Intensity Time Research Articles

Time Intensity Parameters of Sweetness Perceptions in Lager Beers

Lagers are generally brewed to minimise the final sugar content. Residual saccharides, derived from starch, contribute little to sweetness. Despite this, certain lagers exhibit sweet characters. These have not been explored in lagers, but are thought to originate from: maltol; 4-hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF); 4-hydroxy-2(or 5)-ethyl-5(or 2)-methyl-3(2H)-furanone (HEMF); hydroxymethylfurfural (HMF); diacetyl; and certain esters (ethyl acetate, ethyl caproate, ethyl caprylate, and iso amyl acetate). This study used time-intensity (TI) profiling, employing 13 assessors, to study sweetness in 10 lagers, scored similarly for sweetness in rank rating. Single intensity maxima were obtained with all products and all assessors. Data were analysed using ANOVA of curve parameters and non-centred and centred principal component analyses (PCA). In ANOVA only the area under curve (Atot) values differed significantly. However, shape of TI profile, or signature, differed between assessors who could on this basis be divided into two groups. In the multivariate data analyses, non-centred PCA showed significant differences between lagers, parametric modelling and conventional PCA did not. However TI profile data suggested sweetness intensity perceived over the 120 seconds following ingestion could differ, although differences in scoring in rank rating were not significant.

Molecular mobility and the perceived sweetness of sucrose, fructose, and glucose solutions

The general relationship proposed in the literature between molecular mobility of water and the perceived sweetness was investigated. Sucrose, fructose, and glucose solutions, ranging in concentration from 0.15 mol/l to saturation were investigated. The rotational and translational mobilities of water and sugar molecules were monitored using a suite of nuclear magnetic resonance (NMR) techniques. The perceived sweetness was studied using the Time–Intensity (TI) method. Overall, it was found that the perceived sweetness of the sugar solutions, as quantified by the TI method, did not correlate with the measured NMR molecular mobility parameters.

Modelling and analysis of dynamic sensory data

Time intensity (TI) data from earlier reported studies on cream cheese and salad dressing were used to develop models based on both polynomials and ordinary differential equations (ODE) that can be used to describe and interpret TI-data. Polynomials were thus fitted to experimental data. By taking the first and second derivatives of the polynomials one gets new polynomials that express how the perceived intensity changes with time. By integrating the original polynomial one gets a new polynomial that expresses how the classical TI-parameter “Area Under the Curve” is accumulated with time. Graphical display of all these types of polynomials gives an immediate and easily interpretable impression of the influence of different experimental factors on the time dependent perception. In the ODE models experimental factors, both formula and process conditions, were taken into account. Thus it was possible to develop equations that can be used for prediction of TI-curves for intermediate experimental settings.

TIME INTENSITY PROFILES OF FLAVOR POTENTIATORS (MSG, IMP, GMP)

ABSTRACTThis research characterized the time‐intensity (TI) profiles of monosodium glutamate (MSG), disodium 5′‐inosinate (IMP), and disodium 5′‐guanylate (GMP). Twenty subjects rated total taste intensity of single solutions of 2.5, 5 and 10 mM MSG, 0.63 and 2.5 mM IMP and GMP, and some of their mixtures, using the TI method. The profiles generated were atypical of other taste modalities. Time to maximum intensity waslong (16–20s), followed by a plateau at maximum intensity, and a persistent aftertaste (50–96s duration). Maximum intensities of the samples varied (p < 0.001), with mixtures of 10 and 5 mM MSG with 2.5 mM IMP or GMP yielding the highest intensities. Similar differences were found for total duration and area under the curve. These results indicate that flavor potentiators may increase total flavor during consumption. Synergism between flavor potentiators was demonstrated.

Influences of Fat, Thickener and Emulsifier Contents on Salad Dressing: Static and Dynamic Sensory and Rheological Analyses

The effects of contents of fat, thickener and emulsifier in salad dressing were investigated. Twelve types of dressings were produced according to a full factorial design, whereby the fat content was set at three levels, the thickener and the emulsifier contents at two levels. The dressings were analysed by a sensory panel, using both quantitative descriptive profiling and time-intensity (TI) evaluation, and by instrumental/rheological measurements. The two sensory methods were related to each other and the instrumental results were related to the sensory results.All design parameters had a significant influence on the properties of salad dressing, mainly on texture and mouthfeel. Fat content was the most influencing parameter. Interaction effects were found and it can be concluded that the content of the emulsifier was less critical when the fat and thickener contents increased.Dynamic and descriptive sensory analyses were mainly related to each other in the fattiness attribute. There were strong relations between instrumental and sensory analysis according to rheological and texture attributes, ∣r∣≥0.7 (Pearson correlation coefficient) for most texture attributes.

Training a sensory panel for TI: a case study

Time–intensity (TI) is an increasingly used sensory method, however, no proper guidelines for training panellists with TI seem to have been set up, hence comparison of results from different TI studies is difficult. In this paper a three steps approach is proposed: (1) introduction to the method; (2) training for the TI task through a simple product assessment: basic taste beverages; (3) running a TI pilot experiment. The loadings from a principal components analysis (PCA) on TI data have proved to be useful in assessing panel agreement and providing information about individual differences. Pilot profiling proved useful for choosing the attributes to be used in the TI study. This minimises the chance of performing a TI study with irrelevant attributes. It is concluded that, following the steps in this study, most panellists are able to learn to perform a TI task reliably.

Dynamic analyses of sensory and microstructural properties of cream cheese

Flavour and texture in cream cheese depend on the microstructure. The objective of this work was to study the influence of fat content, salt content and homogenisation pressure on the microstructure and sensory properties of cream cheese. Twelve types of cream cheese were produced according to a full-factorial design, whereby the fat content was set at three levels, the salt content at two levels and the homogenisation pressure at two levels. The cheeses were analysed by a sensory panel, using both quantitative descriptive profiling and time intensity (TI) evaluation, and by using a confocal laser scanning microscope, CLSM, whereby the microstructure of the cheeses was analysed. All the design parameters had a significant influence on the flavour and texture, although fat had the largest effect. Interaction effects between the design parameters were also found to influence the character of cream cheese. The results showed that it is possible to create a cream cheese with lower fat content and with sensory attributes similar to the attributes in cream cheese with high fat content, by modification of production parameters.

Comparison of methods of analysis of time-intensity data: application to Scotch malt whisky

Time-intensity (TI) data typically consist of assessments at 1 s intervals of a set of samples by a panel of assessors. Some means of summarising the data must be found, and the data must be represented in a way which allows comparisons between samples. Parameters such as maximum intensity, time to maximum, and total duration are typically used and samples compared by analysis of variance. Thirteen assessors scored sweet taste intensity for 60 s, for 20 whisky samples drawn from 5 types of cask after 4 maturation times. Scaling and then averaging of the transformed data provided the best summary, and ante-dependence modelling showed that the intensity value at each time-point of the curve was dependent on the previous five time-points. Small effects of cask type and maturation time were found on sweet taste in whisky samples.

THE SENSORY PERCEPTION OF FLAVOR RELEASE AS A FUNCTION OF TEXTURE AND TIME: A TIME INTENSITY STUDY USING FLAVORED GELS

The focus in this study was to study time intensity (TI) methodology and procedures of getting the sensory panel acquainted with this technique. By means of a descriptive profiling exercise effects of altering the structure of a β-lactoglobulin gel, laced with banana aroma on the perception of banana flavor were obtained and a suitable attribute for TI was selected. Samples made up by protein, without any fat are not ideal for a TI study of flavor release because of the fast release of aroma. However, although the concentration of banana aroma was identical in the four groups of gels the intensity was perceived as different. This was reflected in the descriptive profiling as well as in the dynamic study. The TI study showed that it is important to minimize distractive, noncrucial information during the exercise. The assessors had different abilities to connect with the dynamic data acquisition procedure and training made the assessments more congruent. The results also indicate a relationship between the appearance of the TI-curve and the score of the total banana aftertaste.

POTENCY OF SWEETNESS OF ASPARTAME, D‐TRYPTOPHAN AND THAUMATIN EVALUATED BY SINGLE VALUE AND TIME‐INTENSITY MEASUREMENTS

ABSTRACTPerceived sweetness of sucrose, aspartame, D‐tryptophan and thaumatin in a sour, citric acid background was analyzed in terms of the potency of these compounds relative to sucrose‐water combinations. Potencies of the sweeteners were determined from (1) maximum intensity using single value and time‐intensity (T‐I) measurements and (2) average intensity calculated as the ratio of area under the T‐I curve and total perceived time. Stevens’ law was applied to sweet responses, either in static or dynamic conditions. It was found that the exponent of the concentration‐response function reflected the relative capacity of a compound to sweeten a given food and stressed differences of potency among sweeteners. Aspartame, D‐tryptophan and thaumatin exhibited a decrease in sweetness potency relative to sucrose as sweetness increased from 10 to 100% of the full scale of response. Across the entire sweetness range, thaumatin showed the greatest potency but its long persistence time led to differentiate this intense sweetener from the other sweeteners evaluated.

Modeling the sweetness response using time–intensity data

A general mathematical model for the temporal intensity response to a transient sweet stimulus was developed. The model is a set of nonlinear ordinary differential equations, expressing the rates of diffusion across a saliva boundary layer and adsorption and desorption to receptor site proteins on the taste bud cells. In this model, the perceived intensity is considered to be the product of a scaling factor and the amount of stimulus bound to receptor sites at any given time. A parameter estimation routine was used to fit the differential equations to the time–intensity (TI) curves for five equisweet stimuli (sucrose, aspartame, thaumatin, monellin, and brazzein). Model parameters were computed for each of 19 trained judges. The predicted TI curves were close to the observed time-intensity responses for all judges and sweeteners. TI parameters varied significantly across both judges and compounds, while model predicted parameters, such as adsorption and desorption coefficients, varied significantly only across compounds. Except for one model parameter (predicted plateau time), there were no significant differences across judges for the model-predicted parameters, indicating that all judges responded similarly to each compound.

Effect of sucrose on the perceived flavor intensity of chewing gum.

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.

Changes in bitterness as beer ages naturally

In order to ascertain changes in bitterness as beer aged naturally, time–intensity (TI) measurements were made by a professional sensory panel using a squeezer transducer system. TI parameters were fitted by variance components models using Restricted Maximum Likelihood (REML). It was shown that bitterness decreased with age, although this age-induced difference was smaller than the original differences among the eight fresh (commercial lager) beer types which spanned about 10 European Bitterness Units (EBU). Intensity-related parameters obtained from the TI curves were more important than time-related parameters for differentiating samples. Perceived bitterness could not be explained entirely by concentrations of five iso-α-acid peaks as measured by High Performance Liquid Chromatography (HPLC). Analytical and sensory data were correlated using Partial Least Squares (PLS2) and by fitting iso-α-acid peak areas in the REML models. ©

Using repeated ingestion to determine the effect of sweetness, viscosity and oiliness on temporal perception of soymilk astringency

Astringency is a persistent sensation which increases upon repeated ingestion. To evaluate the effect of viscosity, sucrose and oil on perception of astringency during consumption of soymilk, a sequential sipping time–intensity (TI) procedure was utilized. For each soymilk, judges sipped the first of four ingestions and initiated the continuous recording of astringency intensity. Each sip was expectorated at 10 s after ingestion, and sipped 10 s after expectoration of the previous stimulus. After the fourth sample, judges rated astringency for 30 s. Traditional TI parameters, as well as rate of onset for each sip and increase in maximum intensity per sip were extracted from the TI curves. Maximum astringency (IMAX) increased significantly with successive sips as did the astringency at the time of sipping. Time to IMAX decreased from sip 1 to 3, but was longer for sip 4, which may be an artifact of the rapid test pace. Although addition of 60 g l −1 canola oil had no affect on astringency, adding 40 g l −1 sucrose or increasing viscosity by 5 cp with CMC significantly lowered all astringency parameters. The reduction in astringency by CMC may result from restoration of salivary lubrication and in part by chelation or hydrogen bonding of CMC to the astringents reducing their ability to bind to salivary proteins. The reduction in astringency produced by sucrose is more probably due to a cognitive process. ©

Bitterness and astringency of flavan-3-ol monomers, dimers and trimers

Intensity of astringency and bitterness of seven flavonoid compounds was evaluated by a time-intensity (TI) procedure. Eighteen trained judges rated intensity continuously from ingestion, through expectoration at 10 s until extinction of the sensation. The seven stimuli included two flavan-3-ol monomers, (+)-catechin and (−)-epicatechin, three dimers and two trimers synthesised from catechin or epicatechin by condensation with (+)-dihydroquercitin. As the degree of polymerisation increased, maximum bitterness intensity (Imax) and total duration (Ttot) decreased whereas astringency Imax increased. The monomers were significantly higher in bitterness at Imax than the dimers, which were significantly higher than the trimers. Astringency Imax of the monomers was lower than the dimers or trimers, although no significant difference was found in Ttot among the polymer classes. The bond linking the monomeric units had an influence on both sensory properties. The catechin-catechin dimer linked by a 4→6 bond was more bitter than both catechin-(4→8)-catechin and catechin-(4→8)-epicatechin. Astringency was affected by both the specific linkage and the identity of the monomeric units with the dimer, catechin-(4→8)-catechin, being lower in astringency than either catechin-(4→6)-catechin or catechin-(4→8)-epicatechin. © 1999 Society of Chemical Industry

Simultaneous instrumental and sensory analysis of volatile release from gelatine and pectin/gelatine gels

Release of volatiles from gels during eating was measured by monitoring the volatile composition of breath, using on-line atmospheric pressure chemical ionisation–mass spectroscopy (APCI–MS), and by simultaneous sensory time–intensity (TI) evaluation. The time–release (TR) and TI curves were very similar, suggesting a simple relationship between changes in volatile concentration over the eating time course and the intensity of volatile perception. Analysis of the T max values (time to maximum intensity) showed that the ratio between the T max for the sensory and instrumental data (sensory T max/instrumental T max) varied with the instrumental T max, such that at low T max values the ratio was >1.0 and, as T max increased, the ratio decreased to below 1.0. This trend suggested that with short eating events there may be a lag in perception after the maximum breath stimulus concentration. Conversely if the eating process took longer, sensory adaptation might occur. ©

TEMPORAL STUDY OF SUCROSE AND FRUCTOSE RELATIVE SWEETNESS

Time‐Intensity (T‐I) and Gustatory Reaction Time (GRT) methodologies were used to study the relative sweetness of sucrose and fructose at 25C. Eleven panelists evaluated nine concentrations (5 to 45%, w/v) of sucrose and fructose by T‐I and seven parameters were determined. Higher values were obtained for fructose at 25, 30 and 35% for Maximum Intensity; at 35, 40 and 45% for the Area Under the Curve; at 40 and 45% for Time to decline the Intensity to half of its maximum value and at 45% for Rate of Increase. Ten subjects evaluated seven concentrations (3 to 15%, w/v) of sucrose and fructose by the GRT procedure. Fructose had shorter GRT than sucrose at 3 and 4.5%. Thus, fructose at 25, 30 and 35%, has a more intense and at 40% more persistent sweetness than sucrose and is detected earlier than sucrose at concentrations near gustatory threshold.

Cohesiveness of Mass Evaluation by Time‐intensity and Single Value Measurements

ABSTRACTThe cohesiveness of mass of three commercial food products and three model systems was determined by Time‐Intensity (TI) and single‐value measurements. Two kinds of TI profiles were identified. The first corresponded to products that initially have a cohesive mass which is broken down during chewing. The second profile was characterized by the development and subsequent breakdown of cohesiveness of mass with oral manipulation. Maximum Intensity (Imax), total duration (DUR), area under the curve (AUC) and time to maximum intensity (Tmax) most significantly differentiated the products. Imax was the TI parameter most closely related to single‐value measures of cohesiveness of mass.

Relation Between Parotid Saliva Flow and Composition and the Perception of Gustatory and Trigeminal Stimuli in Foods

GUINARD, J.-X., C. ZOUMAS-MORSE AND C. WALCHAK. Relation between parotid saliva flow and composition and the perception of gustatory and trigeminal stimuli in foods. PHYSIOL BEHAV 63(1) 109–118, 1998.—The objective of this study was to investigate whether and how parotid saliva flow and composition correlated with the perception of gustatory and/or trigeminal stimuli in foods. Thirty (15 male and 15 female) subjects tasted seven foods or beverages (lemonade, beer, wine, soup, methyl cellulose, peanut butter, and crackers) with three levels each of a gustatory or trigeminal stimulus and rated the perceived intensity of the corresponding sensation over time using the time–intensity (TI) method while their parotid saliva was being collected. Salivary flow rates of males were significantly higher than those of females for all stimuli ( p < 0.001). That did not translate, however, into consistent differences in perception of sensory attributes between males and females. Significant positive correlations were found between saliva flow and (1) TI parameters for adhesiveness of peanut butter and cohesiveness of mass of crackers ( p < 0.05 or lower) and (2) time from intake to swallowing of crackers and peanut butter ( p < 0.05). No correlations were found between saliva composition (e.g., sodium and total protein) and TI parameters. These results indicate that parotid saliva flow may correlate with the perception of some texture and mouthfeel attributes (presumably through oral work and bolus formation) but not with that of the taste attributes examined in this study (at the concentrations studied).

Temporal aspects of perception of juiciness and tenderness of beef

This study evaluated temporal differences amongst panellists in perception of juiciness and tenderness of beef samples and explored the temporal relationship between juiciness and tenderness. Ten panellists evaluated samples from 48 animals using CSA computerized time-intensity (TI) procedure. Grouping of panellists for perception based on chewing behaviour using CSA curves was possible. Use of Principal Component Analysis (PCA) to produce curves based on PC scores over time provided more information about the samples and perception variability than simple averaging. Perception of tenderness was influenced by perceptual differences amongst panellists, and by the stage in mastication at which juiciness was perceived in a sample.