| Starch is one of the richest macromolecule carbohydrates of the nature, and it has been widely used in the areas of food, paper-making, textile, architecture, medicine, petrochemical industry and so on. Starch is widely distributed in plants and its content varied with breed,weather,soil and other vegetal conditions. Starch often consists of amylase and amylopectin, but waxy starch has special structure, scarcely containing amylase (the amylase content≤4%). Waxy rice starch and waxy corn starch were chosen as the experiments materials in this paper, and the granule structure, molecular structure, and the change law of the physico-chemical properties after HPM treatment was studied, and initial approach was carried out to study the mechanism of HPM modification. The results were as follows:(1) Effect of HPM treatment on the granule structure of waxy starch: as the pressure increased, the starch granules were crashed to irregular small granules, its granularity decreased to a great extent, after 160MPa HPM treatment , the average granularity of waxy rice starch decreased from 3912.7nm to 429.1nm, and the waxy corn starch decreased from 11139.3nm to 700.8nm, and the corresponding specific surface area increased; the polarimetric crosses of starch disappeared gradually and the X-ray diffraction intensity of starch weakened after HPM treatment.(2) Effect of HPM treatment on molecular structure of waxy starch: as the pressure increased, the amylopectin content of waxy starch decreased; the average molecular weight reduced; after the infrared determination, it showed that when the pressure increased to a certain value, the absorption peak disappeared when the wavenumber was 857.7cm-1, and the absorption peak of some special functional group showed a blue shift.(3) Effect of HPM treatment on the physico-chemical properties of waxy starch: waxy rice starch and waxy corn starch had higher swelling power and moisture absorption, belonging to non-Newtonian fluid, with pseudoplastic fluid characters. With the HPM pressure increased, the swelling power of waxy starch increased, and the solubility and moisture absorption increased sharply at first, and then the tendency of increasing gradually tended to be gentle when the pressure increased to a certain value; HPM treatment made the characteristics of starch paste tend to be Newtonian fluid, with good fluidity; HPM treatment also changed the thermal characteristic of the starch paste, both the gelatinization temperature and the crystal melting transition temperature reduced ; the transparency of the starch paste increased and the sedimentation volume reduced; the freeze thawing stability changed little; the determination of the iodine blue value showed that HPM treatment could lower the iodine blue value of waxy starch.(4) A preliminary study on the mechanism of HPM modification on waxy starch showed that HPM treatment could change the apparent structure and molecular structure of starch granules. The physico-chemical properties changed due to the granules surface blemishing, the granularity decreasing, the specific surface area increasing, the crystal structure being destroyed, the amylopectin content decreasing, the molecular weight reducing, the functional group changing and so on.
|
PDF Full Text Request