| Sorghum[Sorghum bicolor(L.)Moench]is a grain crop widely grown all over the world.It is rich in nutrients and active ingredients,so it has high nutritional and health functions.Starch is the most important component in sorghum grain,it has low digestibility,and can maintain blood sugar stability after consumption,which can be used as the functional raw material of foods for diabetic patients.The properties and functions of sorghum starch have a direct impact on sorghum deep processing.However,domestic research on sorghum starch started late,and there are fewer studies on sorghum starch.Therefore,it is of great significance to in-depth study the properties and functions of sorghum starch in order to make rational use of its edible and nutritive properties,as well as expand the practical application of sorghum.In this study,sorghum was used as raw material,and its starch characteristics were comprehensively studied.The main research contents and results were as follows.1.The relationship between sorghum varieties and qualities was studied,and the special sorghum variety used for diabetics was selected out by principal component analysis.The results showed that:(1)There were certain differences in grain quality,nutritional composition and digestibility of different varieties of sorghum.The sorghum grains in northern area are a little bit larger,while the particles of southern region sorghum are smaller.Starch is the main component of sorghum,and its content is between 65.29%and 72.72%.The amylose content of sorghum varied from 1.38%to 25.98%,and it can hardly be detected in waxy sorghums.In-vitro hydrolysis showed that sorghum had lower digestibility,and its estimated glycemic index was 55.94-63.17,which was within the realm of medium glycemic index food.(2)Principal component analysis found that the main indicators such as rapidly digestible starch,slowly digestible starch,resistant starch,amylose,amylopectin and estimated glycemic index affecting the quality of sorghum.A principal component score model was established to screen out the sorghum cultivars with higher scores.The Jiliang No 1 sorghum was used as a special sorghum cultivar for the subsequent research2.The extraction process of sorghum starch was optimized,and the composite value of sorghum starch extraction rate and sorghum peeling rate was used as the response value.The results showed that:(1)The significant factors affecting starch extraction from sorghum were soaking temperature,soaking time and milling time.(2)According to the response surface method,the optimum technological? conditions for sorghum starch extraction were as follows:soaking temperature 49.62?,soaking time 36.12 min,milling time 8.18 min.Taking into account the conditions of control in the actual operation,the above conditions were further improved:50? for the soaking temperature,36 min for the soaking time and 8 min and 10 s for the milling time.Under these conditions,the extraction rate of sorghum starch was 54.58%,and sorghum peeling rate was 94.29%.(3)The extracted sorghum starch had a good color which was close to white(L*=91.48).The peeling of sorghum improved the appearance quality of the separated starch.3.The physicochemical properties and digestive properties of sorghum starch were studied and compared with corn starch and wheat starch,the results showed that:(1)The amylose content of sorghum starch(28.75%)was significantly higher(P<0.05)than that of corn starch(22.49%)and that of wheat starch.(19.18%).(2)Most of the sorghum starch granules were irregular polygons.The granules had a rough surface and recessed inwards,and had a honeycomb-like structure.Sorghum starch particles size was mostly 15 to 21 ?m,presented a clear cross-polarized structure under a polarizing microscope.(3)X-ray diffraction showed that the sorghum starch was typical of A-type crystal structure with a crystallinity of 31.82%.(4)Differential scanning calorimetry indicated that the gelatinization process of sorghum starch was endothermic and there was a clear endothermic peak between 67.26 and 77.65?.The starch had a higher initial gelatinization temperature and enthalpy.(5)The gelatinization curve of the rapid viscosity analysis showed that the peak viscosity of sorghum starch was 4119 cp,and the viscosity of starch paste was large,which was due to the fact that more amylose in sorghum starch resulted in higher attenuation and rejuvenation values than corn starch and wheat starch.(6)In vitro simulated digestion showed that the hydrolysis curve of sorghum starch presented a slight upward trend compared with that of corn starch and wheat starch,and the digestion rate was slow.The in vivo digestion in mice showed that the postprandial blood glucose change curve caused by sorghum starch was relatively flat,the postprandial blood glucose peak was smaller,and the time to reach the peak was later.Human digestion showed that sorghum starch had a lower glycemic index(GI=58.14),which had less effect on postprandial blood glucose.4.The effects of sorghum starch on diabetes in db/db mice were studied,and the results showed that:(1)After db/db mice were fed with sorghum starch for 8 weeks,their weight could be significantly reduced(P<0.05)and their obesity could be effectively hindered.(2)Sorghum starch intervention could obviously reduce the fasting blood glucose level and fasting serum insulin level in diabetic mice and improve insulin sensitivity(P<0.05).The serum levels of total cholesterol,triglyceride,and low-density lipoprotein cholesterol were distinctly lower(P<0.05)in db/db mice fed with sorghum starch for a long time.Sorghum starch could effectively improve the disorder of glucose and lipid metabolism in diabetic mice.(3)HE staining results showed that the sorghum starch intervention could visibly improve the structure and morphology abnormalities of liver and kidney in db/db mice,relieved the damage degree of liver and kidney,and reduced the accumulation of abdominal fat in db/db mice. |
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