Harvesting apples is the most time-sensitive task fruit growers deal with each year. If picked even a few days too early, apples will not have started the ripening process and they will stay green and tasteless inside. If picked even a few days too late, the ripening process is too far advanced, the apples quickly become soft, and do not keep well in cold storage. Sample apples are cut in half and wetted with an iodine solution, a process which reveals the apple's starch versus sugar content. Half starch and half sugar is about right.
Growers also use a device to measure the apple's sugar percentage.
A reading of 14 to 15 means the apple is ready to be picked. Finally, the grower physically measures the firmness of the apple flesh with a gauge. While a range of 13 to 18 lbs. of firmness is acceptable to the consumer, only numbers in the upper range will store well. A lower firmness number indicates the apple has had too much time on the tree and is ripening rapidly. The apple is our oldest and most enjoyable fruit.