If you want a detailed breakdown of the contents of fruit (or anything else for that matter), then the best source that I know is the
USDA National Nutrient Database for Standard Reference. You have to know what you are looking for and do a search, but you will then you get lots of details.
However, a word of caution about fruit. These are average figures and they will vary depending upon strains (although the database tells you which strains were used for the assay). More importantly, though, it will also depend upon how ripe the fruit is. The ripening process involves complex carbohydrates breaking down into simple sugars (which is why ripe fruit tastes sweeter than unripe fruit) - so the exact amount of sugars is going to be very much dependent upon exactly what stage in the ripening process your fruit has got to. However, you could usefully use it for making comparisons (for example, it will tell you that apples have a lot more sucrose than pears, slightly less glucose and slightly more fructose - both have negligible lactose, maltose and galactose). This sort of comparison should hold true at any given stage of ripeness (so a moderately ripe apple will have more sucrose than a moderately ripe pear), but it might not hold true if the degree of ripeness is very different (an unripe apple may well have less sucrose than a very ripe pear). If this is the sort of information that you are after, then the USDA will do the job for you.
