Studies on apple maturity

I. Relationship between respiratory climacteric and maturity in McIntosh apple fruits

Abstract

In McIntosh apple fruits, investigations were carried out on the reasonability of application of respiratory climacteric to the determination of the optimum harvest date for storage and the significance of determination of flesh firmness, soluble solids and acid contents for maturity determination. And a new method for maturity determination was devised on the basis of the pattern of the respiration rate variation of a fruit arising from the change of period from picking till measuring. Here, a mention must be made on the terms of RC and rc. The former stands for respiratory climacteric“on the tree”estimated from the respiration rates of fruits picked at different dates, and the latter dose that of at each fruit“off the tree.”
1. Considerable individual variation was observed on the respiration rate on a weight basis in fruits picked at the same time, but this may be neglected by using fruits of uniform appearance.
2. When the respiration rates of each picking for periods of about ten days following harvest were measured, all stages of respiratory climacteric were found at earier pickings but rc-minimum (min.) was not found later and neither rc-min. nor rc-rise at last as fruits were getting ripe.
3. In order to estimate RC, fruits were picked ten times and the respiration rates were measured. In such cases, the longer the time from picking till measuring became, the sooner RC appeard.
4. The usual method for RC estimation requires respiration measurements on the fruits picked several times at successive dates. And an estimation on the time of RC-min. cannot be made before RC-rise appears. Besides, RC pattern varies with the time from picking till measuring. It seems, therefore, that it is not a suitable method for the determination of the best picking date of the fruit for storage. On the contrary, if the difference of the respiration rate between two measurements carried out different hours after picking is applied, RC estimation becomes possible by only one picking. In other words, when the respiration rate measured 24 hours after harvest is smaller than that done after six hours and larger than after 48 or 96 hours it is before RC-min., and in the reverse case it is after RC-min.
5. No index to maturity was found in flesh firmness or acid content. The variation of soluble solids proved to be taken as a reliable index to maturity. But it has no practical use because it does not allow of the determination being repeated on the same fruit and is involved in considerable individual variations.