In order to obtain dough with good processability and noodles with excellent cooking performance, high-quality wheat flour raw materials are required. Raw material quality mainly refers to the protein, wet gluten and ash content of wheat flour. The requirements for producing high-quality instant noodles are: protein content 10.5-12%, wet gluten content 30-36%, wet gluten content 0.4-0.65%.
Uniform water quality during the dough mixing process has an impact on the production process and product quality, in addition to complying with drinking water quality standards (Chinese national standard GB/T5749 or equivalent foreign water quality standards). During the mixing process, the proteins in the flour absorb water and form a gluten network. It is not only affected by the amount of water added, but also by the water temperature. If the water temperature is too low, the protein absorption time will be prolonged. If the water temperature is too high, the protein is easily denatured by heat. When the temperature is appropriate, protein absorbs water and forms gluten faster, and the most suitable temperature is around 30°C. Therefore, when the room temperature in the workshop is lower than 20°C, it is best to mix flour with warm water.
The amount of water added during kneading is one of the main factors affecting kneading performance and is a prerequisite for producing a rich dough with appropriate viscosity, extensibility and plasticity.
The amount of water added to the dough is determined by the water absorption rate of the flour, and the water absorption rate of the flour mainly depends on the protein content of the flour (that is, the level of gluten content). Flours with high protein content have slightly higher water absorption rates, and vice versa.
In order for the protein and starch in the flour to fully absorb water, increasing the amount of water added to the dough is beneficial as long as the dough does not stick to callendering rollers at the next stage. Generally speaking, the amount of water added to 100 kilograms of flour is 28 to 35 kilograms, which should be adjusted according to its protein content and the moisture content of the flour itself. In principle, add as much water as possible. The amount of water added should be measured at one time and added in two batches.
The dough mixing time is closely related to gluten formation. If the mixing time is too short, the water will not be completely mixed with the wheat flour, and the protein will not have enough time to absorb water. If the dough mixing time is too long, the temperature of the dough will rise, which will partially denature the protein and reduce the quantity and quality of wet gluten. At the same time, the gluten will expand excessively and the dough will be "overcooked." The ideal mixing time is 15 minutes.
The quality of the kneading effect is also related to the mixing intensity of the kneader. Stirring intensity is generally expressed by the rotation speed of the stirring shaft (r/min). Mixing too fast may destroy the gluten formed in the dough, while too vigorous mixing will convert more mechanical energy into heat energy and increase the temperature of the dough. In severe cases, it will cause thermal denaturation of protein and weaken the performance of the dough; if the mixing speed is too low, water and wheat flour will not be mixed evenly, which will affect the formation of gluten. The ideal speed is 70-100 rpm.
Resting the dough can improve dough properties naturally over time. The length of time is the main factor affecting the process. In a continuous instant noodle making machine, the resting time is 10 to 20 minutes, generally 15 minutes. The dough after resting should not form large lumps and should not heat up during the entire resting process.
Dough resting must be accompanied by low-speed mixing, otherwise the dough will form lumps after resting for a period of time, making it impossible to proceed with the next step of sheeting. Experiments have shown that a stirring speed of 3 to 4 rpm is more appropriate.
The main factors affecting the calendering operation include dough properties, calendering ratio, number of roller sets, roller diameter, roller speed, etc.
The dough structure, moisture content, moisture uniformity, quantity and quality of gluten formation, dough temperature, etc. all directly affect the calendering process. Appropriate and stable dough moisture content, uniform humidity, sufficient gluten formation, good structure, and appropriate temperature will result in less dough sheet breakage during calendering, easy roller gap adjustment, and stable operation.
Within a certain range, pressure is beneficial to the densification of gluten network organization. If the calendering ratio is too large, it means that the pressure roller exerts too much pressure on the dough sheet. If the dough sheet is over-calendered sharply, the gluten network structure already formed in the dough sheet will be excessively stretched, which exceeds the ability of the gluten to withstand. The formed gluten tears, which deteriorates the process performance of the dough sheet. Within a certain range, increasing pressure is conducive to the densification of the gluten network. If the calendering ratio is too large, it means that the pressure applied by the rollers to the dough sheet is too high. If the dough sheet is over-calendered quickly, the gluten network structure already formed in the dough sheet will be over-stretched, exceeding the bearing capacity of the gluten, causing the formed gluten to tear and the performance of the dough sheet to deteriorate.
If there are fewer rolling passes, the rolling ratio will be larger; if there are more rolling passes, the rolling ratio will be smaller. The ideal number of rolling passes is 8 to 9 passes, of which the compound rolling stage is 3 passes and the continuous rolling stage is 5 to 6 passes. .
The larger the diameter of the pressure rollers, the more conducive to feeding, and the diameter of the pressure rollers are proportional to the pressure on the dough, so the diameter of the pressure rollers of the compound rolling machine are larger. As the dough gradually becomes thinner, the density of the dough gradually increases, the gluten network gradually becomes finer, and the required pressure gradually decreases, so the diameter of the rollers of the continuous rolling machine are relatively small.
Under the specified roller gap, the higher the rotating speed, the greater the line speed of the dough sheet and hence the greater the output; however too fast stretching speed may destroy the formed gluten network structure and make the dough less smoother. The lower the rotating speed, the lower the line speed of dough sheet, the longer the dough sheet pressing time, resulting a firmer and smoother dough sheet, but the outpu is lower.
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