Effects Of Ultra-High Pressure On Buckwheat Starch Granule Structure And Pasting Properties

Buckwheat has high nutritional and pharmaceutical value,buckwheat and its processing products have a broad market prospect and high economic value.The main composition of buckwheat is starch,the quality of buckwheat product was directly influenced by the physical and chemical characteristics of buckwheat starch.Superhigh pressure technology was a wide-used new technology in food processing.For understanding the effects of ultra-high pressure on buckwheat Starch,the influecnes of different pressure treatment,different keeping temperature and time on buckwheat starch granule structure and pasting properties were studied in the paper.The results are as follows:(1) The starch granule structure was changed by the ultra-high pressurization,and it was subjected to different degree of damage,the surface of starch granule was depressed and deformed inward,polarization cross disappeared gradually.Above the pressure of 300 Mpa the surface of buckwheat starch granule depressed inward,above 400 Mpa the starch granule was extruded into bulk and sheet.The change of starch granule structure would direct influence on the physical and chemical characteristics of buckwheat starch.(2) With the increase of pressure,the peak viscosity,viscosity at the biginning of 93℃holding period,viscosity at the beginning of 93℃cooling period,viscosity of final cooling period,and the viscosity at the end of 50℃holding period of buckwheat starch, were all declined.The breakdown can reach the peak value dealing with 10 min of 500 Mpa or 20 min of 400 Mpa in normal temperature,the pasting degree reach the maximal,and even the pressure was increased to 600 Mpa,it still can not make the buckwheat starch throughly pasting.The thermal stability,cold stability and retrogradation of buckwheat starch were improved under 500 Mpa dealing with 10 min in normal temperature,300～400 Mpa dealing with 20 min in normal temperature,200～300 Mpa dealing with 20 min in 40℃or 200 Mpa dealing with 20 min in 60℃above.(3) Under the condition of the same pressure and keeping temperature,the pasting temperature,peak viscosity,viscosity at the biginning of holding period,viscosity at the beginning of cooling period,viscosity of final cooling period,and the viscosity at the end of 50℃holding period of buckwheat starch,were all improved as the extension of keeping time.The longer the keeping time was,the more change would happen on the morphology and structure of buckwheat starch granule,thus generated effect on other characteristics such as heat stability and cold stability of viscosity.(4) The keeping temperature was closer to the pasting temperature of buckwheat starch, the demand of the pressure level making them gelatinized was lower,that is to say,the higher pressure,the lower correspond initial pasting temperature.(5) The increase of ultra-high pressure and extension of keeping time can decline the transmittance,retrogradation value and improve anti-retrograding performance of buckwheat starch paste from Shaanbei area.The transmittance and retrogradation value of the Zefa starch, increased at first then decreased as the pressure increased,and increased constantly as the extension of keeping time.High keeping temperature can decline the transmittance,increase retrogradation,and decline anti-retrograding performance.