Rice noodles drying process
1. Preparation for drying: wet rice noodles go through the cold air setting stage. Since wet rice noodles themselves contain a large amount of
free water, they need to go through a process of slow temperature rise, setting, heat dissipation and dehumidification. Usually, low temperature
is used to strengthen ventilation and air flow. Air is used to promote dehumidification of rice noodles, initially fixing the shape of rice noodles,
and removing surface moisture. The initial drying temperature of rice noodles should be between 25°C and 30°C, and the air humidity should
be between 55 and 65%. The drying time is 1 hour. If the temperature rises too fast in the early stage, it will easily cause the temperature
difference between the inside and outside of the rice noodles to be too large, thus reducing the toughness and making the rice noodles easy
to break.
2: Moisture-maintaining and sweating stage: The temperature gradually rises. During the moisturizing and drying stage, the temperature
gradually rises. The temperature of the hot air in the drying room is higher than the temperature of the surface of the noodles, and the heat
gradually enters the inside of the noodles. As time goes by, It reduces the temperature difference between the inside and outside of the rice
noodles and increases the movement of moisture inside the rice noodles. This stage slowly increases the temperature while using a higher
relative humidity to limit surface vaporization while increasing the rate of internal moisture transfer. The temperature at this stage is 35~45℃,
and the relative humidity is between 50-75%.
Three: Peak dehydration stage: When the internal temperature of rice noodles rises, internal moisture transfer and surface vaporization are
basically balanced. Therefore, the temperature can be raised and the humidity reduced at this time to ensure a large amount of water removal.
As the circulating wind in the drying room increases, heat is transferred to the inside of the rice noodles. When the moisture on the surface of
the rice noodles evaporates, it diffuses into the surrounding dry medium. In this way, the moisture on the surface of the rice noodles is lower
than the moisture inside the rice noodles, creating a moisture ladder. It will gradually spread to the surface. The moisture on the surface of the
wet rice noodles is taken away by the drying medium, and the internal moisture diffuses to the surface and evaporates. This continuous cycle
continues until the rice noodles are dried. At this stage, the temperature is about 50 degrees Celsius, the relative humidity is 55% to 60%, the
time is 90 minutes, and the moisture drops below 10%.
Four: Final drying stage: After the rice noodles have gone through the first few drying stages, most of the moisture in the rice noodles has been
removed, and the structure of the rice noodles is basically fixed. At this time, the temperature of the noodles itself is relatively high, so on the
one hand, this stage reduces the humidity of the rice noodles themselves. and temperature, continue to remove a small part of the water, and
use the waste heat to evaporate a small amount of water. At this stage, attention should be paid to the cooling speed. Generally, it is more
reasonable to reduce the temperature by 1°C in 3 minutes. . The temperature is about 30 degrees Celsius and the time is 90 minutes. On the
other hand, the slow process of adjustment can make the moisture content inside and outside of the rice noodles consistent, eliminate the
drying internal stress of drying shrinkage, enhance the toughness and elasticity, and achieve uniform quality of the rice noodles.
