| Improved extrusion technology(IECT) which was reconstituted from traditional single-screw extruders was designed by our laboratory. IECT can produce texturized rice(TR) and the texture properties of TR was close to polished rice. Using rice starch and a resistant starch(RS) ingredient(High-Maize260, HM) as raw material, TR rich in boiling-stable RS was prepared as staple foods by IECT. The physiochemical properties and edible quality of TR was studied; effect of IECT operating parameters(feed moisture content, screw speed and gelatinization zone temperature) on the RS content and textural properties of TR was studied.TR containing HM and normal rice starch with different proportions were prepared using IECT. Boiling-stable property of resistant starch, swelling power, solubility, hardness, adhesiveness and edible quality of TR were investigated. The results are as follows:(1) The mass fraction of resistant starch in texturized rice, which contained12.5%,25%,37.5%,50%amount of High-maize260, is4.59±0.14%,9.21±0.19%,13.80±0.22%,18.39±0.27%, respectively. The retention rate of resistant starch in texturized rice after cooking was in the range of93.43%-95.37%.(2)Swelling power of texturized rice reduced with the increasing of resistant starch addition, but solubility increased.(3)With the increasing of resistant starch addition, hardness of texturized rice increased, but adhesiveness reduced.(4)An edible quality analysis showed that with resistant starch addition, significant differences were found in the sensory scores of appearance, taste, stickiness, hardness and overall edible quality. When HM addition was25%, texturized rice got the highest edible quality score, even better than transgenic rice containing high amount of resistant starch on edible quality.The content of the amylose of HM is as high as69%, as a result, mixing the exogenous HM with mass fraction of25%into the rice starch with amylose mass faction of14%will significantly increase the content of amylose in the starch system. Moreover, the operating condition of IECT will significantly influence the resistant starch content and textural properties. This article use rotation response surface methodology to study the influence of3main factors for improving extrusion technology—Feed moisture content (26.59-43.41%, wt), screw speed (21.59-38.41rpm), external heating temperature of the gelatinization zone (79.77-130.23℃), on the content of resistance starch of the rice starch and textural properties, and then compare the difference of TR, Youtang rice, Yitang rice and polished rice on resistance starch content, resistant starch cooking retention and texture properties. The results show that in the process of IECT, the moisture content is in positive correlation with the resistance starch content of the texture rice (P＜0.05), The gelatinization zone temperature will significantly reduce the resistance starch content of the texture rice(P<0.05), The screw speed has little impact on the resistance starch content. The optimum conditions for making texture rice with resistance starch using IECT:The additive amount of the high resistance corn starch is25%, the feed moisture content is39.97%, screw speed is25.14r/min, pasting temperature is104℃. The RS content of the texture rice in the optimum condition is11.81%, the retention of resistance starch after cooking is95.93%, the retention of the resistance starch is much higher than the transgenic high resistance rice, the textural properties is slightly better than the transgenic high resistance rice and is slightly worse than the proper polished rice. Preparation process parameters of RS rice were designed and optimized based on IECT to manufacture the products which show the similar taste with natural polished rice and can be used as staple food to meet people with diabetes. |
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