Cxciii. Determination of Maltose in Plant Extracts

DAVIS and DAISH [1912-13] have shown that during the acid hydrolysis of a mixture of maltose and sucrose, appreciable quantities of the resulting laevulose and smaUer quantities of dextrose are destroyed, thereby rendering an estimation of these sugars by acid hydrolysis erroneous. Under conditions recommended by Brown and Morris [1893] for hydrolysing maltose in presence of sucrose, about 30 % of the laevulose is destroyed. A double concentration of the acid, other conditions being the same, destroys nearly 90 % of laevulose and about 6 % of dextrose. Experiments on 1 % maltose solution showed that the hydrolysis of maltose (according to the method of Brown and Morris) had proceeded to the extent of 97 % at the end of 1 hour, increasing to 98 % at the end of 2 hours, but showing a lower value at the end of 3 hours, owing probably to the destruction of dextrose. Prolonged hydrolysis for 24 hours at a lower temperature (700) accounted for only 94 % of maltose. These authors therefore resorted to fermentation methods, involving a long incubation period of 3-4 weeks, which from many points of view are disadvantageous. It therefore appeared desirable to use maltase for the estimation of maltose, as methods of preparing the enzyme in an active state had been worked out in great detail by Krieble et al. [1927].