The Effects Of Repeated Versus Continuous Annealing On Structural, Physicochemical, And Digestibility Properties Of Cereals, Tubers And Beans Starch

At present,a large number of researches focused on the effects of continuous annealing treatment?CANN?on starch structural,physicochemical and functional properties,but this way had limited effects on starch properties.Repeated annealing?RANN?is a new type of processing method,which can be expected to be a new idea for the comprehensive utilization of starch resources to expand the application in food processing.Based on the cereal starch?unfractionated,A-granule and B-granule starch of normal wheat,partial waxy wheat and waxy wheat starch?,tubers starch?potato starch and sweet potato starch?and bean starch?red adzuki bean starch and mung bean starch?as the materials,this study attempts to reveal and contrast the differences between repeated and continuous annealing treatment under the same annealing time on properties of different kinds of starches.Meanwhile,this paper discusses the interrelation among starch structures,various physicochemical characteristics and digestibility properties,and provides theoretical basis for illustrating the annealing mechanism on starch modification through the research.The main conclusions are showed as followed:?1?Normal wheat,partial waxy wheat and waxy wheat starch granules are composed of large A-granule and small B-granule starch.The surfaces of native waxy wheat starch granules seemed to be rougher with the evidence of grooves and indentations than the native partial waxy wheat and waxy wheat starch granules.The degree of indentation of normal wheat,partial waxy wheat and waxy wheat starch was deeper as the increased cycles and treatment time.In addition,the granule surfaces of waxy wheat starch appeared some distinct pores with the extensive time and repeated times.A-granule starch exhibited spherical or elliptical,while B-granule starch presented the spherical or irregular polygonal.In addition,B-granule wheat starch tended to congregate.The degree of dying of normal wheat and partial waxy wheat was stronger than the waxy wheat starch as revealed by confocal laser scanning microscopy?CLSM?,it was because that the amylose content of waxy wheat was inexistence.Under the same treatment time,repeated annealed samples of unfractionated normal wheat starch and B-granule normal wheat starch showed higher crystallinity,the ordered crystal structure and gelatinization enthalpy,and lower solubility,swelling power and peak viscosity compared with the continuous annealed samples.Continuous annealed samples of waxy wheat starch,A-granule normal wheat starch,A-granule partial waxy wheat starch,A-granule waxy wheat starch,B-granule partial waxy wheat starch and B-granule waxy wheat starch had higher crystallinity,the ordered crystal structure and gelatinization enthalpy,and lower solubility,swelling power and peak viscosity compared with the continuous annealed samples.Before treatment for 4 times and 48 h,repeated annealed samples of partial waxy wheat starch showed higher crystallinity,the ordered crystal structure and gelatinization enthalpy,and lower solubility,swelling power and peak viscosity compared with the continuous annealed samples.Repeated annealed unfractionated normal wheat starch,A-granule normal wheat starch and B-granule normal wheat starch possessed higher SDS+RS content than the continuous ones at the same treatment time,while the SDS+RS content of A-granule partial waxy wheat starch?B-granule partial waxy wheat starch and A-granule waxy wheat starch?B-granule waxy wheat starch were lower than the continuous samples.Before annealing 6times and 72 h,the SDS+RS content of repeated annealed unfractionated partial waxy wheat starch was higher than continuous annealed samples,and then showed an adverse result under the same annealing time.?2?It is observed that the surfaces of native sweet potato starch granules seemed to be smooth,oval,round or irregular shaped,with no evidence of pores or fissures.Potato starch granules presented spherical,ovate and polyhedral shapes with glossy surfaces,and the granule sizes were much larger in diameter than other starches.Some distinct grooves and indentations appeared on the surfaces of part sweet potato starch granules after repeated and continuous annealing treatment.There were no apparent detectable changes in location,sharpness and brightness of birefringence of sweet potato starch and potato starch after treatment revealed by scanning electron microscope.Under the same treatment time,before processed 4 cycles and 48h repeated annealed sweet potato starch possessed higher crystallinity,gelatinization enthalpy and order crystal structure,but there was a reversed result after 4 cycles and 48 h treatment.Repeated annealed potato starch showed higher T_o,T_p and T_c?except for the 2 cycles and 24 h?,crystallinity,gelatinization enthalpy and the content of SDS+RS than continuous ones under the same treatment time,while there was not a coincident conclusion in the ordered crystal structure between repeated and continuous annealed potato starch.?3?It is observed that the surfaces of native red adzuki bean starch granules seemed to be smooth,oval,round or irregular shaped,with no evidence of fissures,pores or fractures,and most native granules presented shallow grooves and indentations on the surfaces.There were no disruptive changes on the surfaces of repeated and continuous treated starch granules,but some distinct pores appeared on the granule surfaces which were treated at extensive time and repeated times.Mung bean starches exhibited smooth surfaces and shallow grooves.Large starch granules showed oval and small granules exhibited round.The surface structure,central cavity and growth ring of red adzuki bean starches and mung bean starches were not changed obviously after treatment.Under the same annealing treatment time,the crystallinity of repeated annealed red adzuki bean starch samples was lower than the continuous ones?except for 2 times and 24 h?,the values of T_o,T_p,T_c and?H of repeated annealed red adzuki bean before 4 times and 48 h were higher than continuous ones,while there was an opposite result after treatment 4 times and 48 h.Repeated annealed mung bean starch samples exhibited higher crystallinity,ordered crystal structure,gelatinization enthalpy,T_o,T_p,T_c,?H,RS,SDS,SDS+RS contents,and lower peak viscosity,solubility,swelling power and RDS content compared with the continuous samples.