The Effect Of Apple Young Fruit Polysaccharides On The Inhibition Of α-amylase Activity By Polyphenols And Their Emulsifying Properties

Apple is one of the highest yield and the most popular fruit in the world.Fruit thinning is a key step to ensure the quality and output of apple after harvest,which usually cause a mass of thinned-young apples unutilized.As an accessible and valuable plant resource,thinned-young apple contains numerous nutritional contents,includes polyphenols and polysaccharides.In recent years,polyphenols have been deeply studied,wheareas the study of polysaccharides was mainly focused on the extraction,purification,isolation,and only a few papers regarding of pathological activities of polysaccharides in thinned-young apple.In this study,the thinned young polysaccharides were obtained by hot water extraction from three varieties("Qinyang""Pinklady" and "Jinshiji",respectively)and the structural properties,enzyme activities,antioxidant activities,and emulsifying capacity of the polysaccharides were further investigated.The results are expected to broden the study of the active components in the thinned-young apples.The detailed results are showed as follows:1.Three thinned-young apple polysaccharides were extracted by hot water(880C,130 min),and then the polysaccharide characteristics wereelucidated in terms of their basic compositions,molecular weight and monosaccharide compositions.Besides,their structuralpropertieswere further determined by FTIR,NMR spectroscopy,XRD pattern,thermalanalysis(TG/DTG)and Congo red tests.The results suggested that three polysaccharides had the same monosaccharide componentswith varying molar ratios.In detail,xylose,mannose,galactose and glucose were the four compositional monosaccharides,among which glucose and mannose accounted for～93%of total monosaccharides for "Qinyang",followed by-87.9%for "Jinshiji" and～83%for"Pinklady".The results of molecular weight analysis revealed that"Jinshiji"polysaccharide had the highest molecular weight(293 kDa),followed by "Pinklady"(270 kDa)and "Qinyang" polysaccharide(207 kDa).The results of FTIR and NMR showed that three polysaccharides were low-methylated,and the degree of esterification of "Jinshiji" and "Pinklady" were higher than "Qinyang".In addition,the resultsof XRD showed that three polysaccharideshad amorphous structures and all the polysaccharides had a well thermal stability with a high temperature of thermal degradation(～270℃).Three polysaccharides contained triple helix structureas indicated by Congo red assaies.2.The results of three polysaccharides reduced the inhibitory activity of thinned-young apple polyphenols(’Tinklady’7)against a-amylase showed that all the polysaccharides could weaken the inhibitory activity in the tested concentrations(0.5-2.5 mg/mL)in a concentration-dependent manner.Among them,"Qinyang"polysaccharide had the lowest capacity of reducing the inhibitory activity.The order of addition of polysaccharides could affect the capacity of reducing the inhibitory activity and the capacity of reducing the inhibitory activity as the following order:(polysaccharide+polyphenols)+a-amylase+substrate>(α-amylase+polyphenols)+polysaccharide+substrate.The vitro antioxidant activity of thinned-young apple polysaccharides("Qinyang" "Pinklady" and "Jinshiji")were measured by ferric reducing ability of plasma,DPPH,HO and ABTS free radical.The results showed that three polysaccharides exhibited significant reducing power and the DPPH,HO,ABTS free radical scavenging capacity was in a concentration-dependent manner in the concentration tested."Jinshiji" had the highest antioxidant activities,followed by"Pinklady" and "Qinyang".3.The effects of different polysaccharides on emulsions showed that the emulsifying stability was increased with the increase of polysaccharides concentrations.Thus,the emulsions in this study were prepared by mixing polysaccharides solution(2.0%,w/v)and colleseed oil(4:1).And the effects of pH(2,4,6 and 8),cation type(Na+,Ca2+)and concentrations(20,40,60 and 80 mg/g polysaccharide)on the emulsions were also investigated by measuring the emulsion stability,droplet size and rheological properties of emulsions.The results suggested that all the emulsions exhibited the characteristics of non-Newtonian fluid,with significant shear-thinning properties.pH values can influence the stability of emulsions mainly by alteringthepolysaccharides conformation,and emulsion droplet size were increased with the increase of pH by the imaging of CLSM.The trends of emulsion stability followed the order:"Jinshiji">"Pinklady">"Qinyang".The emulsion stability was decreased as the concentrations of Na+ increased,while the emulsion stability was increased first and then decreased with the increased of Ca2+concentrations.The emulsions were the most stable when the concentration of Ca2+ was 40 mg/g.The emulsions with "Pinklady" and "Jinshiji" were less affected by ion concentrations than "Qinyang".In conclusion,this study investigated the structural characteristics;biological activity and emulsifying properties of three polysaccharides.The results may help establish the theoretical foundation for the further study of thinned-young apple polysaccharides.