为了研究不同干燥条件对白魔芋精粉性质的影响,该研究以新鲜白魔芋为原料,探讨自然干燥、真空冷冻干燥、热风干燥(低温干燥、高温干燥、分段干燥)5种不同的干燥条件对白魔芋精粉色泽、魔芋葡甘聚糖(konjac glucomannan,KGM)含量、乙酰基含量、流变学性质等特性的影响,并通过分子质量、红外光谱(Fourier transform infrared spectrometer,FT-IR)、X-衍射(X-ray diffraction,XRD)、扫描电镜(scanning electron microscope,SEM)进行结构表征。结果表明,自然干燥效率低,所得样品品质较差,真空冷冻干燥虽然能得到较高品质的样品,但对设备要求比较高,干燥效率低。综合考虑,使用100 ℃→60 ℃的热风分段干燥为最佳方法,此时得到的魔芋精粉KGM含量为64.63%、乙酰基含量为23.49%、分子质量为1 102 kDa、色泽较好、结晶度高、颗粒完整且表面光滑,所得水溶胶具有较好的流变学性质。综上,分段干燥方式可以用于白魔芋及其他魔芋的干燥中,所得的魔芋精粉品质良好,为白魔芋的开发应用及干燥工艺提供一定的理论参考。
To study the effects of different drying conditions on the properties of white konjac powder and provide theoretical basis and data support for optimizing the drying process of konjac, fresh white konjac was used as a raw material in this study.The effects of natural drying, vacuum freeze-drying, and hot air drying (low, high, and segwise temperature) on the color, konjac glucomannan (KGM) content, acetyl content, and rheological properties of the white konjac powder were investigated.The structure of the powder was characterized by molecular weight, Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), and scanning electron microscope (SEM).Results showed that the natural drying efficiency was lower and the quality of the samples was the poorest.Although vacuum freeze-drying could get the best quality samples, it required higher equipment and the drying efficiency was lower.In general, the best method was to use hot air drying at 100 ℃→60 ℃.At this time, the KGM content of konjac powder was 64.63%, the acetyl content was 23.49%, the molecular weight was 1 102 kDa, the color was good, the crystallinity was high, the particle was complete and the surface was smooth, and the hydrosols obtained had good rheological properties.In conclusion, the piecewise drying method can be used in the drying of white konjac and other konjac, and the obtained konjac powder was of good quality, which is expected to provide a certain theoretical reference for the development and application of konjac and the drying process.
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