Apparatus for preparation of Sushi rice

Apparatus for preparing Sushi rice, and discharging opening provided at one end thereof, which is openably closed by a lid having a ventilation opening formed in a central portion thereof, the rotatable container being rotatable about a lateral axis of rotation and having a laterally extending partition plate mounted therein, and an air-blowing fan disposed with a space from the ventilation opening so that the ventilation opening can function as an inlet opening and also as an outlet opening for air.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for processing granular 
foodstuffs such as boiled rice in particular for seasoning, flavoring or 
the like. More specifically, the invention relates to an apparatus for 
preparing vinegared boiled-rice, a main foodstuff of the Japanese cuisine 
widely known as Sushi, at a high preparation efficiency utilizing power. 
In the apparatus, a seasoning additive comprising such as a vinegar, sugar 
and a natural or chemical seasoning is added to boiled rice hot from 
boiling, and then the apparatus can mix the boiled rice and the additive 
together homogeneously and rapidly to prepare a desirable boiled and 
vinegared rice. 
In preparing boiled and vinegared rice which is often called Shari in Sushi 
shops and among Sushi-goers, it is necessary to homogeneously apply or 
coat a seasoning mix or additive mainly comprising a vinegar and 
containing such as sugar, salt and a chemical seasoning substance on grain 
surfaces of boiled rice, hot from boiling. For avoiding complexity in 
description, the boiled rice treated as above will hereinafter be referred 
to as Sushi rice. In the preparation of the Sushi rice, it becomes 
important to know how to carry out the vinegaring of boiled rice within a 
short period of time while the rice is still in a softened condition soon 
after boiling and in a manner of not allowing grains of the boiled rice to 
become crushed or to be made a dumpling or doughboy. Whether or not a 
satisfactory vinegaring of boiled rice can be done greatly depends on a 
skill which one can gain only after years of experience and it constitutes 
an important factor greatly influential upon the taste of resulting Sushi 
food. The seasoning mix or additive with which boiled rice is treated 
contains other substances than a vinegar, such as sugar, salt and a 
seasoning material as above, but "vinegaring" of boiled rice as termed in 
the above and will be termed also elsewhere in this specification because 
generally in the cases of Sushi rice, a greater emphasis is placed on 
"vinegaring" than on "seasoning". Also, while "boiled" rice as termed 
throughout this specification, it should be understood that Sushi rice can 
be made also of "steamed" rice: For example, while in household 
preparations of Sushi rice, mostly boiled rice is used, in the cases of an 
industrial-scale preparation as made at such as large-scale Sushi shops 
and other suppliers of processed rice foods, steamed rice is mostly used. 
As noted above, the preparation of Sushi rice involves the requirement for 
a particular skill for a delicate manual handling and/or a particular keen 
sense which one can gain only after experiences for a long period of time. 
However, a limitation is applied to the number of available skilled Sushi 
cooks, and today in newly opening Sushi shop or expanding an existing 
Sushi shop, it is first of all difficult to secure the necessary hands. In 
the circumstances, it has been strongly demanded in the business fields of 
Sushi shops and other suppliers of processed rice foods as well that there 
may be an apparatus provided, by which the vinegaring of boiled rice or 
the preparation of Sushi rice can be carried out easily and rapidly, 
without the need for a skilled cook having a long-term experience in such 
processing of boiled rice. 
As already pointed out, to automatically prepare Sushi rice, it is 
necessary to provide an appropriate mixing apparatus by which operations 
for the preparation of Sushi rice (mixing and/or stirring operations) can 
be worked within a short period of time without causing boiled rice to 
become a dumpling or doughboy or allowing grains of boiled rice to become 
crushed. However, a desirable apparatus for such an automatic preparation 
of Sushi rice has not yet been provided. 
Mixing devices in general comprise a fixed main body provided therein with 
rotatable mixing means such as a mixing blade or blades. In a test, soft 
rice hot from boiling or steaming was put into such an existing mixing 
device together with an additive or a vinegaring mix and an attempt was 
then made to operate a mixer to prepare Sushi rice, when it was found that 
within a short period of the operation time, the boiled rice became 
crushed to completely lose its original state of grains and was turned 
into the form of a Mochi, a Japanese food prepared by pounding boiled rice 
into a cake. From this result of the test, it is told that an ordinary 
mixing device cannot be effectively utilized for the preparation of Sushi 
rice and that for the Sushi rice preparation, it is required to provide a 
particular apparatus by or in which the necessary mixing can take place 
without permitting boiled rice to be subjected to a large force 
application. 
Prior to the making of the present invention, the inventor of the present 
invention developed devices by which two or more kinds of material such as 
livestock feeds can be mixed together within a short period of time 
without greatly changing original shapes of the materials, and proposed 
those devices in Japanese Patent Publications Nos. 62-57371 and 62-57372. 
The above device pertaining to the present inventor's earlier inventions 
comprise a cylindrical rotatable container elongate in the direction of 
axis of rotation, which is provided at one of its longitudinal ends with 
an inlet and outlet opening for the materials. In one of two embodiments 
of the devices, two or more partition plates are mounted in the rotating 
container at an inclination to the axis of rotation of the container, 
while in the other embodiment, the partition plates are supported in an 
end staggered arrangement such that the end of one plate lies outward or 
inward of the corresponding end of another plate near each end of the 
cylindrical container in the direction of axis of rotation. 
Taking into account the technical contents of such earlier inventions and a 
number of technical discoveries made during the making of the inventions, 
the present inventor has conducted a variety of experiments so as to 
effectively apply the acquired techniques to the vinegaring of boiled rice 
or the preparation of Sushi rice, namely an operation for the addition and 
mixing of a vinegar-based additive to and in rice hot from boiling, and as 
a result of the confirmation then obtained that the above described mixing 
devices according to the inventor's earlier inventions can be effectively 
applied to the vinegaring of boiled rice, arrived at the present 
invention. 
SUMMARY OF THE INVENTION 
Therefore, a primary object of the present invention is to provide an 
apparatus by which vinegaring of boiled rice, namely preparation of Sushi 
rice, can be easily made even by a person without a particular skill, 
without the risk of destroying original grain shapes of the boiled rice 
and by which an additive or a vinegaring mix mainly comprising a vinegar 
and containing such as sugar, salt and a natural or chemical seasoning can 
be homogeneously mixed in the boiled rice and coated on surfaces of grains 
of the rice. 
It is also an object of the present invention to provide an apparatus for 
processing granular foodstuffs by which a liquid-type or granule- or other 
particle-type additive can be automatically homogeneously coated on 
surfaces of grains of boiled rice or other granular foodstuffs which 
resemble the rice gains in shape and/or nature, while their original 
shapes are maintained substantially unchanged. 
It is a further object of the invention to provide an apparatus which is of 
a size or volume which is suitable for preparing Sushi rice in an amount 
which is suitable for placement in a Sushi rice pail which is normally 
used in Sushi restaurants. 
It is a further object of the invention to provide an apparatus which, 
after preparation of Sushi rice therein, can be suitably placed at a site 
for hand-shaping of the Sushi rice, without further transfer into separate 
or additional containers. 
The apparatus for processing a granular foodstuff for attaining the above 
objects according to the present invention comprises a rotatable container 
provided at its one end or in its body portion with an opening closable 
with a lid, the container being rotatable about a lateral axis of 
rotation, an air-blowing fan having a discharge opening disposed at an end 
of the rotatable container for supplying cooling air into the container, 
and a partition plate mounted to laterally extend inside the rotatable 
container. 
The apparatus having the above structure, it may be operated to charge a 
material to be processed comprising appropriate proportions of boiled rice 
hot from boiling or soon after boiling and an additive mainly comprising a 
vinegar, namely a vinegaring mix, into the rotatable container through the 
opening, namely a charging and discharging opening for the materials, then 
close the opening with the lid, drive the container to rotate about its 
lateral or horizontal axis of rotation, and while the material undergoes 
mixing as it is received on the partition plate and then drops off the 
plate, send cooling air into and out of the container through a 
ventilation opening of the container to thereby effect a cooling of the 
material or the boiled rice, whereby preparation of Sushi rice can be 
completed at a high operation efficiency. 
Preferably, the rotatable container comprises a cylinder, and it is 
provided at its longitudinal one end with an opening, which is utilized as 
opening for charging a material to be processed and discharging the 
processed material and which can be closed with a lid formed in its 
central portion with a hole, which is utilized as ventilation opening, 
facing which an air discharging opening of an air-blowing fan is disposed 
so that cooling air can be supplied into the rotatable container to cool 
the material charged in the container while it undergoes mixing, and then 
the air can be discharged out of the container. 
It is also possible to provide the charging and discharging opening from 
the material not at a lateral or longitudinal end of the container but in 
a body portion of the container, and provide a lid to openably close the 
opening. 
Although the rotatable container may be of any of a variety of 
cross-sectional shapes, generally containers of a cylindrical 
cross-section are suitably useful in that they are relatively easy to 
manufacture, easy to close with a lid and easy to clean the inside. 
According to the invention, it is required that the rotatable container is 
rotated not about a vertical axis but a lateral or horizontal axis of 
rotation and that the partition plate mounted inside the container can mix 
the soft material to be processed such as boiled rice without the danger 
of destroying the grain or particle condition of the rice or the material. 
Apparatus having two or more partition plates mounted therein at an 
inclination to the axis of rotation of the container is particularly 
suitable in that mixing of the material and motion thereof towards left or 
right can easily take place in the container. Although it is most 
expedient to slantly arrange the partition plates as above, it 
alternatively is possible to mount the plates parallel to the axis of 
rotation of the container. Also, it is possible to arrange two or more 
partition plates parallel to one another or to arrange the ends of the 
plates to be staggered or offset relative to one another in the direction 
of the axis of rotation of the container. 
Further, although the two or more partition plates are normally parallel 
arranged relative to one another as above, it is alternatively possible to 
mount those plates in positions in which they extend in lateral directions 
but not in a mutually parallel relationship. 
As described above, the apparatus of the invention is mainly directed in 
its function to the preparation of Sushi rice which comes under a mixture 
together of boiled rice hot from boiling and an additive mainly comprising 
a vinegar. However, now that it can effect stirring and mixing of soft 
granular or particulate material resembling the boiled rice without 
destroying or impairing their shapes in a cooling atmosphere, the 
apparatus of the invention is effectively useful also as apparatus for 
processing such material and foodstuffs other than boiled rice which 
comprise soft grains, granules or particles including those which have a 
longer and a shorter axes and/or which may comprise a solid body or a 
hollow body.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The apparatus according to the invention can be effectively utilized not 
only for the preparation of Sushi rice but also for a similar processing 
of various other foodstuffs comprising grains, granules or particles, as 
before stated. However, for a simplicity of the description and 
illustration, in the following the invention will be described only in 
connection with the case of preparation of Sushi rice or vinegaring of 
boiled rice. 
The apparatus of the invention is for adding and mixing a liquid additive 
to and in boiled rice which is still hot soon after boiling. In a first 
embodiment of the apparatus according to the invention, illustrated in 
FIG. 1 through FIG. 4, a rotatable container of a cylindrical 
configuration is formed with an opening 2 for charging a material to be 
processed and discharging the processed material, at either of the lateral 
or longitudinal ends thereof, for example at the right-hand end thereof in 
FIGS. 1 to 4, and this opening 2 is openably closed with a lid 2A 
comprising a disk, through a central portion of which a ventilation hole 
or opening 3 is formed, through which cooling air is blown into the 
container 1 by an adjacently disposed air-blowing fan 12. After it has 
cooled the charged material inside of the container, the air is permitted 
to come out of the container through the above ventilation hole 3. 
Within the rotatable container 1, there are mounted two partition plates 4, 
which are disposed parallel to each other and arranged at an inclination 
to an axis of rotation X of the container 1. The partition plate 4 comes 
under a kind of stirring means, and while it may be provided in a number 
of only one or two or more, in each of the illustrated embodiments of the 
invention, two partition plates 4 and 4 are provided. In the present first 
embodiment, two plates 4 and 4 of a same length are secured in a mutually 
parallel arrangement to their respective support members 4A having an end 
portion protruding beyond the corresponding side end of the plate 4, as 
show in FIG. 1. Also as show in FIG. 1, between each longitudinal end of 
the plate 4 and the inner wall surface at the corresponding end of the 
container 1, a gap g is maintained, and between each side edge of the 
plate 4 and the inner wall surface along the corresponding side of the 
container, a gap G is maintained. 
In the present embodiment, the longitudinal ends of one partition plate 4 
are aligned or registered with the corresponding ends of the other 
partition plate 4. Alternative to this, it is possible to arrange the ends 
of one partition plate staggered or offset from the corresponding ends of 
the other plate in the direction of the axis of rotation X so that while 
one of the two ends of one plate 4 is located relatively close to one end 
face of the container, the corresponding end of the other plate 4 is 
located relatively close to the other end face of the container. 
A main body or a body portion of the apparatus which is composed of the 
rotatable container 1 of the lid 2A formed with the opening 2 for charging 
or discharging of the material may be made of any of a synthetic resin, a 
metal, a reinforced glass and wood, the inner wall surface of the body 
portion that undergoes contact with the material to be processed 
comprising boiled rice 14 and a vinegar-based additive may be coated or 
laminated with a tetrafluoro ethylene resin (commercially obtainable under 
the registered trade name of Teflon, at E. I. du Pont de Nemours & Co., 
Inc., U.S.A.) 
Externally, the body portion comprises the rotatable container 1 and the 
disk-type lid 2A may be covered with a thermal insulator as needs be and 
may be further applied with a surface covering of a metallic material or a 
synthetic resin material so that this body portion of the apparatus can be 
utilized as a warm keeping container after the completion of the 
vinegaring of boiled rice. 
The rotatable container 1 is supported on a base stand 6 through two or 
four bearing rollers 8 to be rotated by a motor 7, and it is rotated about 
the horizontal axis of rotation X. To prevent the container from moving in 
the direction of the rotation axis X while it is rotated, the container is 
provided with a guide portion 9, which comprises a ring of a ridge or 
groove extending over a whole of the outer circumference of the container 
1, and a compensatory guide portion 10 is provided on the bearing rollers 
8, comprising a ring of a groove or ridge engageable with the guide 
portion 9. 
By way of an example of practical dimensional specifications of the 
apparatus of the above described first embodiment of the invention, the 
rotation container 1 has a diameter and a length of 400 mm, the 
ventilation opening 3 formed in the disk-shaped lid 2A has a diameter of 
110 mm, and the discharge opening of the air-blowing fan 12 has a diameter 
d (FIG. 5) of 50 mm. 
The above described apparatus employs such an air-flow reversing system in 
which air is caused to flow as shown by arrows A in FIG. 2 so that flowing 
of air into the container and flowing of air out of the container take 
place through a same opening, namely the ventilation opening 3. This 
opening has a tapered configuration such that its bore size is smallest at 
the external end of the opening and is enlarged at the internal end of the 
opening. As a result of this, the material charged in the container 1 can 
be prevented from being sent out of the container. Further, the 
air-blowing fan 12 shown in FIG. 5 is provided with a damper 13 so that 
the rate of blowing of air can be adjusted. 
Using the above described apparatus, vinegaring of boiled rice or the 
preparation of Sushi rice may be carried out according to the following 
described steps (a) and (b). 
(a) Material Feeding Step 
In the condition shown in FIG. 9A in which the axis of rotation X of the 
rotatable container 1 is fixed in a vertical position, the disk-type lid 
2A openably closing the charging and discharging opening 2 may be opened, 
and through the opening 2, boiled rice 14 which is immediately after 
boiling and is still very hot may be rapidly charged into the rotatable 
container 1 in a manner as shown in FIGS. 6A and 6B. The feed amount of 
the rice 14 should be such that when the container 1 is rotated after 
charging of the boiled rice 4, the rice 14 does not come out of the 
container. 
Thereafter, an additive or a vinegaring mix 15 mainly comprising a vinegar 
and containing such as sugar, salt and a natural or a chemical seasoning 
is applied over the rice 14 as shown in FIG. 9B, in an amount in an 
appropriate proportion to the amount of the charged rice 14. 
Then, as shown in FIG. 9C, the lid 2A is applied to cover the opening 2 and 
fixed in position by means of fixing metals 16, whereby the step for 
feeding the material into the container 1 is completed. 
(b) Cooling/Mixing Step 
The rotatable container is charged with the material will then be placed in 
the prescribed horizontal position on the two or four bearing rollers 6 
secured on the base stand 6 as shown in FIG. 9D, and will be rotated in 
the direction shown by an arrow R at a number of rotation of 5 to 10 rpm 
for 2 to 3 minutes. 
During the rotation of the container 1, a shown in FIGS. 7A, 7B, 8A and 8B, 
the material within the container 1 is repeatedly moved up and down, the 
movement of the material including sliding motions, and subjected to an 
effect of mixing by the partition plates 4 mounted at an inclination 
relative to the axis of rotation X and with gaps G and g maintained 
between the side edges and the end edges thereof on the on hand and the 
inner wall surfaces of the container 1 on the other, whereby the boiled 
rice 14 and the additive 15 becomes mixed together to attain vinegaring of 
the boiled rice. 
An important characteristic of the present invention resides in the 
arrangement in which during the step of mixing the boiled rice 14 and the 
additive 15 together, a step is taken to supply air to effect cooling. 
As shown in FIG. 9E, while the vinegaring mix or additive 15 is added to 
and mixed in the boiled rice 14 hot from boiling, air is blown into the 
container 1 by the air-blowing fan 12 to cool the rice 14 to an 
appropriate temperature so that after it is processed, the boiled rice can 
have a savor and glossiness each of which is attractive. 
The air blown out from the fan 12 enters the container 1 through the 
ventilation hole 3 as shown by arrows A in FIG. 2, flows in a diffused 
condition in contact with grains of the rice 14 to cool the latter, then 
reverses direction of its flow and eventually comes out of the same 
ventilation hole 3 as above. That is to say, according to the present 
invention, an air-flow reversing is employed in which the flow of air into 
the container and its flow out of the container are carried out at the 
same time through the single ventilation hole 3 formed in a central 
portion of the disk-type lid 2A. 
The vinegared boiled rice or Sushi rice prepared by the above steps can be 
easily taken out of the container 1 by opening the disk-like lid 2A to 
open the material charging and discharging opening 2. 
As described above, in the apparatus according to the invention, when the 
container 1 is rotated, the material is imparted with the effect of riding 
on the partition plates 4, sliding on the plates 4 and upsetting its 
position, repeatedly. Therefore, in contrast to the cases of ordinary 
mixing devices, in the case of the apparatus according to the invention 
mixing of the material takes place without any large force applied to the 
material, and the material repeats upsetting and rolling. Further, during 
such mixing of the material, air is supplied into the container 1 by the 
air-blowing fan 12, so that a sufficient amount of air can be supplied to 
grains of the rice while they are kept moving, including upsetting 
motions, rolling motions and sliding motions within the container. 
Therefore, the material can be cooled to an optimal temperature and, at 
the same time as this, become imparted with an appropriate degree of 
moisture. 
Now, the series of steps for the preparation of Sushi rice using the 
apparatus of the present invention may be compared with the ordinarily 
operated steps. In ordinary methods of preparation of Sushi rice, fresh 
boiled rice which is very hot soon after boiling is placed in a mixing 
pail of a relatively small depth, and in adding the additive mainly 
comprising a vinegar to the boiled rice in the mixing pail, rice scoop 
held by either hand is handled to quickly upset the rice in portions to 
effect mixing of the additive with the rice, and at the same time as this, 
a hand fan held by the other hand is also quickly operated to send a great 
amount of air to the hot rice. The above manual operations require not 
only a considerable amount of labor but also a particular experienced 
skill to carry out an even upsetting of rice grains and an even effect of 
mixing of the rice and the additive together. 
Using the apparatus according to the invention, the above mixing operation 
and the cooling operation to be made during the mixing operation can be 
carried out at the same time and automatically. 
Now, entering a description into the second embodiment of the invention 
illustrated in FIG. 10, the basic structure and arrangement of and in the 
apparatus of the present embodiment have almost same structural features 
and operational feature as the above considered first embodiment, and same 
parts and elements in respective embodiments are indicated by same 
reference numerals and characters. 
The rotatable container 1 of which FIG. 10 shows a perspective view is 
driven to rotate as it is supported also in a horizontal position, but in 
the present embodiment, the material charging and discharging opening 2 
having the disk-type lid 2A to openably close the opening is provided not 
at an end but in a body portion of the container 1. Same as the above 
described first embodiment, the ventilation hole or opening 3 is provided 
in a central portion at one end of the container 1. 
In operation, the material to be processed, which comprises the boiled rice 
14 and the additive 15, is charged into the container 1 in the condition 
in which the material charging and discharging opening 2 is brought at a 
top position. After charging of the material, the container 1 may be 
rotated in the direction as indicated by an arrow R, when the material 
slides along two partition plates 4 disposed at an inclination to the axis 
of rotation X of the container and moves first towards the left side in 
FIG. 10. Then, as the container 1 is further rotated, the material moves 
in the circumferential direction of the container 1, and as the direction 
of inclination of the partition plates 4 are then reversed, it slides 
along the plates to collect at the right side in FIG. 10 while it moves in 
the circumferential direction. 
As described above, as the container 1 is rotated, the material charged in 
the container repeats motions towards left or right along the axis of 
rotation X, motions in the circumferential direction of the container and 
motions towards up and down, whereby a sufficient effect of mixing of the 
material is attained, when the material charging and discharging opening 3 
may be brought to and set at a bottom position, and the lid 2A may be 
opened to discharge the processed rice towards below out of the container 
1. 
The above-described structure and arrangement according to the second 
embodiment of the invention is expediently applicable particularly to an 
apparatus having a container 1 having a relatively large length in the 
direction of the axis of rotation X for the preparation of a relatively 
large amount of Sushi rice through a single operation cycle. 
Then, in the third embodiment of the invention shown in FIGS. 11A and 11B, 
two partition plates 4 mounted in the rotatable container 1 are arranged 
parallel to the axis of rotation X and with space from the inner 
peripheral surface of the container 1. In comparison with the cases of the 
before described first and second embodiments in which the partition 
plates 4 are arranged at an inclination to the axis of rotation X, both 
the mounting of the plates 4 and the cleaning of the interior of the 
container 1 can be more easily made according to the present third 
embodiment. 
Further, same as in the above first embodiment, in the present embodiment, 
too, gaps are maintained between the periphery of the partition plates 4 
and the inner wall surfaces of the container 1 so that the material can be 
prevented from collecting in any one location within the container 1. 
FIG. 12 shows a fourth embodiment of the invention, and in the apparatus 
according to the present invention, the ends of one of two partition plate 
4 and the corresponding ends of the other partition plate 4 in the 
direction of the axis of rotation X are disposed in a staggered 
arrangement or are offset from one another. According to this arrangement 
of the partition plates 4, even in the case in which two partition plates 
4 are disposed parallel to the axis of rotation X, a sufficient effect of 
mixing of the material can be attained in that the material can repeat 
movements in the direction of the axis of rotation X and movements in the 
circumferential direction of the container 1 and also in that a portion of 
the material tending to attach on the inner wall surface of the container 
1 can be permitted to fall down as it is moved to an upper position within 
the container, this movement of the material also taking place in 
repetition. 
In a fifth embodiment of the invention, which is illustrated in FIG. 13, 
two parallel arranged partition plates 4 are mounted at an inclination to 
the axis of rotation X, same as in the first embodiment illustrated in 
FIGS. 1 to 3. However, in the present embodiment, the two plates 4 are in 
an end-staggered arrangement. That is to say, ends of one of the two 
plates 4 are offset from the corresponding ends of the other plate 4 in 
the direction of the axis of rotation X, same as in the above fourth 
embodiment shown in FIG. 12. According to this arrangement, too, a same 
sufficient effect of mixing as obtained in the first embodiment can be 
obtained. 
FIGS. 14A and 14B in combination illustrate the apparatus according to the 
sixth embodiment of the invention, which is structured same as the 
apparatus according to the foregoing described embodiments, except that 
the partition plates 4 are fixed to the disk-shaped lid 2A, which do not 
touch the inner wall of the rotatable container 1, at all. Thus, the 
apparatus of the present sixth embodiment is characterized particularly in 
that when the disk-shaped lid 2A is disengaged from the rotatable 
container 1, the partition plates 4 can be removed out of the container 1 
together with the lid 2A, whereby an advantage can be brought about such 
that the need for once transferring the prepared Sushi rice in the 
container 1 into a separate Sushi rice pail is effectively cancelled, and 
the container 1 containing the prepared Sushi rice can be intact carried 
onto a Sushi cook's table or to a site or the vicinity of a site at which 
the hand-shaping or hand-rolling of Sushi rice is operated. 
Although in the illustrated embodiment the lid 2A is formed with a single 
ventilation hole 3, through which supply and evacuation of air take place, 
it is otherwise possible as illustrated in FIG. 15 to provide a hole 3 for 
supply of air at a radially central portion of the lid 3A and another hole 
for evacuation at a portion of the lid spaced from the axis of rotation of 
the container 1. 
Further, in the above description of first to sixth embodiments of the 
invention, two or more partition plates 4 are described in each instance 
to be so arranged as to form mutually parallel planes. 
However, it is not always necessary that the plurality of partition plates 
4 are arranged to form mutually parallel planes, and alternative to this, 
they may be mounted to form planes in an A or V arrangement or form planes 
cross each other at a right angle. Also, the shape of the partition plates 
4 is not necessarily limited to the flat surface-forming shape as in each 
of the above described embodiments, but the plates 4 may otherwise have a 
waved shape or have a grid structure. 
Furthermore, while in each of the described specific embodiments the 
rotatable container 1 comprises a cylindrical one, this is only by way of 
an example, and insofar as it comprises a rotatable container, the 
container 1 may of course be of any other cross-sectional shape, for 
example it may have a polygonal shape such as a square or rectangular 
shape, pentagonal shape and so forth in cross-section. 
The above described apparatus for the preparation of Sushi rice or for 
processing granular foodstuffs according to the present invention can 
bring about the advantage that without the need for a skilled hand, an 
additive can be added to and mixed in hot boiled rice without the danger 
of destroying grains of the rice while an effect of cooling is imparted to 
the hot rice, whereby it is possible to easily and rapidly prepare Sushi 
rice having attractive glossiness and savor. 
Particularly, when the apparatus of the invention is used as an apparatus 
for Sushi rice, boiled rice can be prevented from becoming a dumpling and 
grains of the rice can be prevented from becoming crushed during the 
operation steps, and yet an additive mainly comprising a vinegar can be 
homogeneously mixed in the rice, so that a satisfactory Sushi rice can be 
easily prepared in a large amount through each operation cycle. Thus, the 
apparatus of the present invention is highly effective in enhancing the 
operation efficiency in the preparation of Sushi rice or in the processing 
of granular foodstuffs.