Extrusion Characteristics Of Foxtail Millet

Extrusion cooking as a food processing technology has the advantages such as low energy cost, negligible effluent, low nutrition loss, variety of products produced and types of ingredients processed. Foxtail millet(setaria italica) has many kinds of bioactivities and is equal or superior to other major cereals in nutritional value, but its utilization is limited. Extrusion cooking is potential in developing foxtail millet-based foods. Therefore there is a great urgency to study the extrusion properties of foxtail millet. The physicochemical properties of foxtail millet starch and protein were studied firstly, then The influence of operating parameters on system parameters and product properties was analyzed. Physicochemical changes of protein and starch caused by extrusion and the contribution offoxtail millet major composites to the properties of extrudate were studied. The drying and moisture absorption kinetics of extrudates were studied, and the texture changes caused by moisture absorption were modelled. Finally, Residence time distribution during the blend extrusion of millet flour and soybean meal was studied and available lysine loss caused by extrusion was analyzed kinetically. The following results were obtained. Foxtail millet starch paste was less stable and easy to retrogradate. It was strongly shear thinning, and its time-dependent rheology followed a third order kinetics. The swelling power and solubility of the starch increased linearly with increasing temperature at >65℃. Intrinsic viscosity of foxtail millet starch was lower than that of other major cereal starch. Albumin and globulin fractions were very low in foxtail millet. 45.6%of the total protein was prolamin. 21.1% was glutelin, and the rest protein was soluble only in 1%SDS and 1%SDS+2%2-ME solution. The reduced SDS-PAGE demonstrated that both albumin and globulin had a wide range of molecular weight polypeptides. The intensive bonds of albumin were at high molecular weight region, while those of globulin were at low molecular weight region. Prolamin had high concentration of 21.7kD polypeptides. Glutelin had polypeptides in the whole molecular weight range. The protein extracted by 1%SDS and 1%SDS+2%2-ME had polypeptide profile similar to glutelin at high molecular weight region, while similar to prolamin at low molecular weight region. The 60kD polypeptide was starch granule associated protein located in the interior of starch. Compared with other cereal protein, foxtail...