Study On The Development Of Amyloplast And Physicochemical Properties Of Starches Isolated From Taro Bulbs

Taro is an important underground bulb crop whose bulb rich in starch.Taro starch granules are very small,only 1/10 of potato starch,and have unique physicochemical properties,which have potential development and utilization value.However,starch accumulation and amyloplast development have not been reported at home and abroad,and the research on the physicochemical properties of taro starch is not sufficient.To this end,the Lipubinglang taro,Xinghualongxiang taro,Taixingxianghe taro,and Jingjiangxiangsha taro were used as experimental materials in this study.Resin semi thin section,optical microscope and transmission electron microscope as well as image analysis software were used to study the development process of the amyloplast in Binglang bulb.The differences in physicochemical properties of starch among three varieties(Longxiang,Xianghe and Xiangsha)and between mother bulbs and filial bulbs(Binglang)were compared by means of microscopic observation,X-ray diffraction,Fourier transform infrared spectroscopy and so on,separately.The results of the study were as follows:1.During the development of Binglang,the fresh weight of mother bulb was increased and the water content was gradually decreased.The total starch and the soluble sugar content were increased gradually and increased first and then decreased,respectively.The volume of parenchyma cells,numbers,diameter and area of the amyloplast all showed an upward trend,and the number of the starch granule in the single amyloplast was increased.2.The amyloplast of taro was made up of irregular starch granules with different sizes.The proliferation of starch granules was based on large starch granules as the starting point and proliferated around or one side.The edges of the amyloplast were smooth,and the edges of some amyloplast had "a small area" with a few small starch granules arranged loosely.It was speculated that the region was the starting site of the amyloplast proliferation,and the starch granules were closely arranged and larger with other regions.3.According to the characteristics of the development of amyloplast,the accumulation process of starch in taro bulb could be divided into three stages:starch formation stage,which showed the increase of starch in diameter;the rapid accumulation stage of starch,which showed the increase in the number of amyloplast;amyloplast filling stage,which showed the increase in the number of starch granules in amyloplast.4.There were many similarities and differences in morphology and physicochemical properties of starch from three taro varieties.The three kinds of starch showed irregular polyhedron and spherical appearance,single peak distribution of starch granules and similar XRD diffraction peaks.Longxiang showed the smallest average particle size and lowest apparent amylose content,while Xiangsha showed the opposite.The amorphous proportion of starch from high to low was Longxiang,Xianghe and Xiangsha.In terms of relative crystallinity,Longxiang was lower than Xiangsha but higher than Xianghe.Longxiang and Xianghe respectively showed the highest and lowest peak temperature,and Xianghe and Longxiang showed the highest and lowest gelatinization enthalpy,respectively.Xiangsha showed the highest gelatinization parameters such as peak viscosity,trough viscosity and so on,and Longxiang showed the lowest.5.The starch of the mother and filial bulb from Binglang had similar morphology and crystalline type,but compared with filial bulb starch,the average diameter,relative crystallinity,external order degree,swelling power,and the gelatinization parameters of the mother bulb starch were high and apparent amylose content and solubility were low.Combined with the physicochemical properties of this study and the requirements of some industries for starch properties,Longxiang starch was more suitable as cosmetic additive because of its small granule size.Xianghe and Xiangsha had higher starch content and larger particle size,so they were more suitable for industrial production.Amylose starch could improve the brittleness and strength of food than amylopectin,so the Xiangsha starch with high amylopectin content was more suitable for processing expanded food.The mother bulbs starch of Binglang had larger swelling power than filial bulbs starch,which could improve meat quality.The above results can not only deepen the research on the mechanism of amyloplast development and starch synthesis of taro,but also provide valuable reference information for the study of the application of taro starch in food and non-food industries.