CONSTRUCTION OF SENSORY VOCABULARIES FOR PROFILING FOOD

Sensory profiling laboratories rate products for sets of attributes. Order of tasting and carry-over effects from sample to sample are widely recognized. However, within samples, work investigating the possibility of effects due to the order of rating attributes and attribute to attribute carry-over has not been reported. Individual attributes were classified according to whether their presence in a product was perceived to be desirable or not. For both yoghurt and cheese, sample ratings for each attribute were compared when attributes perceived as desirable preceded those perceived as undesirable and vice-versa. In both stimuli, there was evidence that desirable attributes were biased to a lower value when preceded by undesirable ones. Similarly, negative attributes were biased downwards when preceded by desirable ones. For absolute scores, these effects, albeit small, make randomizing attribute ordering desirable. However, lack of evidence of interactions between samples and attribute ordering suggests comparative differences between samples are unaffected.     

COGNITIVE ASPECTS OF DIFFERENCE TESTING: MEMORY AND INTERSTIMULUS DELAY

There are many ways in which a laboratory difference test differs from 'real life' discrimination of foods. One of these is the interval of time between tasting the two stimuli to be discriminated. To investigate this, judges performed same-different discrimination tests using a citrus flavored beverage as a medium. The time interval between tasting the standard and comparison stimuli was varied. In this initial study, short intervals of zero, 30, 60 s were examined. For judges unfamiltar with the stimuli, performance deteriorated as the time interval increased. For judges familiar with the stimuli, the zero time interval elicited best performance but there was no decrease in performance when the interval was increased from 30 to 60 s. The results were explained by hypothesizing different types of memory trace for the standard stimulus being utilized for comparison with the comparison stimulus.     

TRIANGULAR DIFFERENCE TESTING: REFINEMENTS TO SEQUENTIAL SENSITIVITY ANALYSIS FOR PREDICTIONS FOR INDIVIDUAL TRIADS

Using a model system of 3mM NaCl and purified water, predictions were made for subjects’ability to discriminate the odd sample in a set of nine triadic tasting sequences associated with the triangle test. With such individual triads rather than triangular testing protocols which involve more than one triad, it was found necessary to modify the regular Sequential Sensitivity Analysis. The modification required a consideration of sensory adaptation effects caused by repeated tasting of the same stimulus in some of the sequences. Further confirmation was also obtained for the order of magnitude of signal strengths of water and NaCl stimuli tasted after water or NaCl prerinses.     

THURSTONIAN MODELS AND VARIANCE I: EXPERIMENTAL CONFIRMATION OF COGNITIVE STRATEGIES FOR DIFFERENCE TESTS AND EFFECTS OF PERCEPTUAL VARIANCE

For the triangle, duo‐trio, same‐different and 2‐AFC methods, using a model system, mean d′ values for the same subjects, discriminating between the same taste stimuli, were not significantly different. This confirmed the postulated cognitive strategies used for these methods in their respective Thurstonian/signal detection models. Introduction of perceptual variance as a result of the effects of sequences of tasting within a test, forgetting stimulus perceptions and τ‐criterion variation resulted in the 2‐AFC eliciting a significantly higher d′ than the other three methods. Yet, after a warm‐up procedure, which not only significantly increased values of d′ for all methods but also aligned subjects' τ‐criteria, the same‐different test had a d′ comparable to that of the 2‐AFC, while both d′ values were significantly higher than those of the triangle and duo‐trio. This suggested that effects of memory were more important those of sequence of tasting.     

Revisiting sugar-fat mixtures: sweetness and creaminess vary with phenotypic markers of oral sensation

Genetic variation in oral sensation presumably influences ingestive behaviors through sensations arising from foods and beverages. Here, we investigated the influence of taste phenotype [6-n-propylthiouracil (PROP) bitterness, fungiform papillae (FP) density] on sweet and creamy sensations from sugar/fat mixtures. Seventy-nine subjects (43 males) reported the sweetness and creaminess of water or milk (skim, whole, heavy cream) varying in sucrose (0-20% w/v) on the general Labeled Magnitude Scale. Sweetness grew with sucrose concentration and when shifting from water to milk mixtures--the growth was greatest for those tasting PROP as most bitter. At higher sucrose levels, increasing fat blunted the PROP-sweet relationship, whereas at lower levels, the relationship was effectively eliminated. Perceived sweetness of the mixture exceeded that predicted from the sum of components at low sucrose concentrations (especially for those tasting PROP most bitter) but fell below predicted at high concentrations, irrespective of fat level. Creaminess increased greatly with fat level and somewhat with sucrose. Those tasting PROP most bitter perceived greater creaminess in the heavy cream across all sucrose levels. Perceived creaminess was somewhat lower than predicted, irrespective of PROP bitterness. The FP density generally showed similar effects as PROP on sweetness and creaminess, (but to a lesser degree) and revealed potential taste-somatosensory interactions in weakly sweet stimuli. These data support that taste phenotype affects the nature of enhancement or suppression of sweetness and creaminess in liquid fat/sugar mixtures. Taste phenotype effects on sweetness and creaminess likely involve differential taste, retronasal olfactory, and somatosensory contributions to these perceptual experiences.     

Effect of mixing on the washout and steady-state performance of continuous cultures

The effects of mixing on the critical mean holding time for washout and the steady state performance of growth processes in continuous flow reactors are investigated. Macromixing, micromixing, and cell recycle arc considered. The tanks-in-series model composed of N completely mixed flow reactors, the dispersion model, the plug flow model, and a combined model composed of a plug flow reactor and a continuous stirred tank flow reactor connected in series arc used to represent the macro-mixing or residence time distribution. The extreme cases of micromixing, namely, complete segregation and maximum mixedness, as well as intermediate states of micromixing are investigated to determine their effects on washout and the occurence of multiple steady states. A technique for predicting the maximum mixedness washout condition from a knowledge of the residence time distribution is presented and used to determine the washout condition for the dispersion model under maximum mixedness conditions.     

Suppression of Bitterness by Sodium: Variation Among Bitter Taste Stimuli

Taste interactions between salts (NaCl, LiCl, KCl, L-arginine:L-asparticacid, Na-acetate and Na-gluconate) and bittertasting compounds(urea, quinine HCI, magnesium sulphate, KCI, amiloride HCI andcaffeine) were investigated. In each study binary combinationsof three or four concentrations of one bitter compound withfour concentrations (0, 0.1, 0.3 and 0.5 M) of one salt wererated for bitterness and saltiness using the method of magnitudeestimation. In most cases, perceived bitterness was suppressedby salts, although the degree of suppression varied. In general,bitterness suppression was not accompanied by an equivalentreciprocal suppression of saltiness. Only MgSO₄ and amiloridehad suppressing effects on the saltiness of NaCl at the intermediateconcentrations and no bitter compound affected the saltinessat the high concentrations of NaCl. Since salt suppressed thebitterness of urea effectively, a detailed analysis of suppressionof the bitterness of urea by different salts was conducted.Those studies indicated that the key component in this effectwas the sodium or lithium ion for two reasons: first, all threesodium salts and the lithium salt had a suppressive effect onbitterness, whereas KCl did not; secondly, the effect of a salton suppression of the bitterness of urea was independent ofits perceived saltiness; that is, NaCl, Na-acetate (which isperceived as less salty than NaCl), and Na-gluconate (whichis perceived as less salty than Na-acetate) reduced bitternesscomparably. These results suggest that there is a major peripheralcomponent to the suppression of the bitterness of urea, andperhaps other bitter tasting compounds, by sodium. Chem. Senses20: 609–623, 1995.     

Thermosensory intensity and affect throughout the perceptible range

The thermosensory system was evaluated psychophysically in 12 healthy volunteers, spanning the full range of tolerable temperatures. Subjects provided ratings of (1) perceived thermal intensity, (2) perceived pleasantness or unpleasantness, and (3) perceived pain intensity after placing either one hand or foot in a temperature controlled water bath. Of particular interest were the interrelationships among the three perceptual measures, and differences between heat and cold. The relationship between perceived intensity and (un)pleasantness was different for hot vs cold stimuli. Specifically, for a given perceived thermal intensity, cold stimuli were rated as less pleasant or more unpleasant than hot stimuli. Similarly, for a given pain intensity, cold stimuli were rated as more unpleasant than hot stimuli. As warm temperatures increased and as cold temperatures decreased, stimuli were perceived as being unpleasant before they were perceived as being painful. The difference in transition temperatures for unpleasantness vs pain for heat averaged 1.4 degrees C, while the same difference for cold averaged 5.6 degrees C. Thus, there was a fourfold difference in the range of unpleasant but non-painful cold vs hot temperatures. Pain intensity and unpleasantness ratings were significantly higher for heat stimuli applied to the foot vs hand. In contrast, there was no significant body site difference for pain intensity or unpleasantness ratings of cold stimuli. All of these results reveal important differences in the processing of cold vs hot stimuli. These differences could be exploited to differentiate processing relevant to discriminative vs affective components of somesthetic perception, in both the innocuous and noxious ranges.     

SAME-DIFFERENT DISCRIMINATION TESTS WITH INTERSTIMULUS DELAYS UP TO ONE DAY

There are many ways in which a laboratory difference test differs from 'real life'discrimination of foods. One of these is the interval of time between tasting the two stimuli to be discriminated. To investigate this, Cubero et al. (1995) investigated interstimulus delays of up to 1 min. for the same-different test, using a citrus flavored beverage as a medium. The present study extended this research by increasing the interstimulus delays up to 1 day. For judges unfamiliar with the stimuli, performance deteriorated as the time interval increased. For judges more familiar with the stimuli, performance deteriorated but not as much. The results were compatible with Cubero et al.'s hypothesis that different types of memory trace for the first (standard) stimulus were utilized for comparison with the second (comparison) stimulus.     

Studying Mixing in Non-Newtonian Blue Maize Flour Suspensions Using Color Analysis

Background

Non-Newtonian fluids occur in many relevant flow and mixing scenarios at the lab and industrial scale. The addition of acid or basic solutions to a non-Newtonian fluid is not an infrequent operation, particularly in Biotechnology applications where the pH of Non-Newtonian culture broths is usually regulated using this strategy.

Methodology and Findings

We conducted mixing experiments in agitated vessels using Non-Newtonian blue maize flour suspensions. Acid or basic pulses were injected to reveal mixing patterns and flow structures and to follow their time evolution. No foreign pH indicator was used as blue maize flours naturally contain anthocyanins that act as a native, wide spectrum, pH indicator. We describe a novel method to quantitate mixedness and mixing evolution through Dynamic Color Analysis (DCA) in this system. Color readings corresponding to different times and locations within the mixing vessel were taken with a digital camera (or a colorimeter) and translated to the CIELab scale of colors. We use distances in the Lab space, a 3D color space, between a particular mixing state and the final mixing point to characterize segregation/mixing in the system.

Conclusion and Relevance

Blue maize suspensions represent an adequate and flexible model to study mixing (and fluid mechanics in general) in Non-Newtonian suspensions using acid/base tracer injections. Simple strategies based on the evaluation of color distances in the CIELab space (or other scales such as HSB) can be adapted to characterize mixedness and mixing evolution in experiments using blue maize suspensions.     

TEMPORAL ASPECTS OF HEDONIC RESPONSES1

Continuous measurement of degree of liking for chocolate milk varying in milkfat (0–36%) showed significant fluctuations over the 80 s test period. For 17 judges, samples with intermediate fat levels received maximum liking 20–30 s after placement in the mouth then declined to neutral (neither like nor dislike). The nonfat sample gave a flat, neutral response across time while the 36% fat sample was initially neutral, reached maximum dislike at approximately 20 s then gradually returned to neutral. For 5 judges, increasing degree of liking was expressed for increasing fat levels. For both groups, maximum and minimum time-intensity (T-I) measurements correlated significantly with results from conventional hedonic scaling on a 20-cm line. Degree of liking was unaffected by swallowing or expectorating samples by either T-I or scaling. Thus, similar to perceived intensity, hedonic responses are not static, but show systematic changes during tasting, i.e., from the time the sample is placed into the mouth, through expectoration (or swallowing) until a steady (usually neutral) state is reached.     

Qualitative psychophysical studies on the gustatory effects of the sweet tasting proteins thaumatin and monellin

The gustatory effects of the sweet tasting proteins thaumatinand monellin were studied aftei application to small areas onthe anterior third of the tongue or to single fungiform papillae.The sweet sensation caused by thaumatin and monellin developedmore slowly, but reached a higher intensity and had a longerduration than that given by sucrose. Also, the response evokedby these sweet tasting proteins was more pronounced at the lateraledges, whereas that evoked by sucrose was stronger at the tipof the tongue. The taste modifier, miraculin, had no noticeableeffect on the sweet taste elicited by thaumatin, monellin andsucrose. Gymnemic acid abolished the sweet taste of all threecompounds. Experiments with time intervals of less than one minute betweenstimuli showed strong crossadaptation between thaumatin andmonellin, between the two proteins and sucrose, and betweenthe two proteins and miraculin-induced sweet taste of citricacid. While the differences in response to the sweet tasting proteinsand sucrose may be taken as evidence in favor of the existenceof more than one kind of sweet receptor, the cross-adaptationnoted between the various substances tested, would seem to indicatethat, at some point, they engage a common neural mechanism. ¹On leave from Dept. of Prosthetics, Faculty of Odontology,Karolinska Institutet. Present address: Dept. of Histology,Karolinska Institutet, S-104 01 STOCKHOLM, Sweden.     

Recalling sweet taste intensities in the presence and absence of other tastes

Memory for sweet taste intensities in different media during 125 h was investigated using three concentrations (w/w) of sucrose: 4.21% (0.125 M), 8.28% (0.25 M) and 16.06% (0.5 M). Sucrose was dissolved in four media [water with no tastant and water with 0.73% (0.125 M) sodium chloride, 0.04% (0.002 M) citric acid and 0.04% (0.002 M) caffeine] as standard stimuli. Subjects (n = 39) were assigned into four groups, each group performing the memory task in one medium only. After tasting each standard the subjects reproduced the subjective taste intensity immediately and after 12 min and 1, 5, 25 and 125 h by mixing portions of low (0%) and high (29.75%; 1 M) concentrations (w/w) of sucrose and by tasting and retasting (ad libitum procedure). The produced sucrose concentrations increased significantly from the first session to the 125 h time interval. There was a significant difference between immediately reproduced standard concentrations and concentrations produced after all time intervals. Relative differences from standard (delta i/i) differed only between concentrations produced immediately and after 125 h time interval. The low (4.21%) concentration showed larger differences from standard than the high (16.06%) concentration. The added tastant had no effect on the results.      

Phenylthiocarbamide taste sensitivity and its relationship to growth variation

The hypothesis that there is a relationship between the tasting polymorphism and growth variation was tested on a sample of 425 Negro elementary school children. Twenty-seven non-tasters were found by testing with impregnated papers; 13 were male, 14 female, indicating no sex differences in this group. Matchedpair comparisons indicated no differences in weight, a tendency for tasters to be taller, and a stronger tendency for tasters of both sexes to be skeletally more mature. It was felt that the tendency for tasters to be taller might reflect their more advanced maturation status. The relationship to skeletal maturation might be indicative of the decreased thryoid activity found in other studies of phenylthiocarbamide tasting.     

Excitability cycles of direct cortical responses during elaboration of conditioned defense reflexes in dogs]

Direct cortical responses (DCRs) to paired stimuli were studied in chronic experiments in dogs during elaboration of classical and instrumental defensive conditioned reflexes. The DCRs were recorded with 20 to 250 ms intervals between stimuli. Paired and single electrical stimulations of the middle suprasylvian gyrus given with a frequency of one per second were used as conditioned stimuli and were reinforced in a similar way. During electrical cutaneous stimulation of the dog's paw and to an even greater extent during isolated action of the conditioned stimulus the initial negativity of the testing DCR became shorter and the degree of its depression diminished. In the case of a following period of facilitation, its degree became greater. It was higher at a distance of 4 to 5 mm from the point of stimulation than at a distance of 2 to 3 mm. During isolated action of the conditioned stimulus, the degree of facilitation was higher than at the period of the possible action of the unconditioned stimulus. The greatest shorterning of the DCR excitability cycle was observed immediately before and during the conditioned lifting of the dog's paw. Excitability cycles of DCR, and possibly of other evoked potentials as well, are a more sensitive indicator of the function state of the cerebral cortex than responses to single stimuli. For this reason it appears promising to use them in studying conditioned reflexes.     

Face and voice attractiveness judgments change during adolescence

Attractiveness judgments are thought to underpin adaptive mate choice decisions. We investigated how these judgments change during adolescence when mate choice is becoming relevant. Adolescents aged 11–15 evaluated faces and voices manipulated along dimensions that affect adults' judgments of attractiveness and that are thought to cue mate value. Facial stimuli consisted of pairs of faces that were more or less average, more or less feminine, or more or less symmetric. The adolescents selected the more average, symmetric, and feminine faces as more attractive more often than chance, but judgments of some facial traits differed significantly with rater age and sex, indicating a role of development in judgments of facial cues. Vocal stimuli consisted of pairs of voices manipulated to raise or lower perceived pitch. The older but not younger girls selected the lower-pitched male voices as more attractive at rates above chance, while the younger but not older boys selected the higher-pitched female voices as more attractive. Controlling for rater age, increased pubertal development was associated with increased selection of lower-pitched boys' voices by girls and decreased selection of feminized male faces by boys. Our results are the first to demonstrate that adolescents show somewhat similar attractiveness judgments to adults in age-matched stimuli and that age, sex, and pubertal development have measurable effects on adolescents' attractiveness judgments. They suggest that attractiveness judgments in humans, at least for some traits, are facultatively calibrated to the individual's life stage, only reaching adult values upon sexual maturity when mate choice decisions become relevant.     

Spatio-temporal parameters and the three-dimensionality of apparent motion: evidence for two types of processing

The minimum ISI required for perceiving apparent motion in depth was measured as a function of the 2D separation of stimuli and the physical separation of stimuli in depth. It was found that temporal thresholds increased as a function of the separation of stimuli in depth. This supports the results of previous research indicating that the perceived three-dimensionality of apparent motion in depth increases with ISI. In addition, the rate of threshold increase was significantly greater in displays with short 2D separations of stimuli than in displays with large 2D separations. This robust functional dissociation of thresholds indicates that the short-range system may be involved in the processing of apparent motion in depth in the former case.     

影响干红葡萄酒感官质量的因素分析

以116个干红葡萄酒酒样为样本,通过多项式回归构建出反映陈酿时间、酒精含量、残糖量以及是否在橡木桶中陈酿与感官质量之间关系的方程．并且通过回归方程的预测,确定出感官分析结果与各影响因素之间的数量关系。     

Effects of visual priming on taste-odor interaction

Little is known about the influence of visual characteristics other than colour on flavor perception, and the complex interactions between more than two sensory modalities. This study focused on the effects of recognizability of visual (texture) information on flavor perception of odorized sweet beverages. Participants rated the perceived sweetness of odorized sucrose solutions in the presence or absence of either a congruent or incongruent visual context. Odors were qualitatively reminiscent of sweet foods (strawberry and caramel) or not (savoury). Visual context was either an image of the same sweet foods (figurative context) or a visual texture derived from this product (non-figurative context). Textures were created using a texture synthesis method that preserved perceived food qualities while removing object information. Odor-taste combinations were rated sweeter within a figurative than a non-figurative context. This behaviour was exhibited for all odor-taste combinations, even in trials without images, indicating sustained priming by figurative visual context. A non-figurative context showed a transient sweetening effect. Sweetness was generally enhanced most by the strawberry odor. We conclude that the degree of recognizability of visual information (figurative versus non-figurative), influences flavor perception differently. Our results suggest that this visual context priming is mediated by separate sustained and transient processes that are differently evoked by figurative and non-figurative visual contexts. These components operate independent of the congruency of the image-odor-taste combinations.