Harvesting apples is the most time-important part of the yearly work of fruit growing. If picked to early, even by a few days, apples have not started the ripening process and stay green and tasteless inside. If picked too late, even by a few days, the ripening process is too far advanced, the apples become soft, will not store well in cold storage, and definitely will not please consumers. Sample apples are cut in half and wetted with an iodine solution, which shows the starch versus sugar content of the apple. Half starch and half sugar is about right.
Growers also use a device to measure the sugar percentage of the apple.
A reading of 14 or 15 is ready to be picked. Finally, the grower physically measures the firmness of the apple flesh. While a range of 13 to 18 pounds is acceptable to the consumer, only the upper levels will store well. The lower firmness indicates the apple has had too much time on the tree and is ripening rapidly. When it is picked and ready to eat, it's about time.