| Okara, as a byproduct of soy milk, tofu and other soy foods, can be used as a potentialsource of nutrition and health care products because of nutrition value and high protein anddietary fiber content. However, the application and utilization in food of okara is limited forits beany odor, corruption caused by high water content, and poor taste because of high fibercontent. In this study, ultrafine grinding and extrusion-cooking technology were used toimprove eating quality of okara. In addition, the application of the modified products was alsoinvestigated by the evaluation of noodles and cakes added with those okaras.Okara was prepared under different grinding frequency and times, and then the particlesize of the products was studied. More than85%of okara powder in the particle size range of0~40μm was found under the optimal conditions: grinding frequency of80Hz and grindingone time.Functional properties of okara including water solubility, water swelling capacity, waterand oil holding capacity, viscosity and cation exchange capacity were determined. The resultsshow that, ultrafine grinding improves greatly the functional properties of okara.Water-solubility, water swilling capacity, viscosity and cation exchange capacity weresignificantly increased, and under grinding frequency of80Hz the maximum of theseindicators were obtained at34%,12.75mL/g,0.717m2·s-1,0.480meq OH-1·g-1.The qualities of noodles made with the addition of different percentages of okaraprepared under different grinding frequency were measured. The indicators include thenumber of broken noodles, water absorption, cooking loss, sensory quality, TPA texture andtensile property. The results show that ultrafine grinding improves application quality of okarain noodles-the number of broken noodles is less, water absorption and cooking loss are lower,sensory quality is better, and the noodles added with ultrafine-grinding okara is almost nobeany odor. With the addition of the same amount of okara, the total score of sensory qualityof the noodles was found highest with okara powder treated at80Hz. The quality of noodlesmade by adding7.5percentage of80Hz okara powder is similar with traditional noodles.Forexample, no broken noodles, highest water absorption, lowest cooking loss, better TPA texture and tensile property, and more nutritious.Research on the correlation between application in noodles and functional properties ofokara has also been studied. The results show the sensory quality of noodles was negativelycorrelated with oil holding force, positively with and cation exchange capacity of okara,water-soluble and particle size of okara affect greatly water absorption of noodles, oil holdingcapacity. Cation exchange capacity of okara affect greatly on cooking loss of noodles.Okara was extruded under the appropriate conditions, and the functional properties suchas moisture content, water solubility, water holding capacity, water swilling capacity, oilholding capacity, viscosity and cation exchange capacity were measured. The results showthat extrusion technology affects the functional properties of okara to a certain extent. Okaratreated by extrusion under180℃,20Hz of screw speed,20Hz of extrusion feed rate, waterswilling capacity, viscosity, and cation exchange capacity of treated okara increasedrespectively4.5%,12.9%,17.2%compared with untreated okara.Cake was prepared byadding different amount of okara, the qualities of okara such as specific volume, corestructure, taste and appearance of the cake, texture of cake was evaluated by using textureanalyzer. The results show thatextrusion-cooking could reasonably improve applicationquality of okara in cake. The characteristics of those cakes appeared with smaller specificvolume, higher sensory score, smaller hardness, better springness and resilience. In addition,cake is soft with delicate taste and high nutritional value, the highest sensory score is obtainedunder the adding amount of7.5%treated okara. |
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