2019 IEEE 1st Global Conference on Life Sciences and Technologies (LifeTech 2019)

Comparison of The Method of Temporal Dominanceof Sensations and After-tasting Sensory Evaluation
Yuki Ehara, Shogo Okamoto, Takumu Okada and Yoji Yamada
Department of Mechanical Systems Engineering, Nagoya University, Japan

Abstract—The temporal dominance of sensations (TDS)
method can record changes in multiple time-variant sensations
while eating food products. Since this is a relatively new method,
its characteristics remain unclear. This study aims to reveal thecharacteristics of the data obtained by the TDS method compared
to conventional sensory evaluation methods. For this purpose,in the experiment, participants evaluated ten types of pickledplums using both methods. We analyzed the data using principal
component analysis methods and multivariate ANOVA and foundthat both methods could equally discriminate brands of pickledplums. Nonetheless, the brands discriminated by the two methods
did not largely overlap, suggesting that the two methods arequalitatively distinct.

These adjectives describe tastes of food and eating experiences. An assessor pushes the start button when putting samples into his/her mouth and continues to select a button withthe adjective that fairly represents his/her dominant feeling at
the moment. Dominant sensation is defined as the sensation
catching the attention at a given time [2]. The assessor thenpushes the stop button when he/she finishes eating andperceptions in the mouth vanish. The assessor is allowed topush the same adjective button as many times as desired, andis not required to select all adjective buttons at least once.

I. I NTRODUCTION

As a typical example of conventional sensory evaluation
methods, we employed an adjective rating task in which anassessor scores products based on the adjectives as criteriausing a seven -point Likert scale. Each adjective is rated from1 (extremely disagree) to 7 (extremely agree) after eating foodsamples.

Thus far, many sensory evaluation methods for food products have been developed. Most of these methods requireassessors to rate food products after eating them in a nontimely manner. In contrast, some methods were developed torecord the time-series of subjective data while eating foodproducts. The time-intensity [1] and temporal dominance ofsensations (TDS) methods [2] are representative ways tocapture the time evolution of human sensory experiences.
Especially the TDS method has drawn attention as an effective
method for recording multiple subjective sensory attributes
simultaneously. In this method, the changes in dominantly
experienced sensations when eating foods are recorded in realtime. However, since the TDS method is a comparatively
new method proposed in 2009, the characteristics of therecorded data remain unclear, and common analysis methods
have yet to be established whereas qualitative discussion andcanonical variate analysis are frequently used [3]. This paper
aims to reveal the characteristics of the data obtained fromTDS methods by comparing with those obtained from a
conventional sensory evaluation method. Assessors rated 10types of Umeboshi, which are pickled salty plums, using bothtypes of sensory evaluation methods. We then analyzed theobtained data using principal component analysis (PCA) andmultivariate analysis of variance (MANOVA) and investigatedthe differences between two methods from the viewpoint ofproduct classification.
II. T WO TYPES OF SENSORY EVALUATION METHODS
A. TDS Method
In the TDS method, the timings for pressing buttons withadjective labels displayed on a computer screen are recorded.

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B. Conventional sensory evaluation after tasting

III. E XPERIMENT: S ENSORY E VALUATION OF F OODS
A. Participants and Products
The participants were 20 university students ranging in age
from 21 to 26 years old. They voluntarily participated in theexperiment with written agreement. Ten types of Umeboshi
brands labeled P1 to P10 were used. In the experiment, eachbite-sized Umeboshi sample on a spoon was presented in frontof the participants.
B. Selection of Attribute Words
We selected 16 words as criteria of foods, suitably representing the taste, flavor, texture, and affective characteristicsof Umeboshi, out of 163 words expressing tastes or affections.
Eight were related to tastes, flavor, and texture-i.e., sour (salty),smooth (melty), sweet, refreshing, juicy, fruity, watery, andumami- and the other eight were were affective words-i.e.,
like, delicious, classy (elegant), dislike, flavorful, rich (deep),sharp, and arousing. These words were used in both sensory
evaluation methods.
C. Task
The aforementioned two types of sensory appraisal tasks
were conducted for each participant. In the TDS method,he/she closed his/her eyes and pinched his/her nose before
putting samples into his/her mouth. He/she then carried out
the task of pushing buttons. In the task of after-tasting sensory
appraisal, each participant ate a piece of pickle and then rated

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Umeboshi brands among the participants. The ellipses represent their standard deviations. The contribution ratios of
two principal components were 0.40 and 0.17 for after-tasting
sensory evaluation and 0.39 and 0.15 for the TDS method. The
two types of sensory evaluation methods showed differencesin their dimensional structures of the first and second principal
components. Sweet,
umami,
sour and salty, andrefreshing were remarkable for the TDS method whereas
sweet,
sour and salty,
watery, and smooth wereremarkable for the after-tasting sensory evaluation method.
We compared the two-dimensional coordinates of 2 out of
10 arbitrary types of Umeboshi brands by MANOVA. The
number of brand pairs that could be statistically distinguished(p ¡ 0.05 ) by the after-tasting sensory evaluation was 30 outof 45. In contrast, 28 pairs could be distinguished by the TDS
method. Nine pairs could be distinguished by either of the twomethods.
Similarly, the results of affective attributes were analyzed by
PCA and MANOVA. The contribution ratios of PCA s first andsecond principal components for the after-tasting method were0.48 and 0.30, respectively. Those for the TDS method were0.27 and 0.16, respectively. The number of distinguishable
brand pairs were 24 and 22, respectively, for the after-tasting
and TDS methods. Twenty pairs were discriminated by either
method, and the two methods did not largely agree with eachother.

Fig. 1. PCA scores obtained by the conventional sensory evaluation aftertasting (top) and the TDS method (bottom). P1–P10 are the centroids of 10
types of food products. Blue lines are the vectors of major attributes on the1st-2nd plane

all 16 words. He/she rinsed his/her mouth before each trial. Experiments were conducted over two days for each participant.
On the first day, the TDS and after-tasting sensory appraisal
methods were tested. On the other day, they repeated the TDS
task. The order to present food samples was randomized.
D. Analysis and Results
For the normalization of the TDS data, the period during
which each adjective button was selected was divided by
the time from the start to the end of the tasting. For eachparticipant, these periods were averaged among two trials forthe same product. We then applied PCA on these periods.
For the after-tasting sensory evaluation, each adjective score
was converted so that the average value for each participant
became zero, and then, PCA was applied. For both typesof sensory appraisal methods, perceptual attributes including
tastes, flavors, and textures and affective ones were separatelyanalyzed.
Fig. 1 shows the two-dimensional principal componentscores of each food product for the TDS method and aftertasting sensory evaluation as a result of PCA for tasting
adjectives. The red points are the centroids of individual

IV. C ONCLUSION
The characteristics of the data obtained by the TDS method
were investigated through the classification of 10 types ofUmeboshi brands. The perceptual and affective attributes wereevaluated using the TDS method and conventional after-tasting
sensory evaluation method. The data obtained by each method
were analyzed by PCA, which indicated that the dimensional
structures obtained by the two methods were disti
nct. Furthermore, the numbers of distinguishable pairs ofUmeboshi products were investigated by MANOVA for eachmethod. More than half of the product pairs could be distinguished in both types of sensory evaluation methods. However,distinguished pairs did not completely match in both methods.
These results suggest that the TDS method is substantiallydifferent from conventional after-tasting sensory appraisals. Interms of product discrimination, we cannot conclude that oneof them is superior to the other.
ACKNOWLEDGMENT
This study was in part supported by JSPS Kakenhi(17K20002).
R EFERENCES[1] W. Lee III and M. Pangborn, “Time-intensity: the temporal aspects ofsensory perception,” Food technology, pp. 71–78, 1986.
[2] N. Pineau, P. Schlich, S. Cordelle, C. Mathonnière, S. Issanchou, A. Imbert, M. Rogeaux, P. Etiévant, and E. Köster, “Temporal dominance ofsensations: Construction of the tds curves and comparison with time–intensity,” Food Quality and Preference, vol. 20, no. 6, pp. 450–455,
2009.
[3] A. Thomas, M. Visalli, S. Cordelle, and P. Schlich, “Temporal drivers ofliking,” Food Quality and Preference, vol. 40, pp. no. #. 365–375, 2015.

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