Do i have to cook apples and pears before pureeing?

im currently in the process of weaning my 5 1/2 mth old son. last week i stewed some apples and pears then blended them into puree. however my said i dont have to do this, but i was under the impression that this destroyed/reduced acidity in the fruit giving less chance of belly cramps. she just said 'we never used to' but then they use to wean at 3mths and put rusks in bottles,brandy on dummies haha etc etc.. so not realyy sure.