Interaction of volatiles, sugars, and acids on perception of tomato aroma and flavor descriptors.

To better understand the effect of sugars and acid levels on perception of aroma volatiles, intensity of tomato earthy/medicinal/musty, green/grassy/viney, and fruity/floral aroma and flavor descriptors were evaluated using coarsely chopped partially deodorized tomato puree. This puree was spiked with 1.5% to 3% sugar (glucose/fructose combinations), 0.1% to 0.2% acid (citric/malic acid combinations), or water and 2 levels of 12 individual food-grade volatiles reported to contribute to tomato flavor. A panel consisting of 6 to 8 trained members rated 9 aroma, 8 taste, and 1 aftertaste descriptors of the spiked and nonspiked purees. The panelists detected significant differences (P < or = 0.1) for various individual aroma compound/sugar/acid combinations for a range of descriptors. Adding 0.2% acids alone to bland tomato puree decreased green and floral aromas as well as sweet taste. Adding 3% sugars alone increased green and musty aromas and decreased floral aroma as well as sour, citrus, and bitter tastes. Principal component analysis (PCA) explained 56.5% of the variation in the first 3 principal components (PCs) for added acids and volatiles to bland tomato puree. The effect of added acids with the various aroma compounds generally increased perception of overall and ripe tomato taste and aroma, tropical aroma, and sour taste, and decreased sweet, fruity, and bitter tastes. PCA for added sugars with volatiles explained 67.8% of the variation in first 3 PCs, and sugars generally decreased perception of sour, bitter, and citrus tastes and green aroma, while enhancing perception of flavors associated with ripe, tropical, and aromatic tomatoes. Adding sugars, acids, and volatiles together had a similar effect to addition of sugars alone.

Volatile components in aqueous essence and fresh fruit of Cucumis melo cv. Athena (muskmelon) by GC-MS and GC-O.

A comparative study between the aromatic profile of muskmelon aqueous essence and the puree of fresh fruit was carried out using gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). Results obtained show a total of 53 components quantified in the essence and 38 in the fresh fruit. In addition, four new components are described for the first time as contributors to the aromatic profile of muskmelon including 2-methyl-3-buten-2-ol, 2,3-butanediol, methyl 3-phenylpropionate, and ethyl 3-phenylpropionate (found only in the puree of the fruit). The olfactometric analysis revealed the presence of 25 components with aromatic activity. Esters, alcohols, and one sulfur component [ethyl 3-(methylthio)propionate] appear to be the most important contributors to the essence aroma. The aromagram of fresh fruit is richer in high molecular weight components, which have not yet been positively identified and do not present detectable peaks in the flame ionization detector.

Aromatic profile of aqueous banana essence and banana fruit by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O).

Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to determine the aromatic composition and aroma active components of commercial banana essence and fresh banana fruit paste. Totals of 43 and 26 compounds were quantified in commercial banana essence and fresh banana fruit paste, respectively. Five new components in commercial banana essence were identified as methyl butyrate, 2,3-butanediol diacetate, 2-hydroxy-3-methylethylbutyrate, 1-methylbutyl isobutyrate, and ethyl 3-hydroxyhexanoate. A total of 42 components appear to contribute to the aromatic profile in banana. Isoamyl acetate, 2-pentanol acetate, 2-methyl-1-propanol, 3-methyl-1-butanol, 3-methylbutanal, acetal, isobutyl acetate, hexanal, ethyl butyrate, 2-heptanol, and butyl butyrate had high concentrations and were most detected by GC-O panelists in the commercial banana essence. Volatile components found only in fresh banana fruit paste that were detected by aroma panelists include E-2-hexenal, limonene, and eugenol.

Gc-olfactometry with solid phase microextraction of aroma volatiles from heated and unheated orange juice.

Solid phase micro extraction, SPME, the solventless headspace volatile extraction technique, was combined with GC-olfactometry (GCO) to examine changes in aroma active volatiles when orange juice was heated. Juice volatiles extracted from the static headspace using SPME (carboxen-polydimethylsiloxane fiber) were compared to liquid-liquid extracts. The SPME extract contained a greater proportion of terpenes. Limonene, myrcene and alpha-pinene comprised 86% of total FID peak area whereas they only comprised 24% in the pentane:ether extract. Aroma active volatiles were evaluated by three trained panelists using Osme, a GCO time-intensity procedure. Eighteen aroma active peaks were common to both heat treated and untreated juice headspace extracts. Six peaks were observed only in unheated extracts and five were found only in extracts from heated juices. Relative amounts of acetaldehyde decreased with increasing headspace exposure time and elevated desorption temperatures.

Orange, mandarin, and hybrid classification using multivariate statistics based on carotenoid profiles.

A study was undertaken to differentiate citrus on the basis of a carotenoid profile obtained from the HPLC determination of 12 carotenoids found in saponified fresh juice. Mandarin, orange, and various hybrid varieties were analyzed to determine their carotenoid profiles. The resulting peak areas were analyzed using principal component analysis (PCA), canonical discriminate analysis (CDA), and Mahalanobis distances. These were used to develop models for classifying the juices into appropriate groups. Thirty-two samples were analyzed to determine classification techniques. Mandarin and orange juices were quite distinct, with the hybrids scattered throughout the mandarin and orange clusters using PCA. CDA resulted in three distinct groups with only a few of the hybrids in the orange grouping.

Using an ion-trap MS sensor to differentiate and identify individual components in grapefruit juice headspace volatiles.

An ion-trap mass spectrometer chemical sensor has been utilized to differentiate between grapefruit juices that differ only in the concentration of a single component, and the sensor was able to identify that component. Grapefruit juice was fortified with 40 to 2000 ppm vanillin, a low-level naturally occurring compound in citrus juices. Principal components analysis and discriminant analysis of mass spectral data (m/z 50-200) provided clear separation of the grapefruit juice samples. Vanillin was observed in the juice headspace at the 40 ppm level, with identification possible at the 100 ppm level using either MS or MS/MS.

Volatile constituents in fresh and processed juices from grapefruit and new grapefruit hybrids.

Forty-five volatile constituents of juices from grapefruit and grapefruit hybrids were quantified by headspace gas chromatography. The three types of grapefruit juice analyzed include pasteurized juice not from concentrate, reconstituted single strength juice from concentrate, and fresh, unpasteurized juice. Principal component and discriminant analyses were carried out using 48 grapefruit juice samples, and the samples were classified into the three types of juice based on degree of processing. Discriminant analysis was superior to principal component analysis for this purpose. Juices from two recently developed grapefruit hybrids were classified similarly to unpasteurized grapefruit juices from commercial cultivars.

Determination of vanillin in orange, grapefruit, tangerine, lemon, and lime juices using GC-olfactometry and GC-MS/MS.

The presence of vanillin in orange, tangerine, lemon, lime, and grapefruit juices has been identified and confirmed using high-resolution GC retention index values, mass spectra, and aroma quality. The impact of vanillin on the flavor score for grapefruit juice is discussed and reported to be minimal. Vanillin concentrations are determined to be in the low parts-per-million range for the various citrus juices. The calculated concentrations in the orange, tangerine, lemon, lime, and grapefruit juices are 0.20, 0.35, 0.41, 0.35, and 0.60 ppm, respectively. Pasteurization produced an average 15% increase in the concentration of vanillin in grapefruit juices. Vanillin did not correlate well with the overall flavor score despite a rather intense signal using OSME gas chromatography-olfactometry software.

Determination of Key Flavor Components in Methylene Chloride Extracts from Processed Grapefruit Juice.

The relative correlation of 52 aroma and 5 taste components in commercial not-from-concentrate grapefruit juices with flavor panel preference was determined. Methylene chloride extracts of juice were analyzed using GC/MS with a DB-5 column. Nonvolatiles determined included limonin and naringin by HPLC, degrees Brix, total acids, and degrees Brix/acid ratio. Juice samples were classified into low, medium, or high categories, based on average taste panel preference scores (nine-point hedonic scale). Principal component analysis demonstrated that highest quality juices were tightly clustered. Discriminant analysis indicated that 82% of the samples could be identified in the correct preference category using only myrcene, beta-caryophyllene, linalool, nootkatone, and degrees Brix. Nootkatone alone was not strongly associated with preference scores. The most preferred juices were strongly associated with low myrcene, low linalool, and intermediate levels of beta-caryophyllene.

Internal glow discharge-fourier transform ion cyclotron resonance mass spectrometry.

A glow discharge (GD) ion source has been developed to work within the high magnetic field of a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Characterization of this source revealed that the optimum operating voltage, pressure, and current are significantly lower than those for normal glow discharges. The sputter rate was lowered to 1/30th of that found with a normal glow discharge source operated external to the high magnetic field region. Operation of the GD source closer to the FTICR analyzer cell than with previous experimental designs resulted in improved ion transport efficiency. Preliminary results from this internal GD source have established detection limits in the low parts per million range for selected elemental species.