According to the Popular Science News, apples do not sweat after they are gathered in the autumn. Here is an account of what takes place with them.

The skin of a sound apple is practically a protective covering, and designed for a two-fold purpose: first, to prevent the ingress of air and moisture to the tender cellular structure of the fruit; and, second, to prevent the loss of juices by exudation. There is no such process as sweating in fruits. When men or animals sweat, they become covered with moisture passing through the skin; when an apple becomes covered with moisture, it is due to condensation of moisture from without. Apples taken from trees in a cool day remain at the temperature of the air until a change to a higher temperature occurs, and then condensation of moisture from the warmer air circulating around the fruit occurs, just as moisture gathers upon the outside of an ice-pitcher in summer. This explains the whole matter; and the vulgar notion of fruits "sweating" should be dispelled from the mind.

It is almost impossible to gather apples under such conditions of temperature that they will not condense moisture after being placed in barrels. It would be better if this result could be avoided, as dryness of fruit is essential to its protracted keeping.

Our northern autumns are characterized by changes from hot to cold, and these occur suddenly. The days are hot, and the nights cool, and this favors condensation. Apples picked on a moderately cool day, and placed in a moderately cool shed, protected from the sun, will not gather moisture, and this is the best method to pursue when practicable.