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Description  |
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SUMMARY OF THE INVENTION
The present invention relates to a process for improving the properties of
gelatin. As is well known, gelatin is a type of protein derived from
collagen and is widely used, for example, as a raw material for foodstuffs
such as confectionary, medicaments, photographic emulsions, adhesives and
the like. Gelatin is used in the form of aqueous solution. However, it is
not readily soluble in cold water, and thus gelatin solution is prepared,
for example, by immersing a gelatin in cold water with agitation at room
temperature so that the gelatin is swelled, and then either heating the
mixture to 50.degree. C. or continuing the agitation at room temperature
for 24 hours. However, such an operation is time-consuming. The art has
long sought a process for improving the solubility of gelatin in water at
a temperature lower than room temperature. As used in this specification,
the term water-solubility of gelatin denotes the cold water-solubility as
hereinbefore defined.
PRIOR ART
It is known to make gelatin completely water-soluble by drying a gelatin at
100.degree. C. under reduced pressure (U.S. Pat. No. 2,803,548). However,
the gelatin thus-obtained is incapable of being gelled. There is thus a
need to improve the water-solubility of gelatin without feleterious
influence upon other properties of gelatin such as gelling ability, and
the outlook and stability of the gel. Various attempts have been made to
serve this purpose. However, such prior art processes have significant
disadvantages. For example, it is known to improve the properties of
gelatin by freeze-drying a gelatin dissolved in water at a concentration
of 0.1-2% by weight under reduced pressure (U.S. Pat. No. 2,166,074).
However, this process requires a conventional dissolving method for the
preparation of the gelatin solution used as the starting material, and
also the low concentration of the gelatin in the solution makes this
process expensive. U.S. Pat. No. 3,514,516 describes a process for
improving the properties of gelatin, in which a gelatin, having a water
content of not more than 10% by weight, is frozen at a low temperature,
the freeze-drying of the gelatin being started at about 100.degree. C. and
the temperature gradually lowered to about 40.degree. C. This patent
describes that the resultant gelatin is stable at 125.degree. C. for one
hour and that the gel derived from this gelatin is stable at a temperature
above 35.degree. C., in contrast to gels derived from conventionally
improved gelatins. However, this process requires prior adjustment of the
water content of the starting gelatin (gelatins of market grade usually
contain more than 10% by weight of water), and is also complicated and
expensive.
On the other hand, various proposals have been put forward to improve the
water-solubility of gelatin without exerting deleterious influence upon
other properties, which involve the addition of sugar to gelatin. For
example, according to U.S. Pat. No. 2,803,548, a gelatin is dispersed in
water containing sugar in an amount of not more than 10 times by weight of
the gelatin added, and the gelatin is dissolved by heating the dispersion.
A solid material is obtained by evaporating off water under reduced
pressure. This solid is capable of being dissolved in cold water at room
temperature and forms a gel. However, as the strength of the gel prepared
from the untreated raw gelatin is higher than that prepared from the
treated gelatin by 10%, it is necessary to use a larger amount of the
treated gelatin by 10% more. According to U.S. Pat. No. 2,641,498, a 40%
(by weight) aqueous solution containing sugar and gelatin (10-8 and one
part by weight respectively) is spray-dried at 124.degree.-243.degree. C.
to give powders containing 4-5% by weight of water. By dissolving the
powders in cold water, a mixed solution of gelatin and sugar is easily
obtained, this gelatin having analogous properties to those of untreated
gelatin. However, it is only possible by this process to obtain a gelatin
having improved water-solubility in the form of a mixture of gelatin and
sugar. Furthermore, other properties, for example, the gel strength of the
gelatin thus-obtained are not superior to those of untreated gelatin. U.S.
Pat. No. 3,930,053 discloses that the water-solubility of a spray-dried,
funnel dried or drum dried gelatin in association with a powdered
cosmetible component, the use of controlled sizes and proportions of
gelatin and cosmetible component being specified. This gelatin has also
the similar disadvantages to those described above.
SUMMARY OF INVENTION
The present invention teaches the production of a gelatin which is capable
of being dissolved in cold water in simple manner and with quicker speed
by the use of a process involving microwave heating of water-containing
gelatin.
Thus the present invention provides a process for improving the
water-solubility of gelatin, which comprises subjecting a gelatin, having
a water content of more than 8% by weight based on the total weight of the
gelatin and water, to microwave heating to remove at least 35% of said
water content to obtain a treated gelatin having a water content of not
more than 16% by weight based on the total weight of the gelatin and
water.
When an aqueous solution of the treated gelatin of the present invention is
prepared, the use of the gelatin in grnular or powder form is preferable.
When the gelatin is in the form of a fine powder, it is dissolved more
quickly by dividing the gelatin into small fractions and feeding these
fractions stepwise in water. For the purpose of preparing confectionary,
for example, gelatin is usually used in association with sugar. In such
cases, gelatin is often dispersed in sugar, followed by dissolution in
water. When the gelatin treated according to the present invention is
dispersed in sugar, it is possible to add at one time the total amount of
the gelatin and sugar to a desired amount of water, or vice versa. In this
manner, the gelatin may be dissolved quickly. Other edible dispersants
than sugar which may be used for this purpose are exemplified by
sweatening agents (e.g. glucose), taste-enhancing agents (e.g. sodium
glutamate, nucleic acids and succinic acid) and sodium chloride. In these
cases, the amount of the dispersant used is preferably at a ratio of
1-30:1% by weight of the gelatin (dry basis). If desired, it is possible
to add such a dispersant to the raw gelatin before microwave heating
according to the present invention, and the amount of the dispersant added
is preferably approximately 10% by weight of the raw gelatin (dry basis).
As apparent from the following experimental results, the properties of the
jellies prepared from the water-soluble gelatin of the present invention
are identical with those of the jellies obtained by using untreated
gelatin. Accordingly, the water-soluble gelatin obtained by the process of
the present invention may be used in an analogous manner to to that of
conventional gelatin.
The present invention is believed related to improving the water-solubility
of gelatin when the voids in the micelle structure of water-containing
gelatin are expanded and fixed in the expanded state.
The process of the present invention will be fully and clearly described in
the following specification where the following terms are used:
Definition of Terms
Raw Gelatin
A gelatin to be treated with microwave heating according to the process of
the present invention viz. untreated gelatin.
Improved Gelatin
A gelatin, of which properties such as water-solubility, have been improved
by known processes, for example, spray-drying, freeze-drying and the like.
Treated Gelatin
A gelatin obtained by subjecting the raw gelatin to microwave heating
according to the process of the present invention.
All known gelatins produced by treating collagen, for example, with acid,
alkali and enzyme may be used as starting material for the process of the
present invention. It is also possible to use raw gelatin which may
contain impurities (e.g. glue) to a greater or lesser extent if the
gelatin contains more than 8% by weight of water based on the total weight
of the raw gelatin including water and impurities. For the purpose of the
present invention, it is not necessary to add any known additive (for
example, sugar) to the raw gelatin. The raw gelatin may be used in the
form of a sheet, granules or powders (in the case of dry gelatin) and in
the form of a gel or sol containing a large amount of water (in the case
of wet gelatin). Accordingly, when a dry gelatin is used, it is possible
to swell it by water-adsorption or by dissolving it in water before use,
while it is also possible to use a material containing a very large amount
of water, which is directed to be used for the preparation of dry gelatin.
The water content of a raw gelatin according to the present invention is
more than 8% by weight on the basis of the raw gelatin including water and
impurities. However, with reference to the following Experiment No. 1, it
is necessary in some cases to be more than 10% by weight. On the other
hand, the upper limit of the water content is believed to be dependent
only upon the practical applicability and economy of the process of the
present invention. This is true since it is possible to improve the
water-solubility and to obtain good gelling ability even when a gelatin
containing a very large amount of water (e.g. more than 50% by weight) is
used as the raw gelatin. Of course, it is not advantageous for practical
purposes to use a raw gelatin containing an excessively large amount of
water, which may require a very large amount of electric power for removal
of water contained in the raw gelatin. In such a case, it is possible, if
desired, to pre-treat the raw gelatin before microwave heating to give a
suitable water content, for example, by drying the same in sun light or
hot air. On the contrary, it is also possible to increase the water
content of the raw gelatin before microwave heating by water-adsorption.
Especially good results may be obtained when the water content of raw
gelatin is 10-55% by weight. According to JIS (Japanese Industrial
Standard), the water content of commercial grade gelatins is not more than
16% by weight based on the total weight of the gelatin and water, and many
of market grade gelatins usually contain water in an amount of about
10-13% by weight. Thus, the present invention is particularly advantageous
since there is no need of pretreating such a raw gelatin.
The raw gelatin is usually subjected to microwave heating without an
additive. The use of microwave within a range of 30 to 30,000 MHz (for
example, 915 and 2450 MHz) for heating and dehydrating water-containing
materials such as for example, foodstuffs and the like is known per se, as
is disclosed, for example, in "Microwave Heating of Foodstuffs" (1974),
published in Tokyo in Japanese version, which is hereby cited as
reference.
For using the electric energy effectively, it is preferred to enclose the
raw gelatin, for example, in a vessel made of polytetrafluoroethylene,
glass wool, kraft paper and the like or with sheets and films thereof, or
to use these materials as a heat-insulator. These materials are preferably
provided with small holes in such cases. In order to use the heat
effectively, a pile of raw gelatin with a thickness of around 0.2 mm is
preferable. It is also a good idea to use a microwave oven provided with a
belt conveyor for transporting raw gelatin across the oven during
microwave heating.
The amount of electric energy for microwave heating and the period of time
for microwave heating depend upon various factors, such as for example,
the amount of water to be removed from the raw gelatin, the amount of raw
gelatin to be treated and so on. While the degree of water removed from
raw gelatin defines the period of microwave haeting, it generally takes
from 30 seconds to 30 minutes.
Usually, microwave heating may be effected continuously. However, when raw
gelatin is treated for a long time (e.g. 20 minutes or more), it is
possible to continuously effect microwave irradiation, followed by
intermittent irradiation. The temperature of raw gelatin before the
irradiation is not critical, and it is thus possible to pre-heat the raw
gelatin before microwave heating. However, over-heating should be avoided,
since this can deleteriously influence the properties of the treated
gelatin. In the following experiments, the microwave ovens used had an
output of not more than 2.2 kW at 915 or 2450 MHz, the irradiation times
were in general within 20 minutes, and the temperature of the gelatins
during microwave heating was believed to be raised to about
80.degree.-105.degree. C.
As long as more than 35% by weight of the water contained in the raw
gelatin is removed by microwave heating, the lower limit of the water
content in the treated gelatin is not critical. However, from a practical
viewpoint, this lower limit would be about 5% by weight because it has
been observed that the water-solubility of the treated gelatin is liable
to decrease when the treatment is continued further. It is advantageous to
dry the treated gelatin, for example, in sun light or hot air when it is
desired to obtain a lower water content in the treated gelatin. On the
other hand, it is also possible to increase the water content of the
treated gelatin by water-adsorption. In all events, the gelling ability
and water-solubility of the treated gelatin are not significantly changed
thereby.
Various advantages obtained by the process of the present invention are
exemplified as follows:
It is not necessary to use an additive (e.g. sugar) together with the raw
gelatin and furthermore the raw gelatin may, if desired, contain
impurities (e.g. glue) to a greater or lesser extent. Special pretreatment
of the raw gelatin is, in general, not required. The lower limit of the
water content of the raw gelatin required ensures that the conventional
dry gelatins of market grade may be used without pretreatment. On the
other hand, the upper limit of the water content depends upon the
practical applicability and economy. Furthermore, it is also possible to
adjust the water content of the raw gelatin prior to microwave heating, if
desired, and also it is possible to use as raw gelatin a wet material
containing a very large amount of water for the preparation of dry
gelatin, if desired, in a through-put process. On the contrary, it is
believed that it is difficult to select the raw material as freely and
widely in known processes as is the case with the process of the present
invention. The process of the present invention may be carried out simply
and cheaply because the only requirements relate to the amounts of water
contained in the raw and treated gelatins and to the amount of water to be
removed from the raw gelatin. The water-solubility of the treated gelatin
is improved, while other properties such as the gelling ability and
outlook are retained. The mode of the use of the treated gelatin is not
limited, while the stability and strength of the gel formed from the
treated gelatin are substantially unchanged, irrespective of the presence
or absence of additive.
It is sometimes required to produce a gelatin jelly having excellent
transparency and outlook. For this purpose, the present invention teaches
that the raw gelatin is subjected to microwave heating, in association
with an expanding agent.
The term expanding agent used herein denotes edible expanding agents which
are well known in the art, for example, sodium carbonate, ammonium
hydrogen carbonate and the like, which may be used, for example, for
baking powder. The amount of the expanding agent to be added is preferably
about 0.1-5% by weight of the raw gelain (dry basis). It is possible to
dissolve an expanding agent in water, in which the raw gelatin is then
dissolved, or vice versa. If desired, an expanding agent in the form of
solid or liquid may be added to the raw gelatin in gel or sol form,
followed by sufficient agitation. However, the transparency and outlook of
the treated gelatin can not be improved by adding an expanding agent to
the gelatin after microwave heating.
The strength and stability of the gelatin gel is not substantially changed
by using the expanding agent of the present invention. When a gelatin
treated after addition of expanding agent is compared with another gelatin
treated without addition of the same, there is no difference with respect
to Solubility Index (A) and jelly strength and the like (as hereinafter
defined). However, when two types of gelatin jelly are compared with each
other with respect to the taste, appetizing feeling, outlook etc., the
former, that is to say, a gelatin which is treated after addition of the
expanding agent is superior to the latter with respect to the outlook.
On the other hand, jellies were prepared from a gelatin treated after
addition of an expanding agent and from a raw gelatin respectively and
compared with each other with respect to the taste, appetizing feeling and
it was observed that there was no difference of the taste and appetizing
feeling and the difference in the outlook was almost negligible. These
comparisons were effected by using gelatin powders of not more than 250
meshes.
In another embodiment, an edible dispersing agent may be present during the
microwave heating to improve cold water solubility. As used in the
specification and claims, the term "edible dispersing agent" denotes the
materials denoted in U.S. Pat. No. 2,834,683 as "solubilizing agent",
exemplified by taste enhancing-agent, glucose, sugar, maltose, artificial
and natural sweetening agents, citric acid, gluconic acid, "Schardinger
dextrins", sorbital and the like. Said U.S. Pat. No. 2,834,683 is
incorporated by reference.
Various experiments were effected to show the properties of the treated
gelatin and the results are indicated in the following tables and
description, in which the weight of gelatin is indicated on a dry basis,
otherwise specified, and the terms raw gelatin and treated gelatin are as
hereinbefore defined.
In the following Tables 1-4, Test Nos. 4-13, 17-23, 31-37 and 42-48
indicate the results of tests on gelatins treated by the process of the
present invention. Test Nos. 1-3, 16 and 26-28 indicate the results of
tests on gelatins which have been treated, but not in accordance with the
process of the present invention. Test Nos. 14, 15, 29, 30, 38-41 and
49-52 indicate the results of tests on raw (untreated) gelatins. In Table
5, the controls are indicated.
Experiment I
Table 1 indicates (1) Test No., (2) Water content in raw gelatin (%), (3)
Time of microwave heating (second), (4) Water content in treated gelatin
(%), (5) Amount of gelatin dissolved in water (mg/ml), (6) Solubility
Index (A) (%) as hereinafter defined, (7) Jelly strength (g) and (8)
Solubility Index (B) (%) as hereinafter defined.
The experiment was carried out in the following manner.
(1) Determination of the amounts of gelatin dissolved in water (I) and (II)
and Solubility Index (A)
A raw gelatin (weight 100 g on wet basis) containing a known water content
and having a jelly strength of 30 Bloom was powdered to a corn grade of
not more than 80 mesh and was enclosed in a sheet of
polytetrafluoroethylene having a thickness of 0.1 mm. The powders were put
in a beaker made of glss (capacity 2,000 ml) and were treated with
microwave for a pre-determined time by using a microwave oven (output 400
W at 2450 MHz). The gelatin treated was powdered, and the powders of not
more than 80 mesh (weight 4 g) were well mixed with sugar (12 g). The
mixture was then added at once to water having a temperature of 20.degree.
C. (100 ml) and was kept at 20.degree. C. for 3 minutes with agitation,
resulting in an aqueous solution containing gelatin and sugar, which was
filtered by using a double-folded gauze to give a filtrate. The total
nitrogen in the filtrate was determined by the micro-Kjeldahl method, from
which the amount (I) (mg/ml) of the gelatin dissolved in water was
determined. Separately, a corresponding raw gelatin (4 g) without addition
of sugar was treated in a similar manner to that described above to give
an aqueous dispersion containing gelatin, which was heated to 50.degree.
C. in 15-20 minutes. By keeping the dispersion at about 50.degree. C. for
5 minutes, the gelatin was completely dissolved. Its total nitrogen
content was determined in a similar manner to that described above, from
which the amount (II) (mg/ml) of the gelatin dissolved in water was
determined. It was evaluated tht a larger Solubility Index (A) indicated
by the following formula showed a larger relative amount of gelatin
dissolved in water at 20.degree. C. within 3 minutes viz. a higher
water-solubility:
Solubility Index (A)=[amount of gelatin dissolved in water (I)
(mg/ml)/amount of gelatin dissolved in water (II) (mg/ml)].times.100%.
(2) Determination of jelly strength (I), jelly strength (II) and Solubility
Index (B)
An aqueous solution of a treated gelatin (4 g) and sugar (12 g) was
prepared in a similar manner to that used to determine the amount of
gelatin dissolved in water (I), the gelatin containing a predetermined
amount of water correspondingly. Foams were removed from the solution
without filtration. After this, the solution was put in a jelly cup having
a given capacity and was allowed to stand at 17.degree. C. for 18 hours to
form a jelly. Reometer Type R-UDJ (commercial product of Fuji Riko Kogyo
K.K., Japan) was used to determine jelly strength (I) at a room
temperature of 20.degree. C. and a jelly temperature of 7.degree. C.
Separately, the same raw gelatin (4 g) was treated in a similar manner to
that used to determine the amount of gelatin dissolved in water (II) with
the exception that sugar (12 g) was added to obtain an aqueous solution
containing a completely dissolved gelatin. This solution was used to
prepare a jelly in a similar manner to that used for the determination of
jelly strength (I) (g), from which jelly strength (II) (g) was determined.
When the concentration of the gelatin solution was excessively high, it was
difficult to filter the solution and accordingly the amount of gelatin
dissolved in water and also Solubility Index could hardly be determined.
However, it can be said that a larger amount of gelatin dissolved in water
is liable to give a higher jelly strength. When the amount of gelatin
dissolved in water could not be measured, it was evaluated that a lerger
Solubility Index (B) indicated by the following formula corresponded to a
relatively larger amount of gelatin dissolved in water viz. a better
water-solubility:
Solubility Index (B)=[jelly strength (I)/jelly strength (II)].times.100%.
It is noted that jellies used for foodstuffs of market grade preferably
have a range of jelly strength of from several grams to about 20 grams.
When a gelatin used to determine Solubility Index (B) was not completely
dissolved in water and the determination was difficult, the column
indicating "jelly strength" in the tables was filled with the terms of
"swelled" or "swelled and solidified".
(3) In Table 1, Test Nos. 4-13 indicate the data on gelatins treated by the
process of the present invention, and Nos. 1-3 indicate comparative
results. The data shown in No. 14 were obtained by using a raw gelatin (4
g) containing water (15.3%). This gelatin was mixed with sugar (12 g) and
determined in a similar manner to that used to determine the amount of
gelatin (I) dissolved in water. The results shown in No. 14 include the
amount of gelatin (I) dissolved in water (2.49 mg/ml) and Solubility Index
(A) (41.1%). The results in No. 15 were obtained by using a similar
mixture of gelatin and sugar to that used in No. 14. and the amount of
gelatin (II) dissolved in water was determined in a similar manner to that
used to determine Solubility Index (II) as set forth. In No. 15, the
amount of gelatin (II) dissolved in water is conveniently indicated in the
column of the amount of gelatin (I) dissolved in water. Because the
gelatin shown in No. 15 is a control gelatin, its Solubility Index (A) and
(B) are 100%. It is noted that the amount (I) of gelatin dissolved in
water jelly strength (I) are variable, depending upon the treating
conditions, while the corresponding values of raw gelatin are independent
upon the water content.
(4) In Test Nos. 4-13, the data were obtained by using gelatins treated by
the process of the present invention. Each sample was dissolved in water
at 20.degree. C. for 3 minutes. The amount of gelatin (I) dissolved in
water was more than the corresponding amount (I) obtained by using a
corresponding raw gelatin (2.49 mg/ml).
(5) A raw gelatin was mixed with sugar and dissolved in water at 20.degree.
C. for 3 minutes to give a gelatin solution which was then used, without
being filtered, to form a jelly. However, good result was not obtained in
Test No. 14. On the other hand, in Test Nos. 4-13, gelatins were treated
by the process of the present invention and used to form jellies in a
similar manner to that used in Test No. 14, and good results were obtained
except No. 5. It was thus confirmed that gelatins treated by the process
of the present invention were afforded with improved gelling ability.
Particularly in Test Nos. 8, 9 and 10, each jelly obtained had a strength
which was at least equal to the strength of a jelly (40 g in No. 15)
formed by dissolving completely a raw gelatin added with the same amount
of sugar, in water. Although the jelly strength of No. 15 was obtained
from a raw gelatin added with sugar, the gel strength was not markedly
changed by addition of sugar. It is thus concluded that the ability to
form a gel and the jelly strength obtained from the gelatin treated by the
process of the present invention are equal to those of raw gelatin.
(6) In Table 1, Test No. 3 indicates that Solubility Index (A) is improved
at an initial water content of approximately 8% by weight, as may be seen
by comparison with Test No. 14, while jelly is first formed in No. 4 at an
initial water content of 10.5%. Thus it may be concluded that cold
water-solubility is improved at a lower limit of 8% (initial water
content) while the lower water content limit is preferably 10% with
respect to the formation of jellies.
Experiment II (with reference to Table 2)
(I) Table 2 shows the data obtained in a similar manner to that used to
prepare Table 1 except a raw gelatin having a jelly strength of 250 Bloom
was used. Test Nos. 16 and 26-30 indicate the experimental data, in which
Nos. 29 and 30 are the control data and the remaining Nos. 17-23 represent
the data on the gelatins treated by the process of the present invention.
The amount of gelatin dissolved in water was hardly determined except No.
17, in which the amount (I) was 1.88 mg/ml which was larger than the
corresponding amount (I) shown in No. 29 (1.47 mg/ml). The latter was
obtained by using a raw gelatin for control purpose. In Test Nos. 17 and
23, the gelatins used were not jellified. As almost all gelatins treated
by the process of the present invention (Nos. 18-25) were jellified, it
was confirmed that the amount of the treated gelatin dissolved in water at
a given temperature in a given time was larger than the dissolved amount
of the corresponding raw gelatin.
(2) In Test Nos. 19-25, it was difficult to determine the amount of gelatin
participating in the formation of jelly. However, the jelly strength and
Solubility Index (B) of each gelatin in Nos. 19-25 was substantially not
distinguishable from the corresponding value of the control gelatin in No.
30. It may accordingly be concluded that the jelly strength and ability of
forming a gel of the treated gelatin is almost equal to those of the
corresponding raw gelatin.
(3) The results obtained from Nos. 1-5, 15, 17, 19-22, 25 and 27 in
Experiments I and II indicate that, in order to improve water-solubility,
it is necessary to remove more than 35% of the water content from the
untreated gelatin and to ensure that the treated gelatin retains a water
content of not more than 16% by weight.
(4) In Test No. 19, a gelatin (water content 26.5%) was continuously
treated with microwave for 270 seconds and after this an interval of 30
seconds and an irradiation of 15 seconds were repeated (irradiation time
330 seconds in total) to avoid the "burning" of gelatin. The water content
of the gelatin thus-treated was 0.9% (a minimum water content among the
gelatins tested). On the other hand, in No. 23, a gelatin (water content
50.2%) was continuously treated with microwave radiation for 540 seconds
to give a treated gelatin (water content 4.3%). These results were
compared with other test results according to the process of the present
invention to confirm that the operational conditions specified according
to the present invention cover a very wide range and offer consistent
results.
Experiment III (with reference to Table 3)
(1) A raw gelatin (water content 24%; corn grade 4-8 mesh; jelly strength
250 Bloom; weight 12 g) was subjected to microwave heating by using a
microwave oven (output 2.2 kW at 2450 MHz) having therein a conveyor belt
with a speed of 0.6 m/min to convey the gelatin continuously across a
specified area (about 30 cm wide; and about 120 cm in length) at a ratio
of 150 g/min. The raw gelatin was piled up on the belt to have a thickness
of about 3-4 cm. The treated gelatin was taken out and powdered. The
treated gelatin (weight 9.1 kg including a water content of 9.5%) was
obtained in powder form (not more than 80 mesh). A given amount of the
treated gelatin was dispersed in sugar (3 times amount of the gelatin) to
give a sample. The thus-obtained samples were added at once to water (100
ml) at 30, 20, 15, 10 and 5.degree. C. respectively and were kept at these
temperatures for a given time with agitation. After this, foams were
removed from the samples without being filtered. Each sample was put in a
jelly cup having a given capacity and was left at 7.degree. C. for 18
hours to make a jelly. When the samples were dissolved in water at
30.degree. or 20.degree. C., jellies were produced. When the samples were
dissolved in water at a temperature of not higher than 10.degree. C. they
did not give jellies but merely swelled. When the samples were dissolved
in water at 15.degree. C. incomplete jellies were obtained including
swollen fractions and the Solubility Index (B) was not measured.
On the other hand, when a corresponding raw gelatin was mixed with sugar (3
times amount of the gelatin), the mixture did not dissolve in water at a
temperature not higher than 30.degree. C. by treatment similar to that
described above. Accordingly, the temperature was elevated to about
50.degree. C. to dissolve the mixture completely and the jelly strength
was measured in a similar manner to that described above, which was
conveniently indicated in the column of "20.degree. C." in Table 3.
From Table 3, it is apparent that when the treated gelatin of the present
invention was dissolved in water at 30.degree. and 20.degree. C. for a
given period of time respectively, their water-solubility and ability of
gelling were equal or superior to those of the corresponding raw gelatin.
Experiment IV (with reference to Table 4):
(1) An alkali gelatin (corn grade 4-8 mesh; jelly strength 30 Bloom; water
content 15%; weight 1 kg) was enclosed in a sheet (thickness 0.1 mm) of
polytetrafluoroethylene and subjected to microwave heating for 300 seconds
by using a microwave oven without a conveyor belt (output 2.2 kW at 2450
MHz), by which hot air (80.degree. C.) was blown into the oven. A treated
gelatin obtained contained 4.8% of water. The treated gelatin was powdered
(not more than 80 mesh). In Table 4, Test Nos. 49-52 indicate the results
of the raw gelatin. Nos. 42, 43-48 and 49-52 in Table 4 correspond
respectively to Nos. 31, 32-37 and 38-41 in Table 3, and the determination
was carried out in a similar manner to that used in Experiment III.
(2) The water-solubility was greatly improved when the jelly strength of
the raw gelatin was low, and jellies were formed even when the samples
were dissolved in water at 10.degree. C. (Nos. 44-48). When the gelatin
concentration was 0.5% and no sugar was added to the solution, the gelatin
was completely dissolved (No. 42). On the contrary, the corresponding raw
gelatin was swelled but hardly dissolved in water (No. 49).
When the treated gelatin was dissolved at a concentration of 2% for 3
minutes, it was completely dissolved in water at 30.degree.-15.degree. C.
but did not form a jelly. The Solubility Index (B) also decreases
according to the decreased temperature of water, and the gelatin was
almost completely dissolved in water at 15.degree. C.
When the treated gelatin was dissolved at a concentration of 4% for 5-10
minutes (Nos. 46-47), it was almost completely dissolved in water at
10.degree. C. and its jelly strength was equal to the jelly strength of
the corresponding raw gelatin (No. 51). The treated gelatin dissolved in
water at 5.degree. C. was not jellified except No. 48, in which the
concentration of the gelatin used was 6% and the dissolving time was 6
minutes.
On the other hand, a raw gelatin was mixed with sugar (3 times amount of
the gelatin). This mixture was treated in a similar manner to that
described above, but was not dissolved in water at 30.degree. C. Then the
temperature was elevated to about 50.degree. C. and the mixture was
completely dissolved. This solution was treated in a similar manner to
that described in Experiment I to determine the jelly strength which is
conveniently indicated in the column of "20.degree. C." in Table 4.
Tables 3 and 4 indicate that the treated gelatin of the present invention
exhibits excellent water-solubility even at lower temperature, while the
corresponding raw gelatin is swelled but not dissolved in water. In Tables
1-4, the blank columns indicate that the data could not be determined,
unless otherwise specified.
Experiment V
(1) The treated gelatins of Test Nos. 1-4, 8 and 11 (jelly strength 30
Bloom) and No. 21 (jelly strength 250 Bloom) were respectively powdered
(not more than 80 mesh). Each of the samples thus-obtained was divided
into fractions and dissolved in water at 25.degree. C., the amount of
respective fractions being determined so as to give concentrations of 2, 4
and 6% respectively. After the total amount of each fraction was
simultaneously added to water, the water was agitated for 30 minutes. By
way of contrast, each fraction was further divided into several factions
of small amounts and was added to water in stepwise fashion. For control
purpose, raw gelatins corresponding to these treated gelatins were also
respectively dissolved in a similar manner to that described above.
(2) In the case of adding the whole amount of gelatin at one time to water,
the treated gelatins of Nos. 1-3 were almost completely dissolved in water
in 30 minutes. The treated gelations of Nos. 4, 8, 11 and 21 exhibited
granules adhering to each others in water and substantial parts of the
gelatins were not dissolved after 30 minutes. The control gelatin (30
Bloom) was completely dissolved at concentrations of 2, 4 and 6% in about
30 minutes, but the solutions obtained were not clear. Another raw gelatin
(250 Bloom) was completely dissolved at concentrations of 2 and 4% in
about 60 minutes to give clear solutions. No measurement was made at a
concentration of 6%.
(3) In the case of stepwise addition of the whole amount divided into
fractions, the gelatins of Nos. 1-3 were not completely dissolved after 30
minutes as in the case of adding the whole amount at once. The gelatins of
Nos. 4, 8 and 11 were almost completely dissolved at concentrations of 2,
4 and 6% to give clear solutions. The gelatin of No. 21 gave almost same
result, but not measured at a concentration of 6%. The raw gelatin (30
Bloom) corresponding to the treated gelatins of Nos. 4, 8 and 11 was
dissolved completely at concentrations of 2, 4 and 6% in about 30 minutes
to give unclear solutions.
(4) The above data indicate the advantages of stepwise addition of the
treated gelatin, for example, at 20.degree.-30.degree. C. in 5-10 minutes
with agitation.
Experiment VI
(1) An alkali gelatin (granules; jelly strength 100 Bloom; weight 60 g
including water content of 13%) was added to water at 20.degree. C., and
the swelled gelatin was heated to 50.degree.-55.degree. C. for 5 minutes.
From the solution thus-obtained, a jelly (jelly strength 80 g;
concentration 6%) was prepared. The jelly (500 g) was put in a vessel (15
liter) made of glass. The vessel was covered with a plate made of
polytetrafluoroethylene (thickness 0.1 mm) and put in a microwave oven
(output 2.2 kW at 2450 MHz). After a contnuous irradiation for 240
seconds, intermittent irradiations (each for 15 seconds followed by an
interval for 30 seconds) were repeated to given an irradiation time of 360
seconds in total. The gelatin thus-treated was powdered (not more than 80
mesh) to give a sample of the treated gelatin (water content 0.7%; yield
25 g), the physical properties thereof being shown in Table 5.
(2) Separately, sodium bicarbonate (1.5% by weight of raw gelatin on dry
basis) was added to the raw gelatin (60 g), from which another jelly
(concentration 6%) was prepared in a similar manner to that described
above. The jelly prepared was also treated with microwave in a similar
manner to that described above to give another sample of the treated
gelatin which was then powdered (not more than 80 mesh).
(3) The same raw gelatin was used to give a gelatin solution (2%) which was
frozen at -20.degree. C. and dried at -30.degree. C. The freeze-dried
gelatin prepared was powdered (not more than 80 mesh) to obtain a
comparative gelatin.
(4) The thus-prepared two types of gelatins treated by the process of the
present invention were tested by using jellies prepared in the following
manner, the corn grade of the powders of the treated gelatins being
elected to be not more than 250 mesh):
(A) The following materials (indicated by part by weight) were throughly
mixed together.
______________________________________
Gelatin 2
Sugar (powdered) 20
Sodium citrate 1
Citric acid 0.5
Flesh of pine apple (freeze-dried and
powdered) 0.5
Enchi yellow (vitamin B1, commercial
product of Tanabe Seiyaku K.K., Japan)
0.01
Pine apple flavour, artificial
0.4
______________________________________
(B) When water (100 ml) was added to the mixture (25 g) with agitation, the
materials other than gelatin were easily dissolved in water, and the
treated gelatins were completely dissolved in about 4 minutes. When the
gelatin solution was put in a jelly cup and allowed to stand at about
5.degree. C. for 20 minutes, a jelly was formed. A comparative jelly was
also formed by using the freeze-dried gelatin in a similar manner to that
described above. In order to obtain another comparative jelly, a mixture
using the raw gelatin was prepared and water was added to this mixture in
a similar manner to that described above. After this, the raw gelatin was
completely dissolved when the solution was heated to about 55.degree. C.
and the solution was cooled to room temperature. A jelly was formed in a
similar manner to that described above.
(C) There were thus obtained four jellies respectively using the treated
gelatin with addition of an expanding agent, the treated gelatin without
addition of the expanding agent, the freeze-dried gelatin and the raw
gelatin. These jellies had same taste and same appetizing feeling.
However, with respect to the outlook and transparency, the jelly using the
treated gelatin without addition of the expanding agent was inferior to
other three jellies.
In the following tables, jellies 1, 2, 3 and 4 denote those prepared by
using the treated gelatin without addition of sodium bicarbonate, the raw
gelatin, the treated gelatin with addition of sodium bicarbonate and the
freeze-dried gelatin, respectively, and the figures indicate the presons
who evaluated the tested jelly to be superior. These tests were made by
using a panel consisting of 20 persons in Tsuchiura Mill of Kyowa Hakko
Kogyo K.K., and the significance was determined with a risk of 1%.
TABLE (A)
______________________________________
Jelly 1 Jelly 2
______________________________________
Outlook 3 17
Taste 11 9
Appetizing attraction
9 11
______________________________________
TABLE (B)
______________________________________
Jelly 2 Jelly 3
______________________________________
Outlook 9 11
Taste 10 10
Appetizing attraction
9 11
______________________________________
TABLE (C)
______________________________________
Jelly 2 Jelly 4
______________________________________
Outlook 10 10
Taste 11 9
Appetizing attraction
10 10
______________________________________
(5) Foaming ability and viscosity shown in Table 5 were determined in the
following manner.
(A) Foaming ability:
A treated gelatin (1 g) in the form of powder (not more than 80 mesh) and
powdered sugar (12 g) were put in a beaker and throughly mixed together.
Water (40 ml) was added to the mixture with agitation at 20.degree. C. to
give a solution. A Kennwood mixer with a whipper (commercial product of
Kennwood Inc. U.S.A.) was used for agitation. A millet jelly (148 g; solid
content 75 g) and the mixture were combined and stirred for 10 minutes
with a highest speed for foaming. A given volume of the solution was put
in a measure cup and weighed. Foaming ability was determined by the
following formula:
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