| Konjac Glucomannan (referred to KGM) is a water-soluble, high molecular weight polysaccharide, consisting in a kind of taro tube. It has many useful functions such as anti-tumor, improve the immunity et al. Changes in the structure of KGM is its performance reasons for its biological activity. Its formation mechanism and stability haven't been discussed deeply, and furthermore, the formation rule and stability mechanism under different environments also haven't been studied. It has become a barrier for deeply development and biological function regulation of Konjac glucomannan.In this thesis, we attempt to study the KGM for pure and KGM in two physical fields:high voltage pulsed electric fields and ultra-high static field. The structure and structural stability of KGM were studied, which was aimed at providing structural basis of theory for activity regulation of KGM designed to address the biological functions. In this thesis, the main results were as follows:1. Structural characterization of pure KGM Structural characterization(1) In this chapter, the untreated pure KGM were characteried by using infrared spectra, Raman spectra,χ-ray diffraction, scanning electron micrographs. The results were showed that KGM was solid fibers with a regular chain morphology in pure. There were a large number of hydrogen bonds in KGM, andχ-ray diffraction pattern showed the formation of KGM was not stable crystalline solid, but as there was no fixed form, which was consistent with the general literature;(2) TEM figure showed that KGM in solution formed a large number of molecular chains of hydrogen bonds in order to maintain the state of KGM gel in solution, and the size of KGM gel was hundreds nanometer;(3) In order to understand details of KGM, KGM were hydrolyzed byβ-mannase, but the results showed: pure short molecular chains of KGM were not achieved because of large molecular chain and unregularity of repeating unit. All the hydrolysis products were showed as a mixture. It was showed difficultly to achieve pure chain by using phase separation. At the same time because the molecular weight was too large, the current LC-MS technique was difficult to accurately determine its molecular weight.2. Study on the structural stability of KGM treated by high-voltage pulsed electric field(1) Two kinds of high voltage pulsed electric field treatment were used such as 500V and 1000V. KGM treated by PEF were characterized by using infrared spectra, Raman spectra, x-ray diffraction, scanning electron micrographs. Experiment results showed that high-voltage pulsed electric field on solid state KGM fiber chain was not destroyed from the original structure. However, hydrogen bonds might be due to be weakened for resulting in IR and Raman spectroscopy there had been some small changes.2) DSC study on KGM treated by PEF showed that pulsed electric field treatment on the thermal properties of KGM had no significant effect.(3) PEF is the rapid development of a physical approach, this study was providing a theoretical basis to in-depth study of the structure and properties of KGM providing a useful reference particularly associated with the food KGM processing physical fields.3. Study on the structural stability of KGM treated by ultra-high pressure(1) Three kinds of high static pressure processing (100Mpa,300Mpa,500Mpa) were used. KGM treated by UHP were characterized by using Raman spectra,χ-ray diffraction, scanning electron micrographs. Experiment results showed that high-voltage pulsed electric field on solid state KGM fiber chain was destroyed from the original structure. However, hydrogen bonds might be due to be weakened for resulting in IR and Raman spectroscopy there had been some small changes. Experiments showed that the solid state pressure on the existing laws of KGM fiber chain had been destroyed. Under high pressure, the rules of electron microscopy images showed different degrees of fiber chain fracture occurred. However, because KGM molecular chain was long enough, it was also showed as small gel particle with intra-molecular and the formation of hydrogen bonds in the TEM figure.(2) DSC studying on KGM treated by PEF showed that ultra-high pressure treatment on the thermal properties of KGM had some significant effect. Treating for 100Mpa and 500Mpa 20 minutes showed significant effect.(3) The rheological properties study of KGM treated by ultra-high pressure also had significant effects. The processing pressure showed a stronger effect than the processing time. When KGM was treated by 100Mpa processing, the rheological properties significantly changed, the viscosity was significantly decreased and the shear force variation showed the same. With the increase of pressure, the parameter indexes were all picked up. The macroscopic properties and microscopic structure of KGM were studied, which would provides a useful reference and inspiration to in-depth study of the structure and properties of KGM especially for food-related processing such as physical fields to provide a theoretical basis.4. Study on KGM Structure and Stability by using Fluorescent probe(1) This was firstly proposed in the KGM system by added fluorescent probes to study KGM aggregation states in solution and the fluorescence quenching. This study provided a new way of thinking for other polysaccharide structure and their solution properties.(2) KGM treated by high hydrostatic form of the solution was studied by fluorescence probe technique and the results were similar with rheological properties. When treated by 100Mpa, KGM molecular chain was changed obviously on the show that the fluorescence intensity tended to increase.(3) The experimental results showed that it was feasible for the fluorescent probe introduced into the structure and stability of KGM, and because the fluorescence analysis was rapid, highly sensitive, low cost. This new structure study could be conducted in the promotion of some other polysaccharide.
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