Effects Of Autoclaving On The Multiscale Structure And Function Of Soybean Starch And Resistant Starch

In this dissertation,the effects of autoclaving on the structural characteristic and physiological functionality of starch and resistant starch from different types of pulses,as well as the structure-function relationship were studied.We found that the relative crystallinity(C2,from the 16.61-17.23%reduced to 16.01-16.47%),average molecular weight(Mw,from the 1.002-1.559× 107 g/mol reduced to 0.191-0.629×107 g/mol),and ordering degree(DO,from the 1.049-1.109 reduced to 1.017-1.024)of the starch of pulse seeds after autoclaving were significantly reduced though X-ray diffraction(XRD),size exclusion chromatography(SEC-MALLS),solidstate cross-polarization and magic angle spinning nuclear magnetic resonance(13CNMR),and Fourier transform infrared spectroscopy(FT-IR).Comparatively,a certain evolution towards the formation of a predominant B-type crystal structure was noticed in starch samples from the autoclaved pulse seeds,the intensity of the FT-IR absorption peak(3600-3000 cm-1)of the hydrogen bond also changed correspondingly.The results of small-angle X-ray scattering(S AXS)showed that the Bragg distance of the original starch was 9-10 nm,and the original semi-crystalline layer was destroyed after autoclaving.The gelatinization temperature and bile acid binding capacity of starch were also significantly reduced.Among the three types of raw starch,the starch from chickpea seeds had the highest relative crystallinity,degree of order,and double helix content.Simultaneously,the anti-obesity effects of two categories of resistant starch(RS)including RS2(isolated from untreated lentil starch,URS)and RS3(isolated from autoclaved and retrograded lentil starch,ARS)in mice with high-fat(HF)diet-induced obesity and the supramolecular structure-in vivo physiological functionality relationship of RS was investigated.Following 6 consecutive weeks,the obese mice in the two RS administrated groups displayed a depression of body/liver weight gain and an improvement in serum glucose/lipid profile,antioxidant status,and gut microbiota structure.Compared with URS intervention group(47.88 g),the ARS(45.14 g)administration performed a more pronounced effect in controlling body weight,together with a more prominent reduction in blood glucose and triglyceride concentration,as well as a significant increase in HDL-c level in obese mice.ARS group also showed an absolute advantage over URS in suppressing the oxidative stress and regulating the liver function induced by HF diet.Simultaneously,the administration of URS and ARS efficiently suppressed the HF-diet induced alternation in gut microbial ecology,with an obviously decreased ratio of Firmicutes to Bacteroidetes,especially the ARS group(3.24)was more effective compared with URS group(7.05).The structural characterization results revealed that ARS and URS differed significantly in their supramolecular structural characteristics,where ARS exhibited a higher proportion of crystallinity and double helix content with an X-ray diffraction pattern of CB type crystal polymorph and a low proportion of molecular inhomogeneity.The results obtained suggested that the difference in the anti-obesity effect of resistant starches was a consequence of the diversity in their structural features.This paper gives a theoretical foundation to develop and utilize the resistant starch in different types of pulses.