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Three hundred consumers were required to mix a hot and a cooler coffee together until it was at a desired temperature for drinking. They added creamer and sweetener to taste. In a 2nd experiment, 108 consumers performed the same experiment with black coffee only, but repeated it using different coffee strengths. In all experiments, the chosen mean preferred temperature for drinking was around 60 °C (140 °F). Black coffee drinkers chose a slightly higher mean temperature than drinkers with added creamer, and they also chose a slightly lower mean temperature when the flavor was stronger. In all cases, consumers tended to choose, on average, temperatures for drinking coffee that were above the oral pain threshold and the burn damage threshold.
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2774 JOURNAL OF FOOD SCIENCE—Vol. 67, Nr. 7, 2002 © 2002 Institute of Food Technologists
Sensory and Nutritive Qualities of Food
JFS: Sensory and Nutritive Qualities of Food
At What Temperatures Do Consumers Like to
Drink Coffee?: Mixing Methods
ABSTRACT: Three hundred consumers were required to mix a hot and a cooler coffee together until it was at a
desired temperature for drinking. They added creamer and sweetener to taste. In a 2nd experiment, 108 consumers
performed the same experiment with black coffee only, but repeated it using different coffee strengths. In all
experiments, the chosen mean preferred temperature for drinking was around 60 °C (140 °F). Black coffee drink-
ers chose a slightly higher mean temperature than drinkers with added creamer, and they also chose a slightly
lower mean temperature when the flavor was stronger. In all cases, consumers tended to choose, on average,
temperatures for drinking coffee that were above the oral pain threshold and the burn damage threshold.
Keywords: coffee, drink temperature, oral pain threshold
amount of litigation resulting from cof-
fee spills in restaurants and other places
serving coffee; such cases rest on the sup-
position that coffee is served at a temper-
ature that is so high that its risks outweigh
its benefits (Borchgrevink and others
1999). It is thus important to investigate
temperatures at which consumers prefer
to drink their coffee and the relationship
of these temperatures to those that inflict
pain or skin damage.
For coffee, the standard holding tem-
perature, established by the Coffee Brew-
ing Center (U.S.A.) and the Nordic Coffee
Center (Norway) ranges 80 to 85 °C (176 to
185 °F) (Lingle 1996). However, in reality,
serving temperatures might range from
around 71 °C to above 85 °C (160 to above
185 °F) (Lingle 2000). Borchgrevink and
others (1999) report that the hospitality
literature recommends holding tempera-
tures in the range 85 to 88 °C (185 to
190 °F). Such temperatures are higher
than reported pain or epithelial damage
thresholds in the literature.
There have been relatively few studies
on pain thresholds in the mouth. Yamada
and others (1952) mapped the mouth for
spots sensitive to pain, using Miller’s den-
tal broach. Svensson and others (1992)
measured pain thresholds induced by ar-
gon laser stimulation. For thermal pain,
Green (1985) measured mean thresholds
on the dorsal surface of the tongue
(47.8 °C, 118 °F) and the inner wall of the
lower lip (47.5 °C, 11.7.5 °F) with an as-
cending series method. Margarida and
others (1962) measured mean thresholds
on the hard palate, ranging from 46.2 to
47.0 °C (115 to 116.7 °F), using the method
of constant stimuli. Pain thresholds for
coffee may be inferred from these data,
with the caveat that the thresholds were
measured using a thermode stimulator
rather than a mouthful of hot coffee and
that both threshold methods used single
stimulus presentation, which is prone to
response bias from -criterion variation
(O’Mahony 1992).
These oral cavity thresholds were gen-
erally higher than thresholds quoted for
other parts of the body. Green (1985)
made within subjects’ comparisons with
the vermilion border of the lower lip
(46.0 °C, 114.8 °F) and the middle of the
chin (46.3 °C, 115.3 °F). Hardy and others
(1952) quoted thermal pain thresholds all
over the body surface ranging from
45.7 °C (114.3 °F) on the forehead to
42.2 °C (108 °F) on the lower back; this ex-
cludes a higher threshold noted for an
area of calloused skin on the heel. Stoll
and Greene (1959) noted a pain threshold
on the ventral surface of the forearm of
43.2 °C (109.8 °F).
There have not been any studies re-
garding heat damage to the surfaces of
the inside of the mouth, so inferences
must be made from data obtained from
skin on other parts of the body. The extent
of burn damage to the skin depends not
only on the temperature, but also on the
time that the thermal stimulus is present,
as well as the thickness of the skin in-
volved (Johnson and others 1981); this
has been modeled (Buettner 1951; Enale-
jev and Kachalkin 1998; Stoll and Greene
1959). Katcher (1981) has reviewed adult
skin burns drawing on the data of Moritz
and Henriques (1947), who measured
times required to cause complete destruc-
tion of the epidermis on the chest and the
ventral surface of the forearm at various
temperatures. They quote 1 sec at 70 °C
(158 °F), 2 sec at 65.6 °C (150 °F) and 5 sec
at 60 °C (140 °F). These are realistic values
for the time hot coffee may be held in the
mouth. For longer periods of time, lower
temperatures will inflict similar damage
(for example, 30 sec at 54.4 °C (129.9 °F) or
10 min at 48.9 °C (120 °F)), but these data
are not so relevant for drinking coffee.
Stoll and Greene (1959) noted blister for-
mation on the ventral surface of the fore-
arm with a 7.8 sec exposure at 56.7 °C
(130.1 °F). There are also several case
studies where patients have suffered
burns from ingesting hot liquids; the dan-
ger is that the resultant scalding can block
the airways, and, in one case, this ended
in death (Sando and others 1984; Kulick
and others 1988; Cooper and others 1990;
Dye and others 1990; Mellen and others
Thus, from the literature, it would
seem that the normal and recommended
temperatures at which coffee is held for
serving are not only above reported pain
thresholds but also above possible dam-
age thresholds in the mouth. The issue
becomes a question of whether consum-
ers really prefer to drink their coffee at
such high temperatures or whether they
would prefer lower ‘safer’ temperatures.
Borchgrevink and others (1999) stated
rather disturbingly that “…it would ap-
pear that temperatures specified as rec-
ommended temperatures by the hospital-
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Vol. 67, Nr. 7, 2002
Sensory and Nutritive Qualities of Food
Consumer coffee temperature preference . . .
ity and food literatures for brewing and
holding coffee are at odds with the medi-
cal literatures discussion of beverage tem-
peratures that result in burns, permanent
damage, and death. They used a 5-point
just right scale to assess liking for various
temperatures of black coffee. They quoted
the ideal temperature for serving being
between 62.8 to 68.3 °C (145 to 155 °F),
these being the temperatures closest to
the ideal score of 3 on their 5-point scale.
Unaware of their research, Pipatsattay-
anuwong and others (2001) used an R-in-
dex ranking task to determine preferred
temperatures for drinking. The most pre-
ferred temperature was 72.1 °C (161.8 °F)
followed by 60.9 °C (141.7 °F) followed by
76.6 °C (169.8 °F). The least preferred
temperature was 39.2 °C (102.5 °F), the
only temperature in the study that was
below the pain and damage thresholds.
The goal of the present study was to ex-
tend this research by examining preferred
drinking temperatures, not only for black
coffee, but also for coffee with added
creamer. The approach was to present
consumers with a source of hot coffee and
of cooler coffee that could be mixed ad-lib,
until the preferred temperature was at-
tained. This was then measured immedi-
ately with a fast thermocouple. During the
mixing process, creamers and sweeteners
could be added to taste. In Experiment I,
preferred drinking temperatures were
measured for both black coffee and coffee
with added creamer. In Experiment II, the
effect of coffee strength was investigated.
Consistency checks were made in both ex-
Materials and Methods
Experiment I. Three hundred consum-
ers (121 M, 179 F, 18 to 63 y), students,
staff, and friends were sampled from the
Univ. of California, Davis, Calif., U.S.A.
campus. Of these, 107 (49 M, 58 F, 18 to 63
y) consumers reported drinking coffee
once a d or more, 116 (49 M, 67 F, 18 to 52 y)
once a wk or more, 77 (23 M, 54 F, 18 to 44
y) once a mo or more.
Experiment II. One hundred and eight
consumers (54 M, 54 F, 18 to 55 y) were
sampled as in Experiment I; 30 (15 M, 15 F,
18 to 53 y) reported that they drank coffee
once a d or more, 48 (24 M, 24 F, 18 to 53 y)
once a wk or more, 30 (15 M, 15 F, 18 to 55
y) once a mo or more.
Coffee Preparation
Experiment I. Folgers Gourmet Su-
preme coffee (The Folger Coffee Co., Cin-
cinnati, Ohio, U.S.A.) was prepared from a
single brewer (Bunn Single SH: Bunn-O-
Matic Corp., Springfield, Ill., U.S.A.). The
brewer delivered hot water to the coffee
(240gm) in a filter (Bunn Gourmet Coffee:
Bunn-O-Matic Corp., Springfield, Ill.,
U.S.A.) at temperatures ranging from 82.1
to 91.4 °C (179.8 to 196.5 °F). Coffee was
later transferred to 2 servers (Bunn-O-
Matic SH Server, Thermofresh: 1.5 gall ca-
pacity, Bunn-O-Matic Corp., Springfield,
Ill., U.S.A.).
Once the coffee had been brewed, and
before transfer to the servers, it was trans-
ferred to a stainless steel container. More
water was added through the coffee filter
to adjust the volume to a standard
amount, to give a strength of 42.3 gm/ L
(160 gm/ gal). This was because the coffee
brewer did not deliver a sufficient volume
of coffee each time, while it also varied in
the amount it delivered. Having adjusted
the volume, the coffee was delivered to
the servers. For the coffee that was served
at the cooler temperature, the stainless
steel container was kept in an ice bath. Af-
ter adjustment, the coffee was placed in a
server which was switched off and deliv-
ered coffee at approx. room temperature.
For the coffee that was served hot, the
stainless steel container was sometimes
warmed when necessary, before transfer
of the coffee to the server. To enable the
experimenter to test for a longer period of
time, 2 cooler and 2 hot servers were pre-
The temperature of the coffee in the
servers was measured by thermocouple
(Mini-Alarm Thermometer with Probe,
Control Co., Friendswood, Tex., U.S.A.). In
the cooler servers, which were switched
off, the temperature of the coffee ranged
21.1 to 23.8 °C (70 to 75 °F); in the hot serv-
ers, the temperature ranged 85.0 to
90.6 °C (185 to 195 °F).
Also available for adding to the coffee
was a selection of creamers and sweeten-
ers. The sweeteners available were: white
sugar (C&H Pure Cane Sugar; C&H Co,
Crockett, Calif., U.S.A.), brown sugar
(Light Brown Sugar; I.G.A. Inc., Chicago,
Ill., U.S.A.), saccharin (SweetnLow; Cum-
berland Packing Corp. Brooklyn, N.Y.,
U.S.A.), and aspartame (Equal; The Nu-
trasweet Co, Chicago, Ill., U.S.A.). The
creamers were: Nestlé Carnation Coffee
Mate (Nestlé USA, Glendale, Calif.,
U.S.A.), non-fat milk (Crystal Cream &
Butter Co. Sacramento, Calif., U.S.A.) and
half and half (Crystal Cream & Butter Co.
Sacramento, Calif., U.S.A.). To keep them
cool, the milk and the half and half were
served in thermos flasks (Thermos Coffee
Butler; Canadian Thermos Products Inc.,
Scarborough, Ontario, Can.). Stirrers
(Happy Time Drinking Straws; Blue Dia-
mond Straw Inc., Los Angeles, Calif.,
U.S.A.) were also provided.
Experiment II. Coffee preparation was
as in Experiment I, with the modification
that 1 pair (hot and cool) of servers had
the same strength of coffee used in Exper-
iment I (42.3 gm/L) while the other pair
had stronger coffee: 66.9 gm/ L (253 gm/
gal). The cooler servers were again
switched off and contained coffee at tem-
peratures ranging 25.3 to 32.2 °C (77.5 to
90.0 °F). The temperature of the coffee in
the hot servers ranged 83.0 to 92.7 °C
(181.4 to 199.0 °F). Here the coffee was
served black.
Coffee Tasting
Experiment I. After interception, con-
sumers were screened; demographic de-
tails were collected, and instructions were
given. During this time, care was taken to
establish rapport with the consumer. The
exact instructions given depended on the
personality of the consumer but were gen-
erally as follows:
This is an experiment to see at what
temperature you like to drink your coffee.
This pot (indicating hot server) contains
hot coffee; this pot (indicating cooler serv-
er) contains cold. (Experimenter pours a
little hot coffee, approx. 30mL into the cup
and presents it to the consumer). You can
take the hot coffee and add as much cold
coffee or milk as you wish to cool it down to
the temperature you like. If it is too cold,
you can add hot coffee to warm it up
again. You can add as much sweetener and
creamer (indicating sweeteners and
creamers) as you wish. Just make the cof-
fee the way you usually do. When the tem-
perature is just right for you, let me know
and I will quickly measure it.
Care was taken to ensure that the con-
sumer understood the task completely.
Consumers were allowed to respond that
even the hot coffee was too cool, but none
did. Consumers dispensed hot and cold
coffee into an expanded polystyrene cup
(J Cup, 8oz, Dart Container Corp., Mason,
Mich., U.S.A.). Expanded polystyrene was
used for its insulating properties, because
judges were required to judge the temper-
ature of the coffee by using thermo-recep-
tors in the mouth, with minimum interfer-
ence from receptors in the hand. Once the
consumer had mixed his coffee, the tem-
perature was measured using a fast re-
sponding thermocouple (Physitemp,
Model BAT-12: Physitemp Instruments
Inc. Clifton, N.J., U.S.A.).
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Sensory and Nutritive Qualities of Food
2776 JOURNAL OF FOOD SCIENCEVol. 67, Nr. 7, 2002
Consumer coffee temperature preference . . .
From this group of 300 consumers, 33
consumers were chosen to measure con-
sistency. They returned a further 9 times,
giving each one a total of 10 sessions, all
on different d. Of the 33 consumers, 12 (7
M, 5 F, 18 to 31 y) drank coffee at least once
a d, 10 (6 M, 4 F, 19 to 26 y) at least once a
wk, and 11 (3 M, 8 F, 18 to 26 y) at least
once a mo. Session lengths ranged 1 to 8
min. Room temperature ranged from 20.0
to 27.1 °C (68.0 to 80.8 °F).
Experiment II. The procedure was as
for Experiment I, except that only black
coffee was served and all consumers per-
formed the experiment 3 times, at least 1 d
apart. On 1 d, the consumer performed
the experiment with the weaker strength
coffee. On another d, he performed it with
the stronger coffee. On a 3rd d, as a consis-
tency check, half the consumers used the
stronger coffee and half the weaker coffee.
The order of these 3 conditions was coun-
terbalanced over consumers. Session
lengths ranged from 1 to 5 min. Room tem-
perature ranged from 20.4 to 25.7 °C (68.7
to 78.3 °F).
Results and Discussion
ferred temperatures for drinking the
coffee in Experiments I and II. For the 300
consumers tested in Experiment I, the
mean chosen preferred temperature was
59.8 °C (139.6 °F). The median (59.5 °C,
139.1 °F) was close to the mean, suggest-
ing a symmetrical distribution.
For the 102 consumers who drank their
coffee black, the mean chosen preferred
temperature was 61.5 °C (142.7 °F), while
for the 198 who drank their coffee with
added creamer, the mean chosen pre-
ferred temperature was 59.0 °C (138.2 °F).
There was a slight yet significant differ-
ence between the means of the 2 groups
(independent samples t-test, 2-tailed,
p0.02): the black coffee group tended
to choose a higher temperature.
The consistency of the 33 consumers
who performed the experiment 10 times
was examined. Over the ten sessions, the
temperature chosen for drinking varied
considerably for a given consumer. The
mean range of variation over the consum-
ers was 12.0 °C (21.6 °F). The largest varia-
tion for a single consumer was 32.7 °C
(58.9 °F); the smallest was 4.8 °C (8.6 °F).
This puts into perspective the difference
between the mean most chosen tempera-
tures for consumers drinking black coffee
versus coffee with added creamer. It also
indicates that consumers do not have a
specific preferred temperature but rather
a preferred range of temperatures.
In passing, it is worth noting that the
mean variation for the subgroups within
the 33 consumers, varies with the fre-
quency of drinking coffee. For the 12 con-
sumers who drank coffee at least once a d,
the mean variation was 9.6 °C (49.3 °F).
For the 10 who drank coffee at least once a
wk, the mean was 11.6 °C (52.9 °F) while
for the 11 who drank coffee at least once a
mo, it was 14.8 °C (58.6 °F). The difference
between the 2 most extreme groups was
significant (ANOVA, LSD, p 0.05); be-
tween others it was not (p 0.2). This indi-
cated that there was a trend for more fre-
quent drinkers to have less variation in
their choice of preferred temperature.
Experiment II. Some consumers per-
formed the test twice with stronger coffee
and once with weaker coffee, while others
performed it twice with weaker coffee and
once with stronger. Comparisons were
made between temperatures chosen in
successive sessions for stronger compared
with weaker coffees, to see the effect of
coffee strength on chosen temperature.
Comparisons were also made between
temperatures chosen in successive ses-
sions for stronger compared with stronger
or weaker compared with weaker coffees
to check consistency.
From Table 1, for the 108 consumers,
the mean chosen preferred temperature
for stronger coffee was 59.3 °C (138.7 °F),
while for the weaker coffee, the mean tem-
perature was 60.4 °C (140.7 °F). The small
difference between the means was signifi-
cant (t-test, p 0.01). Bearing in mind the
variation for the individual consumers
noted in Experiment I, significance was
more likely to indicate the large sample
size rather than a large effect.
As a consistency check, comparisons
were made between the chosen tempera-
ture in 2 successive sessions using weaker
coffee and 2 successive sessions using
stronger coffee. These 2 conditions were
combined to gain statistical power. Thus,
for all 108 consumers, the mean chosen
preferred temperature in the 1st of the 2
like sessions was 60.6 °C (141.1 °F;
SD = 6.4 °C, 11.5 °F). For the 2nd like ses-
sion, the mean was 59.2 °C (138.6 °F;
SD 6.9 °C, 12.4 °F). This difference was
not significant (t-test, p 0.14), which in-
dicated that the difference between stron-
ger and weaker coffee was a consequence
of coffee strength.
The mean chosen preferred tempera-
ture for both black coffee and coffee with
added creamer for the 300 consumers
tested in Experiment I (59.8 °C) was lower
than the preferred temperature (72.1 °C)
found by Pipatsattayanuwong and others
(2001). It was closer to the 2nd most pre-
ferred temperature (60.9 °C). However,
despite the fact that both studies brewed
their coffee to the same strength, the com-
parison is not justified. This is because the
present study included coffee with cream-
er while the previous study did not. Con-
sidering only the 102 consumers who
drank their coffee black, in the present
study, the mean chosen preferred temper-
ature of 61.5 °C was still lower than the Pi-
patsattayanuwong and others study.
There is a further difference between
the 2 studies. In the Pipatsattayanuwong
and others study, the consumers made
their judgments by taking small sips of the
coffee. In the present study, consumers
adjusted the coffee temperature to be
suitable for drinking larger mouthfulls.
Thus, it is possible that the consumers
were more cautious and chose slightly low-
er temperatures for the present study.
Yet, the comparison between the 2
studies is put into perspective by the con-
sistency study, which indicated that when
Table 1—Preferred temperatures for drinking coffee, determined by a mixing
method used in Experiments I and II
Number of Mean Standard
Consumers Comments Temperature Deviation Range
Experiment I
102 drinking 61.5 °C9.1 °C 36.7 to 88.0 °C
black coffee (142.7 °F) (16.4 °F) (98.1 to 190.4 °F)
198 drinking coffee 59.0 °C7.5 °C 41.6 to 83.8 °C
with creamer (138.2 °F) (13.5 °F) (106.9 to 182.8 °F)
and/or sweetener
300 total 59.8 °C8.1 °C 36.7 to 88.0 °C
(102 + 198) (139.6 °F) (14.6 °F) (98.1 to 190.4 °F)
Experiment II
108 stronger 59.3 °C 6.5 °C 41.0 to 72.4 °C
black coffee (138.7 °F) (11.7 °F) (105.8 to 162.3 °F)
weaker 60.4 °C 6.7 °C 41.9 to 78.5 °C
black coffee (140.7 °F) (12.1 °F) (107.4 to 173.3 °F)
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Vol. 67, Nr. 7, 2002
Sensory and Nutritive Qualities of Food
Consumer coffee temperature preference . . .
the experiment was performed ten times,
there was considerable variation in the
preferred temperatures chosen. The dif-
ferences between the temperatures cho-
sen in the Pipatsattayanuwong and others
study and the present study (13.6 °C) are
comparable to the mean variation noted
in the consistency study (12 °C).
The consistency study also indicated
that consumers did not have a specific
preferred temperature at which they
chose to drink their coffee. Rather, they
had a range of temperatures that were
deemed suitable. It was also worth noting
that consumers who drank coffee more
regularly tended to vary less in their
choice of preferred temperature.
Borchgrevink and others (1999) report-
ed the ideal temperature for serving being
between 62.8 to 68.3 °C, which again is
slightly higher than in the present study.
It is not totally clear whether their judges
sipped small volumes or drank larger
mouthfuls of coffee. If the former was the
case, then the same hypothesis would ap-
ply to these differences as applied to the
differences found by Pipatsattayanuwong
and others (2001).
It is also possible that Borchgrevink
and others (1999) brewed their coffee at a
different strength. In Experiment II, it
was found that the preferred tempera-
ture for drinking coffee was less when the
coffee was stronger (59.3 compared with
60.4 °C). Although this small difference
was significant and greater than the con-
trol differences found in Experiment IIs
consistency check, it was still small com-
pared to the variation of individual con-
sumers found in Experiment I. Yet, the re-
sults suggest the hypothesis that the
consumers might be optimizing their
stimulation from the coffee, by increas-
ing the temperature stimulation when
the flavor stimulation is reduced. Howev-
er, pursuit of this line of argument could
give surprising conclusions. Experiment I
indicated that consumers who drank
their coffee black had a higher mean cho-
sen preferred temperature (61.5 °C) than
those who drank coffee with added
creamer (59.0 °C). From this it could be
inferred that coffee with creamer had a
stronger flavor than black coffee. This
would seem to be counterintuitive. How-
ever, there is a confounding factor; con-
sumers who used creamer had a signifi-
cantly greater tendency than black coffee
drinkers to use a sweetener (chi-squared,
p0.001). It could then be argued that
the added sweetener provided the stron-
ger flavor.
ments I and II were very close. They
tended to be slightly lower than tempera-
tures found by Borchgrevink and others
(1999) and Pipatsattayanuwong and oth-
ers (2001). Yet, the same conclusion can be
drawn from all these studies, that con-
sumers tended to choose on average, tem-
peratures for drinking coffee that were
above those published for oral pain and
epithelial burn damage thresholds. This
poses the question as to why consumers
do not burn their mouth while drinking
coffee at their preferred temperatures.
This is currently under investigation.
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MS 20010590 Submitted 10/20/01, Accepted 4/3/02,
Received 4/8/02
This research was supported by a grant from the Specialty
Coffee Association of America. The authors would like to
thank Ted Lingle for his advice and help.
Author O’Mahony is with the Dept. Food Science &
Technology, Univ. of California, Davis, CA 95616,
U.S.A. Direct inquiries to author O’Mahony (E-mail:,
jfsv67n7p2774-2777ms20010590-WA.p65 9/20/2002, 3:06 PM2777
... Many studies have investigated the consumer acceptability of different coffees [10][11][12][13]. To enhance sweetness, consumers also add milk or cream to their coffee [14]. As many different plant-based alternatives are becoming more popular [15], consumers have begun to use plant-based or non-dairy alternatives in their coffee. ...
... As stated above, the main sensory characteristics of coffee are fragrance and aroma, acidity, body, flavour, aftertaste, and balance [3]. Consumers add milk or cream to increase the sweetness of the coffee [14]. However, if consumers are using PBAs in their coffee, this can also introduce new flavours including beany, earthy, grassy and other off-flavours, which may detract from consumers' liking of the coffee. ...
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Consumers have begun to use plant-based alternatives (PBAs) in their coffee instead of dairy products. PBAs can include soy milk, rice milk, coconut milk, almond milk, oat milk, and hemp milk. The objective of this study was to investigate consumer acceptability and sensory perception of coffee with added dairy milk and added oat, soy, and almond PBAs. Consumers (n = 116) that frequently add milk to their coffee (n= 58) and consumers that usually use PBAs (n = 58) were recruited to participate in the study. They evaluated four different coffee samples with the addition of dairy milk as well as soy, almond, and oat PBAs. Overall, the consumers liking increased when they perceived sweetness in their coffee. The plant consumers (usually added PBAs to their coffee) liked the milk addition significantly less than the dairy consumers (usually added dairy to their coffee). In addition, the plant consumers were able to differentiate between the almond and soy PBAs, while the dairy consumers grouped them together. More studies need to be completed to investigate a wider range of PBAs, dairy products, and varieties of coffee.
... The coffee container technological solutions currently available to hot beverage drinkers, such as the ceramic mug, the insulated metal thermos and the paper sleeve-covered cup, feature substantial manufacturing costs, known impractical recyclabilities, inconvenient form factors and/or large carbon footprints over their lifetimes [21][22][23][24] . Moreover, these containers not only typically possess difficult-to-control heat dissipation properties, but also rarely account for the distinction between the comfortable external temperature range for holding a hot coffee-filled cup (~20-48 °C) and the preferred internal temperature range for drinking the coffee (~55-70 °C) (Fig. 1b) [27][28][29] . Consequently, there is a demand for the development of packaging solutions that exhibit the sustainable manufacturability and desirable recyclability of common metallized films, adaptively manage heat with a minimal external input of energy and accommodate the many different form factors of food and beverage containers. ...
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The implementation of innovative packaging solutions in the food and beverage industry is playing an increasingly important role in driving the global transformation towards sustainability. Within this context, the metallized polymer films most widely used for packaging, which feature static infrared reflecting properties, need to be replaced by green and low-cost alternative materials with highly desirable dynamic thermoregulability. Here we demonstrate the scalable manufacturing of squid-skin-inspired sustainable packaging materials with tunable heat-management properties. The reported composites feature a low estimated starting material cost of around US$0.1 m⁻², sizes comparable to those of common metallized plastic films, the ability to modulate infrared transmittance by >20-fold and heat fluxes by >30 W m⁻² upon actuation with strain, and functional robustness after mechanical deformation or cycling. Furthermore, the composites demonstrate excellent performance in routine practical packaging scenarios, as exemplified by their ability to control the cooling of a model warm beverage within a standard paper container used daily by most adults in the USA. Such materials could represent a technological solution that addresses the combined cost, performance and sustainability pressures facing the food and beverage packaging industry.
... In the current study, the RTD coffee samples were evaluated at hot temperatures between 60 to 65 • C during sensory evaluation for the following reasons. A hot serving temperature is preferred for coffee [31,32] with a long tradition of RTD coffee being sold as a hot beverage from vending machines or at convenience stores, especially in Japan where RTD coffee comprises the majority of coffee sales [33]. Additionally, the basic taste perceptions are known to be the most sensitive around room temperature (30 • C) and exhibit higher threshold values as temperatures increase or decrease [34,35]. ...
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Coffee brew flavor is known to degrade during storage. Untargeted and targeted LC/MS flavoromics analysis was applied to identify chemical compounds generated during storage that impacted the flavor stability of ready-to-drink (RTD) coffee. MS chemical profiles for sixteen RTD coffee samples stored for 0, 1, 2, and 4 months at 30 °C were modeled against the sensory degree of difference (DOD) scores by orthogonal partial least squares (OPLS) with good fit and predictive ability. Five highly predictive untargeted chemical features positively correlated to DOD were subsequently identified as 3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid. The increase in the six acidic compounds during storage was confirmed by sensory recombination tests to significantly impact the flavor stability of RTD coffee during storage. A decrease in pH, rather than an increase in total acidity, was supported to impact the coffee flavor profile.
... The coffee beverages were prepared by infusion method; 45 g of ground coffee beans were brewed with 950 mL of hot water (97 ± 1 °C) in a French press [9]. After 5 min, the brewed coffee samples were served in 200 mL white ceramic cups coded with three-digits random numbers to be assessed by trained at 68 ± 2 °C [10]. For consumer test, samples were poured into thermos flasks of 1.2 L to maintain the temperature. ...
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The objective of this study was to identify drivers of liking for local coffees cultivated in three indigenous regions from Hidalgo, Mexico. A conventional descriptive analysis was conducted to identify the sensory characteristics; 2-AFC discriminative test was performed to determine differences in acidity and bitter among coffee beverages. In addition, overall liking of four coffees was evaluated by 145 coffee consumers using a 9-point hedonic scale. Coffees from Sierra Gorda and Sierra Alta regions presented higher acidity than coffees from Sierra Otomí-Tepehua and coffees from Sierra Alta region were the most bitter (dʹ = 2.45, p < 0.001). Partial Least Square (PLS) regressions allowed the identification of drivers of liking for three clusters: vanilla-smell and nutty aroma were the main drivers of liking for cluster 1; astringency, acidity and bitterness for cluster 2 and roasted smell and taste for cluster 3. The drivers of disliking were green, earthy and roasted notes for cluster 2. This is the first report of drivers of liking of local coffee from the Mexican indigenous regions studied. This information can be used to evaluate the native consumer’s acceptance for coffee from indigenous regions and to generate strategies to improve coffee processing for desirable consumer-driven sensory attributes.
... Water was heated to a target temperature by an OXO Adjustable Temperature Pour-Over Kettle (OXO, New York City, NY, USA). Water extraction temperatures were chosen at 80 °C, the low end of brewing temperatures found acceptable by consumers for hot brewed coffee 24 ; 94 °C, within the range of brewing temperature suggested by the Coffee Brewing Handbook published by the Specialty Coffee Association 25 ; and 99 °C, as close as possible to boiling. The coffee was brewed using a 1-L glass beaker by adding an appropriate amount of water at 80 °C, 94 °C or 99 °C to a constant amount of 30 g of coffee grounds to yield a desired brew ratio. ...
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The sensory qualities of brewed coffee are known to be strongly correlated with the total dissolved solids (TDS) and extraction yield ( E ) of the brew. Here, we derive a predictive model for the TDS and E of full immersion brewed coffee using a pseudo-equilibrium desorption approach. Assuming a single, species-averaged equilibrium constant $$K$$ K yields theoretical predictions indicating that the TDS is approximately inversely proportional to the water/coffee mass brew ratio, while E is independent of the brew ratio. Our experimental results strongly accord with both theoretical predictions, and indicate that E is approximately 21% over a wide range of brew ratios. An analysis of the standard oven-drying method for measuring E indicates that it yields significant underestimates of the true value at equilibrium, due to retained brew within the spent moist grounds. We further demonstrate that $$K$$ K is insensitive to grind size, roast level, and brew temperature over the range 80–99 °C. Taken together, our results indicate that full immersion brewing offers precise control over the TDS at equilibrium but little control over E , and that practitioners should pay careful attention to their brew ratio as the most important parameter for full-immersion brewing.
Conference Paper
With the limited water temperature dispensed by current water dispensers and the varying water temperature desired by consumers, a multiple temperature selections thermoelectric water dispenser was designed to provide the consumer’s demand. This design uses a Thermoelectric module that operates based on the Peltier effect to heat and cool the water in the respective container, thereby eliminating the harmful effects of Freon, a refrigerant used by the current water dispensers process. Arduino Uno’s implementation as a microcontroller provided consumers with a chance to input and be served with their desired water temperature. The experiment results showed that the design is accurate in providing the consumers with their desired water temperature. Thus, the implemented design is successful in meeting the objectives of the study.
Flexible manipulators offer significant advantages over traditional rigid manipulators in minimally invasive surgery, because they can flexibly navigate around obstacles and pass cramped or tortuous paths. However, due to the inherent low stiffness, the ability to control/obtain higher stiffness when required remains to be further explored. In this article, we propose a flexible manipulator that exploits the phase transformation property of low-melting-point alloy to hydraulically drive and change the stiffness by heating and cooling. A prototype was fabricated, and experiments were conducted to evaluate the motion characteristics, stiffness performance, and rigid-flexible transition efficiency. The experimental results demonstrate that the proposed manipulator can freely adjust heading direction in the three-dimensional space. The experimental results also indicate that it took 9.2-10.3 s for the manipulator to transform from a rigid state to a flexible state and 15.4 s to transform from a flexible state to a rigid state. The lateral stiffness and flexural stiffness of the manipulator were 95.54 and 372.1 Ncm2 in the rigid state and 7.26 and 0.78 Ncm2 in the flexible state. The gain of the lateral stiffness and flexural stiffness was 13.15 and 477.05, respectively. In the rigid state, the ultimate force without shape deformation was more than 0.98 N in the straight condition (0°) and 1.36 N in the bending condition (90°). By assembling flexible surgical tools, the manipulator can enrich the diagnosis or treatment functions, which demonstrated the potential clinical value of the proposed manipulator.
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The temperature range for consuming hot drinks includes temperatures that can damage cells on the tongue. We hypothesized that the consumption of very hot drinks can lead to a decrease in the ability to perceive low concentrations of tastants. We evaluated the ability to perceive low concentrations of five prototypical sapid compounds in 42 women and 40 men aged 18–65. A questionnaire made it possible to collect the usual frequencies (number of unit/day) and consumption temperature levels (medium hot/very hot) for four very common hot drinks (coffee, tea, herbal infusions, and hot chocolate). Our results showed that subjects who consumed very hot drinks (versus medium hot) were less sensitive to sweet (p = 0.020) and salty (p = 0.046) tastes. An aggravating effect of high consumption frequencies was only shown for sweet taste (p = 0.036). Moreover, our data also showed that women were more sensitive than men to sour, bitter, and umami tastes (p values < 0.05), as well as that taste sensitivity decreases with age, especially after 50 years old (all tastes; p values < 0.05). These findings strengthen our knowledge about the influence of sex and age on taste sensitivity, and they provide knowledge on the influence of consumption habits related to hot drinks on taste sensitivity.
Coffee is a very complex drink, with different sensory characteristics, which directly influences in its acceptance. In general, the coffee quality assessments by experts do not correspond to consumer preferences. This study aimed to assess consumers' sensory response to coffee treatments classified as special and non-special (by cuppers), with different roasts (light and dark), in sensory tests with and without information about quality, type of roasting and price of coffees. Check-All-That-Apply (CATA) and acceptance tests were performed to evaluate the treatments. In CATA analysis, without information, only one attribute was significant to differ the treatments (p<0.05). Contrastly, in CATA analysis with information, nine attributes were detected that contributed to the differentiation between the special coffees with light roasting and the other coffees. There was no significant difference between the treatments (p>0.05) in the acceptance tests without information, for the flavor and overall acceptance attributes. In general, the scores assigned to special coffees were higher than those assigned to non-special coffees, in the acceptance tests with information. Therefore, the characteristics of special coffees can be used as a marketing strategy by industries, to increase theirs sales and to optimize the consumers’ sensory experience with the drink.
An infant sustained second- and third-degree scald burns of the oropharynx from drinking formula heated in a microwave oven. The circumstances leading to the scald injuries were recreated. Factors contributing to the injury included the volume of formula, the initial temperature of the formula, and the temperature gradient between the liquid core and the bottle surface after microwave heating. These studies indicate that infant formula should be warmed only with extreme care in microwave ovens and should be tested for suitability of temperature prior to feeding.
High-energy light from an argon laser was applied to human oral mucosa in order to investigate regional pain sensitivity. Significant regional differences in sensory and pain thresholds were observed between the test sites on the hard and soft palatal mucosa, the buccal mucosa, the tongue, the lower lip, and the skin on the hand. Pain thresholds were lowest on the tip of the tongue and highest on the hard palate. Sensory and pain thresholds were influenced by different stimulus parameters: pulse duration and laser beam diameter. Blackening of the mucosa in regions with high optical reflectance, such as the hard palate, increased light absorption and, hence, reduced both thresholds significantly. Reflectance spectrophotometric measurements indicated that the hard palatal mucosa reflected argon laser light about 1.5 times more than the tip of the tongue. The different threshold values could, in part, be ascribed to different reflectance and absorption properties of the mucosal areas but also indicated substantial regional variation in pain sensitivity of the human oral mucosa. Measurement of laser thresholds is an appropriate and standardized method for investigating sensory differences in human oral mucosa and may be used to study various pain conditions e.g., burning mouth syndrome.
ABSTRACTR-index measures were obtained from judges who ranked black coffees for preferred drinking temperature. Preferred temperatures were above thermal pain and thermal damage thresholds. The least preferred temperature was below the oral thermal pain threshold. Similar results were obtained with a ranking for temperatures that judges felt were most likely to be served in a coffee shop. Observations of customers in coffee shops indicated that they began sipping coffee at similar high temperatures.
The hospitality and food science literatures specify brewing and holding temperatures for hot beverages such as coffee, while the medical literature states that those very beverage temperatures will cause scalds and harm. These two specifications are at odds with one another, and recommend different approaches to serving and handling hot beverages. Considering the disparate standards it is interesting to note that no one has reported asking consumers of hot beverages at which temperature they prefer to consume their hot beverages. This pilot study is a first step in determining the consumer preferred hot beverage temperature. The research intent is to see if a temperature, or temperature range, can be established at which consumers drink a hot beverage, in this case coffee. The research is particularly relevant given recent litigation relative to spills and burns at foodservice operations, and subsequent changes in holding temperatures at some quick service restaurant chains. The findings suggest that the standard brewing and holding temperatures are too high for consumption, while the temperature identified as the medical literature threshold for burns is too low for consumption. ©
Aproblem central to sensory difference testing is response bias. There are two experimental strategies for dealing with this problem. The first is to use forced choice procedures, like the common duo-trio or triangle tests, while the second is to use signal detection measures like d′, P(A) and the R-index. These strategies are explained and discussed. The relationship between the R-index and the other signal detection measures is explained. The relationship between R-index values obtained by rating and ranking is explored, as are the alternative computations of the R-index by ranking: Rjb and Rmat.
Two experiments demonstrate that the sensitivity to heat pain varies significantly within the oral-facial region. Although the chin, the vermilion border of the lip, and the tonguetip are about equally sensitive, the mucosal lip and the dorsum of the tongue produce thresholds approximately 1.5°C higher. The spatial heterogeneity of heat-pain thresholds is discussed in relation both to local variations in perceived warmth in the same areas and to the neural and physical variables that might underlie them.
Two young children who sustained thermal injuries to the epiglottis (or "thermal epiglottitis") after swallowing hot beverages are reported. Findings, clinically and radiologically, in both children were similar to acute infectious epiglottitis. Children with these injuries are at risk for significant upper airway obstruction which may progress for several hours. Children in whom thermal epiglottitis is suspected should be approached with the same caution and preparedness for emergency airway management and pediatric intensive care afforded those with acute infectious epiglottitis.