JPH0361835A - Evaluation of quality of gelatinized starch gel - Google Patents

Abstract

PURPOSE:To make it possible to evaluate quality in a short time by keeping the temperature of gelatinized starch gel high, using a rotary viscosimeter, performing measurement under shearing deformation, obtaining the curve of relationship between viscosity and time, and analyzing a pattern. CONSTITUTION:Rice which is a raw material for gelatinized starch gel, especially rice cake or rice confectionery, whose water content is 40 - 60%, is cooked. The rice cake whose kneading degree is changed is adjusted. The rice cake shall be sample A. The sample A is held and bonded with parallel disk- shaped cells 17 and 18. A sample mounting attachment to which the sample A is bonded is fixed to an upper platen holder 1 and a lower platen holder 2. The temperature of the sample A is kept at 70 - 100 deg.C with a constant temperature oven 12 so as to obtain the constant temperature. Measurement is performed under shearing deformation by using a rotary viscosimeter. Thus the curve of relationship between viscosity and time is obtained. Then, the obtained relationship curve is analyzed by the analyzing method for a viscosity (stress)-time(strain) relationship curve.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for measuring the viscosity of gelatinized starch gel having high viscosity, particularly for mochi dough, dumplings, etc. made from rice, which hardens easily and is difficult to measure. This relates to quality evaluation by accurately and quickly measuring the viscosity of

Conventional technology There are a wide variety of foods made from gelatinized starch gel with high viscosity, but the following two methods have been used to measure the physical properties of gelatinized starch gel, which is the raw material for these foods. Methods have been proposed that are broadly divided into two.

Namely, they are: (1) basic rheology measurement method and (2) practical test method.

■Basic rheology measurement methods measure the deformation and stress of the object to be measured in a fixed manner, and determine mechanical constants with clear contents and dimensions.

Specific measuring devices include a stress relaxation measuring device that measures changes in stress over time when a constant strain is applied to a sample, and a creep measurement device that measures changes in strain over time when a constant stress is applied to a sample. There are dynamic viscoelasticity measuring machines that measure the response when a minute periodic stress or strain is applied to a sample, and stress-strain measuring machines that obtain stress-strain curves by constant-speed compression and constant-speed extension.

■Practical test methods are those that focus on easily measuring practical deformation and stress of the object to be measured.
Specific measuring instruments include a penetrating card meter penetrometer that detects stress and deformation simultaneously, a tensile type hood rheometer (extenso gelaf) that prioritizes deformation and detects stress, and a compression or There is the Texturometer-1, which is a penetrating mastication tester, and the Plastograph, which measures changes in viscosity during gelatinization of high-concentration starch.

However, as a prior art, no method has been proposed to evaluate the quality of gelatinized starch gel, particularly by directly, accurately and easily measuring the viscosity of rice cake dough, dumplings, etc. made from rice.

In the present invention, we do not clearly distinguish between "mochi dough" and "dango", and products obtained by steaming glutinous rice, non-glutinous rice, and other starches as raw materials are referred to as gelatinized starch gel.

Problems to be Solved by the Invention In the production of gelatinized starch gel, especially rice cakes and rice crackers made from rice, 1M raw rice is steamed and ``pounded.''

The mochi dough is obtained through a process called kneading.

The effect of ``tsuki'' and ``kneading'' in mochi is to break down the structure of the steamed rice and break down the starch granules, giving it the characteristic ``body'', ``nobi'', and ``stickiness'' of mochi.

At this time, if the level of ``sticking'' is weak, the structure of the steamed rice will not be broken down sufficiently and the structure will remain, resulting in an uneven mochi dough with insufficient ``knots''.

Therefore, when the mochi is eaten, it has a grainy texture, and when it is made into rice crackers, it has poor uki (dough expansion rate) and is easily damaged.

Furthermore, in the case of mochi dough that has been subjected to extremely strong ``pounding'' and ``kneading'', the structure of the steamed rice will be destroyed and there will be no remaining structure, but instead the mochi dough will contain many air bubbles and lack ``body''.

Therefore, when you eat the mochi, it doesn't have a chewy texture, and when it is made into rice crackers, it sometimes produces large bubbles.
is more likely to occur.

Therefore, in the production of mochi and rice crackers,
By uniformly distributing the residual structure and air bubbles of the steamed rice in an appropriate amount within the rice cake dough by kneading, a rice cake with appropriate elasticity and elasticity can be obtained.

Furthermore, for example, in the production of rice crackers called "offerings," such as "Kaki no Tane," which is a type of rice cracker,
When the mochi goes through the "pounding" and "kneading" processes and is extruded into a rod shape from the nozzle of the molding machine during the molding process, the mochi, which has a circular cross section, is placed on the removal plate, causing a drop in temperature. At the same time, the weight of the mochi dough itself forms it into a half-moon shape, which is then refrigerated and hardened.

In this case, there is a problem in that the cross section of the rice cake, which lacks ``body'', changes from a circular shape to a half-moon shape and becomes flat.

From the above points of view, it is presumed that there is a close relationship between the viscoelasticity of rice cake and the effects of ``rutting'' and ``kneading'' during the preparation of rice cake.

Therefore, if viscoelasticity can be measured accurately and its relationship with mochi quality can be quantitatively understood, it will be very effective for quality control and process control in the mochi industry or rice cracker industry.
It becomes possible to efficiently set conditions for existing equipment when manufacturing new products, and to appropriately and rationally design and select new equipment and machinery.

Therefore, a practical method for measuring the viscoelasticity of gelatinized starch gels, such as mochi, and a quantitative quality control method based thereon are strongly desired.

In the basic rheology measurement method as a method for measuring the physical properties of gelatinized starch gel in the prior art.

Many of them attempt to explore the internal structure by analyzing the behavior of the sample in the linear region (small deformation region).

However, 1. Large deformation is a problem in terms of the physical properties of starch gel that humans normally perceive, or in terms of quality control.
Moreover, it is often understood in terms of the overall behavior when applied continuously, and it is difficult to correspond to intuitive evaluation by understanding the response due to the application of static or dynamic strain only in the linear region. Sometimes.

In many cases, it was not used as an indicator for quality control. Also.

In particular, in order to measure the behavior of the flow region, there are many methods that require a long time in principle, such as measuring the temporal change in stress (strain) when a certain strain (stress) is applied to the object to be measured. There were a lot of things that didn't make sense.

On the other hand, in practical testing methods, it is necessary to analyze the behavior in the nonlinear region (large deformation region) or fracture, and to pursue the correspondence with sensory evaluation and quality characteristics with respect to characteristic deformation of starch gel. Because of the emphasis placed on materials, the values obtained by measurement vary depending on the measuring device and are not universal.

Difficult to compare with other measurement methods or.

Because the deformation patterns are generally complex, it is difficult to derive mechanical constants with clear contents and dimensions. The gel strength obtained is a mixture of elastic deformation and plastic deformation, and therefore the obtained mechanical constants are unclear.

Furthermore, since the measurement site is localized, it is not particularly suitable for gels such as mochi, which have a non-uniform structure.

In elongation deformation, such as in a food rheometer (extenso gelaf), the volume change of the sample is large, and the sample is continuously elongated even when pulled at a constant speed, so the deformation is not uniform.

The resulting value is uncertain.

Furthermore, in the case of elongation deformation, it is difficult to fix the sample.

It is not suitable for mochi-like gels.

Since a texturometer simulates a human's masticatory motion, it may correspond to sensory evaluation, but the mechanical constants it represents are still unclear.

Plastograph uses 40-50% high concentration R milk powder.
This method continuously measures the temperature change in viscosity when heated to 00°C and then cooled, and is not suitable as a method for measuring the rheology of rice cake dough or dumplings obtained by heating and steaming, which is the objective of the present invention. That's a good enough method.

Means for Solving the Problems The present invention provides gelatinized starch gels, especially rice cakes, which are difficult to measure effectively, accurately, and quickly using basic rheological measurement methods or practical test methods in the prior art. Alternatively, the present invention provides a method for evaluating the quality of gelatinized starch gel by measuring the viscosity of rice cake dough.

The deformation mode is not static strain or dynamic strain, but steady strain that deforms at a nearly constant strain rate, and it is not elongation deformation or compression deformation, but shear deformation that maintains simple and uniform deformation. At the same time, the growth of shear stress is measured after the start of shear flow in a wide deformation range from linear to nonlinear regions.

Therefore, although the method used is only a basic rheology measurement method, the obtained results can be said to be practical.

The present invention is a gelatinized starch gel with a water content of 40 to 60%.

In particular, rice, which is a raw material for mochi or rice crackers, is steamed, mixed with rice cakes, and rice cakes with varying degrees of kneading are prepared, and these rice cakes are attached to an attachment as a sample.

Measure using a rotational viscometer while maintaining the temperature at a high temperature (70°C or higher and lower than 100°C), obtain a viscosity-time relationship curve,
The present invention was achieved by finding a correspondence between the pattern of the relationship curve and the rice cake making conditions.

The reason why the moisture content of the gelatinized starch gel was set to 40 to 60% is because the moisture content of mochi dough, which is normally produced, is 40 to 60%, and in ordinary methods, it is not sufficiently gelatinized when the moisture content is 40% or less. This is because it is difficult to obtain mochi, and mochi dough exceeding 60% has significant fluidity, making it unsuitable and impractical for use as mochi dough for rice crackers.

Furthermore, the reason why the measurement is carried out in the high-temperature section is that as a result of a preliminary test using the stress relaxation measurement method, a difference in starch gel clearly occurs in the high-temperature section.

Also, due to the manufacturing process, the temperature at which the mochi is processed is 70 to 90 degrees Celsius.
There are many fluctuations, and it is difficult to obtain a stable fluid state at temperatures below 70°C, making measurement difficult.

Furthermore, a high temperature of 100° C. or higher is not industrially practical. Therefore, this temperature range is optimal.

l! The quality evaluation method for rice cakes having different number of times of "r" and "kneading" time as rice cake conditions is carried out in the order of (1) to (5) shown below.

(1) Attaching the sample to the rotational viscometer The prepared rice cake is molded to a certain thickness and attached to an attachment, and the attachment is attached to the rotational viscometer.

Alternatively, the prepared rice cake is placed in a pre-installed attachment, and the sample is attached so that it can be sandwiched between the upper and lower attachments.

Maintain a constant temperature between 70°C and above and below 100°C.

After bringing the sample to constant temperature, start measurement.

(2) Start of steady shear flow due to steady shear deformation First, determine the optimal strain rate to clearly express the properties of the sample to be measured.

The determination method is to use the stress relaxation measurement method as a preliminary test to confirm the time after strain application (long time side) where the difference in the degree of "rub" and "kneading" clearly appears, and then Determine speed.

Note that if the strain rate is slower than the appropriate strain rate, the difference in rice cakes will not appear, and if the strain rate is too fast, the nonlinear region at the beginning of stress growth will become larger, resulting in a smaller stress.
Alternatively, depending on the rice cake, the resulting stress may be so large that measurement becomes difficult.

In this way, an appropriate strain rate is determined.

A steady shear strain is applied to the sample at this strain rate, and steady shear flow is started.

(3) Measuring and recording the viscosity (stress) vs. time (strain) of the sample and recording the steady shear flow initiation curve (viscosity vs.
time relationship curve).

(4) Analysis of viscosity (stress)-time (strain) relationship curve (3)
From the viscosity (stress)-time (strain) relationship curve obtained as follows, 12 elements of 7 items of first order are analyzed.

1. Stiffness: Initial tangential modulus (■) Slope of initial curve 2. Magnitude of elastic energy Viscosity at linear limit point and time (■) Area of linear region of viscosity-time relationship curve (■) Viscosity and the area ratio of the linear region of the time relationship curve (■) 3, the total area of the viscosity vs. time relationship curve up to a certain time (■), the total area ratio of the viscosity vs. time relationship curve up to a certain time (■)
) 4. Yield strength: Viscosity at yield point and time (■) Area between viscosity and time at yield point (■) Area ratio between viscosity and time at yield point (■) 5. Degree of stress overshoot ([phase]) 6 , Viscosity during steady flow (0) 7. Overall shape of viscosity and time relationship curve (@) (5)
Quality evaluation of samples based on the analysis of (4) 2 In the case of mochi and mochi dough, those that have a suitable texture with appropriate elasticity and roughness, or that are preferable in terms of the rice cracker manufacturing process are generally
It was found that the value of ~0 was large and the overall shape @ caused stress overshoot.

Example 1 Kneading time: 5 minutes, 10 minutes using a commercially available (one mixer type) mochi pounding machine
4 types of mochi (minutes, 20 minutes, and 30 minutes) each about 8 inches thick! lf
It was made into a sheet shape and hardened by refrigerating it in a refrigerator at about 4°C.

Punch out a cylindrical shape with a diameter of 28 mm using a cutter and use it as a sample.

The sample was sandwiched and bonded with an adhesive using a sample mounting attachment (Fig. 1: parallel disk cell).

A Weisenberg rheogoniometer (manufactured by Sangamo Controls, model R-18) shown in Fig. 2 is used as a rotational viscometer, and the sample mounting attachment to which the sample is glued is attached to upper platen holder 1 and lower platen holder 2. It was fixed to.

In this case, in order to prevent the water content of the rice cake attached to the sample attachment from evaporating, liquid paraffin was added as shown in FIG. 3, and the attachment was fixed to the reservoir 14 with screws.

In this manner, the sample was maintained at 90° C. for 2 hours to reach a constant temperature using the constant temperature bath 12 shown in FIG. 2, and then measurement was started.

The measurement method begins with an appropriate strain rate (in this case 10-'
The gear ratio of the gearbox 4 was determined and adjusted so as to achieve a speed of about 100 mm (S 8 Q-'').

The strain rate was determined from the following relational expression.

yellowRx:P γ'wax: Strain rate applied to the outermost part of the sample (5ea-
) °α: Rotation angular velocity of sample axis (radian-s
ee-1) r: radius of the sample (3) h: thickness of the sample (0) When the rotation switch of the motor 5 is turned on, the rotation of the motor is adjusted (decelerated) by the gearbox, and the reservoir 14 is rotated along with the sample shaft 3. By rotating at a constant rotation speed, shear deformation is applied to the sample at a given strain rate, and steady shear flow is initiated.

Since the steady shear deformation is instantaneously applied by the electromagnetic clutch 6, it is possible to measure a wide range of deformation (time) from immediately after the start of the shear flow to the steady flow state.

The upper platen holder] is fixed to the rotor 7, and the stress (torque) caused by steady sliding deformation is detected from the torsion angle of the torsion bar 8 through a transducer 9.

The detected output signal is read by a transducer meter 10 or recorded using an external recorder 11.

The rotor is kept in the center with high precision by the air bearing 13 and there is no friction, thus achieving high sensitivity.

The viscosity (apparent viscosity: stress) thus measured was determined by the following formula.

Torque=VIIRange・g/Ga1nη: Viscosity poise (dyne 1sec/aJ) Torque
ue: Torque (dyne/cs) r: Radius of the sample (reserve) h: Thickness of the sample (3) 9■ax: Strain rate at the outer periphery of the sample (See-1) σ: Stress (dyne1cxz> ■: Output Voltage (Volt) Range: ?l!Constant rare range/10μ) Gai
n: Amplification factor of the amplifier The obtained relational curve was analyzed based on the above-mentioned method (4) for analyzing the viscosity (stress)-time (strain) relational curve.

As a result of the analysis, mochi with a kneading time of 10 minutes was compared to other mochi.■
The value of ~ ■ is high, causing a large stress overshoot phenomenon, and therefore the rice cake has a strong "firmness", and as time passes (the deformation increases), "r-nobi" occurs, indicating that the rice cake has a favorable texture. Recognize.

On the other hand, the rice cakes with a kneading time of 5 minutes have high values of ■~O and ■ and are strong in ``body'', but the value of [stock] is lower than that of the rice cakes with a kneading time of 10 minutes, which shows that the rice cakes lack r-nobi.

It can be seen that the rice cakes with a kneading time of 20 minutes and the rice cakes with a kneading time of 30 minutes have low values of ■ to ■, and have "nobi" but no "bodiness".

Example 2 Using a stamp-type fully automatic weighing machine for rice cracker production, four types of rice cakes were prepared with the number of times of pounding: 50, 100, 200, and 300 times. It was measured using a parallel plate rotational viscometer of a Weisenberg rheogoniometer.

As a result of the analysis, the values of ■～■ increase in the order of 100 times > 200 times > 50 times > 300 times, and in the micro deformation (linear region) region, the mochi that has been pounded 100 times has the most firmness. I understand.

However, the values of ■～■ and ■ are 50 times > 100 times > 20
In the large deformation region that increases in the order of 0 times > 300 times,
Mochi made 50 times has the most chewiness.

However, since the value of [phase] is small, it can be seen that there is not much r-novi.

On the other hand, it can be seen that the mochi that has been rolled 300 times stretches well but has almost no ``body''.

Therefore, if rice crackers are manufactured 50 times, the texture will be poor and the texture will be poor.

Mochi made 300 times has no chewy texture and tends to produce large air bubbles.

In terms of the rice cracker manufacturing process, the preferred rice cakes have a large amount of stress.
- Shooting phenomenon is occurring. Number of hits: 100 to 2
It turned out to be Mochi from 00 times.

Effects of the Invention The present invention has the effect that quality evaluation by rheological measurement of various gelatinized starch gels can be carried out in a short time, such as within 15 minutes at the earliest and within 30 minutes at the latest.

Rheological measurements of the high temperature region (less than 100°C) of various gelatinized starch gels can be easily performed.

The relationship between the obtained data and the quality of the sample can be quantitatively understood.

It is also effective for process control in the production process.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an attachment for mounting a sample. FIG. 2 is a schematic diagram of a rotational viscometer. FIG. 3 is a cross-sectional view of the attachment including the sample attachment and the reservoir. FIG. 4 is the viscosity-time relationship curve of rice cakes with different kneading times. FIG. 5 shows viscosity-time relationship curves for rice cakes subjected to different number of poundings. FIG. 6 is an analytical relationship curve between the viscosity of rice cake and time. 1... Upper platen holder 2... Lower platen holder 3... Rotating shaft 4... Gear box 5
... Motor 6 ... Electromagnetic clutch 7 ... Rotor 8 ... Torsion bar 9 ... Transducer user 10 ... Transducer meter 11
... Recorder 12 ... Constant temperature chamber 13 ... Air bearing 14 ... Reservoir 15 ... Liquid paraffin 16 ... Screw 17 ... Upper parallel disk 18 ...
・Lower parallel disk 19A・19B...Gear A...
sample

Claims (1)

[Claims] 1. Heat gelatinized starch gel with a moisture content of 40 to 60% at high temperature (70℃
A method for evaluating the quality of a gelatinized starch gel, characterized in that the viscosity-time relationship curve is determined by holding the gel at a temperature between 100° C. and below 100° C., and measuring it under shear deformation using a rotational viscometer, and then performing pattern analysis.