliphatic hydrocarbons, aromatic hydrocarbons, nitrogenous compounds and furan group. The study determined that the compounds of acetaldehyde, nonanal, 2-pentanone, ethanol, acetic acid, propionic acid, butanoic acid, ethyl propionate, ethyl butyrate, n-buthyl acetate, toluene and 6-methylthio-(1)-benzothiazole compounds have a significant share in the volatile compound porfile of Gruyere cheese’s.

A headspace solid-phase microextraction (SPME) method was developed for the determination of secondary compounds from Brazilian sugar cane spirits, or cachaça, by GC-FID. An SPME holder with an 85 microm polyacrylate coating was utilized. The novel method is compared with an optimized method: liquid-liquid extraction (LLE). Both methods showed good linearity, but the repeatability for analyses done with the SPME technique (%RSD = 1.8-3.9) was better than for those done with LLE (%RSD = 10.3-11.7). The concentrations of the analytes obtained in the analysis of 12 cachaça samples with the SPME technique were higher than those obtained with LLE. In the SPME method the extraction wastes are smaller. Cachaça samples were qualitatively analyzed for GC-MS.

Volatile composition of Merlot red wine and its contribution to the aroma: optimization and validation of analytical method

The application of headspace solid phase microextraction (SPME) for flavor analysis has been studied. Headspace SPME sampling was tested for nine common wine flavor compounds in 10% (v/v) aqueous ethanol: linalool, nerol, geraniol, 3-methyl-1-butanol, hexanol, 2-phenylethanol, ethyl hexanoate, ethyl octanoate, and ethyl decanoate. The chemical groups (monoterpenoids, aliphatic and aromatic alcohols, and esters) showed specific behavior in SPME analysis. SPME sampling parameters were optimized for these components. Relative response factors (RRFs), which establish the relationship between the concentration of the compound in the matrix liquid solution and the GC peak area, were estimated for all compounds. Log(10)(RRF) varied from 0 (3-methyl-1-butanol) to 3 (ethyl decanoate), according to their molecular weight. Quantification by SPME was shown to be highly dependent on the matrix composition; the compounds with higher RRF were the less affected. As a consequence, the data obtained with this methodology should be used taking into consideration these limitations, as shown in the analysis of four monovarietal Bairrada white wines (Arinto, Bical, Cerceal, and Maria Gomes).

Muscadine grape (Vitis rotundifolia) is a popular fruit in the Southeastern United States because of its unique aroma and strong antioxidant capacity. Volatile compounds of a locally cultivated muscadine cultivar Cowart were characterized by solid-phase microextraction coupled with GC-MS. Twenty-eight volatile compounds, including fruity short-chain esters, alcohols, terpenes, and carbonyl compounds, were detected based on mass spectra and Kovats indices. Based on principal component analysis and hierarchical clustering, the grapes in stages I and II had relatively similar flavor patterns, which were different from that in stage III. Butyl-2-butenoate, hexyl acetate, propyl acetate, ethyl trans-2-butenoate, hexyl-2-butenoate, ethyl acetate, butyl acetate, 1-octanol, ethyl hexanoate, and β- citral were present as distinct volatile chemicals in stage III, while nonanal, decanal, and β-citronellol were distinct in stage II, and myrcenol, β-ocimene, and l-limonene were biomarkers in stage I. Understanding volatile compounds at each stage can assist farmers in choosing the optimal time to harvest muscadine grapes.