Abstract
Aqueous solution of L-ascorbic acid (20-1000mg/100ml) was stored at 40-60°C for three months in the coexistence of sugars and sugar alcohols (15g/100ml). During the storage period, the total and oxidized vitamin C contents also with browning (an increase in the absorbance at 420nm) of the solution were measured. Change in the composition of sugars and sugar alcohols added to the solution caused by heating was also analyzed. The results obtained were as follows:
(1) During the heating storage, the total vitamin C gradually reduced. With increasing the vitamin C concentration and the volume of air in headspace of a glass-vessel, the reducing rate of vitamin C tended to decrease.
(2) The heating storage brought about, the browning of the vitamin C solution. There was a positive correlation between the reduction of vitamin C and the increase in the browning at the initial stage.
(3) The addition of 15% sugars or sugar alcohols to the vitamin C solution slightly suppressed the reduction rate of vitamin C. On the other hand, the browning was hardly affected by sugar alcohols, but largely enhanced by reducing sugars like as fructose.
(4) Under the conditions of the heating storage, all of the sugar alcohols, fructose, and glucose practically unchanged, whereas sucrose rapidly decomposed to the equal amount of fructose and glucose.
(5) When a portion of fructose was replaced by a sugar alcohol (such as maltitol), promotion of the browning caused by fructose was diminished.
These results indicated that the browning of vitamin C aqueous solution occurred presumably with the formation of the Maillard-type reaction product, and it was enhanced on addition of reducing sugar but suppressed by substitution for sugar alcohol.
