This standard specifies the working principle of using a viscometer to determine the gelatinization characteristics of cereals and starches, as well as the instruments, utensils, reagents, operating procedures and experimental result presentation methods used. This standard is applicable to the determination of the gelatinization characteristics of cereals and starches. GB/T 14490-1993 Determination of gelatinization characteristics of cereals and starches Viscometer method GB/T14490-1993 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Method for determination of cereal and starch gelatinization properties using a viscograph Subject content and scope of applicationWww.bzxZ.net
GB/T 14490-93
This standard specifies the working principle of using a viscometer to determine the gelatinization properties of cereals and starch, as well as the instruments, utensils, reagents, operating procedures and experimental result presentation methods used.
This standard applies to the determination of the gelatinization properties of cereals and starch. 2 Reference standards
Determination of moisture
GB5497 Inspection of grains and oilseeds
3 Principle of the method
Heat a water suspension of cereal powder or starch of a certain concentration at a certain heating rate to gelatinize the starch. After the gelatinization begins, the suspension gradually becomes a paste due to the swelling of the starch due to water absorption, and the viscosity increases continuously. As the temperature rises, the starch is fully gelatinized, a high viscosity peak is generated, and then the starch granules rupture and the viscosity decreases. When the gelatinized material is cooled at a certain cooling rate, the gelatinized material gels and the viscosity value further increases. The viscosity value when cooled to 50°C is the final viscosity value. Through the sensor, sensing shaft, and force measuring coil spring of the viscometer, the resistance change caused by the viscosity change during the entire gelatinization process is reflected to the automatic recorder and the viscosity curve is drawn. From the viscosity curve, various indicators for evaluating the quality of grains and starch are read, including the gelatinization start temperature (C), the highest viscosity value (VU), the temperature at the highest viscosity (°C), the lowest viscosity value (VU), and the final viscosity value after gelatinization (VU). Different grains and starches have different gelatinization characteristics, that is, different evaluation values, due to their different starch structures and properties. The same grains and starches will cause changes in the above evaluation values ​​due to different qualities, different storage times, and different α-amylase activities.
4 Reagents
Distilled water or water of equivalent purity.
5 Instruments and appliances
5.1 Viscometer: mainly composed of force measuring coil spring, sensing vertical axis, sensor (stirrer), measuring bowl, radiation electric furnace, cooling water device, driving motor group, tachometer, timer, contact thermometer, temperature adjustment and automatic control system, cooling automatic control system, automatic recorder, etc. (see Appendix A Schematic diagram of viscometer structure). The main technical parameters are as follows: Measuring bowl speed: 75±1r/min
Heating and cooling rate: 1.5±0.03℃/min
Heating and cooling range: room temperature—-97℃
Approved by the State Administration of Technical Supervision on June 19, 1993 416
Implemented on February 1, 1994
Contact thermometer: scale 1.0℃
Recording paper speed: 0.5±0.01cm/min
Recording paper range: 0-—-1000V.U.
GB/T 14490-93
Force measuring disc spring torque: (34.32±0.69)mN/VU［(350±7)gf.cm/VU］(68.65±1.47)mN/VU ((700±15)gf. cm/VUJ Effective deflection angle of force measuring disc spring: 62°
The metal rod of the sensor and the measuring bowl should be vertical and can be smoothly inserted into the "positioning plate" (instrument accessory). 5.2 Balance: Sensitivity 0.1g.
5.3 Beaker: 600mL.
5.4 Measuring cylinder: 500mL.
5.5 Glass rod (with rubber head) or plastic stirring spoon. 6 Operation steps
6.1 Sample preparation
Crush the grain sample with a grinder so that more than 90% of the sample passes through Pass through CQ24 sieve. 6.2 Determination of sample moisture
Determine according to GB5497.
6.3 Instrument preparation
6.3.1 Check whether the components of the instrument are properly connected and whether they can operate normally: the measuring bowl should be placed in the positioning pin in the electric heating jacket in the middle of the instrument, and the stirrer in the bowl is connected to the vertical axis of the sensor through a pin. Turn on the power switch to "1", the motor starts, check and adjust the measuring bowl speed to 75r/min. Check whether the recording paper is operating normally. Check whether the pointer of the recording pen is pointing to the recording If the instrument is on the 0 line, loosen the screws on both sides of the force measuring coil spring on the upper part of the instrument, rotate the force measuring coil spring position, make the recording pen point on the 0 line, and then tighten the screws. Turn off the power. 6.3.2 Disconnect the stirrer from the vertical axis of the sensor, lift the cooling sleeve rod to a high position, then press the instrument lifting handle down to lift the upper part of the instrument, then turn it 90° to the right and take out the stirrer. 6.4 Weighing samples
6.4.1 For all kinds of grains and starch, the mass (±0.1g) of the sample with a moisture content of 14% (base moisture) and the amount of water added are as follows Table (torque of force measuring disc spring is 700gf·cm/VU). Sample name
Wheat flour (including whole wheat flour)
Rice flour (including, stalk, glutinous rice)
Corn starch
Potato starch
Sample mass
(calculated based on 14% moisture content)
6.4.2 If the moisture content of the sample is higher or lower than 14%, the actual sample weight shall be calculated as follows. A·86
Actual sample weight (g)
(100 = M)
Where: A is the specified sample weight when the moisture content is 14%, gM-the number of grams of moisture in 100g sample.
Amount of water added
6.4.3 If other specifications of force measuring disc springs are used, the mass of the sample can be increased or decreased as needed to make the peak value of the viscosity curve below 800V.U. 6.5 Preparation of sample suspension
GB/T14490—93
Pour the weighed sample into a beaker. At the same time, use a measuring cylinder to measure the amount of water to be added. First pour about 200mL into the beaker, stir the sample with a stirring rod to make it a uniform suspension without lumps, and transfer it to the measuring bowl. Then use the remaining water in the measuring cylinder to wash the remaining sample in the beaker three times and transfer it all to the measuring bowl.
6.6 Determination
6.6.1 Place the stirrer in the measuring bowl and align the stirrer notch with the front of the instrument (Note! Do not let the thermometer touch the stirrer when putting down the body).
6.6.2 Hold the instrument lifting handle tightly, turn the upper part of the instrument 90° to the left, then turn the lifting handle to slowly lower the body, insert the stirrer into the sensor vertical axis pin to connect them tightly.
6.6.3 Lower the cooling jacket rod to the lowest position, turn the cooling water control switch to the "～" (alternating cooling) position, and turn on the cooling water. 6.6.4 Turn on the power switch, and the measuring bowl rotates at 75r/min; turn the temperature control lever to the middle \0" position, turn on the thermometer lighting, and use the contact thermometer adjustment knob to adjust the thermometer pointer to 30℃ or higher than the room temperature. Turn the adjustment knob clockwise to increase the temperature pointer, and counterclockwise to the contrary.
6.6.5 Turn on the timer (timing is about 45min), the heating indicator light will light up, and the sample will start to heat up. When the sample suspension temperature reaches the temperature indicated by the contact thermometer pointer, the indicator light will go out. At this time, turn the temperature control lever down to the "heating" position, and mark the recording pen on the recording paper. The marked temperature is the temperature indicated by the adjustment thermometer. After that, the suspension will automatically heat up at 1.5℃/min, and the gelatinization process will begin.
6.6.6 As the temperature rises to a certain temperature, the recording pen begins to deviate from the baseline of the recording paper. This temperature is the gelatinization starting temperature of the sample. Subsequently, the viscosity increases rapidly. When the temperature When the temperature rises to 95℃, turn the temperature control lever back to "0" and set the timer. At this time, the viscosity usually decreases. When the viscosity value decreases and fluctuates slightly or is relatively stable (about 5 to 10 minutes), turn the temperature control lever upward to "cooling" and set the timer for 30 minutes. At this time, the paste begins to cool at 1.5℃/min until it drops to 50℃. Then turn the temperature control lever back to "0" and set the timer for 3 to 5 minutes. The experiment ends. The viscosity value continues to increase during cooling. When the value rises above 1000V.U., such as when the torque of the force measuring coil spring is 350gfcm/VU, add a 62.5g magnetic code to the instrument code hook, and the viscosity value increases by 500V.U., and add a 125g code to increase the viscosity value by 1000V.U.
6.6.7 Turn off the power, remove the stirrer and the sensor vertical shaft, lift the cooling jacket rod to the highest point, then press the lifting handle to lift the upper half of the instrument and turn it 90 degrees to the right.
6.6.8 Clean the thermometer and cooling sleeve rod, take out the measuring bowl and stirrer and clean them for later use. 7 Determination result expression
Read the following gelatinization characteristic indicators from the viscosity curve drawn on the recording paper, and indicate the specifications of the force measuring coil spring used in the experiment, the sample weight, and the amount of water added. See the figure below.
GB/T 14490-93
1.5℃/min leakage
Viscosity curve
1. 5℃/min De-irrigation
t1 The gelatinization temperature at the beginning, C, the reading is accurate to 0.5℃, A-highest viscosity value, VU, the reading is accurate to 5V.U.t2-Temperature at the highest viscosity (if the peak is flat, the temperature range of the top of the bee can be read, ℃, the reading is accurate to 0.5℃C; B-lowest viscosity value (the trough value of the curve), VU, the reading is accurate to 5V.UC-Viscosity value at 50℃, VU, the reading is accurate to 5V.U.Note, A-B (VU,) = viscosity breakage value
C-B (VU) = gelling value
Above Two indicators can be used to evaluate starch quality. 8 Repeatability
8.1 Use the same sample to make two measurements. The results of the two measurements shall not exceed the requirements of Article 8.2. The average value shall be taken as the measurement result. 8.2 The difference between the two test results of the starting gelatinization temperature is allowed to be 1°C; the difference between the two test results of the highest viscosity value shall not exceed 20% of the average value; the difference between the two test results of the lowest viscosity value shall not exceed 20% of the average value; the difference between the two test results of the final viscosity value shall not exceed 20% of the average value. 419
Additional instructions:
GB/T14490— 93
Appendix A
Schematic diagram of the structure of the viscometer
(supplement)
1---Force disc spring, 2-pulley; 3.-Hook; 4-Temperature adjustment rod; 5-Temperature automatic control system; 6-Contact thermometer; 7-Cooler; 8-Sample cup; 9-Electric furnace protection cover; 10-Radiation furnace; 11-Fork stirrer (sensor); 12 Signal light; 13-Siren switch; 14 Timer; 15-Power switch; 16-Tachometer; 17-Gear drive motor ; 18-Cooling cover; 19-Gear; 20-Temperature control lever; 21-Alternating cooling and continuous cooling switch, 22-Instrument upper lifting handle, 23-Cooling water solenoid valve; 24-Recorder: 25-Fixed recording paper device: 26-~Recording pen This standard is proposed by the Ministry of Commerce of the People's Republic of China. This standard is under the jurisdiction of the Grain Storage and Transportation Bureau of the Ministry of Commerce. This standard was jointly drafted by the Chengdu Grain Storage Science Research Institute of the Ministry of Commerce and the Grain and Oil Chemistry Research Institute of the Ministry of Commerce. The main drafters of this standard are Yang Haoran, Qi Xianmei and Zhou Wei. 420
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