Maltitol is manufactured from maltose syrup. Maltose syrup is reduced to maltitol in high temperature and pressure conditions in the presence of nickel as a catalyst. It's a stable chemical that has a sweet taste and holds colour well. This makes it the additive of choice for several foods.

Here is this sugar replacer's structure:

           CH2 - OH
             |
            CH           OH         OH
          /     \          \       /
   HO = CH       O        CH - CH2
        |        |         |
   HO = CH       CH - O - CH         OH
          \     /           \        /
            CH               CH - CH 
             |                |     \
            OH               OH     CH2 - OH

by me from some 3d model .pdf thing