Study On Protein Recycling From Potato Starch Wastewater And Antioxidant Capability Of Its Hydrolyzate

Potato has become the second largest raw material of starch after corn.Every year, more than1000tons of potato starch wastewater, the by-product in potato starch processing, is dischargedinto rivers and lakes around related areas, which is high in potato protein. The directly dischargeof potato starch wastewater not only wastes natural resources but also causes pollution of watersystem of related areas. Protein recovery and utilization of potato starch wastewater, caneffectively reduce the organic content in the wastewater and reduce the difficulty of subsequentsewage treatment, further more, high-value utilization can produce certain economic benefits. Inthis paper, we firstly simulated production of potato starch and collected wastewater, thenrecovered protein with alkali-solution and acid-isolation as well as ultrafiltration. Finaly westudied the two potato protein’s proteolytic processes and antioxidant activity of potato proteinhydrolyzate. The main findings are as follows:1. Study on alkali extraction and acid precipitation recovery process of potato protein:Response surface methodology was applied to optimize process conditions of the technology ofrecovering protein from potato starch wastewater.Four factor, namely broken ratio of liquid tosolid(mL/g),pH,setting time and temperature were selected.Base on single-factor experimentsprotein recovery rate was as response value, and the effect of such factors on protein recoveryrate was studied.The results showed that protein recovery rate can reach the highest level of79.21%when follow this process conditions:the broken ratio of liquid was2mL/g,pH4.50,setting time was40min and the temperature was35℃.2. Study on ultrafiltration recovery process of potato protein: Ultrafiltration equipment wasused for concentrating the waste liquid of potato starch production and processing, to studyvariation regularity between membrane flux and protein mass concentrations at roomtemperature and0.16MPa, and the mass transfer equation of the potato starch wasteultrafiltration process was got. The mass concentration of potato protein formed a gel layerturned to be Cg=71.582g/L. Establish the model of operating pressure and membrane fluxbased on the resistance model theory, and investigate the influence on membrane flux withdifferent operating pressure. The wastewater should be ultrafiltrated in medium voltage area toconcentration potato starch wastewater, recycling potato protein content after lyophilization is86.56%.3. Study on potato protein hydrolysis process: potato proterin was hydrolysed and thenrecycled by alkali extraction and acid precipitation.With the method of single factor experimentand Box-Behnken Design, the optimum recycling process conditions were determined: the enzyme content is3.90%, hydrolysis temperature is50.00℃, pH is8.00and hydrolysis time of4.50h. Hydrolysis degree of potato protein after alkali extraction and acid precipitation is27.23%; potato proterin was hydrolysed and then recycled by ultrafiltration,With the method of singlefactor experiment and Box-Behnken Design, the optimum recycling process conditions weredetermined:the enzyme content is3.90%, hydrolysis temperature is47.50℃, pH is8.00andhydrolysis time of4.50h, Hydrolysis degree of potato protein after ultrafiltration is28.29%.4. By measuring hydroxyl radical eliminating ratio, DPPH scavenging rate and Cu2+chelatingability of potato protein hydrolysate with different components, its antioxidant activity wasevaluated: antioxidant activity of patota protein after alkali extraction and acid precipitation isalmost lost; scavenging activity of hydroxyl radical and DPPH free radical of patota protein afterultrafiltration remains a part, at the same time, potato protein hydrolyzate has strong chelatingability for Cu2+, the above neans that ultrafiltration method do help maitain its antioxidantactivity.