JPS5881745A - Preparation of swollen starch slurry having high fluidity - Google Patents

Abstract

PURPOSE:To prepare swollen starch slurry having high concentration and neverthless high fluidity, by heating an aqueous slurry of starch, and cooling the slurry before the viscosity of the slurry reaches a specific level. CONSTITUTION:A heating tank having the internal space of 150l and furnished with a heating and cooling coil, is charged with 85kg of water and 15kg of corn starch. The content is heated to 68 deg.C under agitation with a stirrer at about 200rpm to effect the swelling of the starch, and maintained at 68 deg.C for about 1min. When the viscosity of the slurry reaches 720cps, the cooling is started and the content is cooled to 62 deg.C in 2min. Thereafter, the content is left at the temperature for 2hr to obtain an aqueous slurry of starch having a moderate fluidity or a viscosity of 1,230cps.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a slurry of swollen starch particles that does not gel even at relatively high concentrations and maintains good fluidity.

It is known that when starch is heated and swollen in a water slurry, the water slurry increases in viscosity and, especially when the slurry concentration is high, it easily gels and no longer exhibits fluidity. For that reason, for example, Tokugansho! J-7? Coro≦
When trying to produce and dry expanded lIi starch particles that exhibit non-refractive properties while maintaining the shell thin film structure as disclosed in the specification of the patent, the spray-drying method must not destroy the starch particles. This is a very effective method, but as mentioned earlier, the slurry of swollen starch thickens and can only be used at very low concentrations. Therefore, the energy efficiency during drying is extremely poor, and considering the current energy situation, the appearance of a swollen starch slurry with high concentration and low viscosity has been awaited.

Conventionally, it has been generally accepted that such a thickening phenomenon of a swollen starch slurry is a natural phenomenon, and no attempt has been made to suppress the thickening and increase the slurry strength.

JP-A-11-1141300 discloses a method for improving the workability when producing dried pregelatinized starch products.

In this method, the problem of poor fluidity due to the thickening phenomenon of 111 starch slurry is solved by using a stirring kneader that applies strong shearing force, such as a kneader. When handling swollen starch particles that maintain their shell thin film structure, strong shearing force cannot be used because the thin film will be destroyed.

The present inventors investigated in detail the relationship between the swelling of starch granules and the increase in viscosity of 1ilIII starch slurry, with the aim of suppressing the thickening of the swollen starch slurry during heating and making it possible to increase the concentration of the slurry. As a result of the investigation, we found that there is a time lag between the swelling of starch granules in the water slurry and the viscosity increase phenomenon of the swollen starch slurry, and that it takes a relatively short time to suppress the viscosity increase of the swollen starch slurry. They discovered that it is sufficient to lower the slurry temperature to below the starch swelling starting temperature within a certain amount of time.
The present invention has been completed. The present invention is based on this knowledge and aims to obtain a swollen starch slurry with high concentration and good fluidity.

The present invention involves heating a water slurry of starch to an I-water temperature;
The starch is moistened and the water slurry has a maximum of 2000 cp.
This invention relates to a method for producing a jlllIjlF powder slurry having good fluidity, which is characterized by cooling to a temperature below the swelling start temperature while the viscosity does not increase to II.

The swollen starch slurry produced by the method of the present invention has a high concentration and good fluidity, so it can be easily spray-dried and consumes less energy during drying.

Also, the starch obtained by this method is a heavy, non-birefringent starch powder that maintains the outer thin film structure.

In the present invention, the swelling temperature refers to a temperature within a day that is sufficient to swell raw starch without destroying its outer thin film structure. varies greatly depending on

In addition, since starch particles are a natural product, even if they are the same starch, there are variations in the properties of Bizen particles.
The temperature at which each particle starts to swell and the temperature at which the outer thin film structure ruptures due to excessive swelling vary depending on each individual particle. The swelling start temperature in the present invention refers to the point at which the first particle in the starch particles starts swelling. Further, the possible range of the 11114 temperature is any point within the temperature range from the initial concentration of glue 111N until the outer thin film structure of the first particle is broken, and is selected within this range depending on the purpose. . This is because the 1111FM start time of starch particles/@ depends almost only on temperature, and the influence of opening during heating is very small. Therefore, 1IIIIN11! The temperature should be determined depending on what percentage of the starch particles are to be swollen, and can be freely selected within that temperature range. When starch particles are exposed to i1, they lose their inherent birefringence and become non-birefringent. Therefore, Wl of starch! , non-WI111 can be clearly determined by the presence or absence of birefringence. The swelling temperature range varies slightly depending on the heating rate of the starch-water slurry, but in the case of cornstarch, it is a relatively narrow temperature range from around 4J"C to around 70'C, to give one example. There are many.

The starch used is because grain starch has a distinct swelling starting point.
suitable for the purposes of the present invention. Rhizome starch, such as potato starch, swells very quickly and is difficult to control, and is therefore not suitable for carrying out the present invention. Cornstarch is a starch that is stable in quality and has little variation from product to product, and is the starch that best exhibits the effects of the present invention.

In the present invention, starch is used as a water slurry, but the water used as a dispersion medium does not necessarily have to be pure water, and may contain some inorganic salts, organic substances, etc. as long as it does not significantly increase the viscosity. In addition, the water temperature may be any temperature as long as it is below the swelling starting temperature and above the freezing point.

As heating continues near the swelling temperature, the viscosity of the slurry of swollen starch continues to rise, and when the viscosity of the system exceeds 2000 cpm, it becomes extremely easy to gel, and rather than being suppressed by cooling, it gels and improves fluidity. It's easy to lose it. However, in the case of a swollen starch slurry that is cooled to below the 1lII4 starting temperature at the beginning of the increase in viscosity, the increase in viscosity is suppressed after cooling is completed.

The first wI is %/3%, /! % of each slurry - The increase in slurry viscosity when the cornstarch at one temperature was treated at 44"C 11#lIs degree, and the slurry was cooled as soon as the heating temperature reached 64℃, and within 2 minutes. 60
It shows carbonization of slurry viscosity increase rate when cooled to ℃. The WIII starting temperature in this case is 62° C., and it can be seen from this figure that the viscosity increase can be extremely suppressed by cooling treatment.

Regarding the cooling method, it is desirable to do it as quickly as possible, and any other cooling method may be used, such as cooling by injecting cold water into the heated slurry or cooling with a cooling coil. Minimum Q3°
It is necessary to cool at a cooling rate of C/'yk. If the cooling rate is lower than this, the viscosity of the slurry will increase even during cooling, which is undesirable.

As long as the end point of cooling is below the swelling start temperature and above the freezing point, viscosity increase can be suppressed at any temperature, but if you want to have a sufficient effect of suppressing viscosity increase, the temperature should be lower than the swelling start temperature by J″C. In addition, since excessive cooling operation is unnecessary, it is appropriate to set the lower limit to around room temperature.Of course, it cannot be carried out below the freezing point because it will freeze.

Further, since the present invention aims at producing a highly concentrated slurry, even a slurry having a very low concentration has no practical meaning. The effect of preventing an increase in slurry viscosity according to the present invention appears from the lowest slurry concentration, but the effect is particularly large at a slurry concentration of 70% or more. Further, the upper limit of the slurry concentration in the present invention varies slightly depending on the type of starch used, etc., and is at most about coj%, but the upper limit of the normally usable range is about 20%. This is because at concentrations higher than this, the viscosity increases rapidly, and even if the cooling treatment is carried out too long, it will not be effective.

When the starch water slurry is kept near the swelling temperature, the time required for the viscosity of the starch water slurry to increase to 000ep* is:
Although it varies greatly depending on the type of starch, for example, in the case of cornstarch, the ratio of swollen particles is 9m
Total heating time is 1C min at 1i degrees of swelling II)
Toshita time 0<t≦10←0450+7°63) Tata LC
can be expressed as I#l type fraction of slurry 0 degrees (wt%).

This will be explained in more detail in Examples below.

Example 1 Water 12 in a heating/cooling coil additional heat tank with an internal volume of 1 sol
#t9, cornstarch/! 9 and heated to exactly 41"C using a small Satake type stirrer at a rotation speed of about 200 rpm to swell the starch. It was kept at 6rC for about 7 minutes until the slurry viscosity reached 10 ep. After 2 minutes, the slurry was cooled to 4.fC, and the temperature was maintained thereafter.The viscosity of the slurry after 1 hour was 9j□cps, and the viscosity after 1 hour was 30.
epH, and maintained appropriate fluidity. Approximately 9J% of the starch granules in this slurry lost their birefringence and were swollen, while the remaining approximately S% exhibited birefringence. By the way,
When this cornstarch was heated in this heating tank, the swelling starting point was 63°C.

Example: Put water troq and cornstarch /209 into a beaker with an internal volume of 1 liter, and use a laboratory stirrer to stir the mixture to 3001.
While stirring at a rotation speed of 9m, use a hot water bath to accurately
When the slurry was heated to a temperature of J°C and kept at that temperature for 60 minutes, the viscosity of the slurry became /11IOcps. This slurry
When the mixture was cooled to 60° C. over a period of minutes and maintained at that temperature, the viscosity after 1 hour was /9 tOcpt and the viscosity after 1.2 hours was 2010 cps, indicating good fluidity. When this heating device was used, the swelling starting temperature of this cornstarch was 62°C.

Example 3 Using the same heating device and cornstarch as in Example 3, 10 g of cornstarch was added to 900 g of water heated to 69°C, and after heating to 69°C, the concentration was kept at that concentration for 10 minutes. , the slurry viscosity was approximately JJOep■. This slurry was cooled to 39℃ over 10 minutes, and the slurry viscosity was measured after 1 hour.
It was ep-.

EXAMPLE 1 Using exactly the same equipment and corn starch as in Example 3, 1 kg of slurry weighing 10 weight was prepared, heated to 441"C, and the slurry viscosity after 3 minutes was /JjOcpa. The slurry was cooled to 55°C over a period of minutes.The viscosity of the slurry at this time was /3λOcps. When this slurry 9- was left at room temperature of 2j°C for 1 hour, the slurry temperature was Jj'C and the viscosity was /! 10 cpa, indicating good fluidity.

Example J: Add 7j of wheat starch to water 11239 warmed in a beaker of 30 (Hpl) with a laboratory stirrer.
It was heated to 10°C while covered. The three viscosity immediately after heating was 17≦Ocps. When this slurry was immediately cooled to #'C over 75 minutes, the slurry viscosity was /
It was l10cp-. After leaving this slurry in CorrC for 1 hour, the slurry viscosity was measured: /? jOcps and showed good fluidity.

Comparative Example 1 Put corn starch tsq and water zs~ into a heating tank of actual mN/, perform exactly the same operation as in Example 1, and heat to exactly 61"C.
It was heated to. Heating was stopped after reaching 61°C.

When only stirring was continued, the viscosity increased rapidly after about 70 minutes, making stirring difficult. The temperature of the slurry at this time is 4? !
"The viscosity of C1 was over 110,000 cH. However, when looking at the starch particles in the slurry under a microscope, there were approximately 3% birefringent particles and approximately 9,751L non-birefringent particles, and the outer thin film structure was destroyed. No particles were found.

Application example 1 The upper limit of the slurry viscosity of the handled material is approx./! When the slurry obtained in Example 1 was spray-dried using a spray drying device with a speed of 0.00 cps, a good dried product was obtained as the slurry had good fluidity and no troubles.

Normally, the heated starch slurry that can be spray dried with this equipment is /1
Since the upper limit was 1-, it became possible to increase productivity by about 33%.

[Brief explanation of drawings]

No. 11iI shows the difference between the rate of increase in slurry viscosity at the swelling temperature of cornstarch-free and the rate of increase in viscosity when subjected to cooling treatment at 73 weight s and is weight. Patent applicant: Asahi Kasei Industries, Ltd.

Claims (2)

[Claims] (1) Fluidity characterized by heating a water slurry of starch to a swelling temperature to cause the starch to swell, and cooling the water slurry to a temperature below the swelling start temperature while the water slurry does not thicken to a maximum of 0OOcpI. A method for producing a good swollen starch slurry. (2) The manufacturing method according to claim 1, characterized in that cooling is performed at a cooling rate of 0.3° C./min or more.