Research On Preparation Technology Of Yam Powder And Special Medical Staple Food Based On Anti-diabetic Activity

Yam is a traditional medicinal and edible vegetable planted all over China.Because of different climate and soil,the quality of yam varies among different regions.Yam is not easy to store due to its high moisture content.The main way of eating yam is eating it when fresh,and the processing is relatively simple.Yam powder is processed from yam as raw material.The quality of yam powder plays an important role on the quality of subsequent deep processing products.At present,there is a variety of preparation methods for yam powder,but few systematic reports have been published on the effects of different preparation methods on the characteristics of yam powder and few studies have been done on special formula staple foods.Yam has many physiological functions.Much research has been devoted to the effects of yam on diabetes,but most of them are concentrated on yam polysaccharide,the active ingredient in Chinese yam,and few studies have been published on the hypoglycemic effect of yam powder.The main contents and conclusions of this study were as follows:1.To evaluate the quality of 10 species of yam,the physiochemical and digestive properties of these yams were analysed,and one kind of yam variety,suitable for diabetics,was selected using principal component analysis method.Five principal components were extracted by principal component analysis.The variance contribution rates of each principal component were 30.54%,24.81%,19.18%,10.23%,and 8.92%,respectively,and the cumulative contribution rate was 93.683%.The model of principal component composite score was also established.The results showed that Changshanximao yam had the highest score of 1.175,therefore it was selected as the raw material of functional foods for patients with diabetic nephropathy.2.The yam powder was made by hot-air,microwave or freeze drying,combined with ordinary or superfine smashing,and then the physicochemical properties of it were analysed.Results showed that the color of the yam powder from the six processing methods was different.The polarized optical microscopy structure of the starch center had a large shadow and tended to crack after superfine smashing,and the starch granules from superfine smashing had a larger smashing degree than that from ordinary smashing.Comparing the microstructure of yam powder with different processing methods,the yam starch from ordinary smashing adhered to many other components,and the granules were mostly irregular spherical.The yam powder granules from superfine smashing were small,with relatively complete morphology and relatively smooth surface.The X-ray diffraction pattern showed that the yam powder belonged to the C-type starch diffraction peak,and microwave drying could weaken the diffraction peak of yam starch.The contents of fast-digesting starch in the yam powder from the six preparation methods were listed in descending order as follows:MVS,MVO,HAS,FDS,HAO,FDO,while the order of the contents of resistant starch was opposite.The fast-digesting,slow-digesting and resistant starch determine the digestibility of yam powder.The glycemic index sequence of yam powder from different processing methods was MVS>MVO>HAS>FDS>HAO>FDO.3.The yam powder from hot air drying and superfine smashing was selected for the development of specially formulated staple foods suitable for patients with diabetic nephropathy.With sensory score and textural value as evaluation criteria,the ratio of main materials,addition level of yeast and water,and second fermentation time were optimized using response surface method and the modifier formula was optimized using orthogonal test.The optimum condition was as follows:20%of superfined yam powder,20%of wheat flour,37%of potato starch,5%of wheat starch,5%of potato alpha starch,60%of water,1%of yeast,1.5%of baking powder,0.5%of bread improver,0.06%of CMC-Na,0.2%of xanthan gum,0.6%of inulin,0.5%of SSL,15 min of second fermentation time.The results of sensory evaluation and texture profile analysis showed that the sensory score,hardness and chewiness of the low-protein yam steamed bread produced under the optimum condition were approximately 89,1377 g,1125 g,respectively.4.A diabetic model was established by intraperitoneal injection of streptozotocin.Then the effects of yam powder formula feed on the basic indexes(food intake,body weight,mental status,etc.),blood glucose,blood lipids,and pathology of diabetic rats were observed,and the hypoglycemic effect of yam powder was evaluated.The results showed that there was a significant difference in fasting blood glucose among six groups(P<0.05).The fasting blood glucose of the diabetic rats in three groups of yam administration and positive control group was significantly lower than that of the model group(P<0.05).The glycosylated hemoglobin content in the administration group decreased in different degree.There was a significant difference between the normal control group and the diabetic model group(P<0.05),and no significant difference among four administration groups(P>0.05).Compared with the model control group,TC,TG and LDL-C decreased significantly in 30%yam powder group and positive control group,while HDL-C increased significantly(P<0.05).Pathological observation found that the administration group could improve the liver,kidney,and pancreas lesions of diabetic rats to a certain extent,especially 30%yam powder group and positive control group.