Wet Milling Technology Of Corn Starch

The thesis mainly studied the processing technology of corn wet millingwhich was the crosswise project of DA CHENG CORN DEVELOPMENTCOMPANY "the study of crucially technical problems about the steepingtechnology of corn wet milling"。Nowadays, the corn has occupied main position in the procedure of thestarch, and most of starch is produced in the world. To adapt the demand of cornstarch, the processing technology of corn has been remarkable development andhas been important industry. At present, the quality of raw material has greatlyfluctuated, and the difficulty of the exploitation of new technics, which haveseriously restricted the improvement of the starch quality and the advance of theeconomical benefit, which cry for solving through tackling key problem. Thestudy has great significance to technology advancement of the starch enterprise,the quality of starch, economy benefits and the environment benefits.The study obtained the more steeping technology and produced the eligiblecorn starch through taking different steeping conditions to the dried corn, whichwill solve the difficulty of the steeping of dried corn, and create the advantagecondition for corn process.The main contents and conclusions are as follows:1) Through studying the steeping technology of producing corn starch in thelab-oratory, the study obtained sulfurous acid, steeping time and steepingtemperature to the effect of the processing technology of corn wet milling, andcreated the quadratic regression mathematic model:232221231213231248.230.013.920.924170.0971.2260.3680.0011.210.009ZZYZZZZZZZZZZ??= -+++?+??which can obtain the best compages: the steeping temperature is 51.2℃, thesulfurous acid concentration is 0.18%, the steeping time is 52.6h, and the yield o fstarch is 67.01%, which accorded with experimental result.2) Adding lactic acid to steeping solution, which can reduce steeping time,and increase starch yield, and avail to dissolve the protein of binding corn starch,which reduced protein content in the corn starch, and improved the quality ofstarch. And through experiment obtained the best steeping condition that thesteeping time is 48h, the steeping temperature is 52 ℃, the sulfurous acidconcentration is 0.2%, the lactic acid concentration is 0.5%.3) During the steeping, the starch, the fibre and fat of the dried corn innormal temperature and high temperature was not obvious difference. Butcompared with no steeped corn, the components had slight increase, especially theprotein and fibre were obvious, which indicated the drying temperature resulted inpart of protein denaturalization, which made the protein that could not soak outfrom the corn during the steeping.4) During the steeping, the absorbing water rate of corn increased bylogarithmic form before 12 hour, and the absorbing speed was relatively quickbefore 5 hour, and the corn reached saturated moisture. The saturated moisture ofcorn that was dried in 90℃ was the highest, which indicated the protein of corntook place denaturalization because of too high drying temperature, which madethe protein that could not soak out from the corn.5) The drying temperature reached 80℃ which arouse the protein of corndenaturalization, and reduced the capability of corn absorbing water duringsteeping, and resulted in difficultly separated starch and protein from corn. Theyield of starch reduced two percent when the drying temperature reached 80℃,and the yield of starch reduced seven percent when the drying temperaturereached 90℃, at the same time, the content of protein of starch increased too. Inorder to improve the productivity and purity of starch, the drying temperatureshould not beyond 80℃. Therefore the study adopt that the drying temperaturewas 60℃, which the yield of starch was 66.79%, and the protein in starch wasunder 0.4 percent.6) Through studying the effect of the time of cellulase dissolution on cornstarch and other productions, which indicated the productivity of corn starchincreasing with the concentration of cellulase before 12 hour, and the productivityof corn starch reached the max that was 66.1% when the time of cellulasedissolution was 12 hour, but the productivity of corn starch started dropping after12 hour. From the chang of the content of the fibre dregs concluded that thecontent of the fibre dregs ceaselessly reduced with the increasing of the time ofcellulase dissolution.7) Through studying the effect of the cellulase on output of corn starch, theresult indicated productivity of corn starch increased with increasing theconcentration of cellulase. The productivity of corn starch reached the max to67% when concentration of cellulase was 0.3%, but the chang was not obviouswhen continuing adding the cellulase. Therefore the concentration of cellulasemust be kept suit, which could assure the heighest productivity of corn starch.And the result indicated that adding cellulase to the steeping solution of corncould not only reduce the steeping time, the concentration of sulfurous acid, butalso improve the steeping result.8) Through studying the effect of Alcalase on the corn starch process, theresult indicated that the suited pH of Alcalase was 8.5, the temperature was 50℃,and the time of enzyme hydrolyzation was 3h. And hydrolyzed degree of theAlcalase quickly rised when the concentration of it was low, but the chang ofhydrolyzed degree of it was very little when the concentration of it was high.Because the concentration of it was high, the concentration of protein wasrelatively low, and enzyme molecule had reached saturation, part of it could notcombine with protein.9) Through observing the microcosmic structure of corn epidermis indifferent steeping condition, the study indicated that the microcosmic structure ofcorn had little difference in water steeped and in solution including of sulfurousacid steeped before 4h, and the chang was not obvious. When the steeping timewas 12h, the microcosmic structure of corn appeared obvious dent in solutionincluding of sulfurous acid steeped, but the structure of corn had not obviouschang under two conditions after 12h.10) Through observing the microcosmic structure of corn starch in differentsteeping condition, the study indicated that the microcosmic structure of cornstarch had little difference in two condition before 4h, but the microcosmicstructure of corn starch had appeared obvious difference in two steeping condition.The corn was smaller in water sreeped than in solution including of sulfurous acidsteeped, and we could clearly observe the shape of corn starch.The innovation p points of the thesis:1) The based of steeping model:2) Studying the effect of adding lactic acid to the corn steeping solution onthe process of producing corn starch:3) Studying the effect of adding cellulase and Alcalase to the corn steepingsolution on the process of producing corn starch:4) Studying the chang of the microcosmic structure of corn epidermis andstarch.The thesis studied the steeping technology of corn wet milling process,which will broad the field for starch industry. The studying fruit of the thesis willprovide the experimental parameter and conclusion for the enterprise of starchproduction. The means to produce corn starch by adding the enzymes to cornsteeping solution, which will broad the studying direction of the producing cornstarch, and will have a certain extent referenced value to the development of thecorn starch process.