| Both of the harvest area and total production quantity of sweet potato in china are the highestin the world (FAO,2008). At present, the major commercial utilization of sweet potatoes in chinais starch and starchy food production, which generates a huge volume of proteinous residue duringstarch processing. Because the domestic and international research on the nutritional andprocessing characteristics of sweet potato protein is still at a basic level, sweet potato protein (SPP)has not yet been developed and utilized. SPP has been directly discharged into the environment,not only cause a waste of protein resources, but also cause environmental pollution. Therefore, thisstudy intends to isolate and extract SPP from sweet potato starch processing, as well as launch anin-depth study of the nutritional properties and processing characteristics of SPP. The aim of thisstudy is to provide a theoretical basis for the effective and rational use of SPP and development ofnew protein resources.Firstly, amino acid composition, digestion and anti-nutritional properties of the native SPPwere studied. The results showed that the native SPP contained18kinds of amino acids which arehuman body needs, but was deficient in lysine. In vitro digestibility of native SPP just reached to52.9%, which was significantly lower than that of soy protein isolate (92.3%) and whey proteinisolates (97.0%). In vivo digestion experiment results showed that native Sporamin A and B couldnot be digested in the rat stomach, but be completely digested in the intestine of the rat. Thedigestion of Sporamin B was better than Sporamin A in the rat stomach. In addition, native SPPhad a high level of trypsin inhibitory activity (67.84±2.60mg trypsin/g protein).Heat treatment could significantly improve in vitro digestibility of SPP and reduce its trypsininhibitory activity. In vitro digestibility of SPP was increased significantly with the increasedheating temperature (40-127°C) and heating time (0-60min). Trypsin inhibitor activity of SPPwas reduced significantly with increased heating temperature and the heating time. Autoclaving(127°C,0.145MPa,20min) was the most effective method to improve digestibility of SPP andreduce its trypsin inhibitor activity. In reverse, high pressure treatment did not significantlyimprove in vitro digestibility of SPP and reduce its trypsin inhibitory activity.In order to investigate the influence mechanism of heat treatment and high pressure treatmenton digestibility of SPP, the structural changes of SPP before and after heat treatment and pressuretreatment were analysised by DSC, FT-IR, CD and SDS-PAGE. The results showed that both ofheat treatment and high pressure treatment reduced the thermal stability and changed the secondstructure of SPP. After autoclaving, α-helix and β-turn structure contents of SPP increased, and itsβ-sheet structure content decreased. But after high pressure treatment, α-helix and random coilstructure of SPP reduced, and its β-sheet structure increased. The structure changes of SPP mightbe the main influence facor for its digestibility. Finally, the rat balance test was used to confirm the authenticity of aboved in vitro results.The results confirmed that autoclaving can effectively improve the nutritional value of SPP. Thetrue digestibility of SPP was improved from50.4%to95.1%and the PDCAAS value increasedfrom0.36to0.66after autoclaving. Furthermore, the internal organs of the rats had nopathological changes after feeding native and autoclaved SPP for rats. Therefore, autoclaved SPPcould be used as a potential new protein resource for food industry.
|
PDF Full Text Request