Study On Cleaner Production Technology Of Sweet Potato Starch

Sweet potato is one of the main food crops in China,because it is rich in starch,it has become an important resource for starch production.Sweet potato starch is widely used in food,chemical and other industries.In the food industry,sweet potato starch can be used as processing materials,such as processing vermicelli,powder,powder,powder skin,etc.,and it also can be used as food additive;on the other hand,it can be used as thickener,stabilizer,gelling agent and so on after physicochemical modification.At present,the production of sweet potato starch in China is mainly faced with the high concentration of organic matter in starch wastewater,and the difficulty of treatment;the lack of utilization of other nutrients in the starch production process,which leads to the waste of sweet potato resources.On the basis of the traditional production technology of sweet potato starch,this paper has optimized the sweet potato pressing process,starch extraction process,sweet potato starch wastewater treatment process,in order to obtain a kind of technology of Cleaner production of Sweet Potato starch.It can reduce the concentration of organic matter in wastewater and make use of other nutrients in sweet potato,which provides the theoretical basis for the clean production of sweet potato starch and the full utilization of sweet potato resources.The main results are as follows:?1?The effects of colloid grinding on starch free rate,soluble components in potato residue and potato juice,and the ratio of water added in screw press separation were compared,and the effects of water addition ratio on the soluble components in potato residue and potato juice were compared.The optimum processing parameters of sweet potato press were determined as follows:colloid mill clearance 5?m,screw press twice water addition ratio 1:0.3?g/mL?,starch dissociation rate 92.33%,protein in potato residue reduced to 0.66%and and 55.10%lower than that of screw press and water separation.The content of soluble sugar was reduced to less than 0.1 and 99.13%lower than that of screw press and water separation.The sweet potato juice was mixed with the sweet potato juice which was separated by water press,and the protein content and soluble solids content were 1.48%and 10.2%respectively,which could be used for processing sweet potato beverage.By comparing the content of soluble components in sweet potato dregs,sweet potato juice and the yield of sweet potato juice of three kinds of high starch sweet potato varieties,?Shangshu 19,Yushu 17 and Yushu 27?,it was determined that Yushu 27 was the most suitable variety for clean starch production.?2?The effects of different centrifugation conditions on starch precipitation rate,the effects of water ratio and times of coarse starch washing material on starch whiteness and the concentration of pollutants in wastewater were compared.The optimum technological parameters of starch separation in sweet potato mixed juice were determined as follows:centrifugal rotation speed of 4000 r/min,time of 5 min,ratio of washing material to water of 1:3?g/mL?,washing times three times,The precipitation rate of starch was 33.63%,the whiteness of starch was 93.08,the concentration of COD in wastewater was 2909 mg/L,the concentration of SS was 850 mg/L,the color of wastewater was light brown and the chroma was 80 times.?3?The effects of ultrasonic extraction and microwave assisted extraction on the extraction rate of starch from potato dregs were compared.The optimum parameters were determined as follows:ultrasonic power 300W,ultrasonic time 5 min,starch extraction rate 90.59%.?4?On the basis of single factor experiment,the extraction rate of starch was taken as the response value,and the soaking conditions of potato residue were optimized by response surface test.The regression model was obtained as follows:R=90.65+1.23A+1.04B-0.86C-0.30D-0.65AB+1.78AC-0.63BC-0.10BD-1.25CD-8.67A²-8.77B²-8.04C²-0.061D².The optimum technological parameters were obtained as follows:material-water ratio 1:4.9?g/mL?,pH vaule 8.0,temperature20?,time 1h.The extraction rate of starch from potato dregs was 90.97%.The concentration of COD in wastewater was 2800mg/L,the concentration of SS was375mg/L,the chroma was 60 times.The starch content in potato residue was less than3%after soaking.?5?The effects of different ozone ventilation time on the removal rate of COD?chroma and turbidity in wastewater were compared.The optimal ozone ventilation time is 10 min,the corresponding optimal ozone dosage is 0.027 mg _O3/mg_COD,COD removal rate 79.56%,the chromaticity removal rate 25%,but the turbidity removal is not effective.The optimum flocculant combination and its addition amount were determined by single factor experiment of flocculation sedimentation.The COD removal rate was taken as the response value and the regression model was obtained by optimizing the response surface test.The regression model was:R=47.75-2.68A+3.51B+1.27C+3.00AB+4.91AC+0.20BC-6.63A²-9.56B²-14.02C².The optimum technological parameters of flocculation precipitation were:10g/L PAC addition amount 0.92mL,2%PAM addition amount 0.32mL,pH value 7.0.Under this condition,The COD removal rate reached 47.95%,the turbidity removal rate reached91.47%,and the color removal rate reached 98%.?6?The extraction rate of starch,starch quality and the concentration of main pollutants in wastewater were compared between the clean production process of sweet potato starch and the traditional production process.The starch extraction rate of clean production process was 90.46,which was 6.99%higher than that of traditional technology.The starch quality of the two processes reached the national standard of edible sweet potato starch,but the protein content of clean process starch was lower.Compared with the traditional process,the concentration of COD in the wastewater of clean production process is 2652²910mg/L,the content of COD is about 7800mg lower per liter of wastewater,the concentration of suspended matter is 510mg/L,compared with the traditional process,the SS content in the wastewater is about1000mg lower and the chroma is 80 times lower.It is only 10.00%of the chroma of the traditional process wastewater,and the waste water produced by the cleaning process is3.55 tons lower than that of the traditional process for each ton of sweet potato production.The removal efficiency of COD by ozonation combined with flocculation is better than that by ozonation alone or by flocculation precipitation method.The removal rate of COD can reach more than 89%,more than 92%for turbidity,90%for turbidity and 95%for chroma.After the ozonation and flocculation precipitation treatment,the wastewater produced by clean process can meet the discharge standard of starch industry wastewater and can be discharged directly,while the concentration of COD and SS produced by traditional process is still relatively high,which can not reach the standard of direct discharge.