JP3828113B2 - Process cheese production method - Google Patents

Description

The present invention has a heat fusible, a method for manufacturing a stringing of good process cheese.

Conventionally, process cheese having heat meltability is produced by adjusting the types, addition amounts, and the like of molten salt, emulsifier, and stabilizer.
For example, as a method for producing heat-meltable cheese, a method of adding a stabilizer and an emulsifier (see Patent Document 1), a method of adding a molten salt and an emulsifier (see Patent Document 2), and a molten salt , Methods of adding gums, microcrystalline cellulose (see Patent Document 3), and the like are known. In addition, as a type of emulsifier, a method using sodium phosphate (see Patent Document 4) and a method using sodium citrate and calcium lactate (see Patent Document 5) are also known. Furthermore, a method of adding calcium salt and citrate and / or phosphate (see Patent Document 6), a method of adjusting the content of αs casein and molten salt (see Patent Document 7), etc. are reported. ing.
JP-A-4-218334 JP-A-9-103242 JP 2001-29012 A JP 49-80270 A Japanese Patent Publication No. 60-30495 JP-A-4-179442 Japanese Patent No. 3135585

However, when process cheese is produced under conditions such as those reported in the past, the cheese after heating and melting is hard and not elastic, has a poor texture, and has a problem of poor stringiness. there were. The stringing property refers to the property of stringing when processed cheese is heated, melted and stretched.
The present invention, the prior art has been made in view of the problems of the challenges that stringing resistance after heating and melting, and mouthfeel after heating to provide a method of manufacturing a process cheese is good To do.

In order to solve the above problems, the present inventors first focused on the molten salt and examined its appropriate type, blending ratio, and content.
In addition, attention was focused on dynamic viscoelasticity as an indicator of cheese texture. Dynamic viscoelasticity measurement is performed on foods having viscoelasticity such as polysaccharides, and is reported as a method for evaluating physical properties. It is known that dynamic viscoelasticity and the actual food texture of food show a good correlation. However, the dynamic viscoelasticity value that the food feels good for each food is different, and the preferable numerical range cannot be generalized. Furthermore, about cheeses, there is no example reported about the measurement of a dynamic viscoelasticity until now, and nothing is known about the preferable numerical range.
Therefore, as a result of repeating these studies, the present inventors have a heating and melting step of mixing a specific molten salt with a specific mixing ratio and content and then heating and melting the obtained mixture while stirring. Then , the above-mentioned problem is solved by performing the stirring in the heating and melting step using a mixing type stirring blade at a stirring speed in which the peripheral speed at the tip of the stirring blade is in the range of 2 to 5 m / sec. As a result, the present invention has been completed.

That is, the first invention of the present invention, the sodium click enoic acid and sodium polyphosphate, 1: 0.7 to 1 mixing ratio, and for the process cheeses total mass is prepared: 3 to 3 After blending so as to be 1.4% by mass , the obtained mixture has a heating and melting step in which the mixture is heated and melted while stirring, and stirring in the heating and melting step is performed using a mixing type stirring blade, It is a process cheese manufacturing method characterized by performing with the stirring speed which the peripheral speed of the front-end | tip of a stirring blade becomes in the range of 2-5 m / sec .

According to the production method of the present invention, it is possible to produce a processed cheese having good stringiness and good texture.

The manufacturing method of the process cheese of this invention is demonstrated.
First, the processed cheese to be manufactured is designed, the final quality specification value is determined, and a recipe is created. For this, first, the moisture and fat amount in each raw material cheese are analyzed, and the composition of the raw material cheese is determined according to the final quality standard value. At the same time, the amount of water, molten salt, and other additives is determined .
Raw material cheese should just be natural cheese normally used as a raw material of process cheese, and is not specifically limited. For example, gouda cheese, mozzarella cheese, cheddar cheese, edam cheese, and the like can be used. Particularly, gouda cheese, cheddar cheese, and mozzarella cheese are preferable because they have good stringiness and flavor.
As a molten salt, when sodium citrate and sodium polyphosphate are expressed as “sodium citrate: sodium polyphosphate”, they are used at a blending ratio in the range of 1: 3 to 3: 1. A more preferable range of the blending ratio is 2: 3 to 3: 1. By setting the blending ratio within the above range, the stringiness of the processed cheese can be improved. Also, the addition amount of the molten salt, the total mass of sodium citrate and sodium polyphosphate, relative to the weight of the processed cheese is produced, it is to be in the range of 0.7-1.4 wt% The A more preferable content is 0.8 to 1.2% by mass. When the content of the molten salt is within the above range, the stringiness of the processed cheese is good, and the flavor, such as hardness, elasticity, and mouth meltability, is good and the texture is good.
Furthermore, molten salts, stabilizers, emulsifiers and the like other than the above sodium citrate and sodium polyphosphate are used as necessary .
Examples of molten salts other than sodium citrate and sodium polyphosphate include sodium pyrophosphate and potassium pyrophosphate .
The stabilizer is not particularly limited as long as it is conventionally used as a stabilizer for processed cheese, but gums, starches, and the like can be used. Among these, it is preferable to use gums, and specifically, locust bean gum, guar gum, xanthan gum, gellan gum and the like are preferable, and locust bean gum and guar gum are particularly preferable. These are used alone or in combination of two or more.
For example, in the case of gums, the addition amount of the stabilizer is preferably 0.1 to 0.4% by mass with respect to the processed cheese. When the added amount of the stabilizer is within the above range, an appropriate structure and physical properties can be obtained.
The emulsifier is not particularly limited as long as it is conventionally used as an emulsifier for processed cheese. For example, lecithin, glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester and the like can be used. These are used alone or in combination of two or more.

Next, blending (blending) is performed by combining the raw material cheese, molten salt, stabilizer, emulsifier and the like as described above. Blending can be performed using, for example, a mixer, a propeller stirrer, a screw feeder, or the like.
And the process cheese is manufactured by performing the heating-melting process which heat-melts the mixture (raw material mixture) obtained by blending using a melt emulsification pot etc., and melt-emulsifies.
As the melt emulsification pot, a heat melt emulsification pot, a high-speed emulsification pot, a combinator, a botter, or the like can be used.
Among these melt emulsification pots, the heat melt emulsification pot is preferably used because it is easy to prepare the structure and physical properties of the processed cheese within an appropriate range. As a heat-melt emulsification pot, a batch-type heat-melt emulsification pot (Stefan, Kusner, etc.) of a type in which a certain amount of raw material is put into the heating pot and the entire amount is discharged through the overheat sterilization process. Can be used. In addition, a continuous type of type that blends a certain amount of raw material cheese with other raw materials, continuously supplies a constant amount to the heating and stirring device part in the subsequent process, performs heat sterilization, and continuously discharges Heated melt emulsification pots (manufactured by Stefan, Kusner, etc.) can also be used. In addition, as a continuous heating melt-emulsification pot, what has 3-20 steps (4 sheets per step) stirring blades in a stirring part is preferable.

The heating and melting conditions vary depending on the processed cheese to be manufactured, but for example, the following is preferable. That is, the heating and melting temperature is preferably 75 to 95 ° C, and more preferably 80 to 90 ° C. It is preferable that the heating and melting temperature is within the above-mentioned range since an appropriate structure and physical properties can be obtained.
Also, when heating and melting may have rows stirring,該撹拌, using stirring blade of the mixing type, carried out at a stirring speed of the peripheral speed of the tip of the stirring blade is in the range of 2 to 5 m / sec. As a result, Ru can be to the proper organization and physical properties. The “circumferential speed at the tip of the stirring blade” is the rotational speed (circumferential speed) of the tip portion farthest from the rotation center axis of the stirring blade (rotating body).
Further, the stirring and holding time from melting to filling is preferably 0 to 15 minutes, more preferably 0 to 10 minutes. By setting the stirring holding time within the above range, an appropriate structure and physical properties can be obtained.

  Then, if necessary, the processed cheese produced by melt emulsification as described above is filled and packaged. The shape of the packaging is not particularly limited and can be sliced, square, stick-shaped, etc. However, it is preferable that the shape is easy to eat by placing it on bread, so it can be formed into sliced cheese. preferable.

  As mentioned above, by using sodium citrate and sodium polyphosphate as the molten salt and adding them in a specific range to the processed cheese to be manufactured at a specific blending ratio, the stringiness is good. In addition, it is possible to produce a processed cheese that is excellent in hardness, elasticity, and mouth meltability and has a good texture.

Examples of the present invention will be described below, but the scope of the present invention is not limited to these examples.
[Test Example 1]
(the purpose)
This test was conducted for the purpose of examining the influence of the type and amount of the molten salt used on the stringiness and texture in the production of processed cheese.

(Sample preparation)
As raw material cheese, 700 g of Gouda cheese and 500 g of mozzarella cheese are mixed, and after adding molten salt and 3 g of stabilizer (locust bean gum) and blending, test melt emulsification pot (manufactured by Stefan, universal high-speed cutter mixer) UMM / SK5 type, mixing attachment used). The heating and melting conditions were a cheese heating and melting temperature of 80 ° C., a stirring rotation speed of 500 rpm during melting, and a stirring holding time of 1 minute during melting, and about 1500 g of processed cheese having a moisture content of 50% by mass was produced. The produced processed cheese was stretched into a 2 mm thick sheet in a vinyl film, and then refrigerated overnight to obtain sliced cheese.
In designing 1500 g of processed cheese with a moisture content of 50%, which is the final product, the moisture, fat content, etc. in each raw material were analyzed in advance, and the formulation was determined according to the final quality standard. The final adjustment of the finished amount was performed by the amount of water added.

  In the above preparation, as a molten salt, the case where 1.4% by mass of sodium citrate alone was used was designated test number 1, and the case where 1.4% by mass of sodium polyphosphate alone was used was designated test number 2. Moreover, what mixed sodium citrate and sodium polyphosphate by the ratio of 1: 1 was used as molten salt, and the total molten salt amount was 0.5, 0.7, 1.2, 1.4, and 1 respectively. The case where it was set to 6% by mass was designated as test numbers 3 to 7. In addition, all of the quantity of molten salt are the mass% with respect to the processed cheese manufactured.

(Evaluation methods)
About the manufactured process cheese, it tested by the method which shows (1) temperature dependence measurement by a dynamic viscoelasticity meter, (2) stringing property, and (3) cheese food texture below. Furthermore, (4) comprehensive evaluation was performed as shown below.
(1) Temperature dependence measurement with a dynamic viscoelasticity meter A sliced process cheese having a thickness of 2 mm was cut into a circle having a diameter of 25 mm to obtain a sample for measurement. Set the refrigerated sample on the parallel plate of the dynamic viscoelasticity meter (ARES dynamic viscoelasticity meter, manufactured by Rheometric), and raise the temperature to 80 ° C at a speed of 20 ° C per minute. Measurement was started under conditions of 1 Hz and 100% strain, and the temperature was lowered to 30 ° C. at a speed of 20 ° C. per minute. Meanwhile, the dynamic storage elastic modulus and the dynamic loss elastic modulus were continuously measured, and the dynamic storage elastic modulus at 65 ° C. and the dynamic loss elastic modulus at 55 ° C. were obtained.

(2) Evaluation of stringiness A sliced cheese with a thickness of 2 mm and a size of 85 mm × 85 mm is placed on one piece of a square bread bread previously centered in the center, and an electric oven toaster (950 W, trade name: Mitsubishi BO-T5) (Mitsubishi Electric Home Appliances Co., Ltd.) for about 3 minutes. Thereafter, a temperature sensor was inserted between the bread and cheese, and the temperature was measured. When the temperature reached 65 ° C., the bread was horizontally stretched by 50 mm on both sides from the cut at the center of the bread. At that time, the number of the stringed cheeses and the width of the widest stringed string were measured, and the stringing characteristic value was calculated by the following equation.
Stringing characteristic value = (Number of stringing) + (Threading width (cm))
This stringing characteristic value is used as an index that the threading state looks very delicious on the appearance. The higher the numerical value, the better the stringing property, and in particular, the stringing characteristic value is 10 or more. Was defined as a pass (O).

(3) Cheese flavor evaluation (texture evaluation)
A sliced cheese having a thickness of 2 mm and a size of 85 mm × 85 mm was placed on an aluminum wheel, and was taken out by heating for about 40 seconds in the same electric oven toaster as in the test of stringing property in (2). Thereafter, a temperature sensor was inserted into the cheese and the temperature was measured. When the temperature reached 65 ° C., the texture of the cheese was evaluated in terms of hardness, elasticity (gum properties), and mouth meltability. Each item was evaluated between the following 1 to 5 points including the decimal point. As the evaluation criteria, 5 is the hardest and 1 is the softest. Regarding elasticity, 5 is the largest and 1 is the smallest. Further, regarding the meltability of the mouth, 5 was the best and 1 was the worst.
Finally, the evaluation points by 10 professional panelists were averaged to obtain test results. Further, the hardness and elasticity were defined as 3.5 or less, and the mouth melting property was defined as 2.0 or more according to the average value.

(4) Comprehensive evaluation What passed all the average values of the stringing characteristic value and the flavor evaluation was evaluated as pass (◯) in the comprehensive evaluation.

(result)
About the processed cheese of test numbers 1-7, said evaluation test was done and the obtained result is shown in Table 1.

(Discussion)
From the results of Test No. 1 and Test No. 2, when sodium citrate or sodium polyphosphate alone was used as the molten salt, although the taste evaluation passed, the stringing characteristic value after heating was inferior. On the other hand, in Test Nos. 4 to 6 in which the above-mentioned two kinds were mixed as a molten salt in a 1: 1 ratio, the taste evaluation was acceptable, the stringing characteristic value was acceptable, and the stringing property was good. I found out that Moreover, it turned out that it will become cheese which is excellent in stringing property and food texture in the range of 0.7-1.4 mass% with respect to the process cheese manufactured with the addition amount of molten salt.
In addition, processed cheese that has a good stringiness and a good taste from the results of dynamic viscoelastic temperature dependence measurement has physicochemical properties within the range of specific dynamic viscoelasticity measurements. It became clear that That is, the dynamic storage elastic modulus at 65 ° C. is in the range of 15 to 50 Pa, and the dynamic loss elastic modulus at 55 ° C. is in the range of 100 to 400 Pa. Was good .
In the present invention, a temperature dependence test is adopted among the test methods for dynamic viscoelasticity measurement. In this method, the dynamic viscoelasticity is continuously measured by changing the temperature with the frequency and the strain constant. By performing the temperature dependence test, it is possible to accurately grasp changes in physical properties after heating of cheese having heat melting properties.
The dynamic storage elastic modulus at 65 ° C. has a good correlation with the hardness of the texture when the cheese is eaten, and is an index value of the hardness of the cheese. When the dynamic storage elastic modulus at 65 ° C. is in the range of 15 to 50 Pa, a processed cheese having an appropriate hardness and good texture is obtained.
The dynamic loss elastic modulus at 55 ° C. has a good correlation with elasticity (gum property) in the texture when eating cheese, and serves as an index value of cheese viscosity. When the dynamic loss elastic modulus at 55 ° C. is in the range of 100 to 400 Pa, a processed cheese having an appropriate elasticity and a good texture is obtained.

[Test Example 2]
(the purpose)
This test was conducted for the purpose of examining the influence of the blending ratio when sodium citrate and sodium polyphosphate were used as molten salts on the stringiness, texture and the like in the manufacture of processed cheese.
(Sample preparation)
In this test example, sodium citrate and sodium polyphosphate are mixed and used as the molten salt, and the mixing ratio is changed for each test number, and the total molten salt amount is the mass of the processed cheese to be produced in any case. On the other hand, it was fixed at 1.0% by mass. Process cheese was manufactured under the same conditions as in the sample preparation in Test Example 1 except for the above conditions.
When the blending ratio of sodium citrate (A) and sodium polyphosphate (B) is expressed as A: B, A: B = 1: 4, 1: 3, 5: 5, 3: 1, 4: 1 It changed into five steps and each was made into test numbers 11-15.

(Evaluation methods)
In the same manner as in Test Example 1, (1) temperature dependency measurement with a dynamic viscoelasticity meter, (2) stringiness, and (3) cheese texture were tested, and (4) comprehensive evaluation was performed.
(result)
The results are shown in Table 2 for test numbers 11-15.

(Discussion)
From the results of Test Nos. 11 to 15, when mixing and using sodium citrate and sodium polyphosphate as the molten salt, the processed cheese produced when the blending ratio is in the range of 1: 3 to 3: 1 It has been found that the stringing property and texture of this product are excellent.
In addition, the processed cheese containing the molten salt in the above-described blending ratio and having the physical storage modulus and the dynamic loss elastic modulus within the desired ranges as described in Test Example 1 has a stringing property. It was good, had good hardness, elasticity, mouth meltability and good texture.

[Test Example 3]
(the purpose)
This test was performed for the purpose of comparing the processed cheese manufactured by the manufacturing method according to the present invention with other commercially available processed cheese having heat melting property.
(Sample preparation)
In this test example, sodium citrate and sodium polyphosphate were mixed as a molten salt at a mixing ratio of 1: 1, and the total molten salt amount was 0.7% with respect to the mass of the final product. Process cheese was manufactured in the same manner as in the preparation of No. 1.
However, in this test example, the process cheese I was obtained by making the heating and melting pot large (100 kg / batch) and actually manufacturing according to a method of manufacturing a commercially available product.
For comparison, commercially available process cheeses II to IV having heat melting properties were used.

(Evaluation methods)
In the same manner as in Test Example 1, (1) temperature dependency measurement with a dynamic viscoelasticity meter, (2) stringiness, and (3) cheese texture were tested, and (4) comprehensive evaluation was performed.
(result)
The results of I to IV are shown in Table 3.

(Discussion)
Process cheese I produced by the production method according to the present invention has physical properties in which dynamic storage elastic modulus and dynamic loss elastic modulus are within desired ranges, and has good stringiness after heating, The texture was excellent.
On the other hand, the process cheeses II to IV having heat melting properties that are currently on the market are inferior in stringiness and fail in flavor evaluation. In these processed cheeses II to IV, the dynamic storage elastic modulus and the dynamic loss elastic modulus were both outside the desired ranges. Therefore, it was found that it is very effective to use these dynamic elastic moduli as an index for flavor evaluation.

[Test Example 4]
(the purpose)
This test examines the influence of the peripheral speed of the tip of the stirring blade on the stringiness, texture, etc. when stirring using a mixing type stirring blade in the heating and melting step in the production of processed cheese I went for the purpose.
(Sample preparation)
In this test example, sodium citrate and sodium polyphosphate were mixed as a molten salt at a mixing ratio of 1: 1, the total amount of molten salt was 1.0% with respect to the mass of the final product, and stirring during heat melting was performed. The number of revolutions, that is, the peripheral speed of the tip of the stirring blade was changed as follows, and five types of samples were prepared in the same manner as the sample preparation in Test Example 1. Specifically, the peripheral speed (stirring speed) at the tip of the stirring blade is 1.8 m / sec (250 rpm), 2.0 m / sec (300 rpm), 3.5 m / sec (500 rpm), and 5.0 m / sec, respectively. (700 rpm) and 5.3 m / sec (750 rpm) were designated as test numbers 16 to 20.

(Evaluation methods)
In the same manner as in Test Example 1, (1) temperature dependency measurement with a dynamic viscoelasticity meter, (2) stringiness, and (3) cheese texture were tested, and (4) comprehensive evaluation was performed.
(result)
The results are shown in Table 4 for test numbers 16-20.

(Discussion)
From the results of Test Nos. 16 to 20, it is manufactured by using a mixing type stirring blade in the heating and melting step under the condition of stirring the peripheral speed at the tip of the stirring blade within a range of 2 to 5 m / sec. It was found that the processed cheese has excellent stringiness and texture.

EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to a following example.
[Example 1]
As raw material cheese, 700 g of Gouda cheese and 500 g of mozzarella cheese are mixed, and 5.25 g (0.35 mass%) of sodium citrate and 5.25 g (0.35 mass%) of sodium polyphosphate as a molten salt are stable. After adding 3 g of an agent (locust bean gum) and blending, it was put into a test melt emulsification pot (manufactured by Stefan Co., Ltd., universal high speed cutter / mixer UMM / SK5 type mixing attachment). The heating and melting conditions were a cheese heating and melting temperature of 80 ° C., a stirring rotation speed of 500 rpm during melting, and a stirring holding time of 1 minute during melting, and about 1500 g of processed cheese having a moisture content of 50% by mass was produced. The produced processed cheese was stretched into a 2 mm thick sheet in a vinyl film, and then refrigerated overnight to obtain sliced cheese.
In designing 1500 g of processed cheese with a moisture content of 50%, which is the final product, the moisture, fat content, etc. in each raw material were analyzed in advance, and the formulation was determined according to the final quality standard. The final adjustment of the finished amount was performed by the amount of water added.

The physical properties and texture of the processed cheese thus produced were the same as in Test Example 1, and (1) temperature dependence measurement with a dynamic viscoelasticity meter, (2) stringiness, and (3) cheese food The feeling was tested.
In the dynamic viscoelastic temperature dependency measurement test, the dynamic storage elastic modulus at 65 ° C. was 15.1 Pa, and the dynamic loss elastic modulus at 55 ° C. was 103.8 Pa. In the cheese stringing evaluation test after heating, the stringing characteristic value was 12, which was good. In the cheese texture evaluation test, the flavor evaluation average score was good at hardness 3.3, elasticity 3.4, and mouthfeel 2.2.

[Example 2]
As raw material cheese, 700 g of Gouda cheese and 500 g of mozzarella cheese are mixed, and 3.75 g (0.25 mass%) of sodium citrate and 11.25 g (0.75 mass%) of sodium polyphosphate as a molten salt are stable. After adding 3 g of an agent (guagum) and blending, it was put into a test melt emulsification pot (manufactured by Stefan, using a universal high speed cutter / mixer UMM / SK5 type mixing attachment). The heating and melting conditions were a cheese heating and melting temperature of 85 ° C., a stirring rotation speed of 400 rpm during melting, and a stirring holding time of 2 minutes during melting, and about 1500 g of processed cheese having a moisture content of 50% by mass was produced. The produced processed cheese was stretched into a 2 mm thick sheet in a vinyl film, and then refrigerated overnight to obtain sliced cheese.

The physical properties and texture of the processed cheese thus produced were the same as in Test Example 1, and (1) temperature dependence measurement with a dynamic viscoelasticity meter, (2) stringiness, and (3) cheese food The feeling was tested.
In the dynamic viscoelastic temperature dependency measurement test, the dynamic storage elastic modulus at 65 ° C. was 17.0 Pa, and the dynamic loss elastic modulus at 55 ° C. was 114.5 Pa. In the cheese stringing evaluation test after heating, the stringing characteristic value was 10 and was good. In the cheese texture evaluation test, the flavor evaluation average score was good with a hardness of 2.8, an elasticity of 2.5, and a mouth meltability of 3.5.

[Example 3]
As raw material cheese, 700 g of Gouda cheese and 500 g of mozzarella cheese are mixed, and 12 g (0.8% by mass) of sodium citrate and 9 g (0.6% by mass) of sodium polyphosphate as a molten salt, and a stabilizer (locust bean) After adding 5 g of gum) and blending, it was put into a test melt emulsification kettle (manufactured by Stefan, using a universal high speed cutter / mixer UMM / SK5 mixing attachment). The heating and melting conditions were a cheese heating and melting temperature of 83 ° C., a stirring rotation speed of 300 rpm during melting, and a stirring holding time of 0.5 minutes during melting, and about 1500 g of processed cheese having a moisture content of 50% by mass was produced. The produced processed cheese was stretched into a 2 mm thick sheet in a vinyl film, and then refrigerated overnight to obtain sliced cheese.

The physical properties and texture of the processed cheese thus produced were the same as in Test Example 1, and (1) temperature dependence measurement with a dynamic viscoelasticity meter, (2) stringiness, and (3) cheese food The feeling was tested.
In the dynamic viscoelastic temperature dependency measurement test, the dynamic storage elastic modulus at 65 ° C. was 16.8 Pa, and the dynamic loss elastic modulus at 55 ° C. was 121.7 Pa, which was good. In the cheese stringing evaluation test after heating, the stringing characteristic value was 11 and was good. In the cheese texture evaluation test, the flavor evaluation average score was good at hardness 3.4, elasticity 3.3, and mouth meltability 2.5.

Claims (1)

Sodium citrate and sodium polyphosphate, 1: 3 to 3: 1 mixing ratio, and after the total mass is blended so that 0.7 to 1.4 wt% with respect to process cheese manufactured The obtained mixture has a heating and melting step in which the mixture is heated and melted with stirring. The stirring in the heating and melting step is performed using a mixing type stirring blade, and the peripheral speed at the tip of the stirring blade is 2 to 5 m / The process cheese manufacturing method characterized by performing with the stirring speed used in the range of second .