Effect Of Extrusion Parameter On Product Properties Of Job’s Tears

Job’s Tears has solid grains, which are hard to gelatinize under normal cooking, leading toprocessing difficulty. The grain structure of processing Job’s Tears can be lost by using extrusiontechnology that leads to starch degradation, gelatinization and protein denaturation. Meanwhile,the extrusion process can raise Job’s Tears gelatinization degree, which is good for enzymehydrolysis and nutrition absorption. Also, the extrusion needs short processing time, which canreduce processing energy costs. So far, the researches on processing technological parameters arestill lack. This thesis focuses on the influences of different extrusion processing parameters onJob’s Tears physical and chemical characteristics, providing theoretical research basis for Job’sTears deep processing by using extrusion technology, which owns practical values.1. Specific mechanical energy is negative correlated with material water content, sleevetemperature, feeding speed, the interaction item of temperature and water content, as well as theinteraction item of water content and feeding speed, while is positive correlated with screwrotation speed, square value of water content, the interaction item of temperature and feedingspeed, as well as the square value of feeding speed. The products temperature is negativecorrelated with material water content and its square value, while is positive correlated withfeeding speed and sleeve temperature. The extruder torque is negative correlated with materialwater content, sleeve temperature, screw rotation speed, the interaction item of water content andfeeding speed, as well as the interaction item of feeding speed and screw rotation speed, while ispositive correlated with feeding speed, the square value of water content, and the square value offeeding speed. As the rise of screw rotation speed and the rise of water content and temperaturecan cause the reduce of pressure.2. Brightness could be affected by water content. The products brightness reduces as the watercontent rises, and the rising sleeve temperature can raise the products brightness; the feedingvolume is positive correlated with red-green value （a*）and yellow-blue value（b*）; productswater content is positive correlated with red-green value （a*）and yellow-blue value（b*）; otherfactors have less influence on products color.3. Products density rises as their water content rises, and the density reduces as the raise ofsleeve temperature, feeding volume as well as pressure; products length ratio could be reduced byraising water content, while can be raised by raising sleeve temperature and screw rotating speed;as water content rising, products dilatability rises first and then reduces, reaching the peak valueunder zero water content; temperature change has no influence on dilatability, while the dilatabilityrises as the raise of feeding volume and screw rotating speed.4. WSI is only positive correlated with sleeve temperature and not remarkable influenced byother factors; WAI is negative correlated with sleeve temperature and the interaction item betweentemperature and water content, which means the higher temperature is the lower water sucking index is.5. The technic is optimized by reaching the WAI peak value as target. The optimizationtechnological parameters are that the feeding speed fixed at12Kg, screw rotation speed fixed at300rpm，the temperature is at150℃and the water content is at20%.6. The extrusion experiment is going on with the feeding speed fixed at12Kg, screw rotationspeed fixed at300rpm（0Level）, material water content at20%（+2Level）and sleeve temperatureset at30℃,60℃,90℃,120℃,150℃,150℃（-2Level） separately. The WAI value of extrusionproducts is2.72, with the error+1.87%, which is under the range of±5%.7. The type of extruder used in experiment is double-screw Fumach50, with screw diameter50mm, screw length32D, six mold holes with3mm diameter, material water content20%, materialfeeding volume67.5kg/h, screw rotation speed300r/min. To keep the mold tip temperaturebetween125℃to130℃, the sleeve temperature is set at room temperature,30℃,60℃,90℃,120℃,120℃,150℃and150℃in series。The mold tip temperature is127℃under stableproducing and mold tip pressure is9bar-12.7bar. The extrusion products are cut into pellets andplaced on fluid-bed for drying through warm wind. The water sucking index of collected dryproducts is2.59, with error-2.9%, which meets the engineering demands.