The Effect Of Water Contents And Prehesting Temperatures On Starch Retrogradation

When starch is heated in the presence of water and subsequently cooled,the disrupted amylose and amylopectin chains can gradually reassociate into a different ordered structure in a process termed retrogradation.There have been a lot of research in the field of starch retrogradation.However,studies of starch retrogradation have not considered that the effect of preheating to temperatures on starch retrogradation.In this article,wheat and rice were materials.The RVA has been used to simulate DSC heating profiles for the preparation of retrograded starch samples to probe the effect of water contents and preheated to temperatures on retrogradation process.This study would not only help to obtain new insights into the process of starch retrogradation,but also make great importance to improve the stability of starch based food.In this experiment,a protocol is designed that used the Rapid Visco Analyser(RVA)to prepare various water contents and different preheating temperatures of retrograded samples under conditions that resemble DSC heating as closely as possible.We prepared the wheat and rice starch samples as water:starch ratios(v/w)of 0.5:1,0.75:1,1:1,1.5:1,4:1.Each water:starch mixture was heated separately toTc,Tc+10,Tc+20,95?,110?,120?.Below 100 ?,it used that RVA simulated DSC heating for preparation of starch samples.Above 100 ?,it used that prepared the samples for DSC heating.Changes of starch structure have been studied under different water contents and preheating temperatures condition during retrogradation process.The results indicated that starch samples at various water contents after preheating to Tc did not show retrogradation,attributed to the existence of residual starch crystallites.As the retrograded samples of same water content,the enthalpy changes of residual crystallites decreased and for retrogradation increased with increasing preheating to temperatures.As the retrograded samples of same preheating to temperatures,the enthalpy changes of residual crystallites decreased and for retrogradation firstly increased and then decreased with increasing water contents.The maximum enthalpy change was observed for starch retrogradation at water content of 50%.Above 100 ?,retrogradation enthalpy of starch samples at various water contents significantly increased.According to the results of LCM-Raman,the short-range order of retrograded samples was higher than that of gelatinized starch after preheating to Tc.The short-range order of retrograded samples at different water contents increased with increasing preheating temperatures.From the results of XRD,retrograded samples at various water contents presented A-type pattern after Tc.The relative crystallinity of retrograded samples increased with increasing preheating temperatures.In conclusion,preheating to different temperatures and water contents may profoundly affect starch retrogradation.