ripen
Unripened avocados will ripen if you put them into a bag with an apple.
Olives, especially the unripened green ones, are usually very bitter.
If the papaya aren't fully ripened, leave them in a brown bag along with some unripened kiwi fruit, peaches, and pears.
This is a soft, unripened cheese made in France.
These cheeses were known as green cheeses - "green" because of being unripened, unmatured.

SMART Vocabulary: related words and phrases

Various qualities of food
candy coat
candy-coated
citric
cordon bleu
creamily
farmhouse
fruity
halal
herby
homegrown
homemade
hoppy
nutritious
nutty
sharpness
shelf-stable
single-estate
store-bought
sugar-coated
unbalanced