Research On Extrusion Process And Solubility Of Extruded Cereal Powder

The extrusion process and solubility of breakfast cereal powder was studied in this paper.The main conclusions were shown as follows:Firstly, the effect of thermostable α-amylase on the solubility of cereal powder duringdouble screw extrusion cooking was studied. Thermostable α-amylase was added into ricepowder during moisture condition. Optimized parameters were obtained by response surfacemethodology: barrel temperature136°C, screw rotating speed100r/min and enzymeconcentration36u∕g. Compared with the control sample, the rice powder with thermostableα-amylase obtained after optimizing showed better solubility, DSI increased from10.06to10.91, Dextrose equivalent value increased from1.06to13.58, agglomeration rate decreasedfrom32.0%to11.25%, viscosity decreased from113.9mPa·s to88.6mPa·s. The resultsshowed that adding thermostable α-amylase during double screw extrusion cooking canimprove solubility of extruded rice powder.Secondly, compound proportion and the extrusion process of multiple cereals werestudied. Amino acid compositions of seven kinds of cereals were determined; Corn, oat,ormosia, millet, rice, soybean and barley were mixed in proportion of1:1:1.5:2.5:1:1:2with reference to the amino acid pattern recommended by FAO. Optimized parameters wereobtained by response surface methodology: terminal barrel temperature106.3°C,thermostable α-amylase concentration20U/g, screw rotating speed102.5r/min. DSI ofmixed cereal powder achieved33.11%, the agglomeration rate decreased to0.85%.Then four treatments (superfine comminution, methods of preparation, adding sucroseand granulation method) were taken to explore their effects on the solubility of cereal powder.The results showed that when the mean volume diameter of cereal powder was33.69μm andpowder particle size distribution was mainly concentrated in the segment of20~80μm, DSIachieved maximum34.75%, the agglomeration rate decreased to0.75%. Mixed the cerealpowder with60~70°C water at the ratio of2~3, the extruded cereal paste tasted good. As theaddition amount of sucrose increased, DSI increased, the viscosity of the cereal powder pastedecreased. After spraying0.1%gum Arabic,0.1%CMC-Na,0.1%monoglycerides,0.1%sucrose ester and0.1%compound additives, DSI of the cereal powder increased, the effect ofthe CMC-Na was particularly significant, DSI increased to35.36%.Finally, the process of toasting combined with extrusion, double extrusion wereconducted, DSI were32.43%,31.09%respectively. Amino Acid Score (AAS) of cerealpowder obtained from the toasting combined extrusion process was67.3, Essential AminoAcid Index (EAAI) was68.6; the AAS and the EAAI for cereal powder obtained from thedouble extrusion process was64.3,65.7respectively. The results of GC-MS showed thatcereal powder obtained from the toasting combined extrusion process formed pyrazines withcereal baking flavor; cereal powder obtained from the double extrusion process formedmultiple aroma-producing substances such as esters, pyrazines, pyridines. Sensory evaluationdata showed that there were significant differences in scores of color and appearance, smell,taste and overall acceptability between cereal powders obtained from the double extrusion process and the low temperature extrusion process. Gelatinization degree of cereal powderobtained from the double extrusion process was96.12%, which is more easily digested.Considering the solubility, sensory quality and production capacity in a integrated manner, theprocess of double extrusion is more desirable.