Preparation Of Starch From Cadmium Rice And Application Of Starch Adhesives Modified By Oxidized And Crosslinked

Rice,also known as oryza sativa,is the main food for people in most areas of our country.However,with the continuous development of society,the phenomenon of excessive cadmium in rice appears from time to time.In this paper,cadmium-excess rice was used as the experimental material,the technical parameters of preparing rice starch,the physical and chemical properties of the starch,preparation of oxidized crosslinked rice starch adhesive and the effect of surface sizing on the corrugated base paper were mainly studied.The results of this study can provide new ideas for the industrial transformation and application of cadmium-exceeding rice,thereby promoting the sustainable development of my country’s rice industry.After optimizing the single factor and response surface,combined with the actual situation,it can be concluded that the best process for preparing rice starch by the cadmium-exceeding standard rice alkali method was:NaOH mass fraction 0.43%,extraction temperature 45°C,material-to-liquid ratio 1:12,and extraction time 12h.The average starch purity obtained under this condition was 87.66%.The primary and secondary order of factors affecting the preparation of rice starch by alkaline method was:extraction temperature>NaOH mass fraction>extraction time>material-to-liquid ratio.The best process for enzymatic preparation was:the amount of enzyme added was 0.45%,the extraction temperature was52℃,the pH was 8.3,and the extraction time was 7h.The average starch purity obtained under this condition was 87.69%.The primary and secondary order of factors affecting the preparation of rice starch by enzymatic method were:extraction time>pH>enzyme addition amount>extraction temperature.In addition,from the physical and chemical properties of rice starch testing results,it can be found that the starch granules of the two extraction methods are smaller and have irregular polygonal shapes.Among them,the rice starch prepared by the alkaline method has more surface holes.No new functional groups were introduced during the preparation process,so the starch prepared by the two preparation methods had no obvious structural difference.In addition,the gelatinization temperature of starch prepared by the two preparation methods is different,but the gap is smaller.At the same time,the content of cadmium in starch prepared by alkaline method and enzymatic method was 0.356mg/kg and0.253mg/kg lower than that of rice（0.379mg/kg）with excessive cadmium content;the damaged starch content of starch prepared by alkali method was higher than that prepared by enzyme method.After single-factor and orthogonal experiments,it can be concluded that the optimal process ratio of oxidized cross-linking alkaline rice starch adhesive was:based on 20g rice starch prepared by alkaline method,1%Na₂S₂O₃10mL,10%NaOH16mL,10%borax 3mL,30%H₂O₂1mL and 180mL of water.The viscosity（60℃）of the starch adhesive prepared under this condition was 34.46s,and the drying time was 22min.The primary and secondary order of the factors affecting the performance of the adhesive was:H₂O₂>NaOH>Na₂S₂O₃>H₂O;The optimal preparation process ratio of oxidative cross-linking enzymatic rice starch adhesive was:based on 20g enzymatic rice starch,1%Na₂S₂O₃ 15mL,10%NaOH 14mL,10%borax 2mL,30%H₂O₂ 1.5mL and water 140mL.The viscosity（60℃）of the starch adhesive prepared under this condition was 35.18s,and the drying time was18min.The primary and secondary order of the factors affecting the performance of the adhesive was:H₂O₂>NaOH>H₂O>Na₂S₂O₃.Moreover,by analyzing the physical and the water absorption properties of corrugated baes paper,it can be found that under the condition of 6%sizing amount,the folding resistance,tensile strength,ring compressive strength,and water resistance of each quantitative corrugated base paper were relatively low.The sizing corrugated base paper has been significantly improved.When the sizing amount exceeded 6%,the folding resistance,tensile strength,ring compressive strength,and water resistance have no significant changes compared with the 6%sizing amount.At the same time,the foldability,tensile strength,ring compressive strength,and water resistance of low basis weight corrugated paper were improved more than high basis weight corrugated paper.In summary,considering the actual operation and cost saving,the optimal sizing amount of oxidized cross-linked rice starch adhesive was 6%.