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Studies On Physicochemical Properties And Glycemic Index Determined By In Vitro Method Of Kudzu Starch And Lotus Starch

Posted on:2004-10-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:G ZhongFull Text:PDF
GTID:1101360092985610Subject:Agricultural products processing and storage
Abstract/Summary:PDF Full Text Request
The physicochemical properties and functional charactrization were determined with the modern analytical techniques for the wild starches from kudzu vine (Puerariu D. C.) and lotus (Nelumbo nucifera Gaertn), and cassava starch, potato starch, and maize starch. And the glycemic index of carbohydrate foods in vitro was estimated also, trying to start the research in this field domestically. The results showed :The average particle size of the lotus starch was much bigger, and the potato starch was the next, but the k.udzu starch was the smallest; there existed some pores on the surfaces of the maize, tapioca, and kudzu starches through the SEM, but lotus and potato starches were with the smooth surface. The lotus and potato starches displayed a B-type X-ray diffraction pattern, C-type for kudzu starch, and A-type for maize and tapioca starches. The kudzu starch was much difficult to be gelatinizated compared to the others, and the potato starch was the easiest one. The cooling stability of the kudzu starch pasta was much better. Lotus and potato starches were more resistant to pancreatic a -amylase hydrolysis than the others, and kudzu exhibited much higher susceptibility to enzymatic hydrolysis.Modified Schoch method was used to fractionation the kudzu starch and lotus starch, and highly purified amylose and amylopectin from starches were obtained. Light scatter was used to investigate the weight average molecular weights (Mw) for both amyloses and amylopectins of starches. Results from the gel permeation chromatography (GPC) showed the molecular weights for lotus amylose and amylopectin was found to be larger than those of kudzu and maize starches, and the amylopectin molecular weight had a wider distribution in the GPC profile. The similar results for kudzu starch were gained compared tomaize starch, but had a narrow amylopectin molecular weight distribution in the GPC profile. The amylose weight average molecular weights for lotus and kudzu were 4.54 × 106Da and 1.89 × 106Da,separately, while for amylopectins were 130 × 106Da and 60 × 106Da.The effect of water on kudzu and lotus starches retrogradation at 5℃ was studied using *H NMR relaxometry. Gels were made from starches at 25%, 33%, and 40%. Changes in the transverse relaxation time constant (T2) were related to water mobility. Mono-exponential studies showed that, in general, more water retarded starch retrogradation. Distributed exponential studies showed that two distinct regions of T2 were observed in all samples. During aging, the peak values of both regions shifted to lower values for all the gels. Kudzu starch samples showed the most significant shift, and lotus showed the less. For all the samples, the signal intensity of the less mobile region decreased more dramatically than that of the more mobile region during storage.A direct method to quantify the change of resistant starch and an in vitro method to estimate the changes of hydrolysis rate (H), hydrolysis index (HI), and reckoned glycemic index were used in the experiment. The results shown the contents of digestible starches went up apparently, and the resistant starches reduced significantly after heat treatments. The hydrolysis rate for all the starches including lotus starch, kudzu starch, potato starch, tapioca starch, and maize starch, increased under three kinds of heat treatments, that is cooking, microwaving, and heat-pressuring, especially for the microwave. The glycemic index for the heat-treated starches were bigger than 100, and these starch foods were in the range of high glycemic index.Some innovations in the dissertation were as follow: In order to fully utilize the wild starches in food and other industries, that is, lotus starch and kudzu starch from Chongqing, China which were studied firstly, the modern analytical techniques exclusively in starch wereused to investigate the physicochemical and functional properties systematically. CPMG was used domestically to estimate the retrogradation property of starch, and to explore the slow glucose-releas...
Keywords/Search Tags:Wild Starches, Physicochemical Properties, Functional Property, Glycemic Index, In Vitro Digestion
PDF Full Text Request
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