| It is long-time consuming for yuba drying in traditional ways which can't catch up with the needs of modern industry producing. So the study of drying yuba was made. Aiming for reducing the drying time on the basis that dried yuba has good quality in cracking resistance, color and other sensory properties. Fresh yuba is well-known for its soft color, smooth taste, convenient for eating and a variety of nutrition; but the big problem is that it is perishable and difficult to preserve. In order to resolve this problem, three physical methods: ultra high pressure, pressure heat treatment and atmospheric pressure heat treatment for fresh yuba sterilization were studied. And screening out the best way to keep the quality of fresh yuba in sensory and texture, and then verifying its preservation.Firstly, properties of yuba drying at temperature section 60℃~100℃and effects of constant temperature drying on the color, fragmentation and sensory index of dried yuba were studied. The results indicated that: drying at constant temperature 90℃and 100℃significantly reduced the drying time, but the quality was greatly damaged, including color deterioration, surface emitting oil and burned taste; when drying at 60℃~80℃constant temperature, the color value L*a*b* of yuba was similar and a* value was smaller than others. Meanwhile, the value of hardness and fracturability were bigger and had little effect on the sensory quality of yuba, but emitting oil on the surface. Based on this, 5 kinds of temperature gradient drying programs were designed. And finally screening out the best program was: 100℃forced air drying 1 h→80℃f orced air drying 1.5 h→60℃drying 1.5 h. The color value of dried yuba in L* and b* were bigger than others with the smallest a* value. It also had better sensory qualities: light yellow, rich bean flavor, not brittle and easy to rehydrate with the biggest value in hardness and fracturability.For the preservation of fresh yuba, surface microstructure and sensory qualities of fresh yuba were used as evaluation index and three ways of physical sterilization: ultra high pressure, pressure heat treatment and atmospheric heat treatment were studied to filter out the most suitable method for fresh yuba sterilization. The results showed that: ultra high pressure (550 MPa, 20 min) had an effect on the surface microstructure of fresh yuba and the texture changed a lot, but it had little effect on color and flavor; pressure heat treatment (121℃, 20 min) strongly damaged fresh yuba in its surface microstructure, color, flavor and texture; atmospheric heat treatment (85℃, 30 min and 95℃, 30 min)almost had no damage on the surface microstructure of yuba and maintain the color, flavor and texture properties in maximum.Finally, in order to reduce bacterial contamination from yuba producing, the microbial contamination of fresh yuba during producing process was studied. And then, atmospheric heat sterilization and its effect on color and texture of fresh yuba and its preservation were studied. The results showed that fresh yuba was first packaged in aseptic environment with aseptic bags by 0.085 MPa vacuum sealing, and then was sterilized by 85℃for 30 min. This heat treatment had a good sterilization effect on yuba and had little effect on color and texture of fresh yuba. When storing this yuba product at 4℃for 45 days, it showed that coliform bacteria were not detected; total number of colonies was 3100 cfu/ml which is far less than the standard value of soy product DB31/190-2002; volatile basic nitrogen was 2.447 mg/100g which is far less than the soybean physicochemical indexes; pH was in the normal section 7.00~7.27. These data indicated that this kind of sterilized yuba product can be stored at 4℃for 45 days.
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