Hot and cold water infusion aroma profiles of Hibiscus sabdariffa: fresh compared with dried.

UNLABELLED: Calyxes from the Roselle plant (Hibiscus sabdariffa L.) were used to prepare cold (22 °C for 4 h) and hot (98 °C for 16 min) infusions/teas from both fresh and dried forms. Aroma volatiles were extracted using static headspace SPME and analyzed using GC-MS and GC-O with 2 different columns (DB-5 and DB-Wax). Totals of 28, 25, 17, and 16 volatiles were identified using GC-MS in the dried hot extract (DHE), dried cold extract (DCE), fresh hot extract (FHE), and fresh cold extract (FCE) samples, respectively. In terms of total GC-MS peak areas DHE ≫ DCE > FHE ≫ FCE. Nonanal, decanal, octanal, and 1-octen-3-ol were among the major volatiles in all 4 beverage types. Thirteen volatiles were common to all 4 teas. Furfural and 5-methyl furfural were detected only in dried hibiscus beverages whereas linalool and 2-ethyl-1-hexanol were detected only in beverages from fresh hibiscus. In terms of aroma active volatiles, 17, 16, 13, and 10 aroma active volatiles were detected for DHE, DCE, FHE, and FCE samples, respectively. The most intense aroma volatiles were 1-octen-3-one and nonanal with a group of 4 aldehydes and 3 ketones common to all samples. Dried samples contained dramatically higher levels of lipid oxidation products such as hexanal, nonanal, and decanal. In fresh hibiscus extracts, linalool (floral, citrus) and octanal (lemon, citrus) were among the highest intensity aroma compounds but linalool was not detected in any of the dried hibiscus extracts. PRACTICAL APPLICATION: Hibiscus teas/infusions are one of the highest volume specialty botanical products in international commerce. The beverage is consumed for both sensory pleasure and health attributes and is prepared a number of ways throughout the world. Although color and taste attributes have been examined, little information is known about its aroma volatiles and no other study has compared extractions from both fresh and dried as well as extraction temperature differences. This is also, apparently, the first study to identify the aroma active volatiles in hibiscus beverages using GC-olfactometry. Manufacturers and consumers will now have a better understanding of why hibiscus teas prepared in different ways from either fresh or dried forms have a different flavor quality and intensity.

Sulfur volatiles from Allium spp. affect Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), response to citrus volatiles.

The Asian citrus psyllid, Diaphorina citri Kuwayama, vectors Candidatus Liberibacter asiaticus (Las) and Candidatus Liberibacter americanus (Lam), the presumed causal agents of huanglongbing. D. citri generally rely on olfaction and vision for detection of host cues. Plant volatiles from Allium spp. (Alliaceae) are known to repel several arthropod species. We examined the effect of garlic chive (A. tuberosum Rottl.) and wild onion (A. canadense L.) volatiles on D. citri behaviour in a two-port divided T-olfactometer. Citrus leaf volatiles attracted significantly more D. citri adults than clean air. Volatiles from crushed garlic chive leaves, garlic chive essential oil, garlic chive plants, wild onion plants and crushed wild onion leaves all repelled D. citri adults when compared with clean air, with the first two being significantly more repellent than the others. However, when tested with citrus volatiles, only crushed garlic chive leaves and garlic chive essential oil were repellent, and crushed wild onions leaves were not. Analysis of the headspace components of crushed garlic chive leaves and garlic chive essential oil by gas chromatography-mass spectrometry revealed that monosulfides, disulfides and trisulfides were the primary sulfur volatiles present. In general, trisulfides (dimethyl trisulfide) inhibited the response of D. citri to citrus volatiles more than disulfides (dimethyl disulfide, allyl methyl disulfide, allyl disulfide). Monosulfides did not affect the behaviour of D. citri adults. A blend of dimethyl trisulfide and dimethyl disulfide in 1:1 ratio showed an additive effect on inhibition of D. citri response to citrus volatiles. The plant volatiles from Allium spp. did not affect the behaviour of the D. citri ecto-parasitoid Tamarixia radiata (Waterston). Thus, Allium spp. or the tri- and di-sulphides could be integrated into management programmes for D. citri without affecting natural enemies.

Identification of medicinal off-flavours generated by Alicyclobacillus species in orange juice using GC-olfactometry and GC-MS.

AIMS: The objective of this study was to identify compounds responsible for medicinal off-flavours produced by different species and strains of Alicyclobacillus in orange juice using a combination of chromatographic-coupled olfactometric techniques and gas chromatography-mass spectrometry (GC-MS). METHODS AND RESULTS: Each of five Alicyclobacillus strains was inoculated into separate juice samples and incubated up to 28 days at 45 degrees C. Aroma compounds in the juice were analysed by GC-olfactometry (GC-O) and confirmed using GC-MS. GC-O identified three components that were described as medicinal/antiseptic. Microbial populations were enumerated at timed intervals by spiral plating onto Alicyclobacillus agar. Within 28 days incubation, all five strains produced medicinal off-aromas from guaiacol and at least one halogenated phenol. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to evaluate individual juice aroma components produced by Alicyclobacillus species using olfactometry and to demonstrate that at least three medicinal off-flavour compounds are associated with the growth of alicyclobacilli in orange juice.

2-Methyl-3-furanthiol and methional are possible off-flavors in stored orange juice: aroma-similarity, NIF/SNIF GC-O, and GC analyses.

The occurrence of methional in fresh orange juice, and possible occurrence of beta-damascenone in heated orange juice, has been previously suggested. Here we report on the occurrence of 2-methyl-3-furanthiol in the headspace, collected by solid-phase micro-extraction, of fresh, pasteurized, and stored orange juice. The contents of 2-methyl-3-furanthiol and methional were quantified, and the relative level of beta-damascenone was estimated, in the headspace of fresh, pasteurized, and stored orange juices using the nasal impact frequency (NIF) and surface of NIF (SNIF) GC-Olfactometry procedure. 2-Methyl-3-furanthiol concentrations were 2 ng/L in fresh and pasteurized Shamuti orange juice, and 270 ng/L in stored juice of the same variety. Methional concentrations were 550, 830, and 11,550 ng/L in fresh, pasteurized, and stored pasteurized juices, respectively. beta-Damascenone content appeared to have increased during pasteurization and storage. Aroma-similarity experiments strongly suggest that 2-methyl-3-furanthiol and methional, at the levels found in stored orange juice (21 days at 35 degrees C), contribute to stored orange juice off-flavor.

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.

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.

Effects of L-cysteine and N-acetyl-L-cysteine on 4-hydroxy-2, 5-dimethyl-3(2H)-furanone (furaneol), 5-(hydroxymethyl)furfural, and 5-methylfurfural formation and browning in buffer solutions containing either rhamnose or glucose and arginine.

Solutions of L-cysteine (Cys) and N-acetyl-L-cysteine (AcCys), containing glucose or rhamnose, with or without arginine, were buffered to pH 3, 5, and 7 and incubated at 70 degrees C for 48 h. Cys and AcCys inhibited the formation of (hydroxymethyl)furfural (HMF) from glucose and methylfurfural (MF) from rhamnose under acidic conditions. AcCys inhibited the accumulation of 4-hydroxy-2, 5-dimethyl- 3(2H)-furanone (DMHF, Furaneol) from rhamnose, but Cys, under our experimental conditions, enhanced Furaneol accumulation from rhamnose. Cys and AcCys reacted directly with Furaneol but not with HMF or MF. Both Cys and AcCys inhibited nonenzymatic browning at pH 7. At pH 3, however, Cys reacted with both glucose and rhamnose to produce unidentified compounds that increased the visible absorbency.

Flavanone absorption after naringin, hesperidin, and citrus administration.

Disposition of citrus flavonoids was evaluated after single oral doses of pure compounds (500 mg naringin and 500 mg hesperidin) and after multiple doses of combined grapefruit juice and orange juice and of once-daily grapefruit. Cumulative urinary recovery indicated low bioavailability ( < 25%) of naringin and hesperidin. The aglycones naringenin and hesperitin were detected in urine and plasma by positive chemical ionization-collisionally activated dissociation tandem mass spectrometry (PCI-CAD MS/MS). After juice administration, PCI-CAD MS/MS detected naringenin, hesperitin, and four related flavanones, tentatively identified as monomethoxy and dimethoxy derivatives. These methoxyflavanones appear to be absorbed from juice. Absorbed citrus flavanones may undergo glucuronidation before urinary excretion.

Solid-phase extraction and HPLC determination of 4-vinyl guaiacol and its precursor, ferulic acid, in orange juice.

This study is undertaken to develop a simplified, rapid method to determine both immediate and potential off odors due to 4-vinyl guaiacol and its odorless precursor, ferulic acid, from a single sample preparation and chromatographic analysis. Orange juice sample preparation consists of a simple, C18 solid phase extraction. Utilizing a 5-microns, 25-cm, C18 column, both compounds can be separated within 40 min using a one-step, linear gradient beginning with an aqueous 12% tetrahydrofuran (THF)-5% acetonitrile mixture and ending with 35% aqueous THF. Hesperidin and nariutin have been identified as the compounds that interfered with the ultraviolet (UV) determination of sinapic and caffeic acids. Fluorescence detection with wavelength programming offers optimal sensitivity and selectivity. Recoveries of 4-vinyl guaiacol and ferulic acid range from 90 to 103%. Detection limits are 1 ppm and 5 ppm for ferulic acid and 4-vinyl guaiacol, respectively. Other hydroxycinnamic acids such as coumaric, sinapic, and caffeic acids may also be determined from the same chromatogram.

Quantitative analysis of limonin in grapefruit juice using an enzyme-linked immunoassay: interlaboratory study.

Eleven laboratories participated in an interlaboratory study of an enzyme-linked immunoassay for limonin in grapefruit juice. Participating laboratories received training and practice samples until familiar with the procedure. Laboratories then received 8 sample pairs of grapefruit juice as blind duplicates. Samples were refrigerated and analyzed within 4 days of receipt. Results from 1 laboratory and 6 individual samples were excluded from the statistical analysis. Method performance was measured by the one-way component of variance analysis. Repeatability relative standard deviations (RSDr) ranged from 7.0 to 15.6%. Reproducibility relative standard deviations (RSDR) ranged from 12.9 to 29.4%.

Liquid chromatographic determination of naringin and neohesperidin as a detector of grapefruit juice in orange juice.

Naringin/neohesperidin ratios can be used to differentiate orange juice which may contain added grapefruit juice from orange juice which may include juices from other naringin-containing cultivars. The naringin/neohesperidin ratios in juice vary from 14 to 83 in grapefruit (C. grandis) and from 1.3 to 2.5 in sour orange (C. aurantium) cultivars; the ratio is always less than 1 for the K-Early tangelo. Concentrations of both naringin and neohesperidin can be determined in orange juice by using a single liquid chromatographic isocratic reverse-phase system with a C-18 column. The detection limit for both compounds is 1 ppm with a linear working range to 500 ppm. Concentration relative standard deviations range from 0.47 to 1.06% for naringin and from 0.4 to 1.27% for neohesperidin. Naringin and neohesperidin recoveries ranged from 93 to 102% at concentrations of 5 and 50 ppm. Naringin values from blind duplicate samples of orange/grapefruit juice blends could be duplicated to +/- 3%.

Quantitation of polymethoxylated flavones in orange juice by high-performance liquid chromatography.

A quantitative high-performance liquid chromatographic (HPLC) procedure for the determination of the five major polymethoxylated flavones (PMFs) in orange juice has been developed. It employs a unique ternary solvent system with coupled UV-fluorescence detection. The dual detectors were employed to determine the presence of interfering substances and served as a cross check on quantitation. Stop flow UV and fluorescence scanning was used to identify peaks and determine the presence of impurities. Although all five citrus PMFs fluoresce, some HPLC fluorescence peaks were too small to be of much practical use. All five citrus PMFs could be quantitated satisfactorily with the fixed wavelength UV (313 nm) detector. The HPLC procedure has been used to evaluate each step in the preparation. The optimum extracting solvent was selected and one time consuming step was eliminated, as it was found to be unnecessary. HPLC values for nobiletin and sinensetin are in good agreement with the thin-layer chromatographic (TLC) values in the literature. HPLC values for the other three flavones were considerably lower than those reported in the literature. The HPLC procedure is considerably faster than the TLC procedure with equal or superior precision and accuracy.