Study On The Factors And Mechanisms Affecting The Structure And Digestibility Of Jackfruit Seed Starch

Jackfruit is a tropical fruit with high-quality.Its seeds are rich in starch,which accounts for about 60% to 80% of its dry weight.The jackfruit seed starch(JSS)shows high resistant starch(RS)content.In-depth understanding of the factors and mechanisms affecting the digestibility of JSS has certain scientific significance in reducing blood sugar levels and promoting intestinal health.However,the current researches on JSS mainly focus on the improvement of extraction,characterization and modification.There is a lack of systematic research on the digestibility of JSS.Therefore,this paper discusses the influence of different factors on the structure and digestibility of JSS from internal factors(starch plant source,particle size and internal structure)and external factors(processing).The main research results are as follows:(1)Based on the glycerol-assisted centrifugal sedimentation method,the effect of particle size on the structure and digestibility of JSS was studied.The images of scanning electron microscopy and particle size distribution showed that potato starch(PS),maize starch(MS)and JSS were successfully separated.The granular morphology of each fraction was different slightly.There was an increase in the RS content of the fractionated starches with the increasing granule size.The different-sized fractions of JSS,MS and PS possessed similar crystalline type and the value of R1047/1022,respectively.However,relative crystallinity(RC)increased significantly with the increasing granule size.The effect of granule size on the amylose content(AC)of the same starch type was mainly manifested difference in the large-and small-sized granules.For starch samples from different plants,the degree of hydrolysis followed the order: MS>PS>JSS.After 120 min of hydrolysis,only a few grains of JSS showed pits and cracks.The AC of JSS was 24.35?28.29%.It showed a typical A-type crystalline structure.Compared with MS and PS,JSS showed the strongest highest resistance to digestion(67.61?82.42%),the smallest granules(6.08?12.35 ?m)and the value of RC(35.95?38.95%).(2)Based on the chemical surface gelatinization method,the influence of internal structure on the structure and digestibility of JSS was studied.As the granules of JSS were peeled off layer by layer,the surface of the remaining JSS granules became rough and evenly eroded.The flake structure and holes were found when the gelatinization degree(DG)was high.The AC of the remaining granules did not show a significant difference with the increase of DG,and its value range was 24.07?26.62%.Compared with the native starch,the surface short-range ordered structure of the remaining granules after surface gelatinization was significantly reduced,while the values of To,Tp,Tc and ?H decreased and the ?T value increased.The increasing DG caused the crystalline structure of JSS to be removed step by step,which affected the ratio of the amorphous region to the crystalline region.Thus,the RC presented a significant increase and decrease alternately.After the surface gelatinated treatment,the RDS(9.54?27.83%)and SDS content(13.68?32.55%)of JSS were significantly increased compared with the original starch,and the RS content(76.38?45.48%)was significantly reduced.The changes in RS content of samples treated with different DG were consistent with the results of RC.(3)Based on the heat moisture treatment(HMT)and annealing treatment(ANN),the influence of hydrothermal treatment on the structure and digestibility of JSS was studied.After HMT and ANN with lower moisture content(10?15%),the morphology and polarized cross of JSS did not change significantly.However,the strength of some of the polarized crosses reduced and the starch granules after HMT became agglomerate.With the increase of moisture content,the AC and RC of JSS after HMT and ANN increased and then decreased slightly,the To,Tp,and Tc values increased,and ?T and ?H values decreased.Besides,there was an increase in the pasting temperature and a decrease in the peak and final viscosity,setback and breakdown of heat-moisture treated and annealed JSS compared with native starch.Low moisture-treated samples showed a slight effect on the short-range ordered structures.The R1047/1022 of JSS under high moisture content decreased significantly,while that of annealed JSS increased significantly.Both HMT and ANN could increase the RS content under suitable moisture content.The change range of HMT(54.70?85.40%)was greatly higher than that of the ANN(77.75?84.02%).