Research On Noodles Drying Model And Drying Process Control

Drying process of Chinese dried noodle is difficult to control, but it governs the product quality. Irrational drying conditions would lead to not only increase the energy consumption but also make the noodle quality deterioration(noodle crisp, checking and more cooking loss). Now, the processing of Chinese dried noodle has advanced greatly in process equipment and acquired some rudiments of a modern food industrial. But the problem of extensive management, low heat utilization rate and unstable product quality in noodle drying process had not been resolved.In this study, the characteristic of drying medium(air velocity, wind direction, temperature, relative humidity) in a tunnel-type drying chamber and the noodle dehydration process was investigated; the drying characteristic of noodle under a stable condition(temperature and humidity closely controlled and remains constant) was studied. Base on this the noodle drying model was designed and verification. In the same time, this study established a model that monitoring the moisture content of Chinese dried noodle during the drying process by near-infrared reflectance(NIR) spectroscopy and investigated the heat energy constitution of an actual production line which the heat supply is solar and coal.The main conclusions in this paper are as follows:(1)Noodle drying rate is mainly affected by the moisture gradient between the internal of noodle and external environment(drying medium). High relative humidity(RH) led to high water vapor pressure, which hindered the moisture transfer from inside to dry medium. High temperature makes the moisture in noodle get the high kinetic energy, and benefit to the water diffusing. The drying rate is decreased as RH increased at a constant temperature, and increased as the temperature enhanced at a constant RH.(2)The rate of noodle drying is limited by the internal diffusion of water. Noodle drying rate rose at the dry beginning, and then reduced. Speed-rising section, noodle warming, surface moisture removed, which the drying rate is mainly influenced by the relative humidity and the temperature of the drying medium. After noodle warming the drying rate is start falling. The drying rate in falling stage is mainly influenced by the diffusion of internal moisture.(3)Suitable drying technology not only makes the good product quality, but can also improve the energy efficiency. The drying technology which T=40℃,RH=75% is considered the optimal drying conditions. The noodle drying rate under this condition is moderate; the thermal efficiency is higher and also can meet the actual requirement. But in the end of drying the moisture content of noodle product can’t meet the demands of noodle product(≤14.5%).(4)Noodle drying process can divid in three sections according to noodle drying characteristics, pre-drying main-drying and final drying. The tested result of the model has been show that the ideal drying process is(pre-drying: 25℃, 85%, 40 min; main drying: 45℃, 75%, 140 min, final drying: 35℃, 55%, 60 min), with a low equilibrium moisture content and the higher energy efficiency.(5)This work demonstrates the application use of PLS regression and NIR spectroscopy is a simple and efficient technique that can be utilized to monitor moisture content during production of Chinese dried noodle. The prediction results show that the value predicted by the model prepressing by 1st+SNV, has a high correlation(r=0.98) with the measured data.(6)The heat energy constitution study about solar energy assisted heat supply drying during noodle drying process in chamber show that solar energy share 17.51% about whole energy consumption in noodle production of all day. In view of the higher price of solar-thermal conversion device, the economization of solar usage is hard to compete with conventional energy, remains to be policy support.