Study On Effects Of Ultrasonic Treatment On Castanea Henryi Starch Properties And Preparation Of Porous Starch

Castanea henryi is the advantage resources of Fujian province. Castanea henryi is perishable and its storage conditions is strict.There is a great significance of making the most of it. Castanea henryi has high starch content, and the starch is of higher quality with white color. It is of smaller granule and higher amylose content compared to another starch. However, due to the variety of starch research is less, the application of starch has limitations. In recent years, many varieties of starch start to research and improve the applicability of starch processing. So we take the different modified methods to change the character of starch to meet the different needs. Ultrasound is a kind of physical energy. As ultrasound technology spread, they are finding increasing use in food industry for modification of starch.In this paper, the raw material was Castanea henryi, the research object was its starch and ultrasonic was the form of treatment. To determine physicochemical properties and structural characters, we explored their properties of transparency, retrogradation, freeze-thaw stability, gel texture properties, crystal structure and granular structure. The preparation methods for porous starch using ultrasonic-assisted enzymatic extraction method were presented.(1) Physicochemical propertiesThe impact of the ultrasonic power and ultrasonic time were explored on properties of transparency, retrogradation, freeze-thaw stability and gel texture properties. Results showed that, transparency of starch firstly increased and then decreased, with the increased of ultrasonic power and ultrasonic time. Starch pastes presented greater transparency when samples were treated by ultrasonic wave for 240 w、30 minutes. The condensation speed of starch pastes was decreased and its retrogradation was increased after ultrasonic concentration; Freeze-thaw stability firstly decreased and then increased, with the increased of ultrasonic power and ultrasonic time. After ultrasonic concentration, the bleeding ratio of starch plates was decreased. The gel strength of starch plates was decreased with the increased of ultrasonic power and ultrasonic time.(2) ReologyThe reological mode, thixotropy and the apparent viscosity of starch were studied by rheometer. Results showed that, before and after ultrasonic treatment, the starch of Castanea henryi showed the characteristics of non-Newtonian fluid and belonged to yield-pseudoplastic fluid. The treatment of ultrasonic has been changed the thixotropy of starch. Under certain conditions of ultrasonic, the starch showed low thixotropy. However, the thixotropy of starch pastes rised slightly with the increased of ultrasonic power and time. The apparent viscosity of starch plates showed a trend of fluctuation with increasing ultrasound power and time. The apparent viscosity of the starch was decreased with low power ultrasonic and short time ultrasonic, but was increased with high power ultrasonic and short time ultrasonic. The apparent viscosity was higher than the raw starch when ultrasound power was 160 w and ultrasound time was 20 min.(3) Crystal structureThe crystal structure of Castanea henryi starch was determined using the infrared-spectrum and scanning electron microscope. Results showed that, Ultrasonic wave wouldn’t destroyed functional groups of starch, but damaged crystal structure; crystallinity decreased; reaction activity was improved; the surface and interior of the granule was damaged; the surface of the granule became rough and formed some craters, and its surface area became larger.(4) Thermodynamic propertiesThe temperature and enthalpy of gelatinization were studied by differential scanning calorimetry (DSC). Results showed that, the gelatinization temperature (TO, TP, TC) of ultrasound starch was higher than raw starch, this showed that relatively weak crystal structure of starch granules was destroyed by ultrasonic; the temperature differential between the TC and TO was lower than raw starch, this showed that the different stability of the crystals was destroyed by ultrasonic with degrading starch molecular weight; the enthalpy of starch was decreased, since double helix structure of crystallinity and amorphousarea was weakened or destroyed.(5) Porous starchThe impact of five factors (ultrasonic power, ultrasonic time, ratio of enzyme, enzyme concentration, enzymolysis time) were explored on forming holes of porous starch; the main technical parameters were studied by response surface on the basis of one factor test. Results showed that, the oil-absorption rate of starch was high when it was under this process conditions—ultrasonic power 320 w, ultrasonic time 30 min and Enzyme loading 2.2%.