Action Upon Maltose

So recently as 1872 Mr. O'Sullivan* directed attention to the nature of the sugar formed when malt extract is made to act upon gelatinized starch, and his experiments conclusively established the existence of a new sugar, previously, however, pointed out by Dubrunfaut, which is now known as maltose. In composition it agrees with cane sugar, but differs from it in having a specific rotatory power of 150°, and in forming dextrose and not invert sugar when boiled with acids or otherwise hydrated. It also differs in its reducing action upon oxide of copper from either cane sugar or dextrose, for the former has no reducing action upon cupric oxide, while maltose reduces only 61 to 63% of the amount reduced by the same weight of dextrose. Messrs. Brown and Heron have shown that a solution of malt is not able to convert maltose into dextrose, and that it is quite without

*. Journ. Chem. Soc 1872, p. 579. t. Jour. Chem. Soc. 1879. Trans., p. 621.

action upon it. The following experiments will, however, show that the solution of koji possesses the property of hydrating maltose and converting it into dextrose. This will be rendered evident by the change which the solution of maltose undergoes under the influence of koji extract both as regards the weight of oxide of copper reduced by a given weight of the solid, and as regards the specific rotatory power of the product.

The maltose employed was obtained from ame, a kind of sweetmeat prepared by the action of malt in solution upon the starch contained in millet or in rice. Various specimens of ame contained from 68 to 94% maltose, which was separated according to the process described by O'Sullivan*. The specimens employed were in the crystalline state, and contained water sufficient to reduce the specific rotatory power from 150° to 144.5°.

Table 14: Action of Koji on Maltose

Time

Solids in 500 cc after deducting koji

Rotation after deducting koji

Specific rot. power of maltose prods.

10 minutes

2.826

5.8 div.

124.2°

30 minutes

5.3

111.1

1 hour

2.886

4.7

98.5

2 hours

3.7

77.6

The specific rotatory power therefore, fell from 144.5° to 77.6° in 2 hours, and would doubtless have fallen to 59° if the solution had not been used up after 2 hours. The action may be represented in the form of a curve using time and specific rotatory power as abscisse and ordinates respectively (See Figure 3).

The curve shows very clearly how regular the action is, and leaves no doubt about the power of extract of koji to effect the hydration of maltose. It is especially important to establish this, because this property marks in the sharpest manner the difference between malt extract and koji extract. Brown and Heron's experiments leave no doubt about the inability of malt extract to convert maltose into dextrose, and these experiments, I think, establish conclusively the ability of koji extract to do this.

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  • leah
    What is the rotatory power of suguar?
    1 year ago

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