Perceptual interactions in odour mixtures: odour quality in binary mixtures of woody and fruity wine odorants

The qualitative perceptual interactions in three binary mixtures of wine odorants were studied: isoamyl acetate (fruity note)/whisky lactone (woody note), ethyl butyrate (fruity note)/whisky lactone (woody note) and ethyl butyrate (fruity note)/guaiacol (woody note). For each binary mixture, the perceived quality and intensity of 24 stimuli (four supra-threshold concentration levels of each of the two compounds and their 16 possible combinations) were evaluated in five replications by a trained panel of 13 subjects. The application of the Olsson predictive model for odour intensity and quality perception gave quite a good estimation of the evolution of single component identification in the mixture when the intensity proportion of unmixed components varied. However, this model was unable to account for the odour quality dominance in mixtures of iso-intense components. An alternative linear logistic model was proposed to study the qualitative dominance of the woody note in the three mixtures when the perceived intensities of each unmixed compound were equal.     

MODELING OF SWEET, BITTER AND IRRITANT SENSATIONS AND THEIR INTERACTIONS ELICITED BY MODEL ICE WINES

Interactions between taste and irritant sensations elicited by model ice wine solutions were investigated, including the use of U and Γ′ models for predicting the perceived intensity of these sensory interactions. Fifteen solutions of varying ethanol and sugar concentrations representative of commercial ice wine values were evaluated in two trials by a trained sensory panel (n = 12) for perceived sweetness, bitterness and heat intensities. Sweetness perception of lower sugar‐concentration level in ice wine model solution was affected by ethanol concentration. The sweetness intensities of the sugar and ethanol mixtures are higher than the sweetness intensities of sugar solutions. The Γ′ index indicates a slight synergy between ethanol and sugar on sweetness perception. The bitterness intensities elicited by ethanol–sugar mixtures are lower than those elicited by unmixed ethanol solutions. The Γ′ index indicates inhibition of ethanol and sugar perception on bitterness perception. Suppression of heat sensation was found in model base wine solutions across sugar and ethanol concentrations.     

Prediction of Sweetness Intensity for Equiratio Aspartame/Sucrose Mixtures

The Equiratio Mixture Model predicts the responses to a seriesof equiratio mixtures on the basis of the psychophysical functionsfor the unmixed components. The model predicts the sweetnessof mixtures of sugars and sugar-alcohols successfully, but isunable to predict mixture intensity for substances with differentdynamic ranges. In this paper, the equi-intensity concept isintroduced in the Equiratio Mixture Model by transforming thephysical concentrations expressed in molarity into units thatproduce approximately equi-intense sensations. An empiricaltest using aspartame/sucrose mixtures shows that the modifiedEquiratio Mixture Model yields good predictions of mixture intensities.     

An Equiratio Mixture Model for Non-additive Components: A Case Study for Aspartame/Acesulfame-K Mixtures

The Equiratio Mixture Model predicts the psychophysical functionfor an equiratio mixture type on the basis of the psychophysicalfunctions for the unmixed components. The model reliably estimatesthe sweetness of mixtures of sugars and sugar-alchohols, butis unable to predict intensity for aspartame/sucrose mixtures.In this paper, the sweetness of aspartame/acesulfame-K mixturesin aqueous and acidic solutions is investigated. These two intensivesweeteners probably do not comply with the model's originalassumption of sensory dependency among components. However,they reveal how the Equiratio Mixture Model could be modifiedto describe and predict mixture functions for non-additive substances. To predict equiratio functions for all similar tasting substances,a new Equiratio Mixture Model should yield accurate predictionsfor components eliciting similar intensities at widely differingconcentration levels, and for substances exhibiting hypo- orhyperadditivity. In addition, it should be able to correct violationsof Stevens's power law. These three problems are resolved ina model that uses equi-intense units as the measure of physicalconcentration. An interaction index in the formula for the constantaccounts for the degree of interaction between mixture components.Deviations from the power law are corrected by a nonlinear responseoutput transformation, assuming a two-stage model of psychophysicaljudgment. Chem. Senses 21: 1–11, 1996.     

THE TASTES OF ARTIFICIAL SWEETENERS AND THEIR MIXTURES

0s scaled the taste intensity (bitterness, sweetness) of artificialsweeteners, mixtures of artificial sweeteners, and glucose.Sweetness of glucose conformed to a power function, whereasneither sweetness of artificial sweeteners nor their bitternessdid. The total taste intensity of mixtures was often lower thanthe taste intensities of the components, suggesting suppression,although in many instances the suppressive effects disappearedat high concentrations.     

Chlorophyll-Protein Complexes and other Thylakoid Components at the Low Intensity Threshold in Euglena Chloroplast Development

The plastids of dark-grown resting cells of Euglena gracilisKlebs var. bacillaris Cori undergo only limited developmentwhen illuminated at the developmental threshold for light intensity7 foot-candles (ft-c) (27 µW/cm²). In the present work,we have found that these low intensity cells have substantialamounts of electron transport components such as ferredoxin-NADPreductase and Cyt c-552 but only trace amounts of the majorantenna components such as the light-harvesting Chl-proteincomplex (LHCP), the LHCP oligomer, CP la, Chi b and the 26.5kDa apo-LHCP; CP I and CPa are at levels comparable to the electrontransport components. Exposure of the low intensity cells tonormal light intensity causes large increases in major antennacomponents and small increases in electron transport components.The kinetics of accumulation of the antenna components Chi band apo-LHCP during greening of dark-grown resting cells atnormal intensities are the same as for Chi a. The low intensitywild-type cells strongly resemble mutants of Euglena low inChi b grown at normal intensities in lacking major antenna components. (Received April 7, 1987; Accepted June 19, 1987)     

Modelling time-series of photosynthesis and comparisons with the fluorescence yield in Chlorella vulgaris: a study of adaptation, inhibition and recovery

Time-series of ¹⁴C uptake and fluorescence yield (i.e., thefluorescence enhancement after addition of the photosyntheticinhibitor DCMU) were measured in Chorella vulgaris at variouslight intensities. Adaptation and recovery processes after alterationof the light intensity were also studied. At a constant lightintensity, both the rate of ¹⁴C uptake and the fluorescenceyield decreased with time. Comparison of time-series data of¹⁴C uptake at different light intensities showed that this phenomenonconsisted of several processes (i.e., at low light intensitiessmall changes in uptake rates were mainly due to photoadaptation,while at higher light intensities relatively larger changesoccurred, as result of photoinhibition). Transfer of an algalsample to low light intensities after a period of exposure toinhibiting light intensities resulted in an exponential recoveryof the ¹⁴C uptake rate with time, coupled with an exponentialrecovery of the fluorescence yield. A mechanistic model is presented,which describes the algal ¹⁴C uptake rate as a function of timeand light intensity. The model includes adaptation, inhibitionand recovery. Six parameters, characterising the algal suspension,have to be estimated from the results of one P versus I curveand one time-series ¹⁴C uptake, which includes a period of recovery.Using these parameters the model can predict the time-courseof ¹⁴C uptake at every constant light intensity, as well aswhen the light intensity is changed during the experiment. Whenapplied to a culture of C. vulgaris, the theoretical valuesclosely approach the actual measurements. The resemblance betweenthe measured time-series of fluorescence yield and the rateof ¹⁴C uptake indicates, that the changes in the rate of ¹⁴Cuptake are due to changes in the photosynthetic apparatus, ratherthan to changes of diffusion of ¹⁴C into the cell.     

An Empirical Test of Olsson's Interaction Model Using Mixtures of Tastants

In 1994, Olsson published a model predicting the intensity andquality of an odor mixture percept on the basis of the intensitiesof the unmixed components. Whether this model can also be usedfor mixtures of dissimilar tasting substances was investigatedfor sucrose/citric acid mixtures. The identification data revealed asymmetrical mixture suppression,which does not support the model. The intensity responses werein accordance with the definitions employed for level independenceand hypo-additivity. However, the intensity judgements suggestdeviations from symmetry and exhibited compromise, which violatestwo other principles. A comparison with previously publisheddata shows that these violations probably occur for other mixturetypes, too. It is concluded that the Olsson interaction modelcannot describe interactions in mixtures of dissimilar tastingcomponents accurately. Chem Senses 21: 283–291, 1996.     

PSYCHOPHYSICAL CHARACTERIZATION OF MUSK CHEMICALS

The odor intensities of six commercial musks: celestolide, muskolactone,galaxolide, musk 36A^®, tonalid^®, and musk ambrette^*were matched by the method of equal odor intensity. Galaxolidewas arbitrarily used as the reference odorant in order to generatea scale for the determination of relative odor intensities.The odor intensities are expressed in terms of Stevens' psychophysicalpower function with the exponent value, b, ranging from 0.43to 0.73.     

Behavioral discrimination of binary mixtures and their components: effects of mixture interactions on coding of stimulus intensity and quality

There is mounting evidence that mixture interactions resultin a physiological response that is different from that predictedfrom observed responses to individual mixture components. Mixtureinteractions that act to alter the neural coding of mixtureintensity (intensity mixture interactions) or quality (patternmixture interactions) may ultimately lead to dramatic differencesbetween the perceived intensities and qualities of a mixtureand its components. These perceptions could be expressed andobserved at the behavioral level. Toward examining this question,we have tested the ability of the Florida spiny lobster (Panulirusargus) to behaviorally discriminate between three odorant compounds[adenosine 5'-monophosphate (AMP), L-glutamate (Glu), and taurine(Tau)] and their binary mixtures through the use of a differentialaversive associative conditioning paradigm. Six groups of lobsterswere used, each being conditioned to avoid one of the singlecompounds or binary mixtures. Behavioral expression of intensitymixture interactions was evident. Preconditioning response magnitudesto binary mixtures were either less than those to their components(e.g. AMP + Glu) or less than predicted from responses to theircomponents (e.g. AMP + Tau). Behavioral expression of patternmixture interactions was also observed. Relationships betweenthe quality of each binary mixture and the qualities of themixture's components were determined from the results of analysisof variance and multidimensional scaling analysis. Analysesincorporated observed responses to all stimuli and ‘predicted’responses to the binary mixtures. Lobsters easily discriminatedbetween the qualities of AMP, Glu and Tau. The quality of themixture of AMP + Glu was different from either component aswell as from the predicted value for this mixture. The mixtureof AMP + Tau was intermediate between both components and wassimilar to the predicted value. The mixture of Glu + Tau, whilemore similar to Glu than to Tau, was different from the predictedvalue, and there was some indication that the Glu was actingto suppress the response to Tau. Behavioral results for AMP+ Tau, which suggest no pattern mixture interactions betweenthese compounds, are in accordance with results of recentlyconducted binding assays which indicate independent receptorsfor these compounds (Olson et al., 1992). Results, especiallyfor AMP + Glu and Glu + Tau, are consistent with results ofour electrophysiological analysis of the effects of patternmixture interactions on coding of stimulus quality and intensityby olfactory receptor cells (Derby et al., 1991a,b). This providesfurther evidence for the effects of peripherally initiated mixtureinteractions on the coding and perception of the quality ofodorant mixtures. ¹Present address: Departments of Psychology and Biology, GeorgiaState University, University Plaza, Atlanta, Georgia 30303,USA     

Action Potentials Evoked by Light in Traps of Dionaea muscipula Ellis

At low light intensities (less than 50 µmol m^–2s^–1) illumination evokes transient depolarization of membranepotential in mesophyll cells of the leaf-trap of Dionaea muscipulaEllis. Darkening causes hyperpolarization approximately symmetricto the response to illumination. The amplitude as well as therate of potential changes depend on light intensity. After exceedinga definite threshold (usually between 50 and 80 µmol m^–2s^–1)the depolarization plays the role of a generator potential andan all-or-none action potential (AP) is released. Switchinglight off in a depolarization phase of an AP does not changeits shape and the amplitude. When the light intensity is increasedto 80–150 µmol m^–2 s^–1 a single lightstimulus triggers two successive APs. The time interval betweenthe two APs decreases with increasing stimulus strength andreaches the minimum between 300 and 400 µmol m^–2s^–1. At higher light intensities the interval increasesagain, and finally only a single AP is triggered. It was shownthat the effect was evoked by light but not by temperature changeaccompanying illumination. An inhibitor of the photosyn-theticelectron transport chain, DCMU, blocked the generator potentialsmediating between light absorption and APs. Residual responsesto light stimuli in plants treated with DCMU had reverse polarityand strongly reduced the amplitudes. (Received September 16, 1997; Accepted January 16, 1998)     

The influence of fluctuating light intensities on species composition and diversity of natural phytoplankton communities

The influence of fluctuating light intensities on phytoplankton composition and diversity was investigated for 49 days under semi-continuous culture conditions with sufficient nutrient supply, using phytoplankton assemblages from Lake Biwa, Japan. Light conditions were either periodically changed from high intensity (100 µmol photons m^-2 s^-1) to low intensity (20 µmol photons m^-2 s^-1) at intervals of 1, 3, 6 and 12 days, or fixed to constant intensities (permanent high and low light levels). All treatments additionally experienced a day:night cycle of 16:8 h. Phytoplankton abundance increased and reached a saturation level on day 19 of the treatment with permanent high light, but increased continuously until the end of the experiment (day 49) in the treatment with permanent low light intensity. In treatments with periodically changing light intensities, the phytoplankton abundance reached saturation levels between these dates. Under phytoplankton abundance saturation, chlorophytes predominated in the treatment with permanent high light, while either cyanophytes or diatoms were abundant under permanent low light intensity. Treatments with changing light supply had chlorophyte- and cyanobacteria-dominated replicates as well as replicates with balanced proportions of both. Furthermore, species diversity, measured by the Shannon index, was low in cultures under permanent light intensity, while slow fluctuating light at the scale of 3 -12 days resulted in an increased diversity index. These results indicate that species composition and diversity of the phytoplankton were affected by the periodically changing light regime in the order of days, and suggest that temporal changes in weather conditions are a major impediment to competitive exclusion of phytoplankton species in nature.     

Several models of suprathreshold quantitative olfactory interaction in humans applied to binary, ternary and quaternary mixtures

Performances were compared of several mathematical models forprediction of the perceived odour intensities of odorant mixturesfrom the odour intensities and some other related propertiesof the components. The models included Berglund's vectorial,an extension of the U model proposed by Patte and Laffort, aUPL model which utilizes exponents of the psychophysical powerlaw, and some simplified models. Data for the model testingwere obtained from literature and from new experimental measurementsin which the odour intensity of vapours of 28 odorous substancesand their 168 binary, 112 ternary, and 28 duplicated quaternarymixtures were matched vs. 1-butanol. The best performance onthe literature data, which have been obtained by the magnitudeestimation methods, was shown by the U model. The best performanceon the new data obtained by the butanol scale method was bythe simplified vectorial and U models; these used constant valuesof the interaction term cos . ^*Presented in a condensed form at the 3rd Congress of ECRO,Pavia, Italy, and in J. Physiol. (Paris), 1978, 74, 19A.     

Chlorophyll a forms in mesophyll and bundle sheath chloroplasts of Zea mays leaves grown at low light intensity

Mesophyll and bundle sheath chloroplasts were prepared fromleaves of Zea mays grown at light intensities of 1.1 and 240µW/cm², respectively. The mesophyll chloroplasts thatdeveloped at the low intensity and bundle sheath chloroplatsthat developed at both low and high intensities showed higherratios of chlorophyll a/b and P700/chlorophylls compared withthe normal ratios found for the mesophyll chloroplasts thathad developed at the high intensity. Derivative absorption spectrophotometryat 77?K revealed that the low intensity mesophyll chloroplastscontained more of chlorophyll a forms with longer wavelengthred bands than high intensity mesophyll chloroplasts. More ofthe longer wavelength forms of chlorophyll a were also presentin the bundle sheath chloroplasts that had developed at lowand high intensities. All these four types of chloroplasts showedtwo peaks of fluorescence, one at 687 hra and the other at 733or 738 nm. In addition to these peaks, the high intensity mesophyllchloroplasts showed a shoulder at 697 nm, and the two typesof bundle sheath chloroplasts showed a shoulder at 680 nm. (Received June 17, 1974; )     

A comparison of net and gross rates of oxygen production as a function of light intensity in some natural plankton populations and in a Synechococcus culture

In vitrorates of gross and net oxygen production were measuredas a function of light intensity in some plankton communitiescollected from Bedford Basin, Nova Scotia, and in a monoclonalculture of Synechococcus. The rate of gross oxygen productionwas measured by a technique in which the stable oxygen isotope,¹⁸O, serves as a photosynthetic tracer Net oxygen productionwas measured by automated Winkler technique. The rate of communityrespiration in the light was then determined by the differencebetween gross and net rates of oxygen production. In the naturalpopulations examined, neither gross nor net oxygen productionrates were significantly inhibited at the highest light intensitymeasured (500–800 µE m^–2 s^–1) In a samplein which the dark respiration rate was small relative to themaximal rate of production [P_max;sensu Platt et al (1980) JMar. Res., 38, 687–701] the rates of ‘light’respiration were 3 times greater. In two other communities,with high rates of dark respiration relative to P_maxthe ratesof ‘light’ respiration were closer to rates of darkrespiration. In the Synechococcus clone, both gross and netoxygen production rates were inhibited at high light intensities.Rates of ‘light’ respiration were found to varyas a function of light intensity. The greatest rates of respirationwere measured in samples incubated at light intensities thatwere just saturating (100 µE m^–2 s^–1). Therates of ¹⁴C production were also measured as a function oflight intensity The photosynthetic quotients, based on ¹⁴C productionrates and gross oxygen production rates, average 1 9     

Perceptual interactions between characteristic notes smelled above aqueous solutions of odorant mixtures

Twenty-two experienced panelists rated odor intensity of aqueous solutions of citral, octen-1-ol-3, and hexanal. The panel assessed unmixed components and mixtures (9 binary and 4 ternary). In sensory sessions dedicated to mixtures (n = 6), evaluation was focused on one target odor, presented at a fixed concentration. All components had lower odor intensity on mixed presentations. In many cases, information obtained from simpler systems was not extended to complex mixtures. In a mixture, the competition between odorant molecules on qualitative aspects (dominance/suppression) imbalanced components contribution, anticipated from the quantitative distribution. Hexanal appeared to be the potentially weaker odorant in paired combinations, whereas octen-1-ol-3 had a lower relative impact on ternary systems. Suppression of the odor of octen-1-ol-3 and a concomitant increase in the odor of hexanal was common to all ternary mixtures. Reciprocal inhibition of octen-1-ol-3 and citral odors through perceptual interactions was suspected. Mutual suppression is suspected to have eased the perception of hexanal intensity.     

Mixing an enclosed, 1300m3 water column: effects on the planktonic food web

The nutrient, phytoplankton, and zooplankton dynamics in threeenclosed water columns (1300 m³) are described. Two of the enclosureswere mixed using a bubbling chamber at depth. Young chum salmon(Oncorhynchus keta) were added to one of the mixed enclosuresand the unmixed enclosure. No other manipulations were imposed.Copepods appeared in large numbers (e.g. especially Pseudocalanusminutus s.l. and Paracalanus parvus) and population growth rateswere estimated. Ctenophora did not appear in large numbers despitepresumably ideal food environments; it is suggested that inone enclosure this is a consequence of fish predation on thectenophores. The fish experienced high mortalities and low growthrates presumably due to unsuitable prey size. Weekly collectionsof sediment permitted isolation of two major sediment contributors,the first from phytoplankton sinking and the second from biogenkfallout associated with herbivore production. It was found thatthe more oligotrophic enclosure (unmixed) experienced proportionallyhigher utilization of organic carbon. Some of these resultsare explained by our data while others require more sophisticatedexperimentation, both in the design of the containers and inthe types of observations.     

An efficient leaf-disc culture method for the regeneration via somatic embryogenesis and transformation of grape (Vitis vinifera L.)

By manipulating hormone levels, light intensities and temperature, we have developed an efficient leaf-disc method for the regeneration of plants via embryogenesis and for transformation in four genotypes of Vitis vinifera L. In MS basal medium supplemented with 1 mg l^-1 6-benzylaminopurine (BAP) and 0.1 mg l^-1 2,4-dichlorophenoxyacetic acid, leaf discs cultured for 2 weeks under dark conditions produced calli in over 80% of the cultures. These subsequently differentiated into pro-embryos and embryos only if kept under conditions of low light intensity (15 µE m^-2 s^-1) for 2 weeks before being transferred to conditions of high light intensity (60 µE m^-2 s^-1). If the calli were directly transferred to high light intensity, the differentiation into embryos was blocked and the calli turned pink. The somatic embryos germinated at a frequency of about 10% on NN basal medium and about 32% on NN medium supplemented with 1 mg l^-1BAP and 0.1 mg l^-1 indole-3-butyric acid. The embryos, however, germinated when pre-exposed to a low temperature of 4°C for 2 weeks. If they were transferred directly to room temperature under conditions of high light intensity (60 µE m^-2 s^-1), shoot buds were produced, whereas under conditions of low light intensity (15 µE m^-2 s^-1) secondary embryogenesis was induced. About 90-95% of the in vitro grown plantlets could be successfully transferred to soil. The above method was also applicable for developing transgenic embryos whose transgenic nature was monitored using #-glucuronidase as a reporter gene.     

The Effects of Temperature and Light Intensity on Embryo Numbers in Wheat Doubled Haploid Production through WheatxMaize Crosses

Triticum aestivumxZea mayscrosses are now widely used in theproduction of wheat doubled haploids to produce homozygous lines.Seasonal effects are known to influence the number of haploidembryos produced through wheatxmaize crosses, but the effectsof temperature and light have not been quantified. This studyinvestigated the effect of temperature and light intensity onhaploid embryo production. New Zealand wheat cultivars weregrown in a glasshouse until booting when they were transferredto growth cabinets at three temperatures (day/night; 17/12,22/17 or 27/22 °C at an irradiance of 250 µmol m^-2s^-1PAR).In another experiment, wheat lines were transferred to a growthcabinet at one of three light intensities (300, 500 or 1000µmol m^-2s^-1PAR at 22/17 °C day/night, with a photoperiodof 16 h). The temperature and light intensity at which pollinationswere made and subsequent fertilisation and embryo developmentoccurred, significantly (P<0.01) influenced the frequencyof haploid embryo production. The optimal temperature for embryorecovery was 22/17 °C. The greatest number of embryos wasproduced at a light intensity of 1000 µmol m^-2s^-1. Thesefindings will result in improvements in the overall efficiencyof the wheatxmaize system for wheat doubled haploid production.Copyright1998 Annals of Botany Company Intergeneric crossing, temperature, light intensity,Triticum aestivum,wheat,Zea mays,maize.