From a 1989 Chicago Tribune article:
... some said that almost all the bananas they had purchased lately had such an unpleasant, dark center that they were inedible.
We received a more thorough explanation from Chiquita Bananas along with the admission that the problem is occurring with more frequency than ever before. Russ Caid, special director of banana and technical services for Chiquita, said that the condition is called black center syndrome. He explained that once bananas have begun to ripen, they are very fragile and must be handled with care. Dropping a crate of ripening bananas as little as one foot can cause them to have black centers. Banana growers and shippers are aware of that and insulate the bananas from any rough handling. However, once these bananas are closer to their final destination, either at distribution centers or the supermarket, handling may become less careful, causing black center syndrome.
Caid said that at Chiquita they are very concerned about the problem and are trying to orient and train people at all levels of handling to eliminate the condition. Unfortunately, he concluded, there is no way to tell if a banana has black center syndrome until it is peeled.