Hi guys,
The majority of + uncountable noun = singular verb (is)
This structure is somewhat controversial. My dictionary comments that 'Some people feel that majority in this sense should only be used with countable nouns', although it goes on to recognize that we often in fact say things like 'the majority of the work'.
If you want to avoid this issue, you could say 'most of the work', 'most of the sugar'.
Best wishes, Clive