Starch retrogradation: Acceleration, inhibition, and microstructure
Abstract
A method to accelerate and quantitate retrogradation of starch pastes using freeze-thaw cycles (FTCs) and turbidometric analysis was developed, and the steps towards its optimization are described. Using this method and differential scanning calorimetry (DSC) the effects of freezing and thawing temperatures (on waxy maize starch), of retrogradation inhibitors (on waxy maize starch), and of the botanical source of starch on retrogradation were determined. DSC and x-ray diffraction were used to confirm that the crystallites formed during FTCing are the same as those formed in starch pastes held isothermally. Additionally, the microstructure of FTCed waxy maize and common corn starch pastes were examined. Pentyl, hexyl, heptyl, octyl, and nonyl $\alpha$-D-glucopyranosides were prepared and the effects of the glucopyranosides along with their $\beta$-isomers (as well as decyl and dodecyl $\beta$-D-glucopyranosides) on waxy maize starch retrogradation and swelling were evaluated. Results indicated that all glucopyranosides with acyl chain lengths greater than five carbon atoms inhibited retrogradation, although not as well as did sodium dodecyl sulfate (SDS). Glucopyranosides with acyl chains six, seven, eight and twelve carbon atoms in length were the most effective inhibitors. The $\beta$-isomers were slightly more effective than the $\alpha$-isomers of the same carbon chain length. Glucopyranosides enhanced waxy maize starch swelling, but only to a small degree and less than did SDS or sodium stearoyl lactate. Retrogradation of 2% pastes prepared from starches from various botanical sources and held at 4$\sp\circ$C was determined over a 56-day period. Microstructures of the stored pastes were examined both prior to and after centrifugation using iodine staining and light microscopy. Turbidometric analysis showed that retrogradation rates of starch pastes were in order wheat $>$ corn $>$ rice $>$ potato $>$ tapioca $>$ waxy maize. The fresh and stored paste microstructures and granule remnant morphologies were unique to each starch evaluated. Microstructural changes in stored pastes could be related to turbidometric results, as well as to the results of other researchers.
Degree
Ph.D.
Advisors
BeMiller, Purdue University.
Subject Area
Food science
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