Pierre Schneider writes, " Matisse was probably the first artist to have elevated the orange to this rank [king]. (Cezanne and Gauguin had favored the apple.) There is a reason for this and it has to do with the physical nature of the fruit: unlike the apple, or Chardin's beloved peach, the orange has an even intensity of color which resists shading, modeling, and being put in perspective. Whereas the peach, for example is only partly pink, the orange is wholly orange. In the process of transferring this particular object from reality to painting, nothing seems left out, nothing seems added: the orange becomes a bright spot on the canvas without the painter having to do anything about it ... the orange is the fruit d'or, the golden fruit. Thus it has gradually come to replace the apple as the foremost fruit of the garden of paradise ... Thus the orange was to Matisse's personal cult of Elysium what bread and wine are to Christianity."
The above is a 5x7 pastel of an orange. I don't think I can find as deep a quote for the other pastels of garlic, onion, and pear that I have also done.