Study On The Dynamics And Physicochemical Properties Of Starch Accumulation In Ginkgo Biloba

Ginkgo Biloba L.is a living fossil plant,one of the woSrld’s oldest relict plants in China.It has long been consumed as food after fermentation or cooking,and has special properties as a herbal medication in China.Starch is the main component of the endosperm of G.biloba,and its structure and characteristics play an important role in determining the endosperm quality of G.biloba.Therefore,it is necesary to study the starch physicochemical properties and fine structure of Ginkgo biloba as to improve the endosperm quality and thus support useful clues for new varieties breeding.In this study,8 ginkgo varieties including:Qixinguo,Dafozhi,Hongyinyihao,Dongtinghuang,Fozhi,Maling,Dalongyan and Longyan were used for physicochemical and structural properties analysis.In brief,the starch was isolated from the endosperm.Then the morphological characteristics of starch granules was observed by SEM,TEM and Polarizing Microscope;The crystal structure characteristics of starch granules were analyzed by X-ray powder diffraction,Small-angle X-ray scattering,attenuated total reflection-Fourier and Laser Raman Imaging spectrometer;The thermal gelatinization properties of starches were analyzed by Differential scanning calorimeter(DSC).In addition,the effects of the sand reservoirs on the physicochemical properties of the Ginkgo Biloba starch granules during the endosperm maturation process were studied.The study here,can provide a theoretical basis for understanding the Ginkgo endosperm development and the formation of the edible quality of Ginkgo biloba endosperm.Also,this study can provide useful clues for breeding of excellent ginkgo cultivars and seed storage methods.The main researches are as follow:1.We analyzed the structure and physicochemical properties of starch from 8 Ginkgo biloba,and found there are no significant differences in the microscopic morphology between the 8 samples.We found that all the starch granular were mainly round,oval and irregular.Beside,the surface of the starch granules is smooth,with no hole phenomenon and have folding structure inside.There are clear rules and irregular "Maltese Cross" wreath structure with navel point in the center of the starch granules.In terms of the size of starch granules,Qixingguo and Dafozhi has the smallest starch grains,while Fozhi and Maling starch particle size is the largest.Then the crystal structure of the starch samples were analyzed,we found that all of them are type A,and the crystallinity ranged from 31.45%to 33.32%.Also the short order degree of single starch was analyzed,and we found that the short order degree is high on the surface of but lower in the center of a starch granul.As for the crystallinity,and the chain/branched value detected by the Laser Raman Imaging spectrometer,both showed an uniformly structure distributed in a single starch granule.We further analyzed the apparent amylose content of 8 starch granules,and found a relative narrow distribution among the varieties but still with significant difference.For example,Qixingguo showed the smallest amylose level while Longyan showed thelargest.At last,the gelatinization properties of the different starches were determined by DSC,they showed a relative narrow gelatinization type with the gelatinization temperature ranging from 70.19 to 89.56 ℃,and the enthalpy ranging from 13.58 to 15.82 J·G-12.The structure and physicochemical characteristics of starch from different development stages in Ginkgo Biloba were analyzed.We found that the accumulation of starch grains is gradually and it filled from the aleurone layer to the inner endosperm as the endosperm development.In this process,the starch size also become bigger until the endosperm was mature.We found that the Ginkgo starch might developed from the chloroplast-like plasmid and formed new starch granules through budding or constriction.We also found that in the early stage of endosperm development,the morphology of starch grains was mainly irregular,and the Maltese cross structure is not clear,and the average particle size of starch is only about 4.54μm,With the development of the endosperm,the round and elliptical starch granules gradually increased,and also the grain size gradually increased.In the late stage,we found the mature ginkgo starch granules had a large pore structure inside,We also analyzed each type of starch granules and found that the round starch grain has a regular Maltese cross structure,while the elliptic and irregular starches were irregular Maltese crosses,but all the forms of the three starch granules showed an obvious central umbilical point.As for the the size and morphology of starch granules,we found it tended to be stable when the endosperm was mature.We analyzed the crystal characters of the starch during the endosperm development and found that all the starch granules were type-A crystals,and with the development of endosperm,the crystallinity,order degree and peak strength showed a slight decline trend.During the development of endosperm,the crystallinity and direct chain/branch chain value of single starch were distributed evenly,We also found that the content of amylose in ginkgo was increasing as the endosperm develop,but the thermodynamic properties of starch granules were not obvious.3,By analyzing the effects of sand storing in the ripening processing on the starch structure and physical and chemical properties in ginkgo,we found that the sand storing treatment has no effect on the external shape of the ginkgo.The starch granules at room temperature and after sand storing were mainly round,elliptical and irregular,the surface was smooth without holes.and there was no difference in polarized light structure.However,the average particle size of starch granules was significantly larger than that of starch granules stored at room temperature.Both conditions have no effect on the starch crystal type,but we found that the starch granules with sand storing treatment showed a higher order and also a higher peak intensity compared with samples in room temperature storage.We also found that the degree of crystallinity and order in a single starch granules increased while the direct chain/branch chain value in single starch grains decreased with the sand storing treatment.As for the apparent amylose content of starch granules,we found a decreased trend as sand storing treatment,but there was no significant difference in the gelatinization temperature.