PROCESS FOR IMPROVING THE PROPERTIES OF GELATIN

lJ OZ318 The present invention relates to a process for - improving the -prr- e of gelatin.

It is well known that gelatin is a kind of protein derived from collagen, and it is widely used, for example, as a raw material for foodstuffs such as confectionary, medicaments, photographic emulsions, adhesives and the like.

Gelatin is usually used in the form of an aqueous solution, but is not easily soluble in cold water. Accordingly, gelatin solution is prepared, for example, by immersing the gelatin in water with agitation at room temperature so that the gelatin swells, and then either heating the mi,xture to about 50°C or continuing the agitation at room temperature for 24 hours. However, such a method is time-consuming, and thus there is a need to improve the solubility of gelatin in water having a temperature which is lower than room temperature (in this specification, the term "water-solubility" of gelatin denotes the cold water solubility as thus defined).

It is known that gelatin can be made completely water-soluble by drying the gelatin at100°C under reduced pressure (US Patent 2,803,548). However, the gelatin thus obtained is incapable of gel formation. It has thus been desired to improve the water-solubility of gelatin without deleterious effects upon other of its properties such as e.g.

the gelling ability, the appearance, he stability of the gel 'and so on. Various attempts have been made to achieve this, but all have disadvantages.

For example, it is known that the properties of gelatin can be improved by freeze-drying gelatin dissolved in water at a concentration of 0.1-2% under reduced pressure (US Patent 2,166,074). However, this prooess is not especially advantageous because the conventional dissolving method is required to prepare "i • / i the gelatin solution used as the starting material, and als9 the low concentration of the gelatin in the solution makes this process expensive.

U.S. Patent 3,514,516 describes a process for improving •the properties of gelatin, in which gelatin having a water content of not more than 10% is frozen at a low '\ temperature, the freeze-drying of the same is then started at about100°C and the temperature is then lowered to about 40°C. This patent states that the resultant gelatin is stable at 125°C for one hour and •that the gels derived from this gelatin are stable at temperatures above35°C, in contrast to the gels derived from conventionally improved gelatins. However, in this process the water content of the starting gelatin has to be adjusted (gelatins of market gradeusually contain more than 10% of water), and the process is also complicated and expensive.

On the other hand, various proposals have been put forward to improve the water-solubility of gelatin without adversely affecting its other properties, by adding sugar to gelatin. For example, according to U.S. Patent 2,803,548, gelatin is dispersed in water containing sugar in an amount Of not more than 10 times by weight of the gelatin, and is dissolved by heating the dispersion. A solid material is then obtained by evaporating the 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 to a larger amount of the treated gelatin by a corresponding 10%.

According to US Patent 2,841,498, a 40% aqueous solution containing sugar and gelatin (10-8 and one parts by weight, respectively) is spray-dried at a temperature of 124-243 °C to give a powder containing water (4-5%). By dissolving the powder in cold water, a mixed solution of gelatin and sugar is easily obtained, the resulting gelatin having properties analogous to those of untreated gelatin. However, it is only possible to obtain a gelatin having improved water-solubility in the form of a mixture of gelatin and sugar.

Furthermore, other properties, such as e.g. the gel strength of the thus-obtained gelatin having improved water-solubility, are inferior to those of untreated gelatin.

The present inventörs have searched for a process for producing a gelatin which is capable of being dissolved quickly in cold water in a simple manner and have discovered a process involving an inductive heat-treatment using microwaves (herèinafter referred to as an HF-treatment). As indicated in the experimental results given below, various factors such as e.g. the water content of the gelatin before the HF-treatment, the same after'the HF-treatment, the amount of water to be removed, the treating conditions and the like have also been investigated to discover the necessary conditions under which the invention can be performed.

According to the invention there is provided a process for modifying the cold water solubility of gelatin, which comprises subjecting gelatin having a water content of more than 8 % by weight to a dielectric heat treatment using microwave radiation to remove at least 35 % of said water content to obtain a treated gelatin having a water content of no more than 16 % by weight.

It is advantageous to use the treated gelatin of the present invention in granular or powder form since this increases the solubility. When the gelatin is fine powder form, it can be dissolved more quickly by dividing the powder into X small fractions and separately feeding these fractions into water.

For the purpose of preparing confectionary and so on, gelatin is usually used in association with sugar, and in such cases, gelatin is often dispersed in sugar before being dissolved in water. When gelatin produced according to the present invention is dispersed in sugar, it is possible immediately to add the total amount of the gelatin and sugar to a desired amount of water or vice versa. In this manner, the gelatin is dissolved quickly.

Dispersants other than sugar which may also be used for this purpose are exemplified by sweetening agents (e.g.

glucose), taste-enhancing agents (e.g. sodium glutamate, nucleic acid, succinic acid and so on), table salt and the like. In these cases, the amount of the dispersant used is preferably in the ratio of 1-30:1 by weight of the gelatin (Qn a dry basis). If desired, it is possible to add such dispersants to the raw gelatin before the HF-treatment. In this case, the amount of the dispersants added is preferably and approximately 10% by weight of the raw gelatin (on a dry basis).

It is apparent from the experimental results given below that the properties of the jellies prepared from the water-soluble gelatin of the present invention are identical with those obtained by using untreated raw gelatin. Accordingly, the water-soluble gelatin obtained by the present invention may be used in an analogous manner to that of conventional gelatin.

It is theorized that the invention is based on the fact that it is possible to improve the water-adsorption ability of gelatin, and accordingly the water-solubility, when i0 110Z;31, the voids in the micelle structure of a water-containing gelatin are expanded and fixed in the expanded state by the use of microwaves. However, the invention is in no'way limited to this theory.

The process of the present invention will be fully and clearly described in the following description, in which the following terms are used:

Raw gelatin:

Gelatin to be given the microwave treatment according to the process of the present invention, viz. untreated gelatin.

Improved gelatin:

A gelatin, the properties of which, such as the water-solubility, have been improved by a known process, such as e.g. spray-drying, freeze-drying etc.

Treated gelatin:

A gelatin obtained by subjecting a raw (untreated) gelatin to an HF-treatment according to the process of the present invention.

All known gelatins produced by treating collagen with acid, alkali, enzymes and the like, may be used as the starting materials for the process of the present invention. It is also possible to use a raw gelatin which may contain impurities (e.g. glue). For the purpose of the present invention, it is hot necessary to add any known additives (such as e.g. sugar) to the raw gelatin, and the raw gelatin may be used in the form of a sheet, granules or a powder (in the case of dry gelatin) and in the form of a gel or sol (in the case of wet gelatin) containing a very large amount of water. 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 110Z31 amount of water, which is intended to be used for the preparation of dry gelatin.

The water content of the raw gelatin used in the present invention should be, in general, more than 8% (on the basis of the raw gelatin including impurities). However, with reference to Experiment No. 2 below, it is necessary in some cases that the water content be more than 10%. On the other hand, the upper limit of the water content is believed to be dependent only on the practical applicability and economy of the process. This is true since iris possible to improve J the water-solubility and to obtain a good gelling ability even when a gelatin containing a very large amount of water (e.g. more than 50%) is used as the raw gelatin. Of course, it is not advantageous for practical purpose to use a raw gelatin containing an excessively large amount of water, since this may result in the consumption of a very large amount of electrical power for removal of the water. In such a case, it is possible, if desired, to pre-treat the raw gelatin before the HF-treatment to produce a lower water content, for example by drying the same in sunlight or hot air. It is also possible to increase the water content of the raw gelatin before the HF-treatment by water-adsorption, if necessary.

Especially good results may be obtained when the water content of the raw gelatin is 10-.55% by weight. According to JIS (Japanese Industrial Standard), the water content of commercial grade gelatins is more than 16% by weight, and many dry gelatins contain, as a matter of practice, water in an amount of about 13-10%. This fact is particularly advantageous for the applicability of the process of the present invention because there is rio need to pre-treat the raw gelatin, although it is also possible to use a raw gelatin in the form of a gel i0 or sol containinga very large amount of water, as described above.

The raw gelatin is usually subjected to the HFtreatment in the absence of additives.

The use of HF-treatments for heating and dehydrating water-containing materials for foodstuffs is already known, and suitable apparatus for utilizing such methods is also well known, such as the electron oven which radiates microwaves usually at 915 or 2450 MHz.

It is preferred for using the electrical energy effectively to enclose the raw gelatin, for example, in a vessel made of a HF energy-permeable material (e.g. polytetrafluoroethylene, glass wool, kraft paper and the like) or in sheets or films thereof, or to use such materials as heatinsulators. In such cases, these materials are preferably provided with small holes. It is also advantageous for using the heat effectively to make a pile of raw gelatin with a thickness, for example, of around 0.2 rmm. It is also a good idea to use an electron oven provided with a belt conveyor for transporting raw gelatin across the oven during the HF-treatment.

The amount of the electrical energy required for the HF-treatment and the period of time for the HF-treatment depend upon various factors such as e.g. the amount of water to be removed from raw gelatin, the amount of raw gelatin to be treated and so on, and as a result, more than 35% of the water content of the raw gelatin is removed and concurrently no more than 16% of the water content of the treated gelatin is retained.

Usually, the HF-treatment may be effected continuously.

However, when a raw gelatin is treated for a long time (e.g.

minutes and more), it is possible to irradiate with microwaves continuously at first, followed by intermittent irradiation. The temperature of the raw gelatin before the irradiation is not especially important, and it is thüs possible to pre-heat the raw gelatin before the HF-treatment. However, over-heating should be avoided, since it can adversely affect the properties of the treated gelatin.

In the following Experiments and Examples, the electron ovens used had an output of not more than 2.2 kW at 915 or 2450 MHz, and the irradiation times were in general within 20 minutes and were determined according to various factors, such as e.g. the water content of the raw gelatin used and the like. In these Experiments and Examples, the temperature of the gelatins during the HF-treatment was believed to be about 80-105 °C.

As long as more than 35% of the water contained in the raw gelatin is removed by the HF-treatment, there is no need to specify a lower limit for the water content in the treated gelatin. However, from a practical viewpoint, this lower limit would be about 5% 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 sunlight or hot air when a lower water content of the treated gelatin is required. On the other hand, it is possible to increase the water content of the treated gelatin by water-adsorption, if necessary. In all events, thegelling ability and watersolubility of the treated gelatin are not changed thereby.

Various advantages achieved by the process of the present invention are exemplified as follows.

It is not necessary to use additives (e.g. sugar) I18; 318 i0 in the raw gelatin and furthermore the raw gelatin may contain impurities (e.g. glue). No special pretreatment of the raw gelatin is required. The lower limit of the water content of the raw gelatin does not exclude the range of water contained in usual dry gelatin of commercial grade (the water content thereof is not more than 16% according to JIS and in many cases about 13-10%). On the other hand, the upper limit of the water content depends upon the applicability and economy in practice. That is to say, all practically available raw gelatins may be used for the purpose of the present invention, without any pretreatment. Furthermore, it is also possible, if desiredjto adjust the water content of raw gelatin before the HF-treatment, and also to use as the raw gelatin a wet material which contains a very large amount of water and from which it is intended to prepare a dry gelatin. It is to be noted that it is difficult in conventional improving processes to use raw materials having such widely different water contents in such a manner.

The process of the present invention may be carried out quite simply and inexpensively. This is true since what is required is merely to determine 'the amounts of water contained in the raw and treated gelatins and the amount of water to be removed from the raw gelatin. The water-solubility of the thus-obtained gelatin is improved, while other properties such as the gelling ability and appearance are retained. The uses for the treated gelatin are not limited, while the, strength and stability of thegels formed from the treated gelatin are substantially unchanged, irrespective Of the presence or absence of additives.

Various advantages are exhibited by the process of the present invention, as is explained above. However, it is sometimes desirable to produce a gelatin jelly having good transparency and beautiful appearance. For the purpose of producing a gelatin capable of forming such a jelly, an expanding agent may be added to the raw gelatin before the HF-treatment.

The term expanding agent used herein denotes edible expanding agents of the known types, such as e.g. sodium hydrogen carbonate, ammonium hydrogen carbonate and the like, which are used for example for baking powder. The amount of the expanding agent to be added is preferably about 0ol-5% by weight of the raw gelatin (dry basis). It is possible to dissolve an expanding agent in water, in which a raw gelatin is then dissolved, or vice versa. If desired, an expanding agent in the solid or liquid form is added to the gelatin in the gel or sol form, followed by sufficient agitation. However, the transparency and other properties can not be improved by adding an expanding agent to the treated gelatin.

The strength and stability of the gelatingel is not substantially changed by using an expanding agent. When a gelatin treated after the addition of an expanding agent is compared with another treated without such addition, there is no difference with respect to the Solubility Index (A) and the jelly strength and the like (as hereinafter defined). However, when two types of gelatin jelly are compared with respect to taste, appetizing feeling, appearance etc., the former, i.e. a gelatin treated after the addition of an expanding agent, is superior with respect to the appearance. Of course, the appearance was unchanged when a jelly was prepared from the latter (a gelatin treated without the addition of an expanding agent) to which an expanding agent was added.

On the other hand, jellies were prepared from a gelatin treated after the addition of an expanding agent and from the raw (untreated) gelatin respectively and compared with each other with respect to the taste, appetizing feeling and appearance. It was observed that there was no difference in the taste and appetizing feeling, and the difference in appearance was almost negligible. These comparisions were effected by using gelatin powders of not more than 250 mesh.

Various experiments were carried out to show the properties of treated gelatins and the results are indicated in the following description, in which the weight of gelatin is indicated on a dry basis, unless otherwise specified, and the terms raw gelatin and treated gelatin are as defined above.

Experiment I (with reference to Table i) :

Table 1 indicates:- a) Test No.

b) Water content in raw gelatin (%) c) Time of HF-treatment (seconds) d) Water content in the treated gelatin (%) e) Amount of gelatin dissolved in water (mg/ml) f) Solubility indes (A) (%) as hereinafter defined g) Jelly strength (g) h) Solubility index (B) (%) The experiment was carried out in the following manner.

(i) Determination of the amounts of gelatin dissolved in water (I) and (II) and solubility index (A):

A raw gelatin (weight i00 g on a wet basis) containing a predetermined amount of water and having a jelly strength of Bloom was used as a test sample. The sample was powdered to a corn grade of not more tha 80 mesh and was enclosed in a sheet of polytetraethylene (thickness 0.i n a). The sample was put in a beaker made of glass (capacity - 2000 ml). An i0 electron oven (output - 400.W at 2450 MHz) was used for the HF-treatment of the sample ge1 ati; for a pre-deterÆ'ined time.

The treated gelatin was powdered, and the powder of not more than 80 mesh (weight - 4 g) was thoroughly mixed with sugar (12 g)° The mixture was immediately added to water having a temperature of 20°C (i00 ml) and was kept at 20°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 gelatin dissolved in water was determined. Separately, a €orresponding raw gelatin (4g; without addition of sugar) was treated in a similar manner to that described above to give an aqùeous dispersion containing gelatin, which was heated to 50°C in 15-20 minutes. By keeping the dispersion at about 50°C for minutes, the gelatin was completely dissolved. The total nitrogen content in the solution was determined in a similar manner to that described above, from which the amount (II) of gelatin dissolved in water was determined. It was evaluated that a larger solubility index (A) indicated by the following formula showed a larger relative amount of gelatin dissolved in water at 20°C within 3 minutes riz. a higher watersolubility.

[Solubility index (A)]=[amount of gelatin dissolved in water (I) (mg/ml)/amount of gelatin dissolved in water (II) (mg/ml)] x i00 % (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 i i• i0 110 31 to determine the amount of gelatin dissolved in water (I), the gelatin containing a predetermined amount of waters 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° C for 18 hours to form a jelly. Reometer Type R-UDJ (commercially available from Fuji Riko Kogyo K.K., Japan) was used to determine jelly strength (I) at room temperature of 20° C and a jelly temperature of 7° 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 the raw gelatin was mixed with sugar (12 g), to obtain an aqueous solution containing a completely dissolved gelatin. The 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 gelatin solution was excessively high, it was difficult to filter the solution and thus the amount of gelatin dissolved in water and also the 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 larger Solubility index (B) indicated by the following formula corresponded to a relatively larger amount of gelatin dissolved in water riz. a better water-solubility:

Solubility index (B) = [jelly strength (I)/jelly strength (II)] x i00 %.

,4 I l0 110 318 It is noted that various jellies used for foodstuffs of market grade have a preferable 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 Table 1 contains the terms of "swelled" or "swelled and solidified".

(3) In Table i, Test Nos. 4-13 indicate the data on gelatins treated by the process of the present invention, while 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 shown 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 (I) of gelatin dissolved in water. Because the gelatin shown in No. 15 is a control gelatin, its Solubility indexes (A) and (B) are i00 %. It is noted that the amount (I) of gelatin dissolved in water and jelly strength (I) are variable, depending upon the treating conditions, while the corresponding values of raw gelatin are independent upon the water content.

X i0 î[10Z3:[ (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° C for 3 minutes. The amount of gelatin dissolved in water (I) 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° C for 3 minutes to give a gelatin solution which was then used, without being filtered, to form a jelly, but a good result was not obtained in No. 14. On the other hand, in 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 No. 14, and good results were obtained except No. 5. It was thus confirmed that gelatin treated bythe process of the present invention was afforded with an improved ability of gelling. Particularly in Nos. 8, 9 and I0, 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 changed remarkably by addition of sugar to gelatin. It is thus concluded that the ability of forming gel and the jelly strength obtained from the gelatin treated by the process of the present invention are equal to those of raw gelatin.

T i0 110 31 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 the use of a raw gelatin having a jelly strength of 250 Bloom. 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 are the data on the treated gelatins of the process of the present invention.

The amount (I) of gelatin dissolved in water was hardly determined except in No. 17. In No. 17, 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 Nos. 17 and 23, the used gelatins 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 Nos. 19-25, it was difficult to determine the amount (I) of gelatin dissolved in water and accordingly 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 values of the control gelatin in No. 30. It may accordingly be concluded that the jelly strength and ability of forming gel of the treated gelatin is almost equal to those of the corresponding raw gelatin.

(3) The results obtained from Nos. 1-5, 151 17, 19-22, ........ IIOZ818 and 27 in Experiments I and II indicate as follows.

In order to improve the water-solubility, it is , necessary to give a water content of more than 10 % of untreated gelatin, to retain a water content of not more than 16 % of treated gelatin and to remove more than 35 % of the water content.

(4) In Text 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 seconds were repeated (irradiation time 330 seconds in total) to avoid the "burning" of gelatin. The water content of the thus-treated gelatin was 0.9 % (a minimum water content among the tested gelatins). On the other hand, in No. 23, a gelatin (water content 50.2 %) was continuously treated with microwave for 540 seconds to give a treated gelatin containing water of 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 that it is possible always to obtain good results as long as the operational conditions are within the range specified according to the present invention.

Experiments III (with reference to Table 3):

(i) A raw gelatin (water content 24 %; corn grade 4-8 meshes; jelly strength 250 Bloom; weight 12 g) was subjected to microwave treatment by using a electron oven (output 2.2 kW at 2450 MHz), by which a conveyor belt with a speed of 0.6 m/min was provided in the interior to convey the gelatin continuously across a specified area X i0 (wide about 30 cm; length about 120 cm) 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. There was obtained the treated gelatin (weight 9.1 kg including a water content of 9.5 %) in the 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-prepared samples were added at once to water (i00 ml) at 30, 20, 15, i0 and 5° 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° C for 18 hours to make a jelly. When the samples were dissolved in water at 30 or 20° C, there were produced jellies. When the samples were dissolved in water at a temperature of not higher than i0° C, they did not give jellies but merely swelled. When the samples were dissolved in water at 15° C, there were obtained incomplete jellies including swelled 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 was not dissolved in water at a temperature of not higher than 30° C by treating in a similar manner to that described above. Accordingly, the temperature was elevated to about 50° C to dissolve the mixture completely and jelly strength was measured in a similar manner to that described above, which was conveniently indicated in the column of "20° C" in Table 3.

X From Table 3, it is apparent that when the treated gelatin of the present invention was dissolved in wa%er at and 20° C for a given period of time respectively, the thus-obtained water-solubility and ability of gelling were equal or superior to those of the corresponding raw gelatin.

Experiment IV (with reference to Table 4):

(i) An alkali gelatin (corn grade 4-8 mesh, jelly strength 30 Bloom; water content 15 %; weight 1 kg) was enclosed in a sheet (thickness 0oi mm) of polytetrafluoroethylene and subjected to microwave-treatment for 300 seconds by using an electron oven without being provided with the conveyor belt (output 2.2 kW at 2450 MHz), by which hot air (80° C) was blown into the oven. There was obtained a treated gelatin containing 4.8 % of water. The weight of the gelatin including water was 890 g. The treated gelatin was powdered (not more than 80 mesh). In Table 4, Test Nos. 49-52 indicate the data on this sample. No. 42, Nos. 43-48 and Nos° 49-52 in Table 4 corresponds respectively to No. 31, Nos. 32-37 and Nos.

38-41 in Table 3, and the determination was carried out in a similar manner to that of 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 i0° 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).

X i0 When the treated gelatin was dissolved at a concentration of 2 % for 3 minutes (No. 43), it was, completely dissolved in water at 30-15° 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° 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 i0° C and the obtained jelly strength was equal to the jelly strength of the corresponding raw gelatin (No. 51). The treated gelatin dissolved in water at 5° C was not jellied except No. 48, in which the concentration of the used gelatin 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° C. Then the temperature was elevated to about 50° 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° C" in Table 4.

Tables 3 and 4 indicate that the treated gelatin of the present invention exhibits an excellent watersolubility 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, otherwise specified.

W II0 818 lO E._xperiment V:

(I) The treated gelatins of Nos. 1-4, 8 and II (jelly strength Bloom) and No. 21 (jelly strength 250 Bloom) were respectively powered (not more than 80 mesh) to give samples. E ch sample was divided into fractions and dissolved in water at 257 C, the amounts of respective fractions being determined so as to give concentrations of 2, 4 and 6 % respectively. ç en the total amount Of each fraction was at once added to water, the water was agitated for 30 minutes. On the other hand, each fraction was further divided into several fractions of small amounts which were stepwisely added to water. For controlling 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 at once to water, the treated gelatins of Nos. 1-3 were almost completely dissolved in water in 30 minutes. The treated gelatins of Nos.

4, 8, ll and 21 exhibited that the granules were adhered 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 minutes, but the obtainedsolutionswere 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 st a concentration of 6 %.

(3) In the case of adding stepwisely the whole amount divided into fractions, the gelatins of Nos. I-3 were not completely dissolved after 30 minutes llke in the case of adding the whole 110 G18 • ':i __.,..- amount at once. The gelatins of Nos. 4, 8 and II were almost completely dissolved at concentrations of 2,4 and 6 % to give clear solutions. The gelatin of No. 21 gave almost same re-- sult, but not measured at a concentration of 6 %. The raw gelatin (30 Bloom) corresponding to the treated gelatins of Nos. 4.

8 and ii was dissolved completely at concentrations of 2, 4 and 6 % in about 30 minutes to give unclear solutions.

(4) The above-mentioned data indicate that it is advantageous for dissolving the treated gelatin of the present invention with good result to divide the desired amount of the treated gelatin into some fractions which are then added to water stepwisely, for example, at 20-30? C in 5-10 minutes with agitation.

Exoeriment VI:

(i) An alkali gelatin (granular form; jelly strength I00 Bloom; weight 60 g including water content of 13 %) was added to water at 2Q? C, and the swelled gelatin was heated to 50-55? C for minutes. From the thus-obtained s01utíon, a jelly (jelly strength g; concentration 6 %) was prepared. The Jelly (500 g) was put in a vessel (15 litres) made of glass. The vessel was covered with a plate made of polytetrafluoroethylene (thickness O.1 mm) and put in an electron oven (output 2.2 kW at 2450 MHz). After a continuous irradiation for 240 seconds, intermittent irradiation (for 15 seconds followed by an interval for 30 seconds) was performed to give an irradiation time of 360 seconds in total. The thus-obtained treated gelatin was powdered (not more than 80 mesh) to give sample of the treated gelatin (water content 0.7 %; yield 25 g) the physical property thereof being shown in Table J i0 (2) Another jelly (concentration 6 %) was prepared in a similar manner to that described above with the exception that 0.9 g of sodium bicarbonate (1.5 % by weight of the raw gelatin on dry basis) was added to 60 g of the raw gelatin. The thusprepared jelly was also treated with micro-wave in a similar manner to that described above to give another treated gelatin.

This gelatin was powdered (not more than 80 mesh).

(3) To obtain a comparative gelatin, the same raw gelatin was used to give a gelatin solution (2 %). The solution was freezed at -20° C and dried at 300 C. The thus-freeze-dried gelatin was also powdered (not more than 80 mesh).

(4) The thus-prepared two types of the treated gelatin according to the present invention were used for the test carried out by using jellies prepared in the following manner, the corm grade of the powders of the treated gelatin being elected to be not more than 250 mesh):

(A) The following materials are Material well mixed together.

Pa rt Gelatin 2 Sugar (powdered) Sodíum citrate 1 Citric acid O.5 Flesh of pine apple (freezeOdried and powdered) 0.5 Enchi yellow (Vitamin Bl#commerclal product of Tanabe Seiyaku K.K., Japan) O.O1 Pine apple flavour (artificial) 0.4 IIOZ818 I l0 (B) This mixture (25 g) was added with water (i00 ml; ?C) and' stirred. When the gelatin treated by the process of the present invention was used, 'the gelatin was completely dissolved in about 4 minutes. en 'this solution was put in a jelly cup and allowed to stand for 20 minutes in a freezer at about 5° C, a jelly was formed. For comparison, the freeze-dried gelatin was treated in a similar manner to that described above to give a comparative jelly. Another comparative jelly was also prepared from the raw gelatin in the following manner. The mixture of the materials was prepared in a similar manner to that described above and was added with water with stirring like in the abovementioned case, followed by heating to about 55° C.

The mixture was completely dissolved, and the solution was cooled to room temperature and was put in a jelly cup. A similar treatment to that described above gave a comparative jelly.

(C) In this manner, there were obtained jellies respectively by using a gelatin added with an expanding agent and subjected to HF-treatment, a gelatin subjected to HFtreatment without addition of an expanding agent, a raw gelatin and a freeze-dried gelatin, These gelatin jellies were evaluated to give the following results.

Four jellies had same taste and same appetizing feeling. However, with respect to the outlook and transparency, the Jellies prepared from the raw gelatln, HF-treated gelatin added with an expanding agent and .... 110 3:[8 the freeze-dried one were superior to the jelly prepared from a HF-treated gelatin without addition of an expanding agent.

In the following tables, jellies i, 2, 3 and 4 denote those prepared from a treated gelatin without addition of sodium bicarbonate, a treated gelatin with addition of sodium bicarbonate, a raw gelatin and a freeze-dried gelatin respectively, and the figures indicate the persons who evaluated the tested jelly to be superior. The 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 ii 9 Appetizing attraction 9 ii TABLE (B) Jelly 2 Jelly 3 Outlook 9 Ii Taste i0 i0 Appetizing feeling 9 ii TABLE (C) Jelly 2 Jelly 4 Outlook i0 i0 Taste ii 9 Appetizing attraction i0 i0 (5) Foaming ability and viscosity shown in Table 5 were determined in the following manner.

X i0 (A) Foaming Ability:

A treated gelatin (i g) in the form of powder (not more than 80 mesh) and sugar powder (12 g) were put in a beaker and well mixed together. The mixture was added with water (40 ml) and stirred at 20° C to give a solution by using Kennwood mixer with a whipper (commercial product of Kennwood Inc., U.S.Ao). The solution was added with a millet jelly (148 g; solid content 75 %) and stirred for i0 minutes with the highest speed for foaming. A given volume of the solution was put in a measure cup and weighed. Forming ability was determined by the following formula:

Foaming ability (%) _ weight (g) before foaming x i00 weight (g) after foaming (B) ViScosity:

A treated gelatin (i0 g) in the form of powder (not more than 80 mesh) and sugar powder (30 g) were put in a 1,000 ml beaker and well mixed together by using a spoon.

The mixture was added with water (500 ml; 20° C) and stirred well to make a uniform solution. The viscosity of the solution was determined by using B-type viscometer [BL-type viscometer, commercially available from Tokyo Keiki K.K.] with No. 1 rotor. The viscometer was rotated for 3 minutes (60 t.p.m.) and after this the viscosity was measured. A comparison with the freeze-dried gelatin described in U.S. Patent 3,514,518 was tried, but a good result was not obtained by this patented method.

•i " 0f 11 z318 The following non-limitative Examples lllu rnte the invention.

Example I An alkali gelatin in the form of plate(weight 200 g; water content 15 %; jelly strength 250 Bloom) was wrapped "n kraft paper and enclosed in glass wool (thickness i0 mm).

The gelatin was heated for 210 seconds! in an electron oven (output 400 W at 2450 MHz) and »cas then powdered (no% more than 80 mesh) to give a treated gelatin (89 g; water coni0 tent 4.3 %) having the properties shown in Table Example 2 An alkali gelatin in the form of sheet (weight 200 g; water content 13 %; jelly strength I00 Bloom) t'as treated in 'a similar manner to that described in Experiment No. 6 to give a jelly (weight 3 kg; jelly strength I00 g; concentration 6 %) which was concentrated in vacuo (409 C 700 mm Hg) to give a solution (concentration 25 %). This solution was put in a vessel (length 25 cm x width 25 cm x height 32 cm; capacity litres) made of polytetrafluoroethylene and heated for 540 se20' conds in an electron oven (output 2.2 kW at 2450 MHz). The treated gelatin was powdered (not more than 80 mesh) to obtain a gelatin having a water content of 10.3% (weight 120 g).

The properties of the gelatin are shown in Table Example 3 Sugar (20 g) and guar gum (20 g) were dissolved in water (300 ml) with stirring for 20 minutes. An alkali gelatin (granules; jelly strength 30 Bloom; water content 10%; corn grade not more than 60 mesh; weight 500 g) was added to the solution and stirred well to swell the gelatin. The mixture was put in a vessel (20 x 20 x 25 cm; capacity i0 litres) made of polytetrafluoroethylene and heated for 240 seconds in an ele110 1 j ....

ctron oven (output 2.2 kW at 2450 MHz)to give a treated gelatin (water content !0 %). This gelatin was dried with hot air (45 C) for-i0 minutes and powdered (not more than 80 mesh's ..... There " L.

was thus obtained a mixture of the treated gelatin (450 g) in granular form, of which the water-solubility was equal to that of a comparative gelatin preparedin a similarmanne-r fo that described above except without addition of sugar and guar gum. However, the viscosity of the gelatin according to this Example was equa! to the viscosity of the comparative gelatin which was afterwards added with sugar and guar gum, followed by being dissolved. - Tests Nos. 55 and 56 in Table 5 show the control gelatin prepared il% a similar manner fo that described in this Example by subjecting the same raw gelatin to microwave-treatment without addition of sugar and guar gum. No. 63 indicates the data on the gelatin obtained by Example 5. No. 6& shows the data On a gelatin prepared by subjecting a raw gelatin having a same Bloom to micro-wave treatment, followed by addition of sugar and guar gum in the same amounts aS those described in No. 63.

Separately, another treated gelatin was prepared in a similar manner to that described above with the exception that water (300 ml) was added with sodium bicarbonate in an amount of 0.2 % by dry weight of gelatin.. Jellies were prepared from the thus obtained two types of gelatin and compared with each other qualitatively to confirm that the appearance and trans- - 29 IIOZOI8 parency of the gelatin prepared by the addition of sodium bicarbonate were superior to those of the gelatin prepared without the addition of sodium bicarbonate.

Example 4 An acid-treated gelatin (lump; water content 20%; jelly strength 150 Bloom; weight i00 g) was wrapped in a perforated sheet of polytetrafluoroethylene (thickness 0.i mm; having many perforations having a diameter of 0.501 mm) and subjected to micro-wave treatment for 180 seconds in an electron oven I0 (output 2.2 kW at 2450 MHz) to give a treated gelatin which writs then powdered. There was thus obtained a treated gelatin in the form of powder (not more than 80 mesh; water content 7.0%; weight 55 g). The properties a e shown in Table 5 together with the properties of the gelatins of Experiments Nos. 3, 4 and 6 for comparison purposes.

II01 318 r'4 pq I * ,---. o3 4-) ,-- r-t o o .i b.O tIsl -. ,"' l -I-) o - o u ,.i: H ..J r-I u i ;> :

'---..., tO r'-4 0E'' O.r-I 4.) 0,.-11-".

PbO-.-." ,4 4 4 4 : 4 ,õ 4 4 4 4 4 I ........ j o ,,-I H 'I:J I I ò o 0 r.--I oe , 4.a rbO 0 1.0 O" " ,H i 1 0 .t - --C c o ! N o 4 oJ4J r- I co ,-I , I H 31 ,-, I o I TABLE 2 (1) (z) (3) l -(4) Test Treatìn conditions I Water in No. Ïnitial "' 'T' Treated treated water contime(sec) gelatin ......... tent!%) J ' (%) « 25i 26! i 2v ] 12. 0 IG.

26.5 26.5 26.5 26.

50.2 5O. 2 5O. 2 50.2 50.2 50.2 3oi I i I I I i J I I 33O 27O IS5 9O 54O 45O I 4L. 9 5. 2 5. 9 O. 9 3. 2 I0, 0 !4. 0 4. 3 10.2 15.5 20.3 25.5 30. 0 (5) Dissolved amount ( I )mõ/m O. 96 i 1.88 2. 14 I ) (7) SoluJelly bility strength Index i(g) (A)S ! i 15. V * 30.7 * -- 69, -- .73. 7 -- i 74.

-- V4. V - I 74. 2 -- 74 3 74.8 -- V!.

-- 58.

-- 40.! I 35. o { * (8) Solubility Index (B)% 92.7 98.2 99.3 99.6 98.9 99. 0 99, 7 I 95.3 78.0 54, ? (9) Expansion ratio (x) *** 1.2 2 0 1 9 16.5 I - i - 1 7 24. o * I I le. 5 -- - 6. 12 zoo. i 75.0 lO0 I i *-- Swelled and not solidified. *** -- Approximate value.

r,, Co to OJ TABLE 3 TestiGel. Dis. 30 °C No. conc. time Jel. Solu.

(%) in) str. index (g) (B) 31 0.5i i 32 I. 0 3.5 2. 0 3¢ 2.0 2. 0i 36 2. 0 i0 IZ, --« L 3V 4. 0 õ!75. 2 ç I I 38 0.5 -- I 39 I. 0 -- J 2.0 -- 4.1 4.0I-- Jel.

str.

I -- 99. 51 -- I J õ 3. 5 i00. 0 3. 7 I I 2 ll. 5 92. 0I I0.

I 3 12, V ÆO0. 0I !2. 0 I IZ. 4, 99. 2 lí lOO. o 12. 6 IOO. o '75.

-- -- 3.

-- 12.5 '-- VS. 0 i I I- °C I 15 °C Solu.I Jel. Solu.i index str o index (B) (g) (B) . I 9V. 0 -- -- i00. 0 i. ,5 * 84. 0 15. 5 * I- -,x96.0 13.

i00. 0 14. 1 @ J !00. O 15, 6 -x-- 100. 0 82, 5 J ! ........ -í- , I0 °C °C Jel. Solu.

str. index (g) (B) *-X- *%* @* @K- 2 G *** Jei. Solu.

str. index (g) (B) *@ *4@ æ@ @* i Gel. conc.=Gelatln concentration: Dis, time=Dissolving time:

Jel. str°=Jelly strength: Solu. index (B)=Solubility index (B):

*=Contained some swelled fractions: **=Not jellified:***=Swelled.

4- '----I - • "J --s-1 r.-t o o o o ,4 d d • .I rt O xl O" ,':, 4 4 -õ" 0 I 0 0 0 i 0 4 4 4 o õ o o Õ o o J o õ o ' 0"- o o o o o q i o I I I I I I O I I I o I I l .... i I I I I o I I o o r-i ,,-i o4- o ,ri 4- ,-t Il l l Et ID °oe tç 4» (DO Xl oe |1 oe* l/l o TABLE I oi I Test No.

Sample of gelatin prepared in Example (or Experiment) No.

53 Experiment 3 54 I Experiment 3 (control) Experiment 4 56 Experiment 4 (control) 27 Example 1 58 Example 1 (c0 ntr01 ) 59 Experiment 6 * Experiment 6 ( ontrol)* 61 Example 2 62 Example 2 (control) 63 ExampoEe 3 IO0. I 64 Example 3 (control) i00 Example 4 66 Example 4!control) i -- *=Not added with sodium bicarbonate.

Water-solubility Solu.

index (A) 99.5 100. 0 Foaming Jelly SOlUo ability strength index (20°©;0.5 (g) (B) 75.5 75.0 4. 2 4. 0 79.6 80. 3 22.0 21.6 33.0 33.2 3. 8 4. 0 35.0 36.2 ioo ioo ioo !oo 99.1 ioo !oo 100 99.4 !O0 95.0 96,"/ lO0 I 420 viscosity °C ; ) 61.5 8. 6 6. 6 6, 67.7 8. 9 40.8 7. 2 47.

7. 7 58.0 57.8 50.2 8. 0 <D The embodiments of the invention in which an exclusive