| According to the difference of X-ray diffraction characteristics,natural starches can classified into three types:type A,type B and type C.Natural starches are generally poor in heat resistance,acid resistance and shear resistance,so their applications are often limited.Annealing treatment is a kind of mild physical modification method which can ensure the integrity of starch granules.In this study,maize starch(type A),potato starch(type B)and castanea henryi starch(type C)were used as raw materials to explore the effects of different annealing treatment conditions on paste properties,digestibility and freeze-thaw stability of the three types of starches,so as to provide theoretical basis for the physical modification of different types of starch.(1)The annealing treatment significantly reduced the paste transparency of potato starch and improved the paste transparency of maize and castanea henryi starch.Among them,the paste transparency of potato starch was most affected by the annealing temperature,and the change of annealing treatment conditions had the least influence on the transparency of castanea henryi starch paste.Compared with the other two crystal starches,the solubility and swelling degree of potato starch are more susceptible to annealing temperature and time.The solubility and swelling degree of maize starch were negatively correlated with the three annealing factors.After annealing treatment,the degree of swelling and solubility of the castanea henryi starch were lower than that of the original starch,which was less affected by changes in factor levels and not limited by annealing time.After annealing,the To,Tp and Tc of the three crystal starches increased,the ?H varied,the thermal stability developed,and the internal crystallite distribution was more uniform.The viscosity and annealing time of maize starch are inversely proportional.The peak viscosity of potato starch is proportional to the annealing moisture and time,final viscosity is higher than the original starch and proportional to the annealing temperature.The peak and final viscosity of Castanea henryi starch is proportional to the annealing temperature.(2)The effects of annealing treatment on the morphology and digestibility of the three crystalline starch granules were different.The annealing treatment resulted in pits on the surface of maize starch granules,a few cracks on the surface of potato starch,and the disappearance of slight wrinkles on the surface of castanea henryi starch.However,the crystal structure of the three kinds of starch did not change before and after annealing treatment,but their crystallinity all increased.Among them,the change of potato starch was the most significant,with the crystallinity increased from 18.97%of the original starch to 24.09%,indicating that the anneal:ing treatment can promote the molecular arrangement of starch to be more orderly.The contents of RS in the three kinds of starch were all significantly increased after annealing treatment,the SDS contents of maize starch and potato starch were significantly decreased,the content of RJDS of maize starch was significantly increased,the RDS content of potato starch and castanea henryi starch was significantly reduced.After annealing treatment,the hydrolysis index(HI)and glycemic index(GI)of the three crystalline starches were significantly decreased,and their anti-enzymatic hydrolysis ability were enhanced,with that,the hydrolysis equilibrium concentration of maize starch and potato starch decreased by 8.02%and 8.75%respectively.(3)The crystal types of the three crystalline starches were not changed after repeated freeze-thaw-annealing treatment,but the morphology of the particles and the freeze-thaw stability were different.The crystallinity of the samples was higher than that of the original starch except for the maize starch treated by freeze-thawing-annealing once,and increased with the added treatment cycles.The pores and depressions began to appear on the surface of maize starch granules after once and twice treatment cycles.After third cycles of treatment,the lamellae structure appeared,the particles became loose,the water rate of pasteation increased,and the crystallinity increased by 5.19%compared with the original starch.After repeated freeze-thawing-annealing cycles,the grain breakage and fusion of potato starch occurred.After three freeze-thawing-annealing cycles,the crystallinity increased to 24.50%,which was 7.67%higher than the original starch,and the water extraction rate decreased to 16.67%of the original starch,the freeze-thawing stability enhanced.After repeated treatment cycles,the granule aggregation of castanea henryi starch occurred,and the water extraction rate decreased significantly. |
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