Poking a peach: Is testing for ripeness confounded by the skin?

To test whether soft fruit is ripe, one often pokes with a finger. However, the flesh of the fruit itself is significantly softer than when the skin remains intact. In this talk we will address the question of when the indentation stiffness of a soft material coated by a thin, but significantly stiffer, material is affected by the presence of the coating. We demonstrate a substrate-dominated regime and a mixed regime (in which both coating and substrate are important) and show that the size of the indenter is a key parameter separating the two.