Kaolid: a Lid-type Olfactory Interface to Present Retronasal Smell
towards Beverage Flavor Augmentation
Daiki Mayumi1 , Yugo Nakamura2 , Yuki Matsuda1 , Shinya Misaki1 , Keiichi Yasumoto1
1 Nara Institute of Science and Technology

Ikoma, Nara, Japan

2 Kyushu University

Fukuoka, Fukuoka, Japan

ABSTRACT1

In this paper, we introduce Kaolid, an olfactory interface that uses
a lid mechanism to augment the flavor of beverages by delivering
scents as retronasal smell. Kaolid aims to promote the consumption of healthier beverages by intensifying their perceived taste
through the release of scents during drinking. The system features
a compact olfactory display and an IMU sensor, triggering scentsin response to drinking movements. It comes in two models: astraw-type for cold beverages and a cup-type for hot drinks. We
tested the interface using sparkling and hot water and measured
its efficacy in enhancing perceived sweetness when paired withscents. Results showed significant enhancements in all evaluation
metrics (taste satisfaction, perceived sweetness, and preference)with the straw-type device. Notably, the perceived sweetness increased by an amount equivalent to about 2.88 grams of sugar whena retronasal smell was introduced compared to when no scent waspresent. This innovative interface holds promise in elevating theflavor of sugar-free drinks and could support those aiming to limit
sugar consumption. Furthermore, this research contributes to the
future of IoT systems for health support by harnessing the powerof scent, opening avenues for novel approaches in sensory-driven
well-being advancements.

Sugar-sweetened beverages (SSB) have become the primary sourceof sugar in our diets. In developing countries, rising consumption
patterns are linked with urbanization and economic growth, both ofwhich have increased the availability and, consequently, the intake
of SSBs [17, 26, 27, 34]. Habitual consumption of SSBs elevates therisk of obesity [12, 19, 30, 31], diabetes [12, 15], heart disease, andother cardiac conditions [18, 36]. Therefore, initiatives to curtail
SSB intake are vital.
Various strategies have been suggested to counter these threats
and assist individuals in reducing their consumption [14, 32]. Thesemethods might momentarily persuade people to opt for beverages
with lower sugar content. However, beverages with little or nosugar often lack appeal. Thus, a brief intervention might not besustainable, possibly leading to a relapse into the habit of consuming sugary drinks. From a well-being standpoint, it is crucial toseek solutions that gradually decrease sugar content, as drastic
reductions can cause emotional distress for individuals [11].
Recognizing that our sense of smell greatly influences our perception of taste [16, 24, 29], previous research has explored an olfactory interface designed to release a sweet scent during beverage
consumption, thereby enhancing the perception of sweetness [20].
However, these studies indicate that merely presenting scents froma device is challenging in terms of enhancing taste satisfaction.
We detect smells in two primary ways: “orthonasal smell” fromthe nostrils and “retronasal smell” from the mouth that travels
through the nose. Each type of smell is processed differently inthe brain [4, 13, 28]. Notably, retronasal smell, which contributes
to the flavor of food and beverages, is intrinsically linked to oursense of taste [25]. Thus, our interface was revamped to highlight“retronasal smell,” an scent closer linked to flavor.
In this paper, we introduce a lid-type olfactory device named“Kaolid”1 that alters the taste of beverages by introducing scent information through the retronasal pathway during consumption. The
Kaolid is available as both straw and cup-type configurations, each
embedded with a compact olfactory device to facilitate retronasal
smell detection, as depicted in Figure 1. To encourage water consumption, the Kaolid straw-type is designed for room temperature
or cold water, while the cup-type is meant for plain hot water. The
straw-type releases the scent into the straw’s central tube, delivering it to the user’s mouth as they drink. Conversely, the cup-type
introduces the scent through the lid, offering an initial burst ofscent at the onset of consumption.

CCS CONCEPTS• Computer systems organization → Embedded systems; Redundancy; Robotics; • Networks → Network reliability.

KEYWORDS
Olfactory device, Drinking activity recognition, Persuasive technology, Internet of things, Tasting change
ACM Reference Format:
Daiki Mayumi1 , Yugo Nakamura2 , Yuki Matsuda1 , Shinya Misaki1 , Keiichi
Yasumoto1 . 2023. Kaolid: a Lid-type Olfactory Interface to Present Retronasal
Smell towards Beverage Flavor Augmentation. In Proceedings of The 13th
International Conference on the Internet of Things (IoT ’23). ACM, New York,NY, USA, 8 pages. https://doi.org/XXXXXXX.XXXXXXX
Permission to make digital or hard copies of all or part of this work for personal orclassroom use is granted without fee provided that copies are not made or distributedfor profit or commercial advantage and that copies bear this notice and the full citationon the first page. Copyrights for components of this work owned by others than ACM
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to post on servers or to redistribute to lists, requires prior specific permission and/or afee. Request permissions from permissions@acm.org.
IoT ’23, November 07–10, 2023, Nagoya, Japan© 2023 Association for Computing Machinery.
ACM ISBN 978-1-4503-XXXX-X/18/06. . . $15.00
https://doi.org/XXXXXXX.XXXXXXXINTRODUCTION

1 Derived from “Kaori,” which means smell in Japanese.

IoT ’23, November 07–10, 2023, Nagoya, Japan(a) Straw-Type Device

D.Mayumi et al.

(b) Cup-Type Device

Orthonasal Smell

Retronasal Smell

Figure 1: Overview of Kaolid ((a)Straw-type device, (b)Cuptype device)
This paper outlines the design and implementation of the Kaolid
prototype system and presents findings from a study examining
the influence of retronasal smell on taste perception.

2

PRELIMINARY AND RESEARCH QUESTIONSThis section outlines the structure of the human nasal pathway
and provides an overview of the types of odors humans can detect.
We formulate research questions concerning effectively presenting
smells that can modify taste.

2.1

Mechanism of the Human Sense of Smell

Figure 2 illustrates the olfactory mechanism and its two nasal pathways. Retronasal smell plays a pivotal role in determining the tasteof food and beverages. This mechanism, essential for perceiving
flavor, integrates both traditional olfaction and taste. It involves
the sensation produced when odor molecules from food or drink
travel through the nasal cavity during consumption. While the term“smell” often refers to “orthonasal smell”–the direct perception ofodors entering the nose and passing through the nasal cavity–, theretronasal smell is equally vital for experiencing the taste of foodand beverages [25].

2.2

Types of Scents Humans Can Detect

When designing an interface to enhance perceived sweetness, it isessential to understand which odors to choose and present. According to Castro et al.[5], 10 foundational categories represent coredimensions of odor perception. Table1 lists typical descriptors forthe smells within these categories. For the purpose of our interface,
we focused on carbonated and plain water, both non-sugary beverages with potential health benefits, as the primary beverages toaugment sweetness. A review of the odor categories suggests thatcategories C3, C7, and C10 might be effective in boosting perceived
sweetness. Based on empirical compatibility with carbonated andhot water, this study opted to introduce the scents of orange fromcategory C10 and pineapple from category C3.

2.3

Figure 2: Olfactory mechanisms and two nasal pathways [7]Research Questions

This study seeks to answer the following research questions:
RQ1 Can the introduction of fruity flavors through retronasal
smell, using the proposed device’s mechanism, enhance theperceived sweetness and overall flavor satisfaction?
RQ2 Do different scent categories have different sweetness
enhancement effects?

RQ3 How does the perceived sweetness intensity delivered by
the proposed device compare to that of a standard sugarsweetened beverage?

3 RELATED WORK
3.1 Alternatives to SSBs
Artificially sweetened beverages are gaining traction as substitutes
to curb SSB intake. Although these beverages are becoming moreprevalent in daily consumption, they haven’t been notably successful in aiding weight loss. Fowler et al.[10] examined 3,682 adults
over 7-8 years in the 1980s and found that increased consumption of
artificially sweetened beverages was correlated with higher BMIs.
Another study involving 103 adolescents replacing sugar-sweetened
beverages with diet alternatives showed no BMI reduction after
25 weeks [9]. One potential reason is that both sugar and artificial
sweeteners might stimulate human appetite [3].
100% fruit juice is also being considered as a potential SSB alternative. While often deemed healthy due to their nutrient content,some fruit juices can be as calorie-dense and sugary as SSBs, given
the natural sugars present in fruits. Consuming fruit juices has been
linked to weight gain [26] and an elevated risk of type 2 diabetes [2].
Conversely, water, being free of sugars and calories, is deemed
the superior hydrating beverage. As the demand for water options
grows, the emergence of various sparkling and flavored water types
could help habitual SSB users switch to healthier options.

3.2

Olfactory Device Research

Recent years have witnessed the proposal of various olfactory devices and interactions employing them. Examples include headmounted displays [21, 35] and neck-wearable devices [1, 8] designed
for scent delivery. Wang et al. introduced an olfactory device which
can be worn as a piercing, necklace, or face-mounted accessory [33],designed for convenient everyday use. Amores et al. showcased anecklace-style olfactory device, controllable via smartphone, which
can modulate scent intensity and frequency based on biometricand contextual data [1]. Dobbelstein et al. introduced a wearable
device for everyday scent notifications [8]. Meanwhile, Choi et al.
developed 3D-printed glasses embedding a heating module within
the frame, releasing scents when activated [6].

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IoT ’23, November 07–10, 2023, Nagoya, Japan

Table 1: 10 largest-valued descriptors for each of the 10 basis vectors obtained from non-negative matrix factorization. [5]C1
Fragrant
FloralPerfumery
Sweet
Rose
Aromatic
Light
CologneHerbal, Green, Cut Grass
Violets

C2
Woody, Resinous
Musty, Earthy, Moldy
Cedarwood
Herbal, Green, Cut Grass
Fragrant
Aromatic
Light
Heavy
Spicy
Burnt, Smoky

C3
Fruity, Other Than Citrus
Sweet
Fragrant
Aromatic
Light
Pineapple
Cherry (Berry)
Strawberry
Perfumery
BananaC4
Sickening
Putrid, Foul, Decayed
RancidSweatySour, Vinegar
Sharp, Pungent, Acid
Fecal (Like Manure)
Sour Milk
Musty, Earthy, Moldy
Heavy

C5
ChemicalEtherish, Anaesthetic
Medicinal
Disinfectant, Carbolic
Sharp, Pungent, Acid
Gasoline, Solvent
Paint
Cleaning Fluid
Alcoholic
Turpentine (Pine Oil)

It is recognized that 75-95% of human taste is driven by olfaction, with scents accounting for the majority of what’s typicallyperceived as “taste” [16, 24, 29]. Hence, manipulating scents mightalter taste perceptions. Ranasinghe et al. [22, 23] created devices
employing electrical stimuli, scents, and visual effects to enrich
AR and VR drinking experiences, investigating the impact of eachstimulus on taste. While they managed to elevate taste throughmultisensory interactions, pure sweetness amplification remained
elusive. Moreover, their scent delivery method–via a tube inserted
directly into the nose–wasn’t designed for daily use convenience.
Our research group has also proposed a mug-type olfactory interface that amplifies sweetness through scent [20]. We conducteda demonstration test on 33 participants and confirmed that theperceived taste of sweetness was amplified by the scent, but taste
satisfaction was not improved.
In essence, substituting SSBs with artificially sweetened beverages appears insufficient. Instead, promoting water consumption–
devoid of sugars and calories–is more promising. Although scentdriven strategies have been investigated to amplify beverage sweetness, contemporary designs have mainly succeeded in enhancing
sweetness but have not significantly elevated overall taste satisfaction. This research hinges on the variations in human nasal
pathways and introduces a unique olfactory approach. Humans are
known to possess two scent pathways: “orthonasal,” originatingfrom the nose’s tip, and “retronasal,” emanating from the mouthand passing through the nose, with each being distinctly processedby the brain [4, 13, 28]. Notably, retronasal smell, which contributeto the flavors of food and beverages, have a robust correlation with
our sense of taste [25]. In this paper, we detail the design and implementation of the Kaolid prototype—a device specifically tailoredfor retronasal smell presentation. We also present the results ofa study that examines how retronasal smell influence beverage
taste perceptions. Delving into these olfactory interfaces for healthsupport promises to further research on IoT systems that augment
and broaden the human sensory experience.

4 KAOLID: DESIGN AND IMPLEMENTATION
4.1 System Design
Our sense of taste is significantly shaped by our sense of smell,particularly the retronasal smell that characterize the flavors offood and beverages. With this knowledge, we aim to augment
both the perceived sweetness and overall satisfaction of beverages
by incorporating retronasal smell. For this purpose, we designed
Kaolid, a device that recognizes drinking motions and emits targeted
scents to modulate taste perception. The Kaolid system comprises apneumatic pump and an associated circuitry that drives the pump,facilitating the generation of retronasal smell for the experiment.

C6
Minty, Peppermint
Cool, Cooling
Aromatic
Anise (Licorice)
Fragrant
Medicinal
Spicy
Sweet
Eucaliptus
Camphor

C7
Sweet
VanillaFragrant
Aromatic
Chocolate
Malty
AlmondCaramel
Light
Warm

C8
Popcorn
Burnt, Smoky
Peanut Butter
Nutty (Walnut Etc)
Oily, Fatty
AlmondHeavy
Warm
Musty, Earthy, Moldy
Woody, Resinous

C9
Sickening
Garlic, Onion
Heavy
Burnt, Smoky
Sulfidic
Sharp, Pungent, Acid
Household Gas
Putrid, Foul, Decayed
Sewer
Burnt Rubber

C10
Lemon
Fruity, Citrus
Fragrant
OrangeLight
Sweet
Cool, Cooling
Aromatic
Herbal, Green, Cut Grass
Sharp, Pungent, Acid

Figure 3: Device Design of Kaolid
We employed a pneumatic pump (MZB1001T022 ) as the mechanism for scent injection. This pump operates by drawing air fromone side and expelling it from the other. The chosen pump operates
on the principle of a piezoelectric diaphragm pump, and by utilizing ultrasonic vibrations, it achieves high pressure and flow rates
despite its compact and slim design.
As depicted in Figure 3, we devised a mechanism to introduce
scent from the lid’s top into the cup, aiming to facilitate the retronasal
A we affixed a 3D-printed container
smell experience. In Figure 3 ○,on the lid’s top to house both the pneumatic pump and a cottonball imbued with the scent.
In Figure 3, the container, crafted using a 3D printer, encases aBpneumatic pump and its driving circuit. As illustrated in Figure 3○
C the circuitry was designed for placement atop the lid toand ○,
maintain a compact form factor. To operate the pneumatic pump,
the power source voltage is elevated using a Buck-Boost Converter.
Notably, the pump’s output pressure is contingent on its input
voltage, and they share a proportional relationship. For this device,
we set the pump’s input voltage at 15 V, resulting in an air pressureof roughly 1.6 kPa. This pressure setting ensures the scent reaches
the user’s mouth. Aroma oil serves as the scent source, saturating
the cotton housed in the container, from which the pneumatic pumpreleases the scent.
The device affixed to the cup is lightweight and compact, crafted
using a 3D printer. It weighs in at approximately 100 g. Dimensionally, the attached container extends about 30mm upwards and has
a depth of 10 mm. Though there are minor alterations, the overall
weight and size remain relatively close to that of a standard cup,
ensuring users enjoy a familiar experience.

4.2

Prototype of Kaolid

In this study, we devised both a straw-type and a cup-type device
aimed at altering beverage taste by delivering scent to the mouth.
2 https://www.murata.com/ja-jp/products/mechatronics/fluid/overview/lineup/microblower_mzb1001t02

IoT ’23, November 07–10, 2023, Nagoya, Japan

D.Mayumi et al.

drink. This method enabled a comparison of perceived sweetness
with Kaolid to actual sugar content.
This study received approval from the Ethics Committee affiliated with the author’s institution (Approval number: 2020-I-16).

6

RESULTS

We began by aggregating the results for the scents used in thisexperiment (orange and pineapple). Subsequently, we conductedindividual evaluations for each scent to discern differences in taste
perceptions. Lastly, we presented the outcomes from the specificsweetness taste assessment.
Figure 4: Experiment Scene

Recognizing that beverages are typically consumed either cold or
hot, our designs revolve around commonly used drinking tools:
straws and cups.
We developed a straw-type device tailored for cold beverages
and a cup-type device suited for hot beverages. Both are designed
to convey scents to the mouth, enhancing perceived sweetness
and improving taste satisfaction. The straw device, as illustrated in
Figure 1(a), features a separate aperture in its center, channelingthe scent directly into the straw and subsequently to the drinker’s
mouth. The cup-type device, depicted in Figure 1(b), positions ascent-injecting mechanism atop the cup, ensuring that as the user
drinks, the scent is introduced to their palate.

5

EXPERIMENTIn this study, we conducted sensory evaluation experiments using
the Kaolid prototype to examine the effect of various flavors ontaste perception.The experiment involved 20 students in their 20s(average age = 23.5). All participants were in good health, presenting
no symptoms of colds, fevers, or other ailments, and exhibited
normal taste and smell abilities.
Different beverages were provided for each Kaolid prototype.
The straw-type device, intended for cold beverages, was filled with
unscented sparkling water. Conversely, the cup-type device, designed for hot drinks, was filled with plain hot water. For the scentcomponent, orange and pineapple scents were chosen based on
categories C3 and C10 from Table 1. These scents were determined
to be compatible with sparkling and hot water, respectively, fromten distinct odors perceivable by humans [5]. After each test, participants completed a taste-related questionnaire. The questionnaire
incorporated a 9-point hedonic scale where they evaluated perceived taste satisfaction, sweetness intensity, taste preference, andspecific sweetness levels.
For the specific sweetness assessment, participants were presented with ten cups filled with varying sugar concentrations, as
depicted in Figure 4. They were instructed to select the cup mirroring the sweetness they perceived during their drink test. The
sugar water ranged from “1” (unsweetened water) to “9” (a sugarconcentration of 11.3 g/100 ml, equivalent to typical carbonateddrinks). Intermediate sugar water samples had evenly spaced sugar
levels. A “10” rating was available for instances where participants
felt the beverage surpassed the sweetness of a standard carbonated

6.1

RQ1: Influence of Retronasal Smell on Taste
Sweetness and Satisfaction

The results for both the straw-type and cup-type devices are illustrated in Figure 5.
For the straw-type device, the introduction of retronasal smell
generally improved both taste satisfaction and perceived sweetness.
Taste satisfaction saw a median score increase of one point, suggesting the scent delivery method, the beverage, and the chosenscent collectively enhanced taste perception. The middle 50% ofparticipants’ scores fell between the first (Q1) and third quartiles(Q3), indicating consistent satisfaction. Perceived sweetness scoresindicate the device consistently boosted sweetness for most, withexceptions. No significant improvement in overall taste preference.
The cup-type device demonstrated an overall trend of improved
sweetness perception with retronasal smell presentation. The data
indicates consistent sweetness enhancement for the majority of participants. However, certain outliers suggest that while some foundthe sweetness amplified significantly, others didn’t observe a substantial change. For taste satisfaction, the data indicates improved
average taste perception, but overall consistency in enhancement
was lacking. Taste preference results showed a potential decline inevaluations with the introduction of retronasal smell. The distribution of these results suggest that while the cup-type device boosted
sweetness perception, further improvements might be necessary toconsistently enhance taste satisfaction and preference.
To compare evaluations based on scent presence, we used the
Wilcoxon signed-rank test, appropriate for assessing significant
differences between two related sample sets. Test results, summarized in Table 2, revealed significant differences in all evaluation
aspects for the straw-type device. For the cup-type device, significant differences were primarily observed in sweetness perception.
In conclusion, in response to RQ1, our lid-type olfactory device,
Kaolid, successfully introduces retronasal smell that amplify perceived sweetness and improve taste satisfaction.

6.2

RQ2: Effect of Scent Category on Taste
Sweetness

We examined the influence of different scents, specifically orange
and pineapple, on taste perception.
6.2.1 Result of Using Orange Scent. The outcomes from experiments using the orange scent are presented in Figure 6.
For the straw-type device, adding the orange scent generallyheightened both taste satisfaction and perceived sweetness. Taste

Kaolid: a Lid-type Olfactory Interface to Present Retronasal Smell towards Beverage Flavor Augmentation

IoT ’23, November 07–10, 2023, Nagoya, Japan

**
**

**

Figure 5: Overall result (Left:Straw-type,Right:Cup-type)
Table 2: Test results for each evaluation item
Two pairs to compare
Straw-type Device

Cup-type Device

Taste Satisfaction(Sparkling water)& Taste Satisfaction(Sparkling water+Scent)
Taste Sweetness(Sparkling water)& Taste Sweetness(Sparkling water+Scent)
Taste Preference(Sparkling water)& Taste Preference(Sparkling water+Scent)
Taste Satisfaction(Hot water)& Taste Satisfaction(Hot water+Scent)
Taste Sweetness(Hot water)& Taste Sweetness(Hot water+Scent)
Taste Preference(Hot water)& Taste Preference(Hot water+Scent)satisfaction, for instance, saw an increase in both the median andminimum scores, implying a more harmonious pairing of the orange
scent with the carbonated water. Similarly, sweetness perception
scores, both median and minimum, improved, suggesting a consistent perceived sweetness enhancement using the orange scent.
However, while adding the orange scent indicated a narrower rangeof taste preference scores, the maximum score decreased, indicating
challenges in improving overall taste preference.
With the cup-type device, there was a noticeable inclination towards heightened taste satisfaction and sweetness when the scent oforange was introduced. Both the minimum and maximum scores fortaste satisfaction improved, suggesting an overall positive responseto the orange scent when paired with plain hot water. Similarly,
sweetness perception saw a rise in scores, with the median score improving notably. However, taste preference showed a wider range ofscores, suggesting varied individual responses to the orange scent.
6.2.2 Result of Using Pineapple Scent. The outcomes from experiments using the pineapple scent are detailed in Figure 7.
With the straw-type device, evaluations across all categories
leaned towards lower scores compared to those using the orange
scent. This suggests that the combination of carbonated water andpineapple scent was less favored than its orange counterpart. However, there were some participants who rated the pineapple scentpositively in terms of both taste satisfaction and sweetness.
For the cup-type device, the results for pineapple scent weresimilar to the overall outcomes. While there was a trend of enhanced
sweetness perception, significant improvements in taste satisfaction
were lacking. This suggests that while the cup-type device canamplify perceived sweetness, elevating overall taste satisfaction
remains challenging.

P-valueSignificant Difference (p ≤0.05)

1.130×10 −3
2.728×10 −4
1.533×10 −1
6.636×10 −2
3.293×10 −3
7.238×10 −1

!
!
!
-

In conclusion to RQ2, the results indicate that the pairing of carbonated water and the scent of oranges significantly amplified perceived sweetness. On the other hand, plain hot water, when pairedwith the scent of pineapples, also showed enhanced sweetness. This
underscores the interplay between specific scent categories andbeverage types in influencing sweetness perception.

6.3

RQ3: Quantitative Evaluation of Sweetness
Enhancement by Kaolid

The results assessing the specific degree of perceived sweetness areillustrated in Figure 8. The sugar content of standard carbonatedbeverages is denoted by a red line, while that of commercial flavoredwater is marked by an orange line. From the findings, when using
the straw-type device with carbonated water, the introduction of ascent led to an average sweetness enhancement of roughly 2 scale
units. Considering that each unit on this scale corresponds to asugar content of 1.44g/100ml, a median-based comparison indicatesthat the straw-type device facilitated a sweetness enhancement
equivalent to around 2.88g. A median score of 3 in the participants’evaluations suggests that presenting the retronasal smell indeed
amplified the perceived sweetness. Notably, there were high scoresof 6 and 9, hinting that for certain participants, the device was
especially successful in intensifying sweetness perception. Regarding the cup-type device, which was paired with plain hot water,
it demonstrated a similar trend of sweetness enhancement, albeit
not as pronounced as the straw-type. Some participants felt thatthe cup-type device rendered beverages sweeter than conventional
carbonated drinks. These findings suggest that Kaolid can be instrumental in magnifying sweetness perception, potentially assistingin lowering sugar consumption.

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***

Figure 6: Result using orange scent (Left:Straw-type,Right:Cup-type)

*
*

**

Figure 7: Result using pineapple scent (Left:Straw-type,Right:Cup-type)

7 DISCUSSION AND LIMITATION
7.1 RQ1: Kaolid’s Enhancement of Taste
Satisfaction and Sweetness through
Retronasal Smell
Taste evaluations using the straw-type device indicated an upward
trend in ratings for both taste satisfaction and perceived sweetness.
These outcomes suggest an enhancement in taste satisfaction that
had not been achieved with traditional orthonasal smell presentation methods. Many users perceived a notably sweeter taste withthe straw-type device compared to the orthonasal approach. This
matches the idea that retronasal smell, molded by olfaction, is key
in taste judgment. Thus, it is evident that the scent delivery via thestraw-type device was effective.
For the cup-type device, the introduction of a scent mainly led
to heightened perceptions of sweetness rather than overall taste
satisfaction. This may hint that the design of the cup-type device
wasn’t optimal for conveying retronasal smell. However, it is essential to note that all participants in this study were in their twenties.
Future studies should account for demographic factors like age andgender. The potential of the cup-type device to elevate beverageexperiences warrants further exploration. During the experiments,
some participants expressed initial reservations about using an
unfamiliar device. Yet, as they discerned notable taste alterations
throughout the procedure, their intrigue seemed to outweigh theirinitial hesitancy.

Concerning taste variations, the straw-type device appeared
more dynamic to users than the cup-type. One participant remarked,“The taste alteration was more pronounced since the beverage wassparkling water”, while another observed, “The straw seemed to convey the smell directly into the mouth, ensuring no flavor was lost,which led to a more distinct taste change.” Regarding the cup-typedevice, a different participant noted, “Although the change in taste
felt more vivid with the straw-type, I preferred the mouthfeel deliveredby the cup-type.” Such feedback underscores that the direct scentdelivery through the straw-type device made it easier for users todetect taste changes. In our study, the process of injecting scented
air directly into participants’ mouths surprisingly didn’t diminish
their satisfaction. This might be attributed to the choice of carbonated water, which inherently contains air bubbles, thus making thescent injection process feel less intrusive. However, some participants found the straw device more intuitive and comfortable fordrinking than the cup-type, likely because they’re accustomed tothe direct pathway a straw provides.

7.2

RQ2: Taste Sweetness Variation Based on
Scent Category

For the straw-type device, the introduction of the orange scentconsistently led to heightened ratings in both taste satisfaction andperceived sweetness when compared to the general results. Boththe median and minimum values for these evaluations showednotable improvement with the orange scent. These observations
suggest that the combination of carbonated water and the orange

Kaolid: a Lid-type Olfactory Interface to Present Retronasal Smell towards Beverage Flavor Augmentation

10 [12.96g/100ml]

Evaluation of Sweetness

Evaluation Scale

9 [11.52g/100ml]
Carbonated drink
Flavor Water
No Scent
Scent

8 [10.08g/100ml]
7 [8.64g/100ml]
6 [7.2g/100ml]
5 [5.76g/100ml]
4 [4.32g/100ml]

The cup-type device, though less effective than its straw-type
counterpart, also demonstrated a potential to increase perceived
sweetness. It is worth noting that participants in this study were allin their 20s. Subsequent research will expand the participant pool to
include middle-aged and elderly individuals, aiming to offer a morecomprehensive quantitative assessment of sweetness perception
across age groups.

3 [2.88g/100ml]
2 [1.44g/100ml]

7.4

1 [0.0g/100ml]
Straw-type(Sparkling Water)

Cup-type(Hot Water)

Type of beverages

Figure 8: Result of Sweetness Evaluation
scent might be particularly synergistic with the straw-type device.
Conversely, when the pineapple scent was introduced, all evaluation metrics tended to be lower than those recorded with theorange scent. There was also a pronounced variability in the data
across evaluation categories, highlighting a strong divergence in individual preferences among participants. From these findings, andconsidering the patterns in the data, the orange scent appears to be
more universally favored when paired with sparkling water. Scentsfor this experiment were chosen from a palette that humans cantypically differentiate. Future research can further refine the choiceof scents by focusing on those within the orange scent category,aiming to find those that best complement sparkling water.
In the context of the cup-type device, the introduction of theorange scent showed a tendency to amplify perceived sweetness.
However, the taste satisfaction remained largely unchanged incomparison to evaluations without any scent. Consistent with theoverarching findings, participants’ taste preferences seemed to decline upon the introduction of the scent. Conversely, with the introduction of the pineapple scent, while there was a perceptible
amplification in the sweetness of the taste, other metrics like taste
satisfaction, preference, or the overall taste experience remainedlargely unchanged. This suggests that the current design of the
cup-type device primarily accentuates sweetness, irrespective of
the specific scent introduced, and struggles to enhance overall taste
satisfaction. This may indicate challenges in effectively delivering
the retronasal smell experience.

7.3

IoT ’23, November 07–10, 2023, Nagoya, Japan

RQ3: Evaluating Kaolid’s Sweetness as a
Substitute for SSBs

The Kaolid’s ability to induce perceived sweetness was quantitatively assessed. The straw-type device managed to amplify theperceived sweetness equivalent to an average of 2.88g of sugar. On
the other hand, the cup-type device achieved a sweetness amplification corresponding to an average of 1.5g of sugar. While thisdoes not equate to the sweetness levels of sugar-sweetened beverages (SSBs), it demonstrates the potential to enhance sweetness
perception in unsweetened drinks purely through the introductionof scents. Although the current iteration of the device primarily
relies on olfactory stimulation via scents, future designs may incorporate visual stimuli, such as LED light cues, to bolster sweetness
perception through multimodal interactions.

Future WorkIn this experiment, carbonated water was used as the beverage forthe straw-type device. However, it is necessary to conduct similar
experiments on other beverages to demonstrate its effectiveness.
Previous research, apart from carbonated water, has also used plain
water and found that both the perceived sweetness and satisfaction
were significantly amplified when compared to cases without any
scent. By conducting experiments with other sugar-free healthy
beverages like tea and coffee, the potential uses of Kaolid can besignificantly expanded. Additionally, in this experiment, we used
hot water for the cup-type device. There’s a need to experimentwith other warm beverages as well. To determine whether the cuptype device was able to reproduce the retronasal smell, further
exploration of beverages and scent is necessary.
The number of participants in this experiment was 20. In theevaluation of the straw-type device, a significant difference wasconfirmed in both taste satisfaction and perceived sweetness. For
the cup-type device, a significant difference was confirmed onlyin the perceived sweetness. Even with a small number of participants, the significant difference was established. In the future, byincreasing the number of participants and considering factors likeage and gender, we aim to demonstrate the effectiveness of Kaolid
for various demographic groups and design a more versatile device.
Furthermore, in this experiment, subjects’ scent preferences were
not considered. However, analyzing subjects’ scent preferences willallow a valid evaluation of this device in the future.
Our proposed device is currently a prototype, and we acknowledge that several improvements could enhance its real-world applicability. For example, we could improve the aesthetics and portability of the device to make it easier to use and carry. In terms oflimitations, the device currently only supports a limited range ofscents, which may not cover all the possible flavors a user mightwant to experience. In future work, we plan to expand the range of
supported scents and refine the technology based on user feedback.
Moreover, not only olfactory interventions but also visual interventions, such as using LEDs to change the color of the liquid, will
be introduced, aiming for a device that further augments sensory
experiences. And also in the conducted experiment, we powered
the device directly from a main supply. However, for real-world
applications, we envision equipping the device with an internal
rechargeable lithium polymer battery. We aim to design a device
that can provide a full day’s use with a single daily charge.

8

CONCLUSION

The experiment demonstrated that Kaolid significantly enhanced
both taste satisfaction and perceived sweetness compared to scenarios without any scent introduction. Specifically, the findings
indicated a notable increase in taste satisfaction and sweetness for

IoT ’23, November 07–10, 2023, Nagoya, Japanthe straw-type device, while the cup-type device mainly showed adistinct enhancement in perceived sweetness. As IoT continues toinfluence various facets of our everyday life, a novel interface like
Kaolid, which harnesses sensory enhancements using scent, could
pave the way for delving into the next frontier of IoT possibilities.
To further validate Kaolid’s effectiveness, upcoming experiments
will factor in participant variables such as age and gender.
The scent-based analysis suggests that optimal scents might differ depending on the beverage. While orange and pineapple scentswere employed in this study, it is essential to explore compatible
scents for beverages, considering the 10 odor groups humans candetect. Although the straw-type device seems to have achieved
retronasal smell, the same might not be true for the cup-type device. Future research should aim to design an IoT device capable ofdelivering retronasal smell in hot water and other warm beverages.

ACKNOWLEDGMENT
This work was supported by JST, PRESTO Grant Number JPMJPR21P7,
Japan.

REFERENCES[1] Judith Amores and Pattie Maes. 2017. Essence: Olfactory interfaces for unconscious influence of mood and cognitive performance. In Proceedings of the 2017
CHI conference on human factors in computing systems. 28–34.
[2] Lydia A Bazzano, Tricia Y Li, Kamudi J Joshipura, and Frank B Hu. 2008. Intakeof fruit, vegetables, and fruit juices and risk of diabetes in women. Diabetes care
31, 7 (2008), 1311–1317.
[3] Richard M Black, Lawrence A Leiter, and G Harvey Anderson. 1993. Consuming
aspartame with and without taste: differential effects on appetite and food intake
of young adult males. Physiology & behavior 53, 3 (1993), 459–466.
[4] Viola Bojanowski and Thomas Hummel. 2012. Retronasal perception of odors.
Physiology & behavior 107, 4 (2012), 484–487.
[5] Jason B Castro, Arvind Ramanathan, and Chakra S Chennubhotla. 2013. Categorical dimensions of human odor descriptor space revealed by non-negative
matrix factorization. PloS one 8, 9 (2013), e73289.
[6] Yongsoon Choi, Rahul Parsani, Xavier Roman, Anshul Vikram Pandey, andAdrian David Cheok. 2012. Sound perfume: building positive impression duringface-to-face communication. In SIGGRAPH Asia 2012 Emerging Technologies. 1–3.
[7] R. John Davenport. 2004. The Flavor of Aging. Science of Aging Knowledge
Environment 2004, 12 (2004), ns1–ns1. https://doi.org/10.1126/sageke.2004.12.ns1[8] David Dobbelstein, Steffen Herrdum, and Enrico Rukzio. 2017. inScent: A wearable olfactory display as an amplification for mobile notifications. In Proceedingsof the 2017 ACM International Symposium on Wearable Computers. 130–137.
[9] Cara B Ebbeling, Henry A Feldman, Stavroula K Osganian, Virginia R Chomitz,
Sheila J Ellenbogen, and David S Ludwig. 2006. Effects of decreasing sugarsweetened beverage consumption on body weight in adolescents: a randomized,
controlled pilot study. Pediatrics 117, 3 (2006), 673–680.
[10] Sharon P Fowler, Ken Williams, Roy G Resendez, Kelly J Hunt, Helen P Hazuda,
and Michael P Stern. 2008. Fueling the obesity epidemic? Artificially sweetened
beverage use and long-term weight gain. Obesity 16, 8 (2008), 1894–1900.
[11] Jeffrey S Gonzalez, Steven A Safren, Enrico Cagliero, Deborah J Wexler, Linda
Delahanty, Eve Wittenberg, Mark A Blais, James B Meigs, and Richard W Grant.
2007. Depression, self-care, and medication adherence in type 2 diabetes: relationships across the full range of symptom severity. Diabetes care 30, 9 (2007),
2222–2227.
[12] Lee S Gross, Li Li, Earl S Ford, and Simin Liu. 2004. Increased consumption ofrefined carbohydrates and the epidemic of type 2 diabetes in the United States:
an ecologic assessment. The American journal of clinical nutrition 79, 5 (2004),
774–779.
[13] Stefan Heilmann and Thomas Hummel. 2004. A new method for comparing
orthonasal and retronasal olfaction. Behavioral neuroscience 118, 2 (2004), 412.
[14] J.C Hoenink, J.M Stuber, J Lakerveld, W Waterlander, J.WJ Beulens, and J.D
Mackenbach. 2021. The effect of on-shelf sugar labeling on beverage sales inthe supermarket: a comparative interrupted time series analysis of a naturalexperiment. ISBNPA 18, 1 (2021), 1–11.
[15] Fumiaki Imamura, Laura O’Connor, Zheng Ye, Jaakko Mursu, Yasuaki Hayashino,
Shilpa N Bhupathiraju, and Nita G Forouhi. 2015. Consumption of sugar sweetened beverages, artificially sweetened beverages, and fruit juice and incidence oftype 2 diabetes: systematic review, meta-analysis, and estimation of population
attributable fraction. Bmj 351 (2015).

D.Mayumi et al.

[16] B. Lyman. 2012. A psychology of food: More than a matter of taste. Springer
Science & Business Media.
[17] V.S Malik, W.C Willett, and F.B Hu. 2013. Global obesity: trends, risk factors andpolicy implications. Nature Reviews Endocrinology 9, 1 (2013), 13–27.
[18] Vasanti S Malik and Frank B Hu. 2022. The role of sugar-sweetened beverages in the global epidemics of obesity and chronic diseases. Nature Reviews
Endocrinology 18, 4 (2022), 205–218.
[19] Vasanti S Malik, An Pan, Walter C Willett, and Frank B Hu. 2013. Sugar-sweetened
beverages and weight gain in children and adults: a systematic review and metaanalysis. The American journal of clinical nutrition 98, 4 (2013), 1084–1102.
[20] Daiki Mayumi, Yugo Nakamura, Shinya Misaki, Yuki Matsuda, and Keiichi Yasumoto. 2022. Aromug: Mug-Type Olfactory Interface to Assist in Reducing Sugar
Intake. In Adjunct Proceedings of the 2022 ACM International Joint Conference
on Pervasive and Ubiquitous Computing and the 2022 ACM International Symposium on Wearable Computers (Cambridge, United Kingdom) (UbiComp/ISWC ’22
Adjunct). Association for Computing Machinery, 183–187.
[21] Takuji Narumi, Shinya Nishizaka, Takashi Kajinami, Tomohiro Tanikawa, andMichitaka Hirose. 2011. Augmented reality flavors: gustatory display based on
edible marker and cross-modal interaction. In Proceedings of the SIGCHI conferenceon human factors in computing systems. 93–102.
[22] Nimesha Ranasinghe, Meetha Nesam James, Michael Gecawicz, Jonathan Bland,and David Smith. 2020. Influence of Electric Taste, Smell, Color, and Thermal
Sensory Modalities on the Liking and Mediated Emotions of Virtual Flavor
Perception. In Proceedings of the 2020 International Conference on MultimodalInteraction. 296–304.
[23] Nimesha Ranasinghe, Gajan Suthokumar, Kuan-Yi Lee, and Ellen Yi-Luen Do.
2015. Digital flavor: towards digitally simulating virtual flavors. In Proceedings ofthe 2015 ACM on international conference on multimodal interaction. 139–146.
[24] Lawrence D Rosenblum. 2011. See what I’m saying: The extraordinary powers of
our five senses. WW Norton & Company.
[25] Paul Rozin. 1982. " Taste–smell confusions" and the duality of the olfactory sense.
Perception & psychophysics (1982).
[26] Matthias B Schulze, JoAnn E Manson, David S Ludwig, Graham A Colditz, Meir J
Stampfer, Walter C Willett, and Frank B Hu. 2004. Sugar-sweetened beverages,
weight gain, and incidence of type 2 diabetes in young and middle-aged women.
Jama 292, 8 (2004), 927–934.
[27] Gitanjali M Singh, Renata Micha, Shahab Khatibzadeh, Peilin Shi, Stephen Lim,
Kathryn G Andrews, Rebecca E Engell, Majid Ezzati, Dariush Mozaffarian,Global Burden of Diseases Nutrition, and Chronic Diseases Expert Group (NutriCoDE). 2015. Global, regional, and national consumption of sugar-sweetened
beverages, fruit juices, and milk: a systematic assessment of beverage intake in
187 countries. PloS one 10, 8 (2015), e0124845.
[28] Dana M Small, Johannes C Gerber, Y Erica Mak, and Thomas Hummel. 2005.
Differential neural responses evoked by orthonasal versus retronasal odorantperception in humans. Neuron 47, 4 (2005), 593–605.
[29] Barb Stuckey. 2012. Taste what you’re missing: the passionate eater’s guide to why
good food tastes good. Simon and Schuster.
[30] Lisa Te Morenga, Simonette Mallard, and Jim Mann. 2013. Dietary sugars andbody weight: systematic review and meta-analyses of randomised controlled
trials and cohort studies. Bmj 346 (2013).
[31] Lenny R Vartanian, Marlene B Schwartz, and Kelly D Brownell. 2007. Effects
of soft drink consumption on nutrition and health: a systematic review andmeta-analysis. American journal of public health 97, 4 (2007), 667–675.
[32] K. Villinger, D.R Wahl, K. Engel, and B. Renner. 2021. Nudging sugar portions: areal-world experiment. BMC nutrition 7, 1 (2021), 1–5.
[33] Yanan Wang, Judith Amores, and Pattie Maes. 2020. On-face olfactory interfaces.
In Proceedings of the 2020 CHI Conference on Human Factors in Computing Systems.
1–9.
[34] World Health Organization. [n. d.]. Diabetes. Available online: https://www.who.
int/news-room/fact-sheets/detail/diabetes. Accessed: 2022-02-25.
[35] Tomoya Yamada, Satoshi Yokoyama, Tomohiro Tanikawa, Koichi Hirota, andMichitaka Hirose. 2006. Wearable olfactory display: Using odor in outdoor
environment. In IEEE Virtual Reality Conference (VR 2006). IEEE, 199–206.
[36] Jiawei Yin, Yalun Zhu, Vasanti Malik, Xiaoqin Li, Xiaolin Peng, Fang Fang Zhang,
Zhilei Shan, and Liegang Liu. 2021. Intake of sugar-sweetened and low-calorie
sweetened beverages and risk of cardiovascular disease: a meta-analysis andsystematic review. Advances in Nutrition 12, 1 (2021), 89–101.

Received 20 February 2007; revised 12 March 2009; accepted 5 June 2009