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1.
This study aims to follow the kinetics of aroma compound release during model cheese consumption in order to clarify the relationships between flavor release and some oral parameters. Eight subjects participated in the study. Breathing, salivation, chewing, and swallowing were monitored during the eating process. Temporal nosespace analyses were performed using on-line atmospheric pressure ionization-mass spectrometry (API-MS) and off-line solid-phase Micro extraction-gas chromatography-mass spectrometry (SPME-GC-MS). Flavor release profiles were obtained only for ethyl hexanoate, heptan-2-one, and heptan-2-ol. Among them, only the concentrations of ethyl hexanoate and heptan-2-one could be determined by API-MS. Absence of competition between the aroma compounds was checked for both techniques. In-nose maximum concentration (C(max)) varied with aroma compounds. However, C(max) was reached at the same time (T(max)) for the three compounds. Interindividual differences were observed for most of the parameters studied and for all of the aroma compounds. They were related to the interindividual differences among the oral parameters. The aroma release parameters C(max) and AUC (area under the curve) could be related to respiratory and masticatory parameters. In most cases, the same relationships were observed whatever the nature of the aroma compound.  相似文献   

2.
Flavor release from French fries was measured with atmospheric pressure chemical ionization-mass spectrometry (APCI-MS) using both assessors (in vivo) and a mouth model system (in vitro). Several volatiles measured with APCI were identified with MS-MS. The effect of frying time, salt addition, and an alternative process using superheated steam was determined on I(max) (maximum intensity of compounds) and on t(max) (time of maximum intensity). In vitro a "chewing" frequency of 0.60 Hz caused an increased t(max) for low molecular weight compounds compared to the other frequencies tested. Above 0.93 Hz further increase in the frequency did not affect t(max). Trends observed with in vivo experiments could be verified with in vitro experiments. I(max) correlated well with frying time. Addition of salt resulted in a decreased t(max), suggesting a salting-out effect. The alternative process caused a layer of oil on the surface, and this resulted in a higher t(max), but no effect on I(max) was found. This phenomenon may be critical for the sensory quality and would not have been observed with static volatile measurements, demonstrating the value of flavor release measurements.  相似文献   

3.
The ultrastructures of isolated starch granules from Ilpumbyeo (IP), a low-amylose japonica rice, and its mutant, Goami2 (G2), a high-amylose rice, which have extreme contrasts in physicochemical properties, cooking qualities (Kang, H. J.; Hwang, I. K.; Kim, K. S.; Choi, H. C. Comparative structure and physicochemical properties of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464. J. Agric. Food Chem. 2003, 51, 6598-6603. Kim, K. S.; Kang, H. J.; Hwang, I. K.; Hwang, H. G.; Kim, T. Y.; Choi, H. C. Comparative ultrastructure of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464: Scanning and transmission electron microscopy studies. J. Agric. Food Chem. 2004, 52, 3876-3883), and susceptibility to amylolytic enzymes (Kim, K. S.; Kang, H. J.; Hwang, I. K.; Hwang, H. G.; Kim, T. Y.; Choi, H. C. Fibrillar microfilaments associated with a high-amylose rice, Goami2, a mutant of Ilpumbyeo, a high-quality japonica rice. J. Agric. Food Chem. 2005, 53, 2600-2608), were compared. In isolated preparation, IP consisted entirely of well-separated individual starch granules (ISG), whereas G2 consisted of two populations, the large voluminous bodies and the smaller forms, the ISGs. High-voltage electron microscopy revealed that each of the voluminous bodies consisted of tightly packed smaller subunits, the ISGs, indicating that they represent the compound starch granules (CSGs) of G2. This suggests that the structural as well as functional unit of G2 involved in food processing is, unlike IP and other ordinary rices, not ISG but is primarily CSG. ISGs located at the periphery of CSGs were fused to each other with adjacent ones forming a thick band or wall encircling the entire circumference. The periphery of ISGs separated from CSGs of G2 consisted of thin radially oriented filaments arranged side by side along the entire granule surface, whereas no such filaments occurred in ISG of IP. It appears that the thick band and the peripheral filaments surrounding CSGs and ISGs, respectively, function as a structural barrier that limits the entrance of water into the granules and subsequent absorption, causing the low swelling power, incomplete gelatinization, and finally poor quality of cooked rice in G2.  相似文献   

4.
Studies of the constituents of Uruguayan propolis   总被引：4，自引：0，他引：4  
Eighteen flavonoids including two new compounds, four aromatic carboxylic acids, and eleven phenolic acid esters including one new compound were isolated and identified from the ethyl acetate soluble fraction of the 70% ethanol extract of Uruguayan propolis. The new compounds were elucidated as pinobanksin 3-(2-methyl)butyrate (1; recently reported in Usia, T.; Banskota, A. H.; Tezuka, Y.; Midorikawa, K.; Matsushige, K.; Kadota, S. J. Nat. Prod. 2002, 65, 673-676) pinobanksin 3-isobutyrate (2), and 2-methyl-2-butenyl ferulate (24). The constituents isolated from Uruguayan propolis in this study were similar to those of propolis of European and Chinese origin. Thus, it is suggested that the Uruguayan propolis has a plant origin similar to those of propolis from Europe and China.  相似文献   

5.
Efficient liberation of fermentable soluble sugars from lignocellulosic biomass waste not only decreases solid waste handling but also produces value-added biofuels and biobased products. Industrial hemp, a special economic crop, is cultivated for its high-quality fibers and high-value seed oil, but its hollow stalk cords (hurds) are a cellulosic waste. The cellulose-solvent-based lignocellulose fractionation (CSLF) technology has been developed to separate lignocellulose components under modest reaction conditions (Zhang, Y.-H. P.; Ding, S.-Y.; Mielenz, J. R.; Elander, R.; Laser, M.; Himmel, M.; McMillan, J. D.; Lynd, L. R. Biotechnol. Bioeng. 2007, 97 (2), 214- 223). Three pretreatment conditions (acid concentration, reaction temperature, and reaction time) were investigated to treat industrial hemp hurds for a maximal sugar release: a combinatorial result of a maximal retention of solid cellulose and a maximal enzymatic cellulose hydrolysis. At the best treatment condition (84.0% H3PO4 at 50 degrees C for 60 min), the glucan digestibility was 96% at hour 24 at a cellulase loading of 15 filter paper units of cellulase per gram of glucan. The scanning electron microscopic images were presented for the CSLF-pretreated biomass for the first time, suggesting that CSLF can completely destruct the plant cell-wall structure, in a good agreement with the highest enzymatic cellulose digestibility and fastest hydrolysis rate. It was found that phosphoric acid only above a critical concentration (83%) with a sufficient reaction time can efficiently disrupt recalcitrant lignocellulose structures.  相似文献   

6.
The presence of fat in food plays an important role in the way aroma is released during consumption and in the creation of the overall sensory impression. Fat acts as a reservoir for lipophilic volatile compounds and modulates the timing and delivery of aroma compounds in a unique manner. Despite considerable research, reproducible in vitro methods for measuring the effect of fat on volatile release are lacking. An open in vitro cell was used to simulate the open human naso-oropharygeal system and was interfaced with a proton transfer reaction mass spectrometer (PTR-MS) to examine some of the fundamental effects of fat on dynamic volatile release in liquid fat emulsions. Lipid emulsions with various fat contents (0-20%) and droplet sizes (0.25, 0.5, and 5.0 μM) were spiked with flavor volatiles representing a range of lipophilicity (K(o/w) = 1-1380). Preloaded syringes of spiked emulsion were injected into the cell, and temporal changes in release were measured under dynamic conditions. Significant differences in release curves were measured according to the lipid content of emulsions, the vapor pressure, and K(o/w) values of the volatile compounds. With increasing addition of fat, the critical volatile release parameters, maximum concentration (I(max)), time to maximum concentration (T(max)), and the integrated area under the concentration curve (AUC), were affected. The in vitro curves were reproducible and in agreement with theory and correlated with the preswallow phase of in vivo release data. An exponential model was used to calculate changes in mass transfer rates with increased fat addition.  相似文献   

7.
The release of sucrose and menthone from chewing gum was measured in-mouth and in-nose, respectively, during eating. Swabs of saliva were taken from the tongue and analyzed using a rapid, direct liquid-mass spectrometry procedure. Menthone concentration in-nose was monitored on a breath-by-breath basis using direct gas phase atmospheric pressure chemical ionization-mass spectrometry. Simultaneously with the volatile release, trained panelists followed the change in mint flavor by time-intensity (TI) analysis. Two types of commercial chewing gum were analyzed. Both showed that the panelists perception of mint flavor followed sucrose release rather than menthone release. The temporal analysis of the chemical stimuli, with simultaneous TI analysis, provided unequivocal evidence of the perceptual interaction between nonvolatile and volatile flavor compounds from chewing gum.  相似文献   

8.
Recently, this laboratory has isolated from barley and beer extract an isoform of lipid transfer protein (LTP1), which was not fully sequenced (Jégou, S.; Douliez, J. P.; Mollé, D.; Boivin, P.; Marion, D. J. Agric. Food Chem. 2000, 48, 5023--5029). It was named LTP1b and exhibited a molecular weight 294 Da higher than that of the known LTP1. This paper reports the finding of an LTP1 isoform in wheat that also exhibits an excess of 294 Da compared to the native protein. Amino acid sequencing, reduction and alkylation, and mass spectrometry showed that this new LTP1b possesses the same N-terminal sequence as the native LTP1, suggesting that the difference resides in the binding of an adduct which has a molecular weight of 294 Da. The aim of the present paper is to highlight various biophysical techniques that afford the identification of such an isoform-like LTP1 and to correlate this finding with other isoforms of LTP1 that were isolated from other plants but not fully sequenced.  相似文献   

9.
Because wine quality highly relies on the varietal composition of the must, the development of methods allowing the authentication of varieties in musts and wines would be of great value as a guarantee of quality. Microsatellite markers have already been applied to the authentication of grape juices (Faria, M. A.; Magalh?es, R.; Ferreira, M. A.; Meredith, C. P.; Ferreira Monteiro, F. J. Agric. Food Chem. 2000, 48, 1096-1100) and to the analysis of experimental wines (Siret, R.; Boursiquot, J. M.; Merle, M. H.; Cabanis, J. C.; This, P. J. Agric Food Chem. 2000, 48, 5035-5040). In the present paper, we accessed the usefulness of this technology for the analysis of must and wine mixtures. The detection limit of DNA mixtures was first estimated on DNA extracted from leaves: 4% of a foreign DNA can be detected. Analysis of must and wine mixtures (Chardonnay B/Clairette B and Syrah N/Grenache N) was performed on experimental fermentations. DNA was extracted along the fermentation process and analyzed using five microsatellite loci. The 70:30 (v/v) mixtures were successfully analyzed until the end of the fermentation. The applications of these results to commercial purposes are discussed.  相似文献   

10.
This paper reports a study on the hydroxylation of ferulic acid and tyrosine by field bean (Dolichos lablab) polyphenol oxidase, a reaction that does not take place without the addition of catechol. A lag period similar to the characteristic lag of tyrosinase activity was observed, the length of which decreased with increasing catechol concentration and increased with increasing ferulic acid concentration. The activation constant K(a) of catechol for ferulic acid hydroxylation reaction was 5 mM. The kinetic parameters of field bean polyphenol oxidase toward ferulic acid and tyrosine were evaluated in the presence of catechol. 4-Methyl catechol, L-dihydroxyphenylalanine, pyrogallol, and 2,3,4-trihydroxybenzoic acid, substrates with high binding affinity to field bean polyphenol oxidase, could stimulate this hydroxylation reaction. In contrast, diphenols such as protocatechuic acid, gallic acid, chlorogenic acid, and caffeic acid, which were not substrates for the oxidation reaction, were unable to bring about this activation. It is most likely that only o-diphenols that are substrates for the diphenolase serve as cosubstrates by donating electrons at the active site for the monophenolase activity. The reaction mechanism for this activation is consistent with that proposed for tyrosinase (Sanchez-Ferrer, A.; Rodriguez-Lopez, J. N.; Garcia-Canovas, F.; Garcia-Carmona, F. Biochim. Biophys. Acta 1995, 1247, 1-11). The presence of o-diphenols, viz. catechol, L-dihydroxyphenylalanine, and 4-methyl catechol, is also necessary for the oxidation of the diphenols, caffeic acid, and catechin to their quinones by the field bean polyphenol oxidase. This oxidation reaction occurs immediately with no lag period and does not occur without the addition of diphenol. The kinetic parameters for caffeic acid (K(m) = 0.08 mM, V(max) = 32440 u/mg) in the presence of catechol and the activation constant K(a) of catechol (4.6 mM) for this reaction were enumerated. The absence of a lag period for this reaction indicates that the diphenol mechanism of diphenolase activation differs from the way in which the same o-diphenols activate the monophenolase activity.  相似文献   

11.
The influence of flavor solvent [triacetin (TA), propylene glycol (PG), medium chained triglycerides (MCT), or no flavor solvent (NFS)] on the flavor release profile, the textural properties, and the sensory perception of a sugar-free chewing gum was investigated. Time course analysis of the exhaled breath and saliva during chewing gum mastication indicated that flavor solvent addition or type did not influence the aroma release profile; however, the sorbitol release rate was statistically lower for the TA formulated sample in comparison to those with PG, MCT, or NFS. Sensory time-intensity analysis also indicated that the TA formulated sample was statistically lower in perceived sweetness intensity, in comparison with the other chewing gum samples, and also had lower cinnamon-like aroma intensity, presumably due to an interaction between sweetness intensity on aroma perception. Measurement of the chewing gum macroscopic texture by compression analysis during consumption was not correlated to the unique flavor release properties of the TA-chewing gum. However, a relationship between gum base plasticity and retention of sugar alcohol during mastication was proposed to explain the different flavor properties of the TA sample.  相似文献   

12.
The objective of this study was to develop a model to simulate salt release during eating. Salt release kinetics during eating was measured for four model dairy products with different dynamic salty perceptions. A simple in vivo model of salt release was developed to differentiate between the contribution of the individual and of the product to salt release. The most difficult model parameter to determine or predict is the evolution of the contact area between the product and the saliva. Fitting the model to the experimental data showed that the subject's masticatory performance and fracture initiation energy of the product determined the contact area between the product and the saliva generated by mastication. Finally, the role of release dynamics on sensory time-intensity profiles is discussed.  相似文献   

13.
This study aimed to investigate the relationships between sodium release, saltiness, and oral parameters during the eating of lipoprotein matrices (LPM). Sodium release and saltiness relative to 10 LPM were recorded during normal mastication by five subjects with differing oral parameters (chewing efficiency and salivary flow rate). The LPM samples varied in composition (dry matter, fat, salt, and pH levels) and represented a broad range of hardness. Mastication was recorded using electromyography simultaneously with sensory assessment. Differences in chewing behavior could explain most of the variability in sodium release and saltiness among subjects. Subjects with a higher chewing force and lower salivary flow rate experienced higher levels of sodium release and saltiness. In terms of the LPM, sodium release and saltiness were affected by either chewing behavior or food composition.  相似文献   

14.
We have previously cloned and characterized the cDNAs of three isoforms of the 8S globulin of mungbean, expressed the major 8Salpha isoform in Escherichia coli, and purified and successfully crystallized it (Bernardo, A. E. N.; Garcia, R. N.; Adachi, M.; Angeles, J. G. C.; Kaga, A; Ishimoto, M.; Utsumi, S.; Tecson-Mendoza, E. M. J. Agric. Food Chem. 2004, 52, 2552-2560). Herein, we report the physicochemical and emulsifying properties of the native 8S and recombinant 8Salpha globulin or vicilin. The circular dichroism spectra analysis of the native 8S and recombinant 8Salpha globulins revealed that the recombinant 8Salpha formed a secondary structure close to that of the native 8S. Further, gel filtration analysis showed that 8Salpha was able to assemble into trimers. The native 8S and recombinant 8Salpha globulins were soluble at pH 3.4 and at pH 7.4-9.0 at low ionic strength, mu = 0.08. Interestingly, the native 8S was more soluble at pH 7.0 and pH 7.4 than the recombinant 8Salpha at mu = 0.08. Both forms were very soluble at pH 3.4-9.0 at high ionic strength, mu = 0.50. The native form exhibited a higher T(m) (69.2, 79.5, and 83.8 degrees C) than the recombinant form (65.6, 71.6, 77.5 degrees C) at mu = 0.1, 0.2, and 0.5, respectively. The recombinant form was found to have greater surface hydrophobicity than the native form. There was little difference in the emulsifying ability between the native 8S and 8Salpha at pH 3.4 and pH 7.6. The results indicate that the presence of N-linked glycans is not essential in the assembly and stable conformation of the mungbean vicilin. However, the N-linked glycans might have contributed to the higher solubility at low ionic strength, greater thermal stability, and decreased surface hydrophobicity of the native vicilin as compared to the recombinant 8Salpha. On the other hand, the N-linked glycans showed little effect on the emulsifying ability of the protein.  相似文献   

15.
Species differences in the metabolism of acetylenic compounds commonly used in the formulation of pharmaceuticals and pesticides have not been investigated. To better understand the in vivo reactivity of this bond, the metabolism of propargyl alcohol (PA), 2-propyn-1-ol, was examined in rats and mice. An earlier study (Banijamali, A. R.; Xu, Y.; Strunk, R. J.; Gay, M. H.; Ellis, M. C.; Putterman, G. J. J. Agric. Food Chem. 1999, 47, 1717-1729) in rats revealed that PA undergoes extensive metabolism primarily via glutathione conjugation. The current research describes the metabolism of PA in CD-1 mice and compares results for the mice to those obtained for rats. [1,2,3-(13)C;2,3-(14)C]PA was administered orally to the mice. Approximately 60% of the dose was excreted in urine by 96 h. Metabolites were identified, directly, in whole urine by 1- and 2-D (13)C NMR and HPLC/MS and by comparison with the available reference compounds. The proposed metabolic pathway involves glucuronide conjugation of PA to form 2-propyn-1-ol-glucuronide as well as oxidation of PA to the proposed intermediate 2-propynal. The aldehyde undergoes conjugation with glutathione followed by further metabolism to yield as final products 3,3-bis[(2-acetylamino-2-carboxyethyl)thio]-1-propanol, 3-[(2-acetylamino-2-carboxyethyl)thio]-3-[(2-amino-2-carboxyethyl)thi o]-1-propanol, 3,3-bis[(2-amino-2-carboxyethyl)thio]-1-propanol, 3-[(2-amino-2-carboxyethyl)thio]-2-propenoic acid, and 3-[(2-formylamino-2-carboxyethyl)thio]-2-propenoic acid. A small portion of 2-propynal is also oxidized to result in the excretion of 2-propynoic acid. On the basis of urinary metabolite data, qualitative and quantitative differences are noted between rats and mice in the formation of the glucuronide conjugate of PA and in the formation of 2-propynoic acid and metabolites derived from glutathione. These metabolites represent further variation on glutathione metabolism following its addition to the carbon-carbon triple bond compared to those described for the rat.  相似文献   

16.
A reversed phase ion-pair liquid chromatographic method for the determination of nicotine in commercial tobacco products was previously developed and optimized (Ciolino, L. A.; Turner, J. A.; McCauley, H. A.; Smallwood, A. W.; Yi, T. Y. J. Chromatogr. 1999a, 852 (2), 451-463) and provided reliable results for the determination of nicotine in commercial moist snuff (Ciolino, L. A.; McCauley, H. A.; Fraser, D. B.; Barnett, D. Y.; Yi, T. Y.; Turner, J. A. J. Agric. Food Chem. 1999b, 47, 3706-3712). The method uses an aqueous-based sample extraction and provides rapid separation of nicotine from the minor tobacco alkaloids and other commercial tobacco components. In the present work, the method is evaluated for the determination of nicotine in commercial cigarettes and compared to both an official AOAC method for total alkaloids in tobacco (AOAC, AOAC Official Methods of Analysis of AOAC International, 16th ed.; AOAC International: Gaithersburg, MD, 1995; pp 30-31), and a published GC method (Lyerly, L. A.; Greene, G. H. Beitr. Tabakforsch. 1976, 8 (6), 359-361). Good agreement was obtained between the ion-pair LC method and the GC method with relative differences in determined nicotine contents of 0.6 to 5% for a series of commercial and reference cigarettes.  相似文献   

17.
The official methods for the determination of nicotine in commercial tobacco products (AOAC, CORESTA) are based on approaches that are not selective for nicotine (colorimetric measurement, steam distillation, perchloric acid titration), and the availability of published methods based on state-of-the-art chromatographic methods is limited. Reversed phase ion-pair liquid chromatography has been established as a viable alternative for the analysis of basic analytes. A reversed phase ion-pair liquid chromatographic method for the determination of nicotine in commercial tobacco products was developed and optimized in separate experiments (Ciolino, L. A.; Turner, J. A.; McCauley, H. A.; Smallwood, A. W.; Yi, T. Y. J. Chromatogr. 1999a, 852 (2), 451-463). An extensive within-laboratory performance study of the optimized method was subsequently conducted, and results are presented here for the determination of nicotine in commercial moist snuff. Results for the determination of nicotine in commercial cigarettes are presented in a subsequent paper.  相似文献   

18.
The potential utility of micrometer-sized particles as controlled-release devices for the volatilization of insect pheromones for mating disruption applications is evaluated in this study for two pheromone/model compound systems (codlemone/1-dodecanol and disparlure/1,2-epoxyoctadecane). To expedite the measurement of release rates from these particle devices, two techniques based on thermogravimetric analysis (TGA) have been exploited: isothermal TGA (I-TGA) at elevated temperatures (40-80 degrees C) with N(2) convection and volatilization temperature (VT) by dynamic TGA. A correlation between these two methods has been established. Samples that exhibit a higher VT provide a lower release rate from a particle substrate. Using these techniques, it has been demonstrated that chemical interactions between adsorbed liquids and particle surfaces may play a small role in defining release characteristics under conditions of low surface area, whereas parameters associated with total surface area and micropore structure appear to be much more significant in retarding evaporation for uncoated particles containing an adsorbed liquid. Additional regulation of release rates was achieved by coating the particle systems with water-soluble or water-dispersible polymers. By careful selection of particle porosity and coating composition, it is envisioned that the evaporation rate of pheromones can be tailored to specific insect control applications.  相似文献   

19.
The data of Devilieghere et al. (Int. J. Food Microbiol. 1999, 46, 57--70) on bacterial growth in a simulated medium of modified-atmosphere-packed cooked meat products was processed for estimating maximum specific growth rate mu(max) and lag phase lambda of Lactobacillus sake using artificial neural networks-based model (ANNM) computation. The comparison between ANNM and response surface methodology (RSM) model showed that the accuracy of ANNM prediction was higher than that of RSM. Two-dimensional and three-dimensional plots of the response surfaces revealed that the relationships of water activity a(w), temperature T, and dissolved CO(2) concentration with mu(max) and lambda were complicated, not just linear or second-order relations. Furthermore, it was possible to compute the sensitivity of the model outputs against each input parameter by using ANNM. The results showed that mu(max) was most sensitive to a(w), T, and dissolved CO(2) in this order; whereas lambda was sensitive to T the most, followed by a(w), and dissolved CO(2) concentrations.  相似文献   

20.
Interaction of flavor compounds with proteins is known to have an influence on the release of flavor from food. Hydrophobic interactions were found between beta-lactoglobulin and methyl ketones; the affinity constant increases by increasing the hydrophobic chain. Addition of beta-lactoglobulin (0.5 and 1%) to aroma solutions (12.5, 50, and 100 microL L(-)(1)) of three methyl ketones induces a significant decrease in odor intensity. The chosen methyl ketones were 2-heptanone (K(b) = 330), 2-octanone (K(b) = 950), and 2-nonanone (K(b) = 2440). The release of these flavor compounds (50 microL L(-)(1)) was studied by static headspace in water solution (50 mM NaCl, pH 3) with different concentrations of beta-lactoglobulin (0, 0.5, 1, 2, 3, and 4%). Increasing the concentration of protein increases the retention of volatiles, and this effect is greatest for 2-nonanone, the compound with the highest affinity constant, and lowest for 2-heptanone. A mathematical model previously developed to describe flavor release from aqueous solutions containing flavor-binding polymers (Harrison, M.; Hills, B. P. J. Agric. Food Chem. 1997, 45, 1883-1890) was used to interpret the data. The model assumes that the polymer-flavor interaction is reversible and the rate-limiting step for release is the transfer of volatiles across the macroscopic gas-liquid interface. This model was used to predict the equilibrium partitioning properties and the rate of release of the three methyl ketones. Increasing the affinity constant leads to decreased release rates and a lower final headspace aroma concentration.  相似文献   

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