16 research outputs found
Comparison of two headspace solid phase microextraction fibres for the detection of volatile chemical concentration changes due to industrial processing of orange juice
No full textDiscrimination of mango fruit maturity by volatiles using the electronic nose and gas chromatography
No full textMango fruit (Mangifera indica L.), cv. ¿Cogshall¿, ¿Kent¿ and ¿Keitt¿ were harvested at different maturities (61-115 d past flowering and 80-307 average g fresh weight for ¿Cogshall¿) and at different sizes (364-1563 and 276-894 average g fresh weight for ¿Keitt¿ and ¿Kent¿, respectively). Immediately after harvest (green) or after 1 week of ripening at room temperature (ripe), fruit were homogenized or left intact and evaluated by electronic nose (enose) or by gas chromatography (GC) for aroma and other volatiles as well as for soluble solids and acids. Volatile data from the different harvest maturities and ripening stages were discriminated by using multivariate statistics (discriminant factor analysis). Both the enose and GC were able, in most cases, to separate fruit from different harvest maturities, especially for ¿Cogshall¿ mangoes, at both the green and ripe stages as well as discriminate green from ripe fruit and fruit from the different varieties within a maturity stage. Solids and acids data indicated that later harvest maturities resulted in sweeter fruit and later-harvested fruit had a different volatile profile from earlier-harvested fruit. Mango fruit volatiles may be useful as maturity markers to determine optimal harvest maturity for mango fruit that results in full quality upon ripening
Application of glow discharge Fourier-transform ion cyclotron resonance mass spectrometry to isotope ratio measurements
No full textResponse of Four Apple Cultivars to 1-Methylcyclopropene Treatment and Controlled Atmosphere Storage
No full textChanges in antioxidant phytochemicals and volatile composition of Camellia sinensis by oxidation during tea fermentation
No full textDevelopment of electronic nose measurements for mango (Mangifera indica) homogenate and whole fruit
No full textMango fruit from Latin America (cv. Tommy Atkins), were purchased from a local Florida supermarket, homogenized, and sampled for volatile analysis by static headspace method. Some of the material was analyzed using an electronic nose (e-nose) with metal oxide coated or uncoated sensors (500 pL injection volume) and some by gas chromatography (GC) equipped with a polar Carbowax column and a flame ionization detector. Dilution of homogenate and homogenate vol-ume were analyzed to determine effect on e-nose and GC headspace measurements. Mango homogenate (1.0, 1.5, and 2.0 mL) was diluted with Dl water to 50, 25, and 12.5% of original concentration. The resulting a-nose signal intensities (changes in resistance across the metal oxide sensor due to non-selective interactions with volatile compounds in the headspace) were analyzed by discriminant factor analysis (DFA), which resulted in grouping by dilution factor, regardless of sample size. A combination of 2.0 mL and 25% dilution of mango homogenate was determined to be optimal. These results were com-pared to analysis of 13 characteristic mango volatiles by gas chromatography (GC) headspace analysis of the mango homogenate for the same volume/dilution combinations. Concentration of volatiles in the headspace generally increased with volume and decreased with dilution, but there were some exceptions and inconsistencies. The increase in headspace con-centration was not directly proportional to the homogenate volume, indicating matrix effects on aroma partitioning into the headspace, which varied for different compounds. Whole mangoes (cv. Keitt and Kent) harvested in Homestead, Fla., were put in sealed containers for 3 hours to accumulate enough vol-atiles for headspace analysis. A large injection volume injected into the e-nose (2000 pL) was necessary to get ample signal and reproducible results, and separated the two varieties based on their volatile emission to the headspace
Pinneapple juice concentrated by osmotic evaporation
No full textPasteurized pineapple juice was concentrated by osmotic evaporation to produce a 51°Brix concentrate that was reconstituted to single strength juice for evaluation. Headspace gas chromatography (HSGC) showed that the concentrate retained an average of 62% of the volatile components present in the initial juice. A sensory panel preferred initial juice over reconstituted concentrate, and noted a decrease in desirable flavor top notes as well as development of some processed flavor in the concentrate. Similar HSGC analysis of four other commerciaI juice samples showed a wide range of quantitative values for volatile components, with the initial juice being similar to the weakest of these commerciaI juices. Analysis of concentrated juice extracts permitted identification of additional less-volatile components not monitored directly by HSGC of the juice. Relatively low levels of these components were also present in the initial juice. Although this nonthermally produced concentrate retains more volatile components than when traditional thermal processing methods are used, addition of aqueous aroma to the concentrate may be required for satisfactory flavor
Comparison of grapefruit hybrid fruit with parent fruit based on composition of volatile components
No full textQuantitation of ion abundances in fourier transform ion cyclotron resonance mass spectrometry
No full textAbstractTo improve the analytical usefulness of Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), an extensive survey of various methods for quantitation of peak magnitudes has been undertaken using a series of simulated transient response signals with varying signal-to-noise ratio. Both peak height (five methods) and peak area (four methods) were explored for a range of conditions to determine the optimum methodology for quantitation. Variables included dataset size, apodization function, damping constant, and zero filling. Based on the results obtained, recommended procedures for optimal quantitation include: apodization using a function appropriate for the peak height ratios observed in the spectrum (i.e., Hanning for ratios of about 1:10, three-term Blackman-Harris for ratios of ∼1:100, or Kaiser-Bessel for ratios of ∼1:1000); zero filling until the peaks of interest are represented by 10–15 points (generally obtained with one order of zero filling); and use of the polynomial y = (ax2 + bx + c)n and the three data points of highest intensity of the peak to locate the peak maximum, Ymax = (−b2/4a + c)n. In this peak fitting procedure, which we have termed the “Comisarow method,” n is 5.5, 9.5, and 12.5 for the Hanning, three-term Blackman-Harris, and Kaiser-Bessel apodization functions, respectively. Accuracy of quantitation using an optimal peak height determination is about equal to that for peak area measurements. These recommendations were found to be valid when tested with real FTICR-MS spectra of xenon isotopes
