Japan Journal of Food Engineering, Vol. 11, No. 4, pp. 177 - 185, Dec. 2010
◇◇◇ Original Paper ◇◇◇
Flow Properties and the Velocity through the Pharynx of Solutions Prepared
from Commercial Thickening Agents and Those of Yogurt
with Relevance to Liquid-Type Care Foods for Dysphagic Patients
Akiko TASHIRO1, Keiko ONO1, Atsuko HASEGAWA-TANIGOME2, Hitomi KUMAGAI3,
and Hitoshi KUMAGAI1,†
1
Department of Food Science and Nutrition, Kyoritsu Women’s University, 2-2-1 Hitotsubashi, Chiyoda-ku, Tokyo 101-8437, Japan
2
Department of Food Business, Nihon University, 1866 Kameino, Fujisawa-shi, Kanagawa 252-0880, Japan
3
Department of Chemistry and Life Science, Nihon University, 1866 Kameino, Fujisawa-shi, Kanagawa 252-0880, Japan
The viscosity, μ, and the velocity through the phar ynx of solutions prepared from commercial
thickening agents were compared with “fractured yogurt” as a model bolus of yogurt to evaluate their
suitability as care foods for dysphagic patients. From the shape of velocity spectra and the values of
velocity, the flow property of the “fractured yogurt” was considered to be close to that of the bolus of
yogurt. The value of μ for the yogurt-like thickener solution was smaller than the apparent viscosity,
-1
μapp, for the “fractured yogurt” around the shear rate (γ) of 10 s . In addition, the value of Vmax, an
index for the safety of care foods, for the yogurt-like and jam-like solutions was larger than that for
the fractured yogurt. These results indicate that a yogurt-like solution does not necessarily have flow
properties similar to those of yogurt and is less safe for dysphagic patients than yogurt.
Key words: ultrasonic, dysphagia, thickener, yogurt, viscosity
4
1. Introduction
masticating and swallowing. For both gel and sol foods,
the value ranges of “hardness,” determined from the
With the advent of an aged society, the incident of dys-
compression texture measured with a rheometer, were
phagia has increased; dysphagic patients often aspirate
set. As for sol foods, “the value of viscosity, μ, of sol
foods (foods enter not the esophagus but the trachea) [1,
measured with a B- type viscometer (a rotational viscom-
2]. Thin (low viscosity) liquids flow readily with small
eter with a vertical cylindrical rotor) at a rate of rotor
cohesion between particles and, therefore, are easily
rotation of 12 rpm was to be 1.5×103 mPa･s (＝1.5 Pa･s)
deformed during swallowing. Thus, thin liquid may pene-
and above at 20±2℃ after 2min” [5]. The viscosity μ is
trate the larynx and enter the trachea if laryngeal closure
physically a more appropriate parameter than the “hard-
does not occur properly. Many dysphagic patients are not
ness” as an index for liquid-type (sol) foods, since μ
capable of controlling laryngeal closure, and therefore
determines the flow rate for simple systems such as vis-
often aspirate such liquid foods of low viscosity [3, 4].
cous flow in a tube [6]. The Japan Care Food Conference
Thickeners or gelling agents are, therefore, used in
organized by various Japanese food companies set a simi-
foods for dysphagic patients to enhance both the viscos-
lar criterion for “the universal design foods” in 2003.
ity of and cohesion between food particles, and many
Many foods for the care of dysphagic patients have been
commercial foods containing thickeners and gelling
developed on the basis of this criterion. However, the
agents have been developed. However, the appropriate
new criteria set by the Ministry in 2009 do not distin-
physical properties of foods for patients with difficulty in
guish between sol and gel, not including viscosity as an
swallowing have not yet been definitely determined.
index.
In 1994, the Ministry of Health, Labour, and Welfare in
For determination of the appropriate properties of
Japan (hereafter referred to as the Ministry) set the diet
foods for dysphagic patients, an effective approach is to
criteria for gel and sol foods for patients with difficulty in
relate the flow aspects of foods (or the bolus) in the
human pharynx and the physical properties and/or tex-
(Received 26 Jul. 2010: accepted 21 Sep. 2010)
†Fax: ＋81-3-3237-2787, E-mail: [email protected]
ture of the foods. The ultrasonic pulse-Doppler method,
developed by Nakazawa et al. [7], is safer for the human
Akiko TASHIRO, Keiko ONO, Atsuko HASEGAWA-TANIGOME, Hitomi KUMAGAI and Hitoshi KUMAGAI
178
body than videofluorography (VF) [3, 4, 8]; and the
since the viscosity of such brittle and weak gels cannot
velocity distribution of foods (or the bolus) passing
be strictly defined. Therefore, the relationship between
through the pharynx can be obtained without the addi-
the flow properties of a bolus of yogurt and the velocity
tion of a contrast medium. Hasegawa et al. measured the
through pharynx has not been discussed.
velocities of food gels and solutions passing through the
Recently, many thickening agents as care foods for
pharynx by using this ultrasonic pulse-Doppler method
dysphagic patients have come into the Japanese market.
[9-11]. As a result, the maximum velocity of water, which
Most catalogs supplied by food companies describe the
dysphagic patients often aspirate into their trachea, was
procedure for preparing solutions of the following 3
-1
determined to be about 0.5 m s ; whereas the maximum
types: “jam - like,” “yogur t - like,” and “potage - like.”
velocity of yogurt, which is rarely aspirated by them, was
However, the viscosity and the velocity through the phar-
-1
about 0.2 m s . Thus, they concluded that the risk of
ynx of these solutions have not been examined yet.
foods being aspirated by dysphagic patients can be predicted from the maximum velocity of the foods. In addi-
In this present study, “jam- like,” “yogurt- like,” and
“potage- like” solutions were prepared from a typical
tion, they reported that the maximum velocities of thick-
commercial thickening agent as care foods for dysphagic
ener solutions, gels, and diets for dysphagic patients,
patients; and their viscosity and the velocity through the
-1
whose storage modulus, G’, at a frequency of 1 Hz ([s ])
pharynx were measured. In addition, yogurt curd frac-
was larger than 100 Pa and whose dynamic viscosity, η’,
tured by stirring was taken as a model bolus of yogurt,
was larger than 2 Pa･s, was similar to that of yogurt [8,10].
and its apparent viscosity and Vmax were compared with
We previously investigated the velocity through the
those of the thickener solutions.
human pharynx of solutions prepared from widely used
thickeners, i.e., carboxymethylcellulose (CMC), xanthan
2. Materials and Methods
gum, guar gum, and pregelatinized starch. The solution
viscosity μ was measured with 2 types of viscometers, a
2.1 Materials
B-type viscometer and a cone- and- plate one, with which
In a preliminar y test, the rheological properties of
an accurate value of μ can be obtained as a function of
jam-like, yogurt-like, and potage-like solutions prepared
the shear rate, γ [6]. In addition, the relationship
from many commercial thickening agents were found to
between the maximum velocity through the phar ynx,
be similar. In this current study, the rheological proper-
Vmax, and the values of viscosity μ was also examined
ties of yogurt-like solutions prepared with the following
[12]. The value of V max of the thickener solutions
3 thickening agents were examined:
approached that of yogurt as the concentration of the
(A) “Toromeiku” (Meiji Dairies Co., Tokyo, Japan, here-
thickening agents was increased. The values of μ mea-
after referred to as TA-1) composed of polysaccharides,
sured with the B- type viscometer were similar to those
dextran, and potassium chloride.
measured with the cone - and - plate viscometer at
(B) “Sur ukingu” (Kissei Pharmaceutical Co., Ltd.,
selected shear rates. The rate of rotor rotation (12 rpm)
Nagano, Japan, hereafter designated as TA- 2) composed
in the criteria set by the Ministry in 1994 was calculated
of polysaccharides, dextran, and emulsifier.
4
to give a γ value of 2 to 3 s
-1
in the viscosity range of
(C) “Toromipafekuto” (The Nisshin OilliO Group, Ltd.,
thickener solutions for patients with dysphagia. The max-
Tokyo, Japan, hereafter referred to as TA- 3) composed
imum velocity, Vmax, of the thickener solutions correlated
of polysaccharides, dextran, and potassium chloride.
4
well with μ on semi- logarithmic plots (Vmax vs. log μ);
The thickening agents were used without further puri-
and the value of the correlation coefficient, R, at the
fication. Since the rheological properties of solutions pre-
shear rate of 10 s
-1
was larger than those values at the
-1
pared from these 3 commercial thickening agents were
shear rates of 1 and 100 s . Consequently, we concluded
similar, as shown subsequently, the thickening agent
that the viscosity, μ, could be a suitable index for thick-
TA-1 or “Toromeiku” was chosen; and the properties of
ener solutions in care foods for dysphagic patients and
its solutions were examined in detail. As yogurt, “Meiji
that the shear rate should be 10 s
-1
or more, although
-1
Bulgaria Yogur t LB 81” (Meiji Dairies Co., Tokyo,
that corre-
Japan), used in the previous studies [9-12], was selected.
sponded to the rotor rotation rate of 12 rpm set by the
This yogurt is apparently a brittle and weak gel, and
Ministr y. However, the physical properties of yogurt
taken as a “weak gel” rheologically based on the dynamic
used as a reference have not yet been characterized,
viscoelastic data presented previously [9].
this value was higher than the 2 and 3 s
179
Velocity of thickener solutions and yogurt passing through the pharynx
2.2 Preparation of thickener solutions
( f ＝ω/2π) range of 0.02 Hz to 5 Hz for 660 s; and the
Three types (jam- like, yogurt- like, and potage- like) of
storage modulus, G’, and the loss modulus, G’’, were
thickener solutions were prepared as follows: A specific
obtained as a function of ω. The complex elasticity, G*, is
amount of the thickening agent in powder form was dis-
defined by
persed into distilled and deionized water by stirring with
G *＝G’＋i G’’
an impeller, and the solution was then kept at 80℃ for 10
(1)
min in a water bath. All the solutions were degassed at
where i is the imaginary unit. The complex viscosity, η*,
about 60℃ in a desiccator with an aspirator for a few min-
is defined by
utes to remove the bubbles in the solutions. The concen-
η*＝G*/iω
trations of jam-like, yogurt- like, and potage- like thickener solutions were adjusted according to the manual
supplied by the manufacturer.
(2)
The absolute value of the complex viscosity η*, ｜η.｜,
is referred to as η*, as is conventional in rheology [14].
In a preliminary test, each sample put into a subject’s
2.3 Preparation of fractured yogurt as a
mouth was spit out just before swallowing would have
model bolus of yogurt
occurred, and its temperature was then measured. The
In the previous studies [9- 12], we had chosen water
temperature of foods just before swallowing was around
and yogurt as reference foods. The yogurt used was a
25℃, and hence viscoelasticity measurements were made
brittle and weak gel; and, therefore, its μ value could not
at 25℃.
be strictly defined, whereas the viscosity of water could
be measured. However, in the case of solid or semi-solid
2.5 Viscosity measurement
foods, human beings masticate and swallow them as a
A B - type viscometer is commonly used in the
bolus, the apparent viscosity of which would determine
Japanese food industr y, having been adopted by the
the flow velocity through the phar ynx. In this study,
Ministry as the viscometer to be a part of the criterion
yogurt curd was stirred with a spoon by hand for about 1
set in 1994. Moreover, a B- type viscometer is suitable for
minute until the yogurt curd was apparently lost; and the
measuring the apparent viscosity of heterogeneous sam-
sample (hereafter referred to as “fractured yogurt”) was
ples such as a slurr y, bolus, and “fractured yogur t”
used as a model bolus of the yogurt. The apparent vis-
examined in this study, since the “gap” between the rotor
cosity, μapp, of the “fractured yogurt” was measured with
and sample-vessel wall is large. Therefore, the viscosity
the B-type viscometer; and its velocity through the phar-
(μ) of thickener solutions and the apparent viscosity
ynx was compared with that of the solutions prepared
(μapp ) of “fractured yogur t” were measured with a
from the commercial thickening agent.
B-type viscometer by the method similar to that used in
the previous study [12].
2.4 Measurement and analysis of dynamic
viscoelasticities
A B-type viscometer BL/50 (Toki Sangyo Co., Ltd.,
Tokyo, Japan) was used with the following rotors: No. 1
Dynamic viscoelasticities reflect dispersed and/or
(65 mm in height and 19 mm in diameter), No. 2 (6.8 mm
entangled structures of polymers in food hydrocolloids
in height and 18.8 mm in diameter), No. 3 (1.5 mm in
[13]. Hydrocolloids are therefore rheologically charac-
height and 12.8 mm in diameter), and No. 4 (30 mm in
terized according to the angular frequency (ω) depen-
height and 3.2 mm in diameter). The approximated γ
dence of the storage modulus, G’, a measure of elasticity,
was calculated by the method described by the manufac-
and the loss modulus, G’’. The dynamic viscoelastic prop-
turer. The shear rate, γ [s ], is related to the rate of
erties of the thickener solutions were measured by using
rotation N [rpm] as follows:
4
4
a rheometer, Rheosol- G5000 (UBM Co., Ltd., Kyoto,
-1
γ＝K N
(3)
4
Japan), equipped with a cone- and-plate fixture (a cone
-1
-1
with a 40-mm diameter, a 2° cone angle, and a gap of 50
where K [s
μm) were used.
shear rate constant); its values are 0.233, 0.259, 0.244,
rpm ] is the empirical parameter (the
Each sample solution was loaded between the cone
and 0.215 for rotor No. 1, No. 2, No. 3, and No. 4, respec-
and the plate. Preliminary tests were done to determine
tively. Fig. 1 shows the dependence of γ on the rotation
the linear viscoelastic range for each sample. Stress was
rate for each of the 4 rotors. The shear rate at the rate of
measured under a logarithmically increasing frequency
rotation of 12 rpm was calculated to be γ＝2 to 3 s
4
4
-1
over
Akiko TASHIRO, Keiko ONO, Atsuko HASEGAWA-TANIGOME, Hitomi KUMAGAI and Hitoshi KUMAGAI
180
frequency suitable for measuring a relatively shallow
part of the body. The subject sat on a chair with her head
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fixed and back straightened at a room temperature of
23℃. An ultrasonic probe was set against her neck, so
that the ultrasonic pulse was directed at an upward angle
of 60° . The samples tested had been kept at 15℃ prior to
㨯
use. The subject scooped up a sample of 6 g, put it into
her mouth, and swallowed it in a single swallowing movement. Immediately thereafter, measurements were taken
in the B-mode (used to identify a region of the pharynx,
based on the fact that the reflection of ultrasonic waves is
different among organs) and the color Doppler mode
7KHYDOXHRI1LQWKH&ULWHULRQ
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(the signal obtained by the pulse Doppler method is illustrated in color). A velocity distribution spectrum, bright-
7KHUDWHRIURWDWLRQ 1>USP@
Fig. 1 The relation between the rate of rotation, N, and the
shear rate, γ, for a B- type viscometer. The rotor used: ○,
4
No. 1; □, No. 2; △ , No. 3; ◇, No. 4
ness being a function of the passage time and velocity
through the pharynx, was obtained, where the brightness is proportional to the volume of “food particles”
(small portions of food detectable with the ultrasonic
probe) at a given passage time and velocity. In the present study, the velocity distribution of the thickener solu-
the viscosity range examined.
tions through the pharynx of a single subject was there-
The temperature of each sample solution in a 500- ml
fore investigated as in the previous study [12], since
beaker (85 mm in inner diameter) was kept at 25℃ in a
velocity data on a single subject are more appropriate for
water bath. The viscosity of the sample solution was mea-
grasping the dependence of velocity on the thickener
sured at 25℃ with an appropriate rotor and at a selected
concentration (or the viscosity) than data on many sub-
rotor rotation rate; and μ was obtained as a function of
jects.
the approximated value of γ.
2.6.3 Analysis of velocity distribution
4
spectra
2.6 Measurement and analysis of the
Velocity distribution spectra (n＝20-30) measured as
velocity of the thickener solutions passing
described above were averaged by using computer soft-
through the pharynx
ware, Image-Pro Plus ver. 5.0 (Nippon Roper Co., Ltd.,
The velocity of the thickener solutions through the
Tokyo, Japan), to obtain a color velocity distribution
phar ynx was measured and analyzed by the method
spectrum. In a color spectrum, the volume fraction of
described in the previous studies [9- 12].
“food particles” is higher in the order of red, green, and
2.6.1 Subject
blue. The maximum velocity, Vmax [ms ], and the mean
-1
-1
A young female subject (height, 155 cm; circumfer-
velocity, vm [ms ], were calculated from the spectra. In
ence of neck, 31 cm; age, 23), without difficulty in swal-
order to reduce background noise, we defined the maxi-
lowing and without phar yngolar yngeal or cer vical
mum velocity, Vmax, as the velocity at which the value of
lesions, participated in this study. We adhered to the
the brightness was 12 dB lower than that of the bright-
Helsinki Declaration, and carried out the experiments
ness in the statistical mode of velocity [9-12].
after they had been approved by the in- house Ethics
Committee of Kyoritsu Women’s University.
3. Results
2.6.2 Measurement of velocity through the
pharynx by the ultrasonic pulse Doppler
method
First, rheological proper ties of solutions prepared
from commercial thickening agents were examined.
An ultrasonic apparatus for diagnosis, ECCOCEE
Figure 2 shows rheological properties of yogurt- like
(SSA-340 A type; Toshiba Medical Systems Co., Tokyo,
solutions prepared from the 3 thickening agents TA-1,
Japan) equipped with a linear scan probe, PLF- 703NT,
TA-2, and TA-3. The 3 figures at the left show the angu-
for pulse Doppler measurements, was used at 6.0 MHz, a
lar frequency (ω) dependence of the storage modulus,
181
Velocity of thickener solutions and yogurt passing through the pharynx
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Fig. 2 Rheological properties of yogurt-like solutions prepared from the 3 commercial thickening
agents. Thickening agents: (A), TA-1 (2.0%); (B), TA-2 (2.0%); (C), TA-3 (2.0%). Three figures at
left: Angular frequency (ω) dependence of G’ and G’’. Three figures at right: The dependence of
the viscosity μ on the shear rate γ and that of the complex viscosity η* on ω.
4
G’, and the loss modulus, G’’; and the 3 figures at the
these 3 solutions decreased about 1 order of magnitude
right, the dependence of viscosity μ on shear rate γ and
as the value of γ increased 1 order of magnitude; and
that of the complex viscosity η* on ω. G’ was slightly
the degree of the shear thinning was similar to that of
larger than G’’, and both moduli were only slightly
xanthan gum solutions reported previously [12]. The
dependent on ω. Hence, these solutions can be taken as
dependence of μ on γ is superimposable upon that of
weak gels [13]. The decrease in μ with increasing γ
the complex viscosity η* on ω for many polymer solu-
(so- called shear thinning [16- 19]) was observed for all
tions, as stated by the empirical Cox-Merz rule [14, 15].
of the samples (3 figures at the right). The value of μ for
For the Cox-Merz rule to be applied, it is necessary that
4
4
4
4
Akiko TASHIRO, Keiko ONO, Atsuko HASEGAWA-TANIGOME, Hitomi KUMAGAI and Hitoshi KUMAGAI
182
the structure that determines the mechanical properties
respectively. Shear thinning was observed for all of the
of a material should remain intact under steady flow. At
samples. The degree of the shear thinning for all thick-
high extents of coil overlap, polymer samples fail to obey
ener solutions was similar to that of xanthan gum solu-
the Cox-Merz rule due to the formation and breaking of
tions [12]. The values of μ decreased in the order of
non-covalent bonds [14]. Ikeda and Nishinari reported
jam- like, yogurt- like, and potage- like solutions at the
that a weak gel- type κ - carrageenan solution did not
same value of γ. The values of μ at γ＝2.5 s
obey the Cox- Merz rule [14]. As shown in Fig. 2, com-
like, yogurt- like, and potage- like solutions were 4.7, 3.1,
mercial thickener solutions examined in this study were
and 0.85 Pa･s, respectively, the values for jam-like and
taken as weak gels; this would result in failure to obey
yogurt- like solutions being larger than 1.5 Pa･s, the
the Cox-Merz rule. As can be seen in Fig. 2, the rheolog-
value of μ in the criteria set by the Ministry in 1994. The
ical properties of solutions prepared from commercial
values of μ at γ＝10 s
thickening agents were found to be similar. Therefore,
potage-like solutions were 1.3 Pa･s and 0.92, and 0.28,
the flow properties and the velocity through the pharynx
respectively. The value of μapp of the fractured yogurt
of jam-like, yogurt- like, and potage- like solutions pre-
was 3.0 Pa･s at γ＝2.5 s , which was close to that of μ
pared from TA-1 were examined.
of the yogurt- like solution. However, the mean values of
4
4
4
-1
-1
for jam-
for jam-like, yogurt-like, and
-1
4
Figure 3 shows the dependence of G’ and G’’ of the
the apparent viscosity of the fractured yogur t were
jam-like, yogurt- like, and potage- like solutions prepared
between those of μ for yogurt-like and jam-like solu-
from the thickening agent TA- 1 on ω. These solutions
tions at higher γ values.
can be also taken as weak gels [13].
4
Figure 5 shows typical velocity distribution spectra of
the samples, with those of water and yogurt shown for
comparison. The spectrum for water was distributed over
TA-1 and the apparent viscosity, μapp, of the fractured
a wider velocity range than those spectra of the other
yogurt on γ. The data on the fractured yogurt were scat-
samples, whereas that for yogurt showed the narrowest
tered, probably due to heterogeneity of the sample. The
range of all of the samples, as repor ted previously
solid and broken lines are the linear best- fit computa-
[9-12]. The spectra for the thickener solutions at a low
tions for thickener solutions and the fractured yogurt,
concentration were distributed over a wider velocity
4
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Fig. 3 Angular frequency (ω) dependence of G’ and G’’ for
the solutions prepared by using the commercial thickening
agent TA-1. Solid symbols (■, ▲, ●), storage modulus, G’;
open symbols (□, △, ○), loss modulus, G’’. Solutions: (■,
□), jam-like (2.5%) ; (▲, △), yogurt-like (2.0%) ; (●, ○),
potage-like (1.0%)
9LVFRVLW\ PRU$SSDUHQWYLVFRVLW\ PDSS>3D㨯V@
Figure 4 shows the dependences of μ of the jam-like,
yogurt- like, and potage- like solutions prepared from
6KHDUUDWH J㨯>V@
Fig. 4 The dependence of viscosity, μ, of the thickener
solutions and the apparent viscosity, μapp, of the fractured
yogur t on shear rate γ. The thickening agent used was
TA-1. Solutions: ■, jam-like; ▲, yogurt-like; ●, potage-like;
fractured yogurt, ○. The solid lines are the linear best- fit
computation for the thickener solutions. The broken lines are
the linear best-fit computation for the fractured yogurt.
4
183
Velocity of thickener solutions and yogurt passing through the pharynx
Fig. 5 Color spectra showing velocity through the pharynx for the various samples. The thickening agent
used was TA-1. The velocity spectrum for water, which dysphagic patients often aspirate into their
trachea, is also shown for comparison.
range in the order of potage- like> yogurt- like> and jam-
Figure 7 shows the relationships between the maxi-
like solutions. The spectrum for the yogurt- type thick-
mum velocity, Vmax, and the viscosity measured at the
ener solution was distributed over a wider velocity range
shear rates of γ＝2.5 s
than those spectra for “yogurt as is” and “the fractured
7[b]). The values of μ at γ＝2.5 s and 10 s were eval-
yogurt.” The shape of the spectrum for the fractured
uated by the linear regression curves shown in Fig. 4.
yogurt was similar to that for the “yogurt as is.”
The value of Vmax of the thickener solutions decreased as
4
-1
(Fig. 7[a]) and 10 s
-1
4
-1
(Fig.
-1
In Fig. 6, the data for the mean (vm) and the maximum
the value of viscosity increased, as previously reported
(Vmax) velocity of the samples through the pharynx calcu-
[12]. On the other hand, the value of Vmax of the frac-
lated from the velocity spectra (Fig. 5) are shown. The
tured yogurt was the smallest, in spite of the fact that the
difference in the mean velocity, vm, among the samples
value of the apparent viscosity μapp for the fractured
was slight; whereas the values of Vmax differed among
yogurt was similar to that of the viscosity for the yogurt-
the samples, as previously reported [9- 12]. The values of
like solution at γ＝2.5 s
Vmax for the thickener solutions were larger in the order
the yogurt-like and the jam-like solutions at γ＝10 s .
4
-1
and between those values for
4
-1
of potage - like> yogur t - like> and jam - like solutions,
being larger than that value for yogurt even in the case
4. Discussion
of the jam-like solution. The value of Vmax for the fractured yogurt was similar to that for the “yogurt as is.”
Human beings chew foods, mix them with saliva, and
swallow them as a bolus in the case of solid or semi- solid
foods [3, 4]. The yogurt (brittle and weak gel) used in
9HORFLW\WKURXJKWKHSKDU\Q[>PV@
this study would be swallowed as a bolus probably with-
/HIW 9PD[
out chewing by the teeth and with mixing with little
5LJKW YP
saliva. The shape of the spectrum (Fig. 5) and the value
of Vmax (Fig. 6) for the fractured yogurt were similar to
those for the “yogurt as is,” indicating that the flow prop-
erty of the fractured yogurt was similar to that of the
bolus of the “yogurt as is.”
The spectrum for the yogurt- type thickener solution
(TA- 1) was distributed over a wider velocity range than
)UDFWXUHG
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that for “yogurt as is” or the fractured yogurt, as seen in
Fig. 6 The velocities of passage of the various samples through
the pharynx, with TA-1 used as the thickening agent.
thickener solution was 0.34 m s , being larger than that
:DWHU
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Fig. 5. In addition, the value of Vmax for the yogurt- type
-1
of “yogurt as is” or the fractured yogurt, as was shown in
Akiko TASHIRO, Keiko ONO, Atsuko HASEGAWA-TANIGOME, Hitomi KUMAGAI and Hitoshi KUMAGAI
184
7KHPD[LPXPYHORFLW\9PD[>PV@
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-1
＝2-3 s ) with a B-type viscometer. On the other hand,
the material type and viscosity range for commercial
thickener solutions have been determined empirically by
clinical trials. As shown in Fig. 4, the values of μ at γ＝
3RWDJHOLNH
4
2.5 s
larger than the threshold value, 1.5 Pa･s. However, the
value of Vmax for even the jam- like solution was 0.30,
-1
being larger than that of yogurt (0.2 m s ). The thresh-
old value of 1.5 Pa･s at γ＝2- 3 s
4
-1
is, therefore, consid-
ered to be inappropriate for evaluating the suitability of
thickener solutions for care foods.
9LVFRVLW\ PDWJ䍃 V>3D㨯V@
As shown in Fig. 7, the value of Vmax for the thickener
solution decreased as the value of μ increased. However,
E
the value of Vmax of the fractured yogurt was the small-
7KHPD[LPXPYHORFLW\9PD[>PV@
for jam-like and yogurt-like solutions were 4.7
and 3.1 Pa･s, respectively, the μ values of which were
<RJXUWOLNH
-DPOLNH
-1
est, even though the value of μapp for the fractured
yogurt was smaller than that of the jam- like thickener
-1
solution at both γ＝2.5 and 10 s . In our previous study,
3RWDJHOLNH
4
the shear rate of a liquid through the phar ynx was
roughly estimated to be 10 s
<RJXUWOLNH
or somewhat larger than
10 s in the pharynx at its narrowest part [20]. From the
-DPOLNH
-1
-1
results given in Fig. 7, the threshold value of μ for care
food for dysphagic patients should be determined at γ＝
4
10 s
-1
-1
or more rather than at γ＝2.5 s . The threshold
4
value should be above 1.1 Pa･s (μapp of fractured yogurt)
4
9LVFRVLW\ PDWJ䍃 V>3D㨯V@
-1
-1
at γ＝10 s in order to have Vmax＝0.3 m s .
In the diet criteria set by the Ministry in 1994, viscosity was included as an index for sol- type care foods.
Fig. 7 Relationship between the maximum velocity through
the phar ynx, Vmax, and the viscosity measured at the shear
-1
-1
rates of γ＝2.5 s (a) and 10 s (b). ○, thickener solutions
prepared with the thickening agent TA-1; ●, The fractured
yogurt
4
However, in the new criteria set by the Ministry in 2009,
the value ranges of 3 parameters, i.e., “hardness,” “cohesiveness,” and “adhesiveness” determined from the compression texture measured with a rheometer were specified; whereas the viscosity was eliminated from the criteria set in 1994, probably because μ was considered to be
Fig. 6. From these aspects, the velocity distribution in
inappropriate as an index for care foods for dysphagic
the pharynx for “yogurt- like” thickener solution was dif-
patients. However, the problem would have been that the
ferent from that for yogurt. The “yogurt- like” thickener
measurement of μ in the criteria in 1994 was determined
solution is considered to be less safe for dysphagic
-1
at the shear rate (γ) of 2- 3 s (the rate obtained with a
patients than yogurt (brittle and weak gel type) with
rotor rotation of 12 rpm with a B- type viscometer). If the
respect to the velocity through the pharynx. As shown in
viscosity is measured at γ＝10 s
Fig. 4, the value of μapp for the fractured yogurt was
reflect the flow properties of a liquid through the phar-
close to that of μ for the yogurt- like thickener solution
ynx. From a physical point of view, the viscosity is a more
-1
at a low γ of 2- 3 s ; and the mean value of μapp was
appropriate parameter than the “hardness,” “cohesive-
between those values of μ for the yogurt- like and jam-
ness,” and “adhesiveness” as an index for liquid- type
like solutions as γ increased. Perhaps the types of com-
(sol) foods. Moreover, “hardness,” “cohesiveness,” and
mercial thickener solutions should be determined by the
“adhesiveness” are not physical properties, their values
4
4
-1
value of μ at a γ value of 2- 3 s (N＝12 rpm).
4
4
4
-1
or higher, it would
depending on sample size, material of the plunger, and
In the criteria established in 1994, the threshold value
rheometer used. Therefore, μ should be included as an
of μ was 1.5 Pa･s at a rate of rotor rotation of 12 rpm (γ
index of liquid (sol) - type care foods for dysphagic
4
Velocity of thickener solutions and yogurt passing through the pharynx
patients; and the threshold value of μ should be set at a
shear rate (γ) of 10 s
4
-1
or more where the rate of rotor
rotation for a B- type viscometer is more than 40 rpm
according to Fig. 1.
185
Effect of physical properties and oral perception on transit
speed and passing time of semiliquid foods. J. Texture Stud.,
33, 585-598 (2003).
9) A. Hasegawa, A. Otoguro, H. Kumagai, F. Nakazawa; Velocity
In the previous [12] and present studies, the value of
the Vmax for the thickener solutions approached that
of swallowed gel food in the pharynx by ultrasonic method, J.
Jpn. Soc. Food Sci. Technol., 52, 441-447 (2005).
value of yogur t as the thickener concentration was
10) A. Hasegawa, F. Nakazawa, H. Kumagai; Mass dependence
increased, but was larger than that of yogurt (larger than
of velocity of swallowed foods through the pharynx by ultra-
-1
0.24 ms ). Not only the viscosity of the bolus but also
sonic method. J. Jpn. Soc. Food Sci. Technol. (in Japanese),
cohesion oriented by the gel-network might influence
55, 330-337 (2008).
the velocity through the pharynx in the case of a gel.
11) A. Hasegawa, F. Nakazawa, H. Kumagai; Velocity of swal-
As for solid and semi- solid foods, the steady shear vis-
lowed food for dysphagic patients through the phar ynx
cosity μ cannot be defined. Further investigation of the
by ultrasonic method, J. Jpn. Soc. Food Sci. Technol., 55,
relationship between bolus viscosity of semi- solid foods
other than yogurt and velocity in the human pharynx is
thus necessary.
541-548 (2008).
12) H. Kumagai, A.Tashiro, A. Hasegawa, K. Kohyama, H.
Kumagai; Relationship between flow properties of thickener
solutions and their velocity through the pharynx measured
Acknowledgment
by the ultrasonic pulse Doppler method. Food Sci. Technol.
Res., 15, 203-210 (2009).
This work was supported partly by the Japan Food
Chemical Research Foundation.
13) K. Nishinari; Rheology of physical gel and gelling processes.
Rep. Prog. Polym. Phys. Jan., 43, 163-192 (2000).
14) S, Ikeda, K. Nishinari; “Weak gel”- type rheological
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「日本食品工学会誌」, Vol. 11, No. 4, p. 187, Dec. 2010
◇◇◇ 和文要約 ◇◇◇
市販の増粘剤から調製した溶液とヨーグルトの流動特性
および咽頭部流速（嚥下障害者用介護食に関連して）
1
1
2
3
田代晃子 ，小野景子 ，長谷川（谷米）温子 ，熊谷日登美 ，熊谷仁
1
1,†
共立女子大学家政学部食物栄養学科， 2 日本大学生物資源科学部食品ビジネス学科，
3
日本大学生物資源科学部生命化学科
嚥下障害者（dysphagic patients）用介護食としての
安全性を評価するために，市販の増粘剤から調製した
溶液の粘度μおよび咽頭部（phar ynx）での流速を，ヨー
グルトのモデル食塊（bolus）である“（カードを）破
壊したヨーグルト”（以下，“破壊ヨーグルト”）と比較
・
-1
ずり速度（γ）が 10 s 付近において，
“破壊ヨーグルト”
の見かけの粘度μapp の値より小さかった．また，介護
食の安全性の指標である最大流速 V max の値に関しては，
“ヨーグルト状”や“ジャム状”の増粘剤溶液の方が“破
壊ヨーグルト”の値より大きかった．これらのことは，
した．流速スペクトルの形状と流速とから，“破壊ヨー
“ヨーグルト状”の増粘剤溶液は，ヨーグルトの食塊と
グルト”の流動特性はヨーグルトの食塊に近いと考え
同じ流動特性をもたず，ヨーグルト程度に誤嚥しにく
られた．“ヨーグルト状”の増粘剤溶液の粘度μの値は，
いとはいえないことを示している．
（受付 2010 年 7 月 26 日，受理 2010 年 9 月 21 日）
1 〒101- 0003 東京都千代田区一ツ橋2- 6- 1
2 〒252- 0880 神奈川県藤沢市亀井野1866
3 〒252- 0880 神奈川県藤沢市亀井野1866
† Fax: ＋81- 3- 3237- 2787, E- mail: kumagai@kyoritsu- wu.ac.jp