Automated fruit grading system with image processing

I have a question regarding image processing using Matlab.In my dissertation, i want to do mango grading by single mango in image ..my flow of dissertation : all mango image are collected from conveyer belt.Mango images are then preproceesed and color feature are extracted and mango will be classified with NN,Fuzzy or SVM then it will be graded in GRADE 1,Grade 2,Grade 3 and diseased category...i have implemented upto boundry extraction of mango ..but now not getting what to do ...my guide had told me that i have to remove the backgroud of image then appy boundry smoothing and then detect edges and after detecting boundry of image super impose boundry in orignal image...then appy any color featrure extraction algorithm,,,so not getting what to do?..plz help me