| Ultra-high pressure is a non-thermal processing technology that can make starch paste at room temperature,and has broad application prospects in the field of starch processing.annealed refers to a physical modification method in which the structure and properties of a starch are changed when the starch is maintained at a temperature lower than the gelatinization temperature in the presence of excess water(>60%)or a moderate amount of moisture(40%-55%).While maintaining the granular state,the internal aggregation structure of the particles was adjusted.This project uses potato,corn and pea starch as raw materials,and treats three types of starch with different annealed time and pressure,using scanning electron microscopy,confocal scanning electron microscopy,polarized light microscopy,differential scanning calorimetry,and X-ray diffractometer,rapid Viscosity Analyzer,etc.And it studied the effect of different annealed time on ultra-high pressure gelatinization of three kinds of starch under the conditions of 52 ℃,57 ℃ and 53 ℃,and moisture content of 70% for potato,corn and pea starch respectively.The main research contents,results and conclusions are as follows:(1)annealed results on the surface morphology and internal structure of the three starch ultrahigh-pressure gelatinized granules showed that the granular structure of the three starches still existed when the annealed time was less than48 h.After 3 hours and 24 hours of tanning,the surface morphology of the three starch granules observed by scanning electron microscopy showed little change.However,the starch particles after fluorescent dye APTS staining were observed by laser scanning confocal scanning electron microscopy and the fluorescence intensity inside the granules was reduced.That is,the interior of the particle is more dense.After 48 hours of annealed,the surface of potato starch became rough,and the inner umbilical point structure was destroyed;maize starch became sticky or pitted,and the inner center cavity and channel became wider;the surface of pea starch formed a certain pit,and there was a crack inside.The original potato starch appeared layered off after ultra-high pressure treatment at 600 MPa,but remained granular,indicating that it was only slightly gelatinized;the starch of corn and peas lost most of their grain profile after being treated at 500 MPa and 600 MPa,respectively.The phenomenon of agglomeration indicates that gelatinization has been evident at this time.After 3h and 24 h of potato and corn starch,pea starch was toughened for 3 hours.Compared with the original starch,the potato starch(600 MPa)particle structure remained intact under the same ultra-high pressure treatment conditions,and no obvious hollow structure was formed inside.The grain profile of maize(500MPa)and pea starch(600 MPa)still existed,indicating that the annealed conditions can improve the ultra-high pressure treatment tolerance of the three starches.After 48 h of potato and corn starch,pea starch was significantly gelatinized after being treated at 600 MPa,400 MPa,and 400 MPa,respectively,after 24 h and 48 h of annealed,indicating that this annealed condition cannot increase Ultra high pressure treatment resistance of the three starches.(2)X-ray diffraction,polarized light microscopy,and differential scanning calorimetry were used to investigate the effects of annealed on the crystal structure of three starches after ultrahigh pressure gelation.The study found that annealed of no more than 48 h will not change the starch type of potato(B type)and corn(A type),but the conversion of C-type to A-type crystals occurs after pea starch is toughened for 48 h.The longer the annealed time,the higher the initial gelatinization temperature of the three starches and the lower the gelatinization enthalpy.annealed will reduce the relative crystallinity of corn and pea starch,but the relative crystallinity of potato starch increases first and then decreases with the extension of annealed time.No matter whether the potato starch is toughened or not,the UHP treatment will not change the crystal type.The original starch of maize was toughened for48 h and treated under 600 MPa.annealed for 3 h,24 h and treatment at 400-600 MPa resulted in the transformation of type A crystals into type B;The pea starch has been gradually transformed from the C type crystal to the B type as the pressure increases,and it has been transformed into the B type crystal at 600 MPa.Potato starch was toughened for 3 h,24 h,and treated with 500-600 MPa;corn starch was toughened for 24 h and treated with 500 MPa;pea starch wastoughened for 3 h,and its relative crystallinity was higher than that of the original starch after 400-500 MPa treatment.The higher the pressure,the lower the enthalpy of the three starches;but compared with the original starch,the enthalpy of the three starches after annealed decreased with the increase of pressure.Before and after the annealed of corn starch,the gelation of the corn starch after treatment at 600 MPa was 0 J/g,indicating that the pressure will completely gelatinize the corn starch.(3)The viscosity of the three starches was studied using a rapid viscosity analyzer.The study found that potato starch annealed 3 h,24 h,the valley viscosity,final viscosity increased,while the peak viscosity,attenuation value decreased;annealed 48 h,viscosity peak disappeared,the overall viscosity decreased.The changes in the viscosity curve of maize starch and pea starch were not significant,but all the measurable viscosity parameters were significantly reduced.It shows that the degree of ordering of starch molecules increases after annealed,and the swelling capacity of starch decreases.annealed increased the gelatinization temperature and retrogradation value of potato starch after ultra-high pressure treatment,and decreased the viscosity parameters of corn and pea starch.Potato and corn starch with moisture content of 70% were toughened at 52℃ and 57℃ for no more than 24 h,and pea starch at 53℃ for 3h could significantly improve the ultrahigh-pressure treatment tolerance of the three starches. |
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