Study On The Morphological Structure And Gelatinization Characteristics Of Taro Starch During The Steaming And Boiling

As one of the main traditional miscellaneous grains in China,taro has been cultivated for more than 2,000 years.The taro bulbs are rich in starch,and the starch granules are extremely delicate and easily absorbed by the human body,which has great economic development potential.However,the relationships between starch structure and taste quality during steaming and boiling in the domestic and foreign countries has not been reported in detail,especially the characteristics of starch after gelatinization.To this end,the study selected the representative scorpion(Xianghe)and burdock(Longxiang)widely planted in Jiangsu area as experimental materials.The relationships between starch structure change and taste quality in the process of steaming and boiling was studied by gradient sampling method,scanning electron microscope and taste tasting method.Rapid viscosity analysis,Fourier transform infrared spectroscopy,Solid NMR and other techniques were used to study the physicochemical properties changes of starch after gelatinization at different temperatures.The main findings are as follows:1.In the process of steaming and boiling,the morphology of starch changes in the form of granules,continuous filamentous and flaky,then to smooth and compact,finally to form a"netted hollow" shape.The water content of the taro bulbs first increased and then stabilized.Soluble sugar and total starch content increased first and then decreased.Compared with boiling way,steamed glutinous starch has a shorter gelatinization time,a slower water content growth speed,and less soluble sugar and total starch loss.2.When the power is constant,the more dosage of taro,the longer starch gelatinization;when the dosage is 500 g,the steaming and boiling speed are the fastest.The results of taste evaluation showed that the steaming and boiling time of best eating quality for Xianghe was 20 min and 25 min,respectively.But for Longxiang were 25 min and 30 min,respectively.The cross-section structure corresponding to this time point is the smoothest and tightest.3.In general,there are some similarities between the changes of gelatinization characteristics of Xianghe and Longxiang starch at different temperatures.According to microstructure,with the increase of gelatinization temperature,the structure of starch granules gradually changed from "angular" to "flaky" or "elliptical",and finally formed a continuous"flocculent" structure.Peak viscosity,final viscosity,dilution value,retrogradation value,swelling potential,solubility,hydrolysis rate and amorphous area of taro starch increased with the increase of gelatinization temperature.The apparent amylose content,relative crystallinity,ordered structure and proportion of single and double helix structure of taro starch were negatively correlated with the increase of gelatinization temperature.4.Due to the different sources of taro starch,there are also many differences in gelatinization process.Compared with Longxiang starch,Xianghe starch is more easily gelatinized.The peak viscosity,final viscosity,lean value and regenerative value,solubility and hydrolysis rate of Xianghe starch were higher than those of Longxiang starch.But the amorphous area,swelling potential and apparent amylose of Xianghe starch are lower than those of Longxiang starch.In addition,the optimum gelatinization temperatures of two kinds of taro starches were also found to be different.The optimum gelatinization temperatures of Xianghe starch and Longxiang starch were 85 ℃ and 90 ℃,respectively.5.Through the relationships between morphological structure and taste quality of taro during the steaming and boiling,we worked out a scientific and convenient new method of taro steaming and boiling.In addition,according to the application demand of starch gelatinization characteristics in industrial production process,taro starch with high gelatinization viscosity,higher solubility and easy hydrolysis is suitable for the elderly,children and patients as supplementary food and could also improve industial production efficiency.However,taro starch gelatinized at low temperature was similar to natural starch,and its amylose content was relatively high and was not easily digested.It is suitable for people who are easy to gain weight or for long-tern storage.The above results could not only deepen the research of taro in food cooking and starch gelatinization properties,but also provide valuable theoretical basis for the future development of taro food and the application of taro starch in industrial production.