An overripe kiwi will feel very soft to the touch, almost mushy, and may have a fermented or moldy smell. You might also see bruises or dark, sunken spots on the skin.
Determining if a kiwi is past its prime involves a few key observations. First, gently squeeze the kiwi. A ripe kiwi should yield slightly to pressure, similar to a ripe peach. However, if it feels excessively soft or mushy, it's likely overripe. Second, examine the skin. While some minor blemishes are normal, avoid kiwis with large bruises, dark sunken spots, or signs of mold. Finally, give it a sniff. A fresh kiwi has a subtle, slightly sweet aroma. An overripe kiwi may have a fermented, sour, or even moldy smell. If you notice any of these signs, it's best to discard the kiwi.
To extend the shelf life of your kiwis, store them in the refrigerator, away from ethylene-producing fruits like apples and bananas, which can accelerate ripening. If you want to ripen them faster, place them in a paper bag with an apple or banana at room temperature.