Technological Research On Drying The Soybean Sauce Residue With Superheated Steam

The superheated steam drying (SSD) is a dehydration method which the drying media contacts with the drying materials directly. Compared with hot air drying, the exhaust of SSD is all steam and can be reused with condensation.SSD has many advantages, such as good products’quality.no explosive danger, high efficiency of heat and mass transfer and energy saving, so SSD is a novel drying technology.This paper mainly studied drying characteristics of SSD with soybean sauce residue and a series thin layer drying experiments on SSD were did on a self built SSD dryer. Temperature, flux of drying media and the bed thickness are all evaluations of drying rate; the experiment also tested the content change of salt or protein in soybean sauce residue. The results showed that:a condensation phenomenon happened in the initial stage of SSD, condensation number was related to temperature of super steam. The temperature and flux of superheated steam had obvious influence in drying rate, soybean sauce residue(6g. 7.5mm)was dried at superheated steam flux of 0.58kg/m2·s, temperature of 115℃, which needed 41min, while the temperature of 160℃,the drying time was 15min, which shortened the drying time by 25min; the drying time of soybean sauce residue (6g) at superheated steam flux of 0.34kg/m2·s, temperature of 145℃ was 33min, when the superheated steam flux changed to 0.81kg/m2·s, the drying time was 11min, so the increase of temperature and flux of superheated steam improve the drying efficiency widely. The drying time of 6g (7.5mm)soybean sauce residue at the temperature of 145℃,flux of 0.58kg/m2·s is 38min, when changed the mass to 10g(12.2mm), the drying time is 18min, the bed thickness also affected drying characteristics obvious.Testing the content of the chloride by the method of ion chromatography and the salt content of soybean sauce residue decreased 30% after SSD; measuring the protein content of soybean sauce residue with kay type nitrogen determination method (KDN), the protein content was the same. So SSD has a good advantage for the soybean sauce residue re-use.