Effects Of Traditional Damp Heat And Microwave Heat Treatment On The Physicochemical Properties Of Coix Seed

Coix seed is its ripe seeds and has high nutritional value and efficacy of health care. Coix seed is one of production and application value of cereals. The starch content of Coix seed were about 60%. Therefore, the changes of the nature of Coix seed directly affect the development and utilization. In the study, the Coix seed starch was preparated by the ultrasonic-microwave synergistic and optimize the process conditions. Then the using the Alkaline protease purified starch. Furthermore, the purified Coix seed starch with different conditions was subjected to traditional heat-moisture and heat-moisture combined with microware treatment. Secondly, the physical and chemical properties of the treated starch were analysed by scanning electron microscopy, X-ray diffraction, fast viscograph, differential scanning calorimetry and other modern instruments on such factors as garanular structure, state of crystallization, viscosity, thermal property and digestibility. The results were showed as follows:The Coix seed starch were extracted by ultrasonic-microwave collaborative. To study the effect of various factors on the starch extraction yield, I optimized the preparation of the Coix seed starch through the response surface method. The optimum conditions were: the material to liquid of 1︰9(g/mL), the mass fraction of NaOH solution of 0.30%, the extraction temperature of 34℃, the microwave power of 134 W and the extraction time of 150 min. The optimal process for the purification of starch by Alkaline protease were: the material to liquid of 1︰5(g/mL), the dose of Alkaline protease was 120 U/mL, the pH was 10, the enzymolysis temperature was 50℃ and the enzymolysis time was 2h.The effect of traditional heat-moisture and heat-moisture combined with microwave of the different processing time, the processing humidity to the physical and chemical properties of the Coix seed starch after purification were studied. The different conditions of treated starch was compared with native starch. The starch garanular structure wasn’t changed, but the potholes appeared. The contents of the amylose starch, the slowly digestible starch(SDS) and the resistant starch(RS) increased, and the pasting temperature and the pasting stability increased. While the transmittance, frozen-thaw stability, solubility, swelling power, viscosity, breakdown value, setback value, gelatinization enthalpy and crystallinity decreased. The influence of humidity on modified starch properties was remarkable. But the different conditions of treated starch maintained the A-type the crystal structures. There were significant correlation between most starch properties and processing time.The traditional heat-moisture and heat-moisture combined with microware treatment could improve the performance of the Coix seed starch. It also improved the digestibility and enhanced the thermal stability of the Coix seed starch. The application of these treatments might promote the accumulation of data physical modified starch, and lay the foundation for the development of Coix seed products.