Dear John,

In general many of the researchers use the specific gravity for the calculation by utilizing the weight of the fruit in water and than in air or their respective densities in water and air.

As you have measured volume and wight you can simply calculate it in g/cm3or converting g in kg and then calculating it kg/cm3 as fruit must have been heavy.

For mango I have a following reference:

http://docsdrive.com/pdfs/medwelljournals/jftech/2009/38-42.pdf