Cereal Chem. 76(2):292-298Four maize genotypes (common, waxy, ae du, and ae su2) were examined by differential scanning calorimetry (DSC) in the presence of four surfactants (sodium dodecyl sulfate [SDS], dodecyltrimethylammonium bromide [DOTAB], sodium hexadecyl sulfate [SHS], 1-monolauroyl-racglycerol [ML]) to characterize the starch-lipid complexes produced and provide evidence of differences in starch structure. The ionic surfactants with a C 12 hydrocarbon tail reduced the gelatinization onset temperature, a phenomenon that does not occur typically with neutral surfactants or with surfactants with longer hydrocarbon tails. Subtracting the DSC curves, the exotherm we suspected was caused by starch-lipid complexation, which occurs concomitantly with the gelatinization endotherm, was identified and provided evidence of the existence of amylopectin-lipid interactions. Apparent starch amylose content correlated well with enthalpies of amyloselipid complexes. Complexes formed from DOTAB produced DSC endotherms that were broad and shallow and that shifted to lower temperatures as the DOTAB concentration increased. This was in contrast to other surfactants that normally produce amylose-lipid complex endotherms at temperatures independent of surfactant concentration.

The objective of this research was to develop a greater understanding of the mechanism by which salts inhibit gelatinization of starch granules. Using hydroxypropylation of corn starch in the presence of sodium sulfate under conditions employed industrially as the control reaction, reactions with propylene oxide were done with different salts at levels that matched the control reaction in anion molal concentration, cation molal concentration, and total ion molal concentration. Salts used were selected based upon their position in the lyotropic series. Reactions were characterized by determining reaction efficiency and ion concentrations. Sodium and potassium citrates, salts exhibiting a strong lyotropic effect, were extremely effective as gelatinization inhibitors, but resulted in low reaction efficiency. Salts without a strong lyotropic effect (sodium and potassium chlorides) exhibited a weak protective effect, probably at least in part based upon generation of a Donnan potential. In the hydroxypropylation reaction, sodium citrate greatly reduced swelling; sodium chloride was ineffective as a swelling inhibitor, resulting in pasting of granules, and sodium sulfate allowed restricted swelling, most likely as a result of a moderate lyotropic effect and some generation of a Donnan potential. That reaction efficiency parallels granule swelling was confirmed.

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