All the more reason for us to understand the ripening process and learn some tricks for telling which fruit is ripe now and which will get ripe once you take it home from the market. With some fruits, you can tell they're ripe by their color. As the acidity changes, the green chlorophyll breaks down. Other, like tomatoes, make their red-orange compound at the same time that the chlorophyll breaks down. Bluish-red berries become a deeper, more intense red as they ripen.
Aroma hints strongly at flavor.
Chemical changes take place in ripening fruits that cause them to produce sensuous, luscious-smelling volatile compounds. Feel for a tender texture. If a plum is rock hard, it isn't ripe. The squeeze test is especially useful with fruit that doesn't have a hard or thick rind, so squeeze stone fruit, pears, kiwis, and avocados . This doesn't work well with melons or pineapples, but even with these rough-coated fruits, a little give is a good sign.