Firmness evolution through the ripening process is a complex phenomenon that involves modifications in cell turgor, cell
anatomy, relative importance of intercellular spaces, and chemical composition of the cell wall and middle lamella, as well as spatial arrangement of all of the polymer constituents of the cell wall structure (18, 19). Nondestructive measurement of fruit firmness using optical methods (NIR spectroscopy or scattering profiles) has been tested on a number of fruit, including apple, peach, mango, tomato (3, 20), cherry, and green pea. Results obtained are in the 0.60-0.80 coefficient of determination range, somewhat low in absolute terms, but still useful, considering that firmness is a quality criteria of major importance.