| In recent years,the number of patients with diabetes has continued to grow and showed a rapid growth trend as a whole.There is no effective method to cure it in clinical practice.In clinical practice,patients’blood sugar is mainly controlled through insulin injection and other drug treatments.Research has confirmed that changing the daily dietary structure can prevent and control elevated blood sugar,and is an effective self-care method.Colored rice is rich in bioactive substances,which have high edible value and health benefits.Qiongbei red rice is an indispensable member of China’s colored rice resources,but there are no reports on its hypoglycemic activity and development and utilization.This experiment systematically studied the slow digestion effect of red rice pigment on starch by optimizing the extraction of Qiongbei red rice pigment,providing theoretical support for the subsequent preparation of recombinant red rice with low GI extrusion.In this paper,red rice is provided by Hainan Jingyi Agriculture.The main conclusions are as follows:Firstly,the optimum extraction process and components of Qiongbei red rice pigment were studied.According to the analysis of the ultraviolet spectrum of red rice pigment,the characteristic absorption peak of Qiongbei red rice pigment exists at 280 nm,and does not appear at 530 nm,which conforms to the red rice type with proanthocyanidins as the main colorant.On the basis of single factor,by using Box-Behnken response surface experiment to optimize the pigment extraction process,the optimal extraction process of red rice pigment is obtained as follows:extraction time 95 min,extraction temperature 50℃,ethanol concentration 75%,material-liquid ratio 1:20 g·m L-1.Under this extraction condition,the yield of red rice pigment was 6.22±0.13 mg·g-1,higher than 4.37±0.02 mg·g-1 of red rice in Harbin Zhonghe Town,and the error was 1.47%compared with the predicted value,which proved that the extraction process was reliable.The crude extract of red rice pigment was refined with AB-8 resin.The refining conditions were as follows:the volume of water washing was 2 BV,the eluent was 70%ethanol,and the elution volume was 3 BV.The purity of red rice pigment after purification was 74.53±2.79%.According to the analysis of ultraviolet spectrum and infrared spectrum,the proanthocyanidins of red rice pigment is a proanthocyanidins polymer with（epi）catechin as the structural unit.The red rice pigment was further detected and analyzed by HPLC-MS/MS technology,and quercetin,（epi）catechin,（epi）gallocatechin,type B proanthocyanidins dimer,type C proanthocyanidins trimer,and type A proanthocyanidins dimer were detected.Secondly,the effects of red rice pigment on the physicochemical properties and in vitro digestion properties of starch were studied.Through the experiments of iodometry,scanning electron microscope（SEM）and rapid viscosity analysis（RVA）,it is known that the red rice pigment combines with starch through non-covalent interaction,disrupts the arrangement and position distribution of the original starch chain,destroys the crystal structure of starch particles,and thus affects the digestibility of starch.The presence of red rice pigment could inhibit the hydrolysis rate of starch in vitro.When the pigment content increased from 0%to1%,the content of fast digestible starch（RDS）decreased from 42.41%to 28.27%,the content of resistant starch（RS）increased from 48.11%to 63.71%,the hydrolysis sensitive value（k）decreased,and the predicted glycemic index（p GI）of starch decreased from 94.40%to 73.81%.The results showed that red rice pigment could reduce the sensitivity of starch to starch hydrolase.Then,study the effect of red rice pigment onα-Amylase andα-Effect of glucosidase activity.Red rice pigment pairα-Amylase andα-The inhibition types of glucosidase activity were competitive inhibition and mixed inhibition,with IC50 values of 0.927 mg·m L-1 and1.669 mg·m L-1,respectively.The results of UV spectrum and fluorescence spectrum showed that with the increase of the concentration of red rice pigment,the UV absorption intensity of starch digestive enzyme also increased correspondingly,and there was a redshift phenomenon;The fluorescence intensity of starch digestive enzyme decreased accordingly,and the fluorescence quenching ofα-amylase andα-glucosidase by red rice pigment was static quenching and dynamic quenching,respectively.The results of circular dichroism and molecular docking experiments show that red rice pigment can combine with the amino acid residues in the enzyme protein,change the secondary structure and microenvironment of the starch digestive enzyme,resulting in poor conformational stability,increase the probability of wrong folding of the peptide chain,and then inhibit the activity of the starch digestive enzyme.Finally,the Qiongbei red rice was extruded and recombined by twin-screw extrusion technology.The extrusion parameters are set as follows:the temperature of zone I,II and III is 40,80 and 100℃respectively,the host frequency is 15 HZ,the feeding frequency is 10 HZ,and the cutting frequency is 9 HZ.Due to the poor appearance,grain shape,bulk weight,and cooking index of the recombinant red rice obtained by extrusion according to Formula three,its color is graying,and its paste degree is low,so Formula three is eliminated.Subsequent experiments found that the gelatinization characteristics of extruded recombinant red rice were lower than those of Qiongbei red rice,and the indicators of recombinant red rice obtained by extrusion according to formula one were lower than those of formula two.Extrusion recombination can improve the disadvantages of Qiongbei red rice,such as hard taste,poor elasticity,and adhesion.The rheological properties of the samples showed that the starch paste of the recombinant red rice was easy to form an elastic gel structure,and the viscoelasticity of the recombinant red rice extruded according to the two formulas was similar.The results of in vitro digestion and sensory evaluation showed that the hydrolysis rate of recombinant red rice was lower than that of Qiongbei red rice,and the RS content increased,while the RDS content of starch decreased.At the same time,the GI values of the recombinant red rice obtained by extrusion according to Formula one and Formula two were 64.92 and 50.88,respectively,and there was no significant difference in sensory evaluation scores between the two.Formula two reconstituted red rice meets the requirements of grain shape,cooking and eating quality and low GI,and has the potential to be eaten by patients with diabetes.Therefore,Formula two is the optimal formula for reconstituted red rice. |
PDF Full Text Request