Alkaline degradation of starch

The degrading effect of alkali has been known for some time. Schoch, Wilson and Hudson146 concluded, from the fact that methyl /3-maltoside is stable when heated in 0.1 M caustic soda for considerable periods of time, that alkaline degradation of starch occurs only through the reducing end... 

Starch derivatives may also undergo hydrolysis and degradation under alkaline conditions. The hydrolysis of the nitriles, amides, and esters resulting from the reaction of starch with corresponding vinyl monomers is obvious. Considerable attention has been paid to the alkaline degradation of starch dialdehyde. It de-polymerized readily supposedly as a result of -elimination at C-5, although such a questionable -elimination should not be facile).70... 

The catalytic effect of the hydroxide ion would normally be represented as part of the reaction rate constant (k ) for each temperature, because catalyst concentration normally remains constant. However, in the case of alkaline degradation of starch or cellulose, organic acids are produced which are converted to their salts by the alkali present, thus reducing the hydroxide ion concentration. Therefore, it seemed that this degradation reaction could be represented by second-order kinetics, with the hydroxide ion concentration determined by the stoichiometry of conversion of starch or cellulose to organic acids. 

Polysaccharides. See also. Carbohydrates, Cellulose, Dextran, Dextrins, Fructans, Glycogen, Glycosiduro-nic acids (poly-), Pectin materials, Starch, and Xylan, alkaline degradation of, 13,289-329 associated with wood cellulose, 10, 283-333... 

R. L. Whistler, P. K. Chang, and G. N. Richards, Alkaline degradation of periodate-oxidized starch, J. Am. Chem. Soc., 81 (1959) 3133-3136 Compare I.-L. Andresen, T. J. Painter, and O. Smidsrod, Concerning the effect of periodate oxidation upon the intrinsic viscosity of alginate,... 

Figure 1. Effect of time on thermochemical degradation of starch in alkaline solution according to Equation 3.

Figure 4. Effect of time on organic acid production from thermochemical degradation of starch and cellulose in alkaline solution.

In a study of the degradation of starch by 7-irradiation, the effect of pH on gelatinization of starch after irradiation has been investigated.Paste viscosities were markedly affected by pH on gelatinization, and the granule structures of irradiated starch easily disintegrated at alkaline pH. 

No dialdehyde groups are detectable in modified celluloses obtained by oxidation of cellulose with persulfate, hypobromite, hypochlorite, permanganate, nitric acid, or dichromate. " Alkaline-hypochlorite oxidized starches, which have already been partially degraded by alkali, are more resistant to alkaline degradation than are unmodified starches, and the alkali-lability slowly decreases with increasing oxidation because of the resulting oxidation of reducing ends."... 

The similarity in maximum yields for the identified product acids from starch and cellulose suggests similar or identical reaction pathways. The slower rate for acid formation from starch could be explained by dissolved starch polymer or partially degraded starch polymer interfering with additional degradation of initial conversion products. The greater ease with which starch polymer dissolves in alkaline solution compared to cellulose is consistent with this possibility. 

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