Study On The Extraction Of Sweet Potato Dietary Fiber And Its Prevention, Treatment Effect On Obesity Of Wistar Rat

Sweet potato is one of the main crops planted in china. At present, the primary processed goods ofsweet potato are starch and starchy food production in our country. However, the industrial processingof sweet potato starch generates a high-volume, low-value sweet potato residue (SPR) which containsrich source of biologically functional dietary fiber and a lot of residual starch. Traditionally, SPR wasdiscarded or used as animal feed, which which leads to serious environmental pollution ans waste ofresources. In my study, SPR was used as raw material to extact sweet potato dietary fiber (SPDF). Theextraction method, physic-chemical properties, functional properities and the prevention and treatmentto obesity of SPDF were discussed in my research, with the purpose to provide theoretical basis for theeffective use of SPR and the development of SPDF health food.Mechanical screening method was used to remove the embedding starch and extract SPDF fromSPR. SPR was crushed by three kinds of mechanical equipment-ultrasonic cell disrupter, homogenizerand high pressure homogenizer, and then screened. Three kinds of sweet potato dietary fibers (SPDFs)were obtained and the composition, physicochemical properties and functional properties thereof wereinvestigated. Results showed that dietary fiber composition of three SPDFs had no significantlydifferences, but SPDF crushed by high pressure homogenizer had the highest purity of78.8%and thesmallest D4,3of21.88μm. In addition, SPDF crushed by high pressure homogenizer also exhibited thehighest α-Amylase inhibitory ratio and pancreatic lipase inhibitory ratio, which were16.34%and18.29%, respectively.Thermostable α-amylase method was used to hydrolyze starch and extract SPDF. The parametersof thermostable α-amylase method to extract SPDF were optimized by Box-behnken experiment. Thestudy also evaluated the two kinds of SPDFs extracted by thermostable α-amylase method under theoptimum process parameters and AOAC991.43method, respectively. The results showed that: whenthe liquid-solid ratio was23mL/g, dosage of thermostable α-amylase was12.5μl/g, enzymatic time was25min and enzymatic temperature was82°C, the starch could be almost removed, and its purity had nosignificant difference compared with the SPDF extracted by AOAC991.43method. In addition, SPDFextracted thermostable α-amylase method also exhibited the higher swelling capacity, glucose absorpti-on capacity, α-amylase activity inhibitory ratio and pancreatic lipase activity inhibitory ratio, but lowerwater holding capacity, oil holding capacity and emulsitying activity than SPDF extracted by AOACmethod.Thermostable α-amylase method of extracting SPDF was selected to conduct pilot scale test in thepaper. The reason was that: the purity of SPDF extracted by thermostable α-amylase method was89.64%which was higher than the SPDF extracted by mechanical screening method; SPDF extracted bythermostable α-amylase method also showed higher water holding capacity, oil holding capacity,swelling capacity, glucose absorption capacity, α-amylase activity inhibitory ratio and pancreatic lipaseactivity inhibitory ratio. The specific technological parameter of SPDF extraction by thermostableα-amylase method in pilot scale test was: the liquid-solid ratio was10-11mL/g, dosage of thermostable α-amylase was4.17mL/kg, enzymatic temperature was90°C and enzymatic time was15min. Followingthese parameters, the purity of the SPDF in pilot scale test was87.33%.At last, Wistar rat was used as experimental animals. The study discussed the prevention andtreatment of SPDF to obesity according to the analysis of body weight, food consumption, plasma andliver index, content of short chain fatty acid in cecum. The result showed that:6%and10%SPDF-supplemented diet could lose weight and prevent and treat dyslipidemia and pathoglycemia;10%SPDF-supplemented diet could improve the sensitivity of insulin and leptin, and also could increade thecontent of the insulin stimulation hormone, such as adiponectin and glucagon-like peptide;SPDF-supplemented diet could also decrease the level of inflammatory factors in plasma, such as freefatty acid (FFA), tumor necrosis factor-α (TNF-α), interleukin-6(IL-6). Meanwhile, the result showedthat SPDF-supplemented diet could decrease the content of liver lipid which presented negativecorrelation to the dosage of SPDF. Live pathology slices also showed that SPDF-supplemented dietcould prevent and treat cell denaturation of Wistar rat’s liver, and reduce the degree of fatty liver. Inaddition, through the analysis of the content of short chain fatty acid in crcum, it was interesting to findthat the dosage of SPDF-supplemented diet has an apparent correlation to the content of acetic acid,propionic acid and butyrate acid in crcum, which may be the mechanism of prevention and treatment ofSPDF to obesity. Therefore, future research should focus on the relationship between short chain fattyacids and the pathogenesis of obesity.