system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do grapes turn into raisins without the grapes spoiling?
gpt
Grapes are small enough that they don't usually rot before they turn into raisins.  Also, the high concentration of sugar and low water content resist bacterial and fungal growth.  The outside of the grape is made sure to be dry prior to drying.

Besides that, other than dark raisins, most fruit like tomatoes and raisins that get "sun-dried" are treated with sulfites that extract oxygen, further resisting bacterial and fungal growth.