Study Of The Mechanism Of Hydroxypropyl Distarch Phosphate In Ketchup

The stability of ketchup for long-term storage is inferior, the water exudation iseasy to occur, causes the separation of solids and liquid, resulting in inferior sensory ofketchup. The addition of modified starches (i.e. hydroxypropyl distarch phosphate)could enhance the stability of ketchup. But the mechanism of modified starches on thestability in ketchup is still unknown. The primary objective of the present research wasto investigate the effect of modified starch---hydroxypropyl distarch phosphate (HDP)on the stability in ketchup.To achieve this objective, we tested some physicochemical properties of HDPwhich was used in this study. We made5kinds of ketchup, the differences of theirformulations were the kinds and amounts added in the ketchup. No starch was added inKetchup1;3%(w/w) native starch were added in Ketchup2; HDP were added inKetchup3, Ketchup4, Ketchup5at levels of3%,4%5%, respectively. The pH, totalsoluble solids content and moisture content were explored, to make sure the ketchupwere consistent to commercial ketchup.We investigated the rheological properties of ketchup samples. According to stresssweep and frequency sweep, the ketchup with HDP added showed strong gelrheological properties compared that to the ketchup with native starch added. And gelhardness was improved with the increasing of HDP levels. And the strengthen gelexerted positive effect on the stability of ketchup.Zeta potential showed that the Zeta potential of ketchup was enhanced by additionof native and HDP, as a result, the repulsion between ketchup particles were enhanced.It helped to the stability of ketchup. But this kind of stable effect was not providedfrom the electrostatic adherence between tomatoes and starches.The particle size and particle size distribution were tested. The average particlesize of ketchup turned out smaller by addition of native starch and HDP. The particlesize distribution results indicated that there were much more large particles in theketchup with native starch added compared with which added HDP, although theaverage particle size were almost the same.The color staining experiment revealed that HDP was dispersed in the system ofketchup homogeneously and extensively. However, native starch were aggregated.Scanning Electron Microscope and Atomic Force Microscope illustrated nativestarch and HDP filled up the interspaces in the ketchup. The roughness of the ketchup added HDP was better than that in the ketchup added native starch, it means that thehomogeneity in the ketchup with HDP added was better.HDP, added into ketchup, exerted its ability of good gelatinization and waterholding capacity. Then, HDP was homogeneously dispersed into ketchup. So, HDPprovided a steric hindrance effect, separated the tomatoes away to prevented theaggregation of tomatoes; in addition, the hydroxypropyl groups are hydrophilic groups,these hydrophilic groups absorbed water to creat a water film, and the water filmcontributed to against the aggregation of tomatoes, as a result lowered the averageparticle size of ketchup. Stable samples contained smaller particles. Although, theaddition of native starch also provided a hindrance effect, lowered the average particlesize. The dispersion of starch was heterogeneous due to the poor physicochemicalproperties, caused aggregation of starch. There were much more large particles in theketchup, and it caused bad influence on the stability of ketchup.