| During the production of soy protein isolates, an industrial organic wastewater called"soy whey"also was generated. Its biochemical oxygen demand and chemical oxygen demand were 10 times more than the wastewater discharge standards. Every year, about 200 million m3 soy whey was discharged in our country. If those whey is direct discharged, both of the resource-wasting and environmental pollution must be huge. Owing to the requirements of social and the needs of companies, sepration methods and the properties of whey protein from soy whey were studied.In this study, whey soy protein (WSP) was pretreated by the method of centrifugation. The optimum technological parameter was 3000×g, 15min. The protein retained consistensy was 1.431±0.090 g/L, and the ash was 4.00±0.07 g/L.In the experiments of whey soy protein's flocculation, by examed fourteen flocculants'flocculation rates and flocculation selectivities, flocculant LT was selected as its effective ability. And its flocculation rate was 90%. The flocculant LL also was chose for its selective flocculation ability of lipoxygenase andβ-amylase. Then the experiments of coagulant LT-LL's ablitity showed that the flocculation rate of compound flocculants was 50%. But it significant lower than flocculant LT's. The research in the flocculation conditions of flocculant LT with WSP showed that the optimum technological parameters were existed. The system pH was 3.0 and the temperature was 25℃. LT's addition level was 2.5 g/L. By flocculation in this parametrs and centrifugation in 3000×g,15min, the protein removal rate was 93.86%.In the research of separation and concentration of WSP by the method of flocculation-microfiltration, eleven flocculants'ability in increasing the size of protein aggregates were studied. According to the results and the availability in membrane, flocculant LT and flocculant LX were selected. Both of them can increase the size form 109 nm to 436 and 443 nm . Through the experiment in LX, its the best flocculation pH range of 7-8 was found. Considering soy whey's pH was 4.5, it was not chose as a suitable flocculant. After the research of the relationship between flocculant LT dosage and protein particle size, The optimum dosage was 0.02 g/L. In the followed membrane process, the optimum technological parameter was system temperature 40-50℃, press 0.2 MPa, and in 70 min, the membrane maintained a high flux, low protein concentration of the permeate. At this point the membrane flux was 319.83 L/(m2?h)and the protein concentration was 6.21 mg/L.In study of WSP gathered by the method of flocculation- microfiltration, experimental results showed that WSP optimum solubility pH is 3, and the solubility was 8.6%; protein thermal denaturation temperature was 84.75℃; and the ash was 86.01±0.52%. In the followed research, we tested the desalination effects of two kinds of desalination methods. The results were that dialysis was more suitable than ultrafiltration for desalination.By doing this study, two methods of flocculation-centrifugation and flocculation-microfiltration were got. They can efficiently separate whey soy protein from the waste. And this study can provide a certain amount of theoretical and methodologiccal basis for the treatments of soy whey and other waster water too. |
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