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Study On The Effects Of Different Electric Fields Treatments On The Physicochemical Properties Of Corn Starch

Posted on:2012-03-26Degree:DoctorType:Dissertation
Country:ChinaCandidate:Z HanFull Text:PDF
GTID:1111330374976425Subject:Sugar works
Abstract/Summary:PDF Full Text Request
The effects and mechanism of electric fields (pulsed electric fields and ohmic heating) onthe physicochemical properties and digestibility of corn starch were studied in this paper.Meanwhile, the energy analysis of electric fields treatments was also done. The mainconclusions obtained were introduced as follows.1) The effects of pulsed electric fields (PEF) on the physicochemical properties of cornstarch were systematically studied. The granule size, molecular weight, relative crystallinity,swelling power and solubility of corn starch were decreased as the increasingamylose/amylopectin ratios(Waxy>Normal>G50>G80). After being treated by PEF, somecoarseness or damage had been generated on the surface of the corn starch granules and thegranule size was increased. Meanwhile, molecular weight, relative crystallinity, swellingpower and solubility of corn starch and the values (G′, G″and η*) of corn starch pastes wereall decreased as the increasing electric fields strength and treatment time. However, the PEFtreatments did not change the chemical structure of corn starch by TGA and NMR analysis.2)The effects of ohmic heating (OH) on the physicochemical properties of corn starcheswere also systematically studied. After OH treatments, especially being heating to65℃, thesurface of corn starch granules was broken and starch granules could tarch granule couldmore effectively absorb water and swell, which led to an increase of granule size and thedamage of crystalline region. Meanwhile, swelling power and solubility of corn starches weredecreased, resulting in the decrease of the values (G′, G″and η*) of corn starch pastes. Andfrom TGA and NMR analysis, the chemical structure of corn starch was not affected by OHtreatments.3)The PEF and OH treatments can both increase the enzymic hydrolysis rate of cornstarches. For digestibility, after PEF treatments, RDS and RS were increased while SDS wasdecreased as the electric fields strength and treatment time were increased; after the OHtreatment, RDS was increased whereas SDS was decreased.4)The input energy of PEF treatmen was increased up to238.50J·g-1to affect thebehaviour of corn starch, and for the OH treatments, the highest value was286.23J·g-1. The mechanism of PEF treatments on corn starch was space charge polarization, and themechanism of OH treatments on corn starch was heated-swelling.
Keywords/Search Tags:starch, amylose/amylopectin ratio, pulsed electric fields, ohmic heating, physicochemical property
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