| Soybean protein has high nutritional value and it is perfect protein. The amino acids are balance except the methionine and cysteine value are below the commendation value of FAO. Soybean protein can be mixed with cereal foods and achieve amino acids complementary, soybean protein can also have many functional properties, such as emulsifying ability, WHC and OHC. Therefore, the soybean protein can be used in varies kinds in food process.Using defatted soybean meal as the material and in two-screw extruder, the optimized technology conditions was determined, the effect of extrusion on functional and nutritional properties of soybean was studied. And using the product as material of the optimization conditions, the effect of adding soybean protein on rheology of wheat flour and baking qualities were studied. The main study results were as follows:1 Using in vitro digestibility as the assess index and using quadratic general rotary design, the optimum technological conditions of soybean extrusion cooking were determined: moisture content 35%, extrusion temperature 155℃,feed rate 0.4kg/min, screw speed 150r/min, at this condition, the in vitro digestibility can reach 95.83%.2 Extrusion modification can change the functional qualities of soybean, compared to the soybean protein material, after extrusion, the WHC and OHC increased, but the emulsifying ability and foaming property reduced.3 Extrusion modification can keep the nutritional quality of soybean, after extrusion, the remain rate of available lysine was 86.9%, the remain rate of soybean flavones was 81.6%, the remain rate of soyasaponin was 95.4%, the passivation of urease activity of the product was over 98%.4 Adding extrusion modification soybean effected the rheology of wheat flour and the baking qualities remarkably. As the adding amount increased, the water absorption increased, the developing time of dough increases, the stabilize time of dough lengthened, the anti-extension ability increased and the extension of dough declined; the bread specific volume reduced, the water content and the bread core hardness increase; Adding soybean protein can avoid water movement and delay bread maturing; when the dosage surpass 9%, the sensory quality began to deteriorate, therefore, With our experiment condition the proper dosage of the modified soybean meal is no more than 9%. |
