h will hydrolyze sucrose into its component hexoses, which then readily
ferment.

When hydrolyzed by acids, or by the enzyme "invertase," it yields a mixture
of equal quantities of glucose and fructose. Sucrose is dextrorotatory, but
since fructose has a greater specific rotatory action to the left than
glucose has to the right, the mixture resulting from the hydrolysis of
sucrose is levorotatory. Since the hydrolysis of sucrose changes the
rotatory effect of the solution from the right to the left, the process is
usually called the "inversion" of sucrose, and the resultant mixture of
equal parts of glucose and fructose is called "invert sugar." As has been
pointed out, solutions of invert sugar become optically inactive when
heated to 82 deg. C., because of the reduction in the rotatory power of
fructose due to the higher temperature.

The probable linkage of the two hexoses to form sucrose, in such a way as
to produce a non-reducing sugar, is illustrated in the following formula:

------O-------
| |
CH_{2}OH.CHOH.CH.CHOH.CHOH.CH
|
O
|
CH_{2}OH.CHOH.CHOH.CH.C.CH_{2}OH
\ /
O

=Trehalose= seems to serve as the reserve food for fungi in much the same
way that sucrose does for higher plants. It is composed of two molecules of
glucose linked together through the aldehyde group of each, as trehalose is
a non-reducing sugar. This linkage is illustrated in the following formula:

------O-------
| |
CH_{2}OH.CHOH.CH.CHOH.CHOH.CH
|
O
|
CH_{2}OH.CHOH.CH.CHOH.CHOH.CH
| |
------O-------

Trehalose may be hydrolyzed into glucose by dilute acids and by the enzyme
"trehalase," which is contained in many yeasts and in several species of
fungi. It is strongly dextrorotatory (specific rotatory power, +199 deg.).
It is not fermentable by yeast.

Trehalose appears to replace sucrose in those plants which contain no
chlorophyl