Studies On Technological Parameters For Grain Processing By Extrusion

Corn, rice, millet, and their multi-grain were extruded in the twin screw extruder (Brabender Lab-station of DSE-25). The extrudate properties index of different grain, effects of technological parameters on the system parameters and extrudate properties index, as well as relationship between the system parameters and extrudate properties index were studied. The results showed that the system parameters and extrudate properties index were affected significantly by barrel temperature, moisture content, screw speed, and feeding rate. For the importance of the effect of technological parameters on the system parameters and extrudate properties index, the order from the great to the minor could be as follows: for the torque and breaking strength, barrel temperature >moisture content >feeding rate >screw speed; for the pressure, diametric expansion, and color index, barrel temperature >moisture content; for the water solubility index, barrel temperature >moisture content >screw speed> feeding rate; for the water absorption index, moisture content >screw speed. With increase of barrel temperature and moisture content, the torque, 4th zone pressure, 5th zone pressure, and diametric expansion were decreased, while the loss of moisture content and water absorption index trended towards increase. The brightness index and water solubility index trended towards increase, while the moisture content of product, red-green index, yellow-blue index, breaking strength, and breaking energy were decreased with increase of barrel temperature and decrease of moisture content. The diametric expansion and moisture content of product were significantly related to red-green index, yellow-blue index, th4 zone pressure, and difference of pressure between th4 zone and th5 zone, significantly and negatively related to the brightness index and water solubility index. The moisture content of product was significantly related to the breaking strength and breaking energy. The best technological parameters of corn extrudate for Brabender Lab-station of DSE-25 could be described as: barrel temperature was 180℃(th5 zone), moisture content was 16%, screw speed was 120r/min, feeding rate was 16r/min. The system parameters and rice extrudate properties index were affected significantly by moisture content and barrel temperature. With increase of barrel temperature and moisture content, the torque, 4th zone pressure, 5th zone pressure, and diametric expansion were decreased. The moisture content of product trended towards decrease with increase of barrel temperature and decrease of moisture content. The system parameters and millet extrudate properties index were affected significantly by barrel temperature, moisture content, millet varieties, and their mutual effect. With increase of barrel temperature and moisture content, the torque, 4th zone pressure, 5th zone pressure, as well as diametric expansion trended towards decrease. The water solubility index trended towards increase, while the water absorption index and moisture content of product trended toward decrease with increase of barrel temperature and decrease of moisture content. Compared with Jiyou No.2, the extrudate of Xiaoxiang millet and Jigu 17 had lower moisture content of product, lower diametric expansion, and higher water solubility index. The system parameters and mutual-grain extrudate properties index were affected significantly by proportion of mutual-grain, content of sucrose, content of distilled monoglyceride, and their mutual effect. With proportion of millet increasing or proportion of corn decreasing, the diametric expansion decreased, and aroma of corn reduced. The diametric expansion reached the maximum when content of rice was 20%. The torque, 4th zone pressure, 5th zone pressure, diametric expansion, moisture content of product, breaking strength and breaking energy were decreased with increase of the content of sucrose and distilled monoglyceride. The water solubility index and red-green index trended towards increase, while the water absorption index, brightness index, and yellow-blue index trended toward decrease with increase of content of sucrose and decrease of content of distilled monoglyceride. When the content of distilled monoglyceride became 1% or more, the flavor of extrudate became less. The suitable content of sucrose was 7%-9%. The best technological parameters of mutual-grain extrudate for Brabender Lab-station of DSE-25 could be described as: barrel temperature was 180℃(th5 zone), screw speed was 120r/min, moisture content was 16%, feeding rate was 16r/min, diameter of die was 6mm, proportion of corn, rice, and millet were 6:2:2, content of salt was 0.5%, content of sucrose was 8%, and content of saccharose was 0.1%.