Research On Gelatinization And Retrogradation Properties Of Restructuring Brown Rice

Based on brown rice powder as raw material,different gelatinization degree of brown rice treated by twin-screw extrusion were investigated.The main results of the experiments were as follows:(1) After the extrusion process,the main components of the brown rice were changed.Starch、protein、fat、ash content and the content of soluble reducing sugar were decreased in different degrees.Scanning electron microscopy(SEM) results showed that the rice starch granule surface was rough,with regular appearance,but there were no full of starch granules after squeezing.And the greater the degree of gelatinization,the larger the surface was damaged.The hold strength、final viscosity and setback of brown rice were significantly higher than restructuring groups(P<0.01), the peak time was significantly lower than the restructuring groups(P<0.01),but cold peak and breakdown had no significant difference(P>0.05).DSC results showed that the heat enthalpy value reduced with the increase of gelatinization degree.X- ray diffraction analysis method was used to determine the changes of crystal structure of starch granules. The characteristic peaks of starch by extrusion process was destroyed,and the crystalline region suffered serious damage.Gelatinization degree and fat content,ash content,reducing sugar content was significantly negative correlated(P<0.05). The gelatinization degree remarkably influenced on the content of fat,but not significantly correlated with the content of starch and protein(P>0.05).Gelatinization degree of samples and cold peak、raw peak、 breakdown and peak time of RVA was very significant(P<0.01),and was significantly negatively correlated with the hold strength、final viscosity and setback(P< 0.05),while the peak area was not significant(P >0.05).Gelatinization degree of samples and DSC,the correlation among the characteristic value difference was small.There was a very significant negative correlation(P<0.01) between gelatinization degree and heat enthalpy, but the initial temperature、peak temperature and final temperature was not significant(P> 0.05).(2) The amylose content significantly effected on the Avrami parameter n(P<0.01),while the maximum degree of retrogradation of amylopectin was no significant effect(P > 0.05).At the same time,there was significant negative correlation between the parameter n and the growth rate of K(P <0.01),indicating the formation of crystal nucleus and the slower,more dispersed(n more),the rate of crystal growt was small(less K).The maximum degree of retrogradation and crystal growth rate of K was significant negative correlation(P<0.05),indicating the growth rate was slower,the higher the maximum degree of retrogradation.(3) In order to get the linear regression equation of classical gelatinization degreee,the rapid detection method of gelatinization degree of rice starch was discussed,the relationship between classical enzymatic starch gelatinization degree and eight RVA feature and four DSC feature values were established by using the statistical software SPSS.Two equations were followed:classical gelatinization degree=-112.199+0.654 ×cold peak+0.105×raw peak-0.081×hold strength-0.183×break down-0.063×final viscsity +0.060 ×setback+23.810×peak time +0.087 ×peak area;classical gelatinization degree=152.982-0.171×initial temperature+0.243×peak temperature-0.637×final temperature-18.538×enthalpy value.