Other Sulfur-Containing Starches

Heating starch with sulfur and alkali for 12 h resulted in a product described as thiostarch, but its structure remains unknown.2667 The structure is probably a starch complex of low molecular weight, for example, a thiaheterocyclic compound, as suggested by the other authors2668,2669 who observed formation of these compounds 

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The effects of sulfonic acids on starch are discussed later (p. 375). Dimethyl sulfoxide and carbon disulfide are the only other sulfur-containing compounds that have been examined with respect to their complex formation with starch. For example, a complex of potato starch with carbon disulfide was prepared via the starch-acetone complex on refluxing. It was reported that this complex contains 5.8-5.9% of CS2.682 Dimethyl sulfoxide causes expanded coiling of amylose without the formation of a helix.378 Banks and Greenwood385 reviewed the Mark-Houwink exponent for Me2SO-starch solutions. Reported variations in this exponent are believed... 

Some of the innumerable reagents used in TEC are based on reactions with more or less well-established mechanism. Eor example, sodium iodobismuthate (Dragendorff reagent) is widely used among others for alkaloids and quaternary ammonium compounds, 4-dimethylaminobenzaldehyde for primary amines and amino acids, 2,4-dinitrophenylhydrazine for aldehydes and ketones, ninhydrin for amino acids and some antibiotics, fluorescamine for primary and secondary amines, phosphomolybdic acid for lipids, various steroids, and other compounds, chlorine vapor followed by Kl/starch for amines and amides. More complex is the mechanism of the reactions with some other reagents, containing high concentrations of sulfuric acid, vanillin/sulfuric acid, phosphoric acid, aluminum chloride, antimony(III)... 

Two other important observations regarding flours, which are not apparent from Food Composition Table F-21, are that (a) the cereal flours are deficient in the amino acid lysine, which is supplied abundantly by the noncereal flours (with the exceptions of arrowroot and tapioca flours, which are almost all starch) and (b) many of the noncereal flours are deficient in the sulfur-containing amino acids (cysteine, cystine, and methionine), which are supplied in greater proportions by the cereal flours. Therefore, it makes good sense to use combinations of cereal and noncereal flours, so that there might be optimal utilization of the proteins in these foods. 

Peiser - has pretreated wheat starch by gelatinization in water, precipitation by alcohol and drying. Acetylation was effected in the cold with 6 parts of acetic anhydride and 0.05 part of sulfuric acid. After eight hours, only 14% of the starch dissolved to produce an acetate containing 46.7% acetyl. At 55 , the acetyl content of the dissolved starch is reported as 47.3%. On the other hand, Haworth, Hirst and Webb on following Peiser s procedure have not obtained a similar product. 

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