Qualitative and aqualitative intensity components of odour mixtures

The perception of the intensity of components of odorous mixturesis related to the overall mixture intensity in a complex mannerwhich has not so far been adequately modelled. Hypoadditivity,where the total perceived intensity of a mixture is less thanthe sum of the component intensities which arise when the substancesare presented in pure form at equivalent chemical concentrations,has been known for many years. An experiment on series of 56mixtures of amyl butyrate and bergamot at supra-threshold concentrationsfound that the total qualitatively unspecified intensity ofsuch mixtures can be greater than the sum of the identifiedcomponent intensities as judged in the context of the mixture.To reconcile an apparent contradiction, and to bring into onepsychophysical framework results from diverse procedures, amodel of mixed qualitative and aqualitative odour intensityis advanced, incorporating some evidence on the difference betweendetection and recognition processes. Each component in a mixturemay, in this theory, both partially mask the qualitative intensityof the other, and simultaneously convert some part of the other'sintensity into an aqualitative form.     

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.     

Odor intensity of binary mixtures of odorous compounds

This paper presents the MBO model for the perceived intensity of odour mixtures. This model is based on an equation previously reported by our team, intended to model the whole stimulus-response intensity curve of pure odorous compounds. The MBO model was applied to a set of published data, and compared to other published models. The results show a high modelling efficiency of the MBO model compared to other proposed equations, especially for binary mixtures exhibiting significant asymmetry of intensity for different ratios of the two components. Furthermore, the MBO model includes parameters specific to the respective effects of each component in the mixture, which may help to clarify the masking and synergy effects that are often sought in odour mixtures.     

Sequence matters – selective adaptation in electroantennographic response to binary odour mixtures by the Colorado potato beetle

Chemically mediated behaviour of insects is often strongly affected by mixtures of odour stimuli and their temporal characteristics. Both sensory transduction and central processing of odour mixtures can give rise to several different kinds of interaction, which can influence how individual components are perceived and processed. In particular, odour mixtures have been examined in model experiments as premixed binary mixtures in comparison with pure odour stimuli. Only in few experiments, the influence of the temporal structure of odour mixtures on odour perception has been taken into account. Natural odour stimuli often have a pulsed structure and may in general be superimposed on a background of irrelevant or interfering compounds, which can fluctuate with different frequencies, depending on their source. To achieve a better representation of these natural conditions, our odour mixing experiments apply a new kind of stimulation protocol: odours were not premixed but superimposed with a specific time pattern; one odour stimulus was presented as a longer persisting background and the second stimulus was a superimposed short test signal. To gain an overview of odour interaction patterns in the Colorado potato beetle by causing adaptation of one receptor population at naturally occurring levels of concentration and time intervals, electroantennographic recordings were made on excised antennae. A matrix of 12 stimulus compounds led to 132 pairs of compounds tested, each in the role of background and test stimulus. In 64 cases, the interaction was significantly different, when the role of background and stimulus was exchanged. Interaction patterns ranging from no interference (independence) to suppression were found and assigned to four clearly distinguishable types. We discuss that the observed effects of the presentation sequence in odour mixtures may contribute to the mechanisms of olfactory pattern recognition and olfactory contrast perception by insects.     

Confusing tastes and smells: how odours can influence the perception of sweet and sour tastes

This study investigated the relationship between perception of an odour when smelled and the taste of a solution to which the odour is added as a flavorant. In Experiment 1 (E1) sweetness, sourness, liking and intensity ratings were obtained for 20 odours. Taste ratings were then obtained for sucrose solutions to which the odours had been added as flavorants. Certain odours were found to enhance tasted sweetness while others suppressed it. The degree to which an odour smelled sweet was the best predictor of the taste ratings. These findings were extended in Experiment 2 (E2), which included a second tastant, citric acid, and employed four odours from E1. The most sweet smelling odour, caramel, was found to suppress the sourness of citric acid and, as in E1, to enhance the sweetness of sucrose. Again, odours with low sweetness suppressed the sweetness of tasted sucrose. The study demonstrated that the effects of odours on taste perception are not limited to sweetness enhancement and apply to sour as well as sweet tastes. The overall pattern of results is consistent with an explanation of the taste properties of odours in terms of prior flavour-taste associations.     

Evaluation of the key odorants of foods by dilution experiments, aroma models and omission.

The state of the art in aroma analysis is reviewed with emphasis on aroma-recombination studies using synthetic blends of odorants (aroma models) which have been prepared on the basis of analytical data. The model that matches the original aroma is the starting material for omission experiments which are performed to establish the odorants that actually contribute to the aroma. These experiments are discussed in detail for the aromas of two wine varieties, three olive oils of different provenance, French fries, boiled beef and coffee. The results indicate that odorants with higher odour activity values (OAV, the ratio of the concentration to the odour threshold) are frequently essential for the aroma. However, there are exceptions where odorants with high OAVs are suppressed in the aroma and compounds with lower OAVs are important contributors. These findings are discussed in the light of model experiments which have been reported in the literature to obtain an insight into the perceptual interactions of odorants in mixtures.     

贮藏保鲜中SO2伤害对红提葡萄香气组分的影响

采用固相微萃取技术及气相-质谱联用技术对不同SO2漂白伤害程度的红提果实进行香气成分的提取与鉴定,以探讨SO2漂白伤害对贮藏葡萄果实中香气组分的影响.结果表明,果实经漂白伤害后其具有芳香气味的气体所占比重明显下降,主要成分醇类化合物下降最多,而具有刺激难闻气味的酸类化合物所占比重明显上升;此外,4-萜烯醇、正己醇、月桂醇、松油醇、芳樟醇、橙花醇、乙酸萜烯酯及青叶醛等具有葡萄特征性香味的化合物在香气中所占比例明显下降或消失,而异辛醇、1-辛烯-3-醇、壬酸、辛酸、正癸酸、乙酸、己酸、2,6-二叔丁基对甲酚及2-丁基-5-(2-甲基丙基)-噻吩等具有臭味或刺激性气味的化合物出现或所占比重上升.说明,SO2伤害对红提果实香气的影响主要表现为香味化合物所占比重的减少或消失及异味化合物的产生.     

Aroma volatiles of Cynara scolymus and Helianthus tuberosus

Samples of the aroma volatiles of globe artichoke and Jerusalem artichoke were obtained by well established methods and were analysed by routine GC and GC/MS. Eight sesquiterpene hydrocarbons afforded the major group of components (over 42%) in globe artichoke samples, with β-selinene (ca 32%) as the main constituent. Previously reported caryophyllene could not be detected. α-Cedrene was found to have globe artichoke aroma characteristics on odour evaluation of separated components at an odour port at the exit of the GC column. Jerusalem artichoke samples contained one major component (β-bisabolene, ca 51%) and a range of saturated long-chain hydrocarbons (ca 22%). The sesquiterpene presumably contributes appreciably to the characteristic flavour of Jerusalem artichoke. Both types of artichoke gave a low concentration of total volatiles.     

INTERRELATIONS AMONG LIKING ATTRIBUTES FOR APPLE PIE: RESEARCH APPROACHES AND PRAGMATIC VIEWPOINTS

Liking is a key measure for applied product development. All too often, however, the liking attributes are simply reported, but other than analyzing overall liking ratings no other analysis is done on the ratings. Much more remains for applied product testers to learn from these liking attributes. This paper presents a detailed analysis of the interrelations among different liking attributes for apple pie. It shows that panelists discriminate among samples using different liking scales, but many of these scales correlate with each other creating a great deal of redundancy in the list of attributes. Factor analysis reveals one major dimension for liking of the entire pie, and three dimensions for liking of slices. A different way of analysis shows potentially more utility for developers. A linear model relating overall liking to each attribute liking reveals different slopes, suggesting different importance levels for the attribute liking scales. Furthermore, one can create an integrated liking model. The liking ratings can be combined into a single, overall product model, allowing the researcher to understand how changes in one liking attribute simultaneously affect all other liking attributes.     

Binary taste mixture interactions in prop non-tasters, medium-tasters and super-tasters

It is generally assumed that the mutual, but asymmetric, suppression of the components in binary taste mixtures is an invariant property of the human psychophysical response to such mixtures. However, taste intensities have been shown to vary as a function of individual differences in sensitivity, indexed by the perceived bitterness of 6-n-propylthiouracil (PROP). To determine if these variations in taste perception influence taste mixture interactions, groups of PROP super-, medium- and non-tasters assessed four binary taste mixtures: sweet-bitter [sucrose/quinine hydrochloride (QHCl)], sweet-sour (sucrose/citric acid), salty-bitter (NaCl/QHCl) and salty-sour (NaCl/citric acid). In each experiment, subjects received factorial combinations of four levels of each of two tastants and rated individual taste intensities and overall mixture intensity. For each taste quality, super-tasters typically gave higher ratings than either medium- or non-tasters, who tended not to differ. There were also group differences in the interactions of the mixtures' components. Super-tasters rated the overall intensity of the mixtures, most likely reflecting integration of the taste components, as greater than medium- and non-tasters, who again showed few differences. In sweet-bitter mixtures, non-tasters failed to show the suppression of sweetness intensity by the highest QHCl concentration that was evident in super- and medium-tasters. These data show that the perception of both tastes and binary taste mixture interactions varies as a function of PROP taster status, but that this may only be evident when three taster groups are clearly distinguished from one another.     

INFLUENCE OF GLASS SHAPE ON WINE AROMA

Differences in the physical shape of glasses could potentially influence proportions of aromatic compounds trapped in the headspace of a wine glass, altering the perception of a wine. Blindfolded, naïve subjects assessed the aroma of a California Cabernet Sauvignon presented in 4 different glasses. Two of these were from a speciality line of crystal wine glasses, one designed for Chardonnay, the other for Bordeaux/Cabernet Sauvignon. A restaurant-style wine glass and a leaded crystal goblet were the remaining vessels used. The nonexpert judges assessed wine aroma for total intensity, fruitiness, vinegariness, oakiness, and mustiness, as well as liking.
The only significant difference found in the aroma intensity ratings was for the Bordeaux glass, which was rated as having a significantly lower total intensity than the other three glasses. However, several significant correlations were found between the attribute intensity ratings and physical characteristics of the glasses. This suggests that the glass does have a limited, but subtle, impact upon the olfactory experience of wines.     

An assessment of binary mixture interactions for nine sweeteners

Binary mixtures of acesulfame K, aspartame, sodium cyclamate,fructose, glucose, stevioside, sodium saccharin, sucrose andxylitol were assessed using factorial mixture designs. A simpleadditive model was used to generate predictions for the sweetnessof the mixtures and these predicted responses were comparedto the observed sweetness ratings of the mixtures. It was foundthat the mixtures tended to exhibit superadditivity at low concentrations,additivity at intermediate concentrations and subadditivityat high concentrations. Synergistic and suppressive effectsin the mixtures were evaluated by comparing mixture responsesto the sweetness ratings of ‘self-mixtures’. Self-mixturedata were generated by treating a mixture of a substance withitself as if it were a mixture of two different substances.Synergism was defined as a mixture response that was greaterthan the sweetness of the component self-mixtures, and suppressionwas defined as a mixture response that was less than the sweetnessof the component self-mixtures. Of the 31 binary mixtures studied,18 showed synergism, two showed suppression and 11 did not differsignificantly from their components. It is hypothesized thatmultiple sweetness receptors or release from bitter suppressionmay account for the synergistic effects.     

Intensity and hedonic judgments of taste mixtures: an information integration analysis

Anderson's (1981) information integration approach was usedto examine taste mixture integration for intensity and hedonicjudgments of sucrose/sodium chloride and sucrose/citnc acidsolutions. In Experiment I, total intensity and hedonic ratingswere made for factorial combinations of sucrose and sodium chlorideor citric acid. The total intensity judgments produced an integrationpattern characterized by extreme subadditivity at high soluteconcentrations. (Subadditivity refers to the tendency for totalmixture intensity to be rated as less than the sum of the unmixedcomponent intensities.) The intensity judgment integration patternswere essentially identical for the two mixture types. However,the pattern of integration for the sucrose/sodium chloride andsucrose/citric acid mixtures differed for the hedonic ratings.Sucrose tended to eliminate the unpleasantness associated withincreasing concentrations of citric acid, while it only modulatedthis trend for sodium chloride. In Experiment II, subjects ratedthe individual sweet, salty and sour components of the mixturesto determine whether mixture suppression of the component tastescould account for the subadditivity of the total intensity judgmentsand/or the pattern of results for the hedonic ratings. It wasfound that sucrose suppressed the sour component of the sucrose/citricacid mixtures more than the salty component of the sucrose/sodiumchloride solutions This difference in component suppressionseemed to account for the hedonic integration patterns of thetwo mixture types which suggests that mixture suppression isan important factor to consider when predicting the pleasantnessof simple taste mixtures.     

SENSORY-SPECIFIC SATIETY FOR SELECTED BREAD PRODUCTS1

Subjects rated the intensities of 42 different attributes for 26 different bread products. Principal component analysis was used to categorize the breads based on their attribute ratings. The first two principal components were interpreted as a richness dimension and a nutrition/fiber dimension. The influence of these dimensions on sensory-specific satiety in bread products was investigated. Subjects tasted and rated their liking of small portions of a set of bread products representative of the extremes of the richness dimension and the nutrition/fiber dimension before and after eating a 400 calorie serving of one of the breads. Measurements of hunger were taken before and after the meal. Bread appeared resistant to sensory-specific satiety. The richness of the breads did not affect the amount of sensory-specific satiety. The high nutrition/fiber breads decreased hunger and tended to decrease liking more than the low nutrition/fiber breads.     

THE EFFECT OF INFORMATION RELATED TO FAT CONTENT AND TASTE ON CONSUMER RESPONSES TO A REDUCED-FAT FRANKFURTER AND A REDUCED-FAT CHOCOLATE BAR

The effects of product information on responses to frankfurter sausages and chocolate bars were studied by comparing sensory and hedonic ratings in two conditions: blind tasting and tasting with information present. Furthermore, the effect of information alone was investigated by having the subjects rate the expected sensory and hedonic intensities of the products on the basis of packages with different claims. Three groups of subjects were tested by giving them different information: The basic group (no added claims, n=31), the reduced-fat group (products claimed to have reduced-fat, n=29) and the flavorful group (products claimed to have full meat/chocolate flavor, n=31). Product information increased the rated pleasantness of the frankfurter in all three information groups compared to the blind ratings. The information did not affect the pleasantness of the chocolate bars. The expected attribute intensities of the frankfurters and chocolates were rated lower by the reduced-fat group than by the other groups. Overall, the effect of product information was more clearly seen in ratings of sensory attributes than in pleasantness ratings.     

Volatile flavour components of mango fruit

An essence of fresh Venezuelan mango fruit obtained by well-established procedures possessed the characteristic aroma of the fruit. It was analysed by GC/MS using both EI and Cl. The fruit produced a relatively small quantity of aroma volatiles (ca 60 μg/kg fresh fruit), less than that obtained from many similar tropical fruits. Terpene hydrocarbons comprised ca 68% of the sample, eight monoterpenes contributing ca 54% and four sesquiterpenes contributing ca 14%. Important constituents included α-pinene, car-3-ene, limonene, γ-terpinene, α-humulene, β-selinene, acetophenone, benzaldehyde and a dimethylstyrene. Car-3-ene (26%) was the major constituent, and on odour evaluation of separated components at an odour port during GC, the peak due to this compound was described as having an aroma of mango leaves. This compound has not previously been detected among mango volatiles. The only other component providing mango aroma was a dimethylstyrene, and this too is a new mango volatile.     

A comparison of the detection thresholds of odour mixtures and their components

It was the purpose of the present study to investigate whetherthe perception of odour mixtures differs from the perceptionof their components with regard to (i) the reliability of detectionthreshold measurements and (ii) the threshold values themselves.Detection thresholds for a variety of unmixed odorants and 3-,6- or 12-component mixtures were determined for a total of 44subjects, tested repeatedly in five separate sessions usingsniff bottles and an ascending staircase method. Threshold determinationsfor the mixtures were found to be as reliable as for the unmixedsubstances, with intra- and interindividual variability in thresholdvalues actually decreasing with increasing stimulus complexity.The four mixtures for which a systematic comparison of the thresholdvalues of components in the mixed and unmixed state was conductedfailed to provide evidence for the hypo-additive effects ofcompromise or compensation, but rather suggested a positive,sub-threshold interaction between components and possibly evenenhancement. Finally, a significant improvement in individualthreshold scores was seen across test sessions, with experiencedpanelists showing the most stable performance.     

Relationships among taste qualities assessed with response-context effects

Psychophysical judgments often depend on stimulus context. For example, sugar solutions are judged sweeter when a tasteless fruity aroma has been added. Response context also matters; adding a fruity aroma to sugar increases the rated sweetness when only sweetness is considered but not when fruitiness is judged as well. The interaction between stimulus context and response context has been explored more extensively in taste-odor mixtures than in taste-taste mixtures. To address this issue, subjects in the current study rated the sourness of citric acid mixed with quinine (bitter), sodium chloride (salty), and cyclamate (sweet) (stimulus context). In one condition, subjects rated sourness alone. In another, subjects rated both sourness and the other salient quality (bitterness, saltiness, or sweetness) (response context). Sourness ratings were most sensitive to response context for sour-salty mixtures (i.e., ratings of sourness alone exceeded ratings of sourness made simultaneously with saltiness) and least sensitive to context for the sour-sweet mixtures (sourness ratings made under the 2 conditions were essentially identical). Response-context effects for the sour-bitter mixture were nominally intermediate. The magnitudes of these context effects were related to judgments of qualitative similarity between citric acid and the other stimuli, consistent with prior findings. These types of context effects are relevant to the study of taste-taste mixture interactions and should provide insight into the perceptual similarities among the taste qualities.     

SENSORY PROPERTIES AND CONSUMER PERCEPTION OF 'HOME-MADE'AND COMMERCIAL DAIRY ICE CREAM

Sensory properties and consumer perception of 2 'home-made'and 4 commercial dairy ice creams were examined. Conventional profiling by a trained panel found that most samples differed significantly in all attributes, but distinction of 'home-made'from commercial products was limited to few attributes. Principal component analysis separated the 'home-made'products from the commercial ones mainly on the basis of differences in appearance, aroma, creamy flavors and textural attributes. A consumer group (n=105) recorded preconception of 'home-made'ice cream acceptance, then received the product samples, in unlabeled condition, for assessment of degree of liking (DOL) and for identification as 'home-made'or commercial. Internal preference mapping of the DOL ratings showed that consumers were more closely grouped around samples which had higher intensities of certain attributes. Higher 'denseness', 'vanilla'aroma and 'buttery'flavor, were associated with more liking for commercial products. The 'home-made'high fat sample, although liked, tended to be grouped with commercial products. More marked textural attributes of 'ice crystals'and 'breakage'aided identification of the low-fat 'home-made'formulation, which was less liked overall. Overall, differences between the 'home-made'and commercial samples were small but consumer perception of the term 'home-made'was viewed favorably for dairy ice cream.