The breakdown of carbohydrates by ultra–violet radiation has been studied, using as the principal substrate the amylose component of potato starch. Two distinct types of photodegradation are recognised– One type, occurring in the presence of oxygen, is a photo–oxidation (for which zinc oxide is a powerful sensitiser) followed by a light–sensitised hydrolysis and further oxidation, which results in the complete conversion of the amylose to carbon dioxide, via the intermediate products formaldehyde and formic acid, all three of which have been'identified. The photo–oxidation is believed to be similar to oxidation effected by the periodate ion, which oxidises the α–glycol group situated at C 2 and C 3 of the glucopyranose ring, with the production of two aldehyde groups. Hydrolysis of the oxidised amylose liberates fresh a–glycol groups, and further oxidation then ensues. The results of the aerobic photodecompositions of potato starch, potato amylopectin, maltose, glucose, and a–methyl glucoside agree with, and provide additional support for this hypothesis. The second form of photodegradation takes place in the absence of oxygen, and has been studied in an atmosphere of highly purified nitrogen. The final products, as yet unidentified, do not include those of the aerobic degradation, and are characterised by a marked resistance to subsequent photo–oxidation.
|Original language||English (US)|
|Number of pages||10|
|Journal||Journal of the Society of Dyers and Colourists|
|State||Published - Jan 1 1949|
ASJC Scopus subject areas
- Polymers and Plastics