Study On Extraction Technology Of Raffinose From Cottonseed Processing Waste Liquid

Xinjiang is the largest cotton producing area in China.As an important by-product of cotton,cottonseed has an abundant part of its resources.Cottonseed is rich in high nutritional value components such as oil,protein and raffinose,having high commercial value.At present,cottonseed processing enterprises mainly process and produce cottonseed meal,cottonseed oil,cottonseed protein and other products.In the process of cottonseed protein production in cottonseed processing enterprises,a large amount of cottonseed processing waste liquid will be produced.The waste liquid has complex components,including gossypol,raffinose and other substances,which are usually treated by industrial wastewater purification method and then discharged directly,resulting in a large waste of resources and serious environmental pollution.Therefore,breaking through the key technology of extracting raffinose from cottonseed processing waste liquid,turning waste into wealth,is conducive to improving the utilization rate of cottonseed resources,reducing the environmental pollution caused by enterprise production,and thus playing a strong role in promoting cotton planting and cottonseed processing technology in Xinjiang to a new level.In this thesis,cottonseed processing waste liquid was used as raw material,and after pretreatment,to study its decolorization and dephenolization process.On this basis,raffinose was obtained by alcohol precipitation,crystallization and drying.The raffinose was purified by recrystallization and membrane filtration to obtain high purity raffinose,and its physical and chemical indexes were detected.The main results are as follows:1.Decolorize the pretreatment liquid of cottonseed processing waste liquor by adsorption decolorization method.By comparing the decolorization effects of five decolorizing agents on carbon particles,carbon powder,Al₂O₃,macroporous adsorption resin D3520 and S-8,the results showed that the decolorization effect of activated carbon（powder）was the best.Activated carbon powder was selected as the decolorizer of cottonseed processing waste liquid and the decolorization and dephenolization conditions of cottonseed processing waste liquid were optimized by single factor response surface experiment to obtain the optimum process parameters:p H=4.7,decolorization temperature 65℃and time 47 mins.Under these conditions,the decolorization rate of cottonseed processing waste liquid could reach 96.29%.2.Preliminarily purify the crude raffinose by recrystallization.It is found that the insertion of the crystal nucleus can increase the crystallization rate of raffinose.Researcher carried out single-factor experiments by inserting crystal nucleus to study effects of crystallization time,crystallization temperature,ethanol concentration,p H and liquid-material ratio on the crystallized precipitation of raffinose.The recrystallization process was optimized by response surface methodology to obtain the best parameters,which are ethanol concentration 76.00%,crystallization temperature-14℃and crystallization time 3 h.Under these conditions,the crystallization precipitation rate of raffinose was 91.28%.At the same time,by repeating the crystallization process of raffinose,the results showed that the removal rate of gossypol decreased and the purity of raffinose reached a high level when recrystallizing them four times.At that moment,the purity of raffinose was 99.3%and the gossypol content was 72.1 mg/m L.3.Desalt raffinose by Membrane dialysis method.Compared with the effects of 100 D and 300 D dialysis membranes on desalting effect,it was found that the desalting rate and sugar retention rate of 100 D dialysis membrane were better.On this basis,single factor experiments were carried out to study the effects of raffinose concentration,temperature and time on the desalination effect,and the optimal parameters were obtained by response surface optimization and the data are solution concentration=100 mg/m L,dialysis temperature 33℃and time 59mins.Under these conditions,the desalination rate of raffinose solution was78.68%and the purity of raffinose reached 99.6%.After testing the physical and chemical indexes of high-purity raffinose,the results revealed that raffinose contained no protein,nucleic acid,precipitation,reducing sugar and other substances,having good water solubility,poor alcohol solubility,basically no hygroscopicity,good thermal stability,and appearing acicular crystal under scanning electron microscope.To sum up,high-purity raffinose can be obtained from cottonseed processing waste liquid by decolorization,dephenolization,recrystallization and membrane filtration.Realizing the waste utilization of cottonseed processing waste liquid is helpful to optimize the regional distribution of cotton in Xinjiang;to improve the competitiveness of cottonseed processing industry in Xinjiang;to improve the utilization rate of cottonseed byproduct resources,providing the possibility for the large-scale production of raffinose to realize sustainable development.