Starting with the products of the reproducible alkaline degradation of sucrose as model substances and of molasses we tried to characterise the browning products.
The brown colour of alkaline sugar solutions as well as of molasses results from the sum of a number of yellow to brown coloured components.
The molecular weights of these coloured products range between 110 to 5.103 for the alkaline sucrose decomposition and 120 to ca 45.103 in molasses. The IR- spectroscopic studies points to a structure similar to sugar. A dienolcarbonyl- group has been identified in most of the coloured products. The double bonds – determined by bromination – seen to have some influence on the colour producing effect.
The browning product with a molecular weight of 110 – 140 and an intense brown colour seems to have a particular significance. This product, which can also be found in molasses, appeared in the alkaline decomposition of sucrose already after 2 hrs reaction time and probably contributes a lot to the colour of the solution.
With increasing decomposition time, the concentration of this component reaches a maximum value which then decreases by the formation of higher molecular weight coloured products.
No relation was found between the condensation degree and the intensity of colour.
The absorption band at 330 nm – belonging to the melanoidins – was only found in two fractions (mol. weight ^ 5 000) of comparatively weak colouration.
The hypothesis, that particular dark coloured browning products are formed by the reaction of carbohydrate fragments with amino compounds could not be confirmed.
High molecular weight amino compounds (peptides) have only a molecule- enlarging effect on the browning products.
The formation of bigger molecules from small and intermediate products of the alkaline and the thermal degradation is probably due to the condensation reactions preferred in alkaline medium.
Proceedings: CITS 1971
pdf download: CITS1971-77-90.pdf