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G. E. Hamerstrand, B. T. Hofreiter, and C. L. Mehltretter. Copyright 1960 by the American Association of Cereal Chemists, Inc. The rate and extent of cross-linking of starch with epichlorohydrin was investigated by determining the quantity of unreacted epichlorohydrin in reaction filtrates. The unreacted epichlorohydrin was converted to glycerol by hot alkali. Periodate oxidation of the glycerol solutions yielded formaldehyde, which was estimated colorimetrically using the chromotropic acid color reaction. Under the reaction conditions described a maximum extent of reaction of 90% was obtained. A blank correction was required to account for alkali-solubilized material from starch, which under the conditions of analysis yielded an apparent value for epichlorohydrin. It was required, for valid application of these analyses, that the epichlorohydrin-starch reaction be conducted in a gas-tight system. The quantities of epichlorohydrin reacted, as indicated by the analyses, are not necessarily exclusively involved in cross-linking. It was found that with molar ratios of anhydroglucose units to epichlorohydrin as low as 1,200 to 1, marked inhibition of the granule to swelling in hot water resulted. |
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