Comparison Study Of Heat Treatment And Cross-linking Reaction On The Properties Of Potato Starch

In this paper,potato starch and waxy potato starch were used as materials treated with DHT,HMT and CLT.The effects of three different treatments on the structure and physicochemical properties of starches were compared.As raw materials,potato starch and waxy potato starch were treated at pH=7 and 110?.The reaction time was 0.5h-2.5h.The results showed that DHT had different effects on the structure and physicochemical properties of these starches.The surface of native starches was smooth.As time goes on,the SEM and polarized cross of potato starch had no significant change.The surface of waxy potato starch appeared some scallops.Some cavities appeared on middle of the particle cross.Solubility and swelling power increased after DHT.On the one hand,DHT made the starch structure loose.On the other hand,it reduced the ability of the amylose chain to form a single helix complex with iodine.Beacues of the combination of these effects,DHT had little effect on the amylose content.DHT made the crystalline type of both the starches changes.There was a tendency to convert from B to A,and the relative crystallinity was also gradually reduced.But,the effect of crystal type on waxy potato starch was bigger than that of potato starch.DHT reduced the gelatinization temperature of the starches.Gelatinization enthalpy value also decreased.The peak viscosity of potato starch increased first and then decreased with the time extension.But the peak viscosity of waxy potato starch continued increase.In addition,the samples after DHT had poorer thermal paste stability,poorer shear resistance.The RS content of potato starch was higher than that of waxy potato starch.DHT enhanced the digestibility of these starches.Under 25% moisture condition,starches were treated at 100°C?110°C?120°C?130°C and 140°C for 2.5h.Results indicated that some potato starch granules appeared uneven on the surface after HMT,while some waxy potato starch showed pits and breakages.The polarized crosses were all partially weakened.The potato starch after HMT was difficult to expand so that solubility and swelling power were reduced.Although waxy potato starch after HMT was difficult to expand,the particles swelled and dissolved at 95°C,which made the solubility and swelling power were higher than that of native starch.The crystalline type of both starches was changed from B to A,and the relative crystallinity was also gradually reduced.But potato starch was more resistant to HMT.HMT increased the gelatinization temperature of starch and decreased the peak viscosity.The change range of potato starch was larger than that of waxy potato starch.The breakdown value and setback value were all decreased,which indicated HMT enhanced the shear resistance and stability.HMT reduced the digestibility of two starches,but the waxy potato starch vary more.In order to compare the effects of physical treatment and chemical treatment on the two starches,the cross-linking agent(sodium trimetaphosphate: sodium tripolyphosphate = 99:1)was added in an amount of 0.01% to 3% by mass of the starch dry basis.The study found that the cross-linking reaction did not have significantly affect on the surface structure and polarized cross of both starches.With the addition of the cross-linking agent,the sedimentation volume of treated samples almost was identical with that of native starch firstly,and then gradually decreased.The degree of cross-linking was negatively correlated with the sedimentation volume.When the amount of cross-linking agent was low,the solubility and swelling power were not much different from that of native starch.When the amount increased,the solubility and swelling power were reduced vastly.The cross-linking reaction reduced the amylose content of both starches.It did not change the crystal type of both starches,and the relative crystallinity did not change.The cross-linking reaction increased the paste temperature and decreased the gelatinization enthalpy.The peak viscosity first increased and then decreased.Finally,starch did not gelatinize.The peak viscosity increased at low cross-linking degree and decreased at high cross-linking degree,which was the same as DHT.HMT was the same as high cross-linking reaction.The cross-linking reaction had little effect on the digestibility of potato starch,but reduced the digestibility of waxy potato starch.