The Development Of The Product Containing The High Content Of Dendrobium Officinale Polysaccharide And Its In Vitro Hypoglycemic Activities Evaluation

Natural plant polysaccharides have a variety of bioactivities and little side effects.Dendrobium officinale polysaccharide（DOP）has been proved to have the bioactivity in regulating blood glucose.However,due to its high viscosity and poor instant solubility,it has not been applied in the field of functional food.In the food industry,the application of granulation technology in the preparation of polysaccharide products is an effective means to improve the instant solubility of polysaccharide and protect its bioactivities.In this study,DOP was prepared and its extraction rate,molecular weight and dissolution time were determined.In vitro experiments were used to verify its regulating blood glucose activity.The product containing the high content of Dendrobium officinale polysaccharide were prepared by spray drying and wet granulation technology.The yield,polysaccharide content and dissolution time were used as evaluation indexes to select the best products.The activity of regulating blood glucose was tested in vitro and compared with DOP.The main work of this paper is as follows:1.The formulation of large-scale preparation strategy of DOP.DOP was prepared by hot water extraction with solid-liquid ratio of 1:20,extraction temperature of 80℃,and extraction time of 4 h.The yield of DOP was 12.18±0.87%,the weight average molecular weight was 249.3 k Da and the number average molecular weight was 25.3 k Da.However,DOP had a long dissolution time in water（223.69±11.37 s）and poor dispersibility.It is necessary to optimize its instant dissolution effect by granulation to expand its application in the food industry.2.The regulation of blood glucose activity of DOP was verified in vitro.Theα-glucosidase inhibitory activity,the kinetics ofα-glucosidase inhibitory,glucose adsorption capacity,glucose dialysis retardation index andα-amylase inhibitory activity were used to evaluate the regulation of blood glucose activity of DOP in vitro.The results showed that the inhibition rate ofα-glucosidase increased with the increase of DOP concentration in the range of 1-10 mg/m L.When DOP was 10mg/m L,IC₅₀was 4.17 mg/m L,and the inhibition rate was up to 80.87±1.74%（p<0.05）.The kinetic experiments results showed that the inhibition of DOP onα-glucosidase activity belonged to the competitive and non-competitive mixed inhibition type.The results of glucose adsorption capacity measurements showed that glucose adsorption capacity of DOP increased with the increase of glucose concentration in the range of 20-100 mg/m L（p<0.05）.The results of glucose dialysis retardation index measurements showed that the GDRI value of DOP increased rapidly and then decreased gradually within 15-150 min.α-amylase inhibitory activity experiments showed that the inhibition rate of DOP onα-amylase was only43.96±2.84%at the concentration of 10 mg/m L.The above in vitro evaluation methods verified the glucose-regulating activity of DOP.3.Preparation,screening and evaluation of the product containing the high content of Dendrobium officinale polysaccharide.The product containing the high content of Dendrobium officinale polysaccharide were prepared by spray drying（DOP-SD）using maltodextrin,apple fibre,orange peel fibre and Dendrobium officinale fibre as excipients.The product containing the high content of Dendrobium officinale polysaccharide were prepared by wet granulation（DOP-WG）with 30%,50%,70%and 90%volume concentration of ethanol solution as binder,and labeled as DOP-WG-30,DOP-WG-50,DOP-WG-70 and DOP-WG-90,respectively.The yield,polysaccharide content,instant solubility,apparent morphology and solution stability of DOP-SD and DOP-WG were detected.The highest yield of DOP-WG was78.54±1.02%,while the highest yield of DOP-SD was only 50.67±0.50%（p<0.05）.In terms of polysaccharide content,DOP-SD samples had the highest content of35.17±1.51%,while DOP-WG samples had about 70%（p<0.05）.In terms of dissolution time,the shortest in the DOP-WG samples was 60.05±5.02 s,while the shortest in the DOP-SD samples was 169.78±4.23 s（p<0.05）.The experimental results showed that the best product was the product containing the high content of Dendrobium officinale polysaccharide were prepared by wet granulation with 70%volume concentration of ethanol solution as binder.The yield was 78.54±1.02%,the polysaccharide content was 70.85±1.67%,and the dissolution time was 60.05±5.02 s.The above three evaluation indexes showed that DOP-WG were better than DOP-SD.In addition,DOP-WG had better dispersibility than DOP,although the polysaccharide content of DOP-WG was only about 70%.In summary,DOP-WG had the best performance.4.Verification and evaluation of regulating blood glucose activity in vitro of the product containing the high content of Dendrobium officinale polysaccharide.The regulating blood glucose activity of DOP-WG was determined and analyzed byα-glucosidase inhibitory activity,the kinetics ofα-glucosidase inhibitory,glucose adsorption capacity,glucose dialysis retardation index andα-amylase inhibitory activity,and it was compared with DOP.The results showed that the inhibitory effect of samples onα-glucosidase was DOP>DOP-WG-50>DOP-WG-70>DOP-WG-30>DOP-WG-90.The results of kinetic experiments showed that the inhibition type of DOP-WG onα-glucosidase was the same as that of DOP,which belonged to the competitive and non-competitive mixed inhibition type.The results of glucose adsorption capacity and glucose dialysis delay index showed that the glucose adsorption capacity and glucose dialysis retardation index of all DOP-WG samples were lower than those of DOP.DOP-WG-50 and DOP-WG-70 were higher,DOP-WG-30 and DOP-WG-90 were lower.The results ofα-amylase inhibitory activity showed that all DOP-WG samples had lower inhibitory activity than that of DOP.The inhibitory activity of DOP and DOP-WG onα-amylase was lower than that onα-glucosidase under the same conditions.The above results showed that it was feasible to prepare products with good dispersion,high polysaccharide content and bioactivities by wet granulation technology.The product containing the high content of Dendrobium officinale polysaccharide had the potential to become functional food raw materials.This study was of great significance to improve the deep processing technology and comprehensive utilization of resources of Dendrobium officinale.