Studies On The Preparation And Properties Of Multi-modified Granular Cold-water Swelling Starches

Preparation of multi-modified granular cold-water swelling (GCWS) cassava starches byalcoholic-alkaline treatment and other chemically modified methods, as well as properties andapplication in yoghourt of these kinds of modified starches were investigated and discussed in thisdissertation.Firstly we got the optimum parameter for preparing GCWS starches by orthogonal experimentas follows, 100g cassava starch, 700mL ethanol, ethanol concentration of 50%, reaction temperature35 ℃ , and 15g NaOH. The differences of properties between GCWS cassava starch andpregelatinized cassava starch were compared. Scanning electron micrographs (SEM) showed thatgranules of GCWS starches remained intact and also indented appearances, and its pastes wasshear-thinning, which should belong to Pseudoplastic Liquid, GCWS starch pastes had betterproperties such as transparency, resisting retrogradation, freeze-thaw stability and high-temperaturestability.The preparation of cross-linked GCWS starches was studied. By single factor tests andorthogonal experiment, we got the optimum parameter as follows, reaction temperature 40℃, 14gNaOH, ethanol concentration of 45%, 0.005% sodium trimetaphosphate(STMP) for viscosity, andreaction temperature 45℃, 18g NaOH, ethanol concentration of 65%, 0.010% STMP for dispersingproperty. By orthogonal experiment and principal component analysis, we got the optimumparameter for synthetical evaluate index in preparing cross-linked and GCWS acetylation of starchas follows, 0.01% STMP, 10% acetic anhydride, reaction temperature 35℃, pH 9.5, reaction time2h.We researched the structure of three kinds of starch by modern instruments. Infra-redspectrometry showed the pattern of GCWS starch and cross-linked GCWS starch were consistent inraw starch, and there was a peak in 1728 cm-1 for cross-linked and GCWS acetylation of starch,indicating acetic anhydride and starch were linked by ester bond;SEM revealed that three kinds ofstarch still remained granule shape and also were indented;The X-ray pattern showed that threekinds of starch probably were the mixture of sub-crystal and V type crystal;The absorption patternof starch-iodine complex showed that their absorption index reached maximum in the range of605~634nm.The transparency, dispersing, resisting retrogradation parameters of cross-linked and GCWSacetylation of starch were between GCWS starch and cross-linked starch, and its freeze-thawstability was better than others. The Brabender viscosity curve revealed that resisting acid-base andshearing of GCWS starch was weak, but others were very good.At last, the application of modified starch in the yoghourt was discussed. When additionvolume of starch was 0.5~1.0%, cross-linked and GCWS acetylation of starch showed very goodeffects.