Effects Of Different Processing Methods On The Structure And In Vitro Glycolytic Properties Of Pea Resistant Starch

Resistant starch(RS)is a type of starch that cannot be digested in intestinal by healthy individual,but can be fermented in the colon by the gut microorganisms.Its physiological function is similar to that of dietary fiber.In this study,pea starch was modified by microwave cooking(MCP),autoclaving(ACP),and combined treatments of autoclaving with acid hydrolysis(AHP),ultrasonication(UP),or pullulanase debranching(PDP),respectively.We compared the relationship between processing treatments with the structural and physicochemical properties of modified pea starch,and further explained the influence of processing treatments on the multiscale structure of the processed starch.On this basis,the changes of the structural characteristics of pea starch prepared by five different methods and native pea starch after purification by enzymolysis(ACPRS,MCPRS,UAPRS,AHPRS,PDPRS and NPRS)were also compared.At the same time,the effect of the structure of pea resistant starch on the intestinal flora changes after in vitro fermentation was investigated.The influence of different processing treatments on the structural and physicochemical characteristics of pea starch was investigated by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),solid-state 13C nuclear magnetic resonance(13C NMR),environmental scanning electron microscope(ESEM)and small angle X-ray scattering(SAXS).The results showed that the starch molecules were degraded and recrystallized by processing and ACP,MCP,AHP,UAP and PDP were transformed from C-type crystals to(B+V)-type crystals,and the relative crystallinity was decreased,in especial pullulanase debranching treatment could promote the crystallization.Because of gelatinization and molecular rearrangement,the order degree of molecules decreased,the structure of semi-crystal layer disappeared,especially the effect of combined treatments of autoclaving with acid hydrolysis was the greatest.The influence degree of different processing on starch structure was significant.In general,the destruction degree of starch structure by acid decompression heat was large.In order to understand the effects of different processing methods on RS structure,the above samples were further purified by enzymatic method.The results showed that AHPRS had the strongest bile acid binding ability,which might be related to its highest molecular order degree,double helix content and relative crystallinity,while PDPRS had the weakest bile acid binding ability.MCPRS has the largest multi-dispersion coefficient,which is due to the rapid rise in temperature during microwave heating and the uneven heating of starch solution,so it limits the expansion and rupture of particles,resulting in the non-uniform degradation of starch and wider molecular weight distribution.The different physicochemical characteristics of RS was correlated with the differences in their structural features,which might be due to the interaction of multiple structural characteristics.To clarify the influence of RS structure changes on the intestinal health,in this study,fructo-oligosaccharide(FOS)was used as the positive control,and three different types of RS(AHPRS,PDPRS and NPRS)with the most pronounced structural differences were chosen to explore their in vitro fermentation characteristics and prebiotic properties.The results showed that after in vitro fermentation,the production of short-chain fatty acids in the RS groups were higher than that of the Control Sample(CS)and FOS,especially the production of PDPRS and NPRS were higher than that of AHPRS.In vitro fermentation also showed a significant effect on modifying the RS structure,in which the crystalline type of RS did not change,whereas the relative crystallinity was significantly increased,especially for NPRS.Upon fermentation,the surface became relatively looser,with the appearance of several blocklets structures,especially for PDPRS and AHPRS.The results of diversity index of intestinal flora showed that PDPRS had the greatest influence upon intervention.From the genus level,the number of Bacteroides,Bifidobacterium and Ruminococcusthem increased significantly after the interference of RS.The metabolites of these flora in the intestine are short-chain fatty acids(especially butyrate),Whereas the number of pathogenic bacteria or potential pathogenic bacteria such as Escherichia and Prevotella was significantly reduced.