1978 Volume 47 Issue 1 Pages 87-96
To study the ripening phenomena in Golden Delicious, Starking Delicious and Fuji apples, fruit samples were taken at 7-14 day intervals with a total of 2 to 6 harvests during the period of maturation and ripening. The physicochemical components and quality were measured at harvest or after holding at 15°or 20°C, and the internal C2H4 concentration was also measured 1 day after harvest.
1. As harvest was delayed, there were increases in fruit weight, soluble solids and non-reducing sugars, and decreases in firmness, titratable acidity, alcohol insoluble solids (AIS), starch and total pectin.
2. During the 7-day period after harvest, soluble solids, non-reducing sugars and reducing sugars increased, except that in late harvested Fuji apples nonreducing sugars decreased, and titratable acidity, AIS and starch decreased, and softening also occurred except in Fuji apples. The amount of AIS decreasing was nearly equal to that of starch decreasing, which was nearly equal to the amount of total sugars increasing except in Fuji apples. In Starking Delicious apples, the higher the internal concentration of C2H4, the smaller the increase in non-reducing sugars during the 6-day period after harvest, while the increasing rate of reducing sugars was almost constant.
3. In Starking Delicious apples, firmness was correlated with fruit weight and starch, and multiple regression analyses showed stronger relationships of firmness at 1 day after harvest with fruit weight and of firmness at 7 days after harvest with starch, respectively. There was also a strong relationship between firmness at 7 days after harvest and internal C2H4 concentration. Non-reducing sugars and starch were significantly related to internal C2H4 concentration, and these relationships were little influenced by fruit weight.
4. When the decreases in titratable acidity and starch, and the increases in fruit weight and non-reducing sugars, proceeded in fruits on the tree, a rapid increase in internal C2H4 concentration occurred and then an acceptable quality was developed. Starking Delicious apples having a high internal concentration of C2H4 became overripe 7 days after harvest, as a result of a great loss in firmness.
5. These data suggest the following : When an increase in non-reducing sugars with a concomitant decrease in starch, and a decrease in firmness resulting in part from an increase in fruit size, and other ripening phenomena such as fruit coloring proceed with advancing maturity in fruits on the tree, a rapid increase of C2H4 production in fruit begins and subsequently the fruits reach a full maturity. During the 7-day period after harvest, the fruits having a low internal concentration of C2H4 at harvest do not develop an acceptable quality, despite gains in sugars and losses in acidity and starch. On the contrary the fruits having a high internal concentration of C2H4 become overripe with poor quality.
