木薯淀粉制备热转化糊精及其特性研究

Preparation and characteristics of pyroconversion dextrin from tapioca starch

为了探究淀粉在热转化过程中的变化,以木薯淀粉(TS)为原料、盐酸为催化剂、膳食纤维含量和白度为评价指标,使用干法制备热转化糊精(PD)。通过单因素试验和正交优化试验确定PD的最佳工艺条件,并对其理化特性进行研究。结果表明:在热转化温度170℃、热转化时间150 min、盐酸用量14%的条件下制备的PD膳食纤维含量为60.79%,白度为45.27,此时PD在冷水中的溶解度为93.81%。与TS的溶解度相比,最优条件下制备的PD冷水溶解度显著增加。在光学显微镜下观察,PD为黄色的颗粒且形态保持完整,但偏光十字现象减弱。X-射线衍射结果显示,TS在热转化过程中的结晶结构被破坏,相对结晶度由29.41%降低到9.48%。以还原糖含量变化反映PD的酸热稳定性,当加热(85℃/0.5 h)时,PD仅在pH为1溶液中的还原糖含量最高,为13.25%;室温条件下贮藏(25℃/24 h)时,PD在pH值为1~7溶液中的还原糖含量的增加量小于1%;加热(85℃/0.5 h)时,PD在pH值为2~7的溶液中的还原糖含量的增加也在1%内。

To explore the changes of starch in pyroconversion process,pyroconversion dextrin(PD)was prepared from tapioca starch(TS)under the catalysis of hydrochloric acid by dry method.The optimal preparation process of PD was obtained by single factor and orthogonal test based on the indicators of dietary fiber content and whiteness.The properties including morphology,solubility,crystallinity,and acid-thermal stability of PD were determined.The results showed that the dietary fiber content of PD was 60.79%,whiteness was 45.27,and solubility in cold water was 93.81%at the pyroconversion temperature of 170℃,the pyroconversion time of 150 min and the addition amount of hydrochloric acid of 14%.Compared with the solubility of native starch,the cold-water-solubility of PD was significantly improved.Microscopy characterization showed that PD from TS performed a yellow color and its granule morphology remained intact in 100%glycerol.In addition,the birefringence of PD was weaker than that of TS.The relative crystallinity decreased from 29.41%(TS)to 9.48%(PD).The results of X-ray diffraction revealed that crystal structure of TS was destroyed by pyroconversion.The acid-thermal stability of PD was reflected by the change of reducing sugar content.The increase of reducing sugar content was less than 1%when PD was stored(25℃/24 h)at pH 1-7 and heated(85℃/0.5 h)at pH 2-7.The change of reducing sugars content was in the range of 1%when PD was stored(25℃/24 h)at pH 1-7 and heated(85℃/0.5 h)at pH 2-7.