Effect Of Konjac Gum On The Rheological And Texture Properties Of Wheat Starch Gel Under Alkaline Condition

Gelatinized starch tends to age during cold storage.It is well established that konjac gum can improve the properties of starch.In order to better understand the application of konjac gum in starch processing,we studied the effect of konjac gum and alkali on the pasting and texture properties of wheat starch.We investigated the effects of alkali?0.1%-0.2%?and konjac gum?5%-10%?on pasting properties and texture properties of wheat starch using Rapid Viscosity Analyzer?RVA?and Texture Profile Analyzer?TPA?.With the addition of konjac gum,the peak viscosity,final viscosity and Setback,breakdown decline,but the gelatinization temperature increased.Meanwhile,the hardness of starch gradually decreased,resulting in the increase of elasticity and cohesiveness.We also found that the peak viscosity and final viscosity declined with the addition of alkali,and the reduce degree is Na OH>Na₂CO₃>Na HCO₃.It is indicated that,the mixed system was pseudo-plastic fluid.The lag ring area of wheat starch decreased with the additation of konjac gum.And we further found that the lagging ring area depend strongly on the amount of konjac gum.It drasticly decreased with the increase of the konjac gum.After adding alkali,the area of the lagging ring decreased obviously.Wheat starch?WS?gels subjected to repeated freezing and thawing tend to decrease in quality.We investigate the effect of alkali and konjac gum?KGM?on crystallinity,microstructure and texture properties of wheat starch in order to improve the freeze-thaw stability of wheat starch gel,.Wheat starch gels containing alkali and konjac gum were treated to 7 freeze–thaw cycles.From the results of X-ray diffraction,we can conclude that the crystallinity of wheat starch gels increased with the addition of konjac gum.The crystallinity of wheat starch gels increased obviously with the addition of alkali.It indicated that the konjac gum and alkali cannot inhibited the recrystallization of the starch gel.As illustrated in the SEM images,the pore size of the freeze–thaw gels becomes bigger as the concentration of the konjac gum increased.Meanwhile,the surrounding matrix becomes weaker.Besides,we found that the matrix became thinner and crisper with the addition of alkali.The hardness of starch gradually decreased.It demonstrated that konjac gum was not an effective agent for preserving the quality of freeze–thawed wheat starch gels and inhibited the retrogradation of wheat starch gel.