Changes in acidities of several kinds of fruits during their development

Abstract

Changes in acidities of fruits during their development have been studied by many investigators. In almost all cases, however, their concern was in the ripening stage and not in the younger stage of fruits. So this study was made to determine the changes in acidities of fruits from bloom to ripening stage except grapes which were not sampled until one week after bloom, and to compare the patterns among several different kinds of fruits.
Used fruits were Satsuma orange‘Owari-kei Futsu Unshu, ’early Satsuma orange‘Miyagawa Wase Unshu, ’grapes‘Delaware’and‘Campbell′s Early, ’ Japanese pear‘Kikusui, ’and peach‘Hakuho.’ Titratable, total, and combined acidities were determined on the water extract of whole fruits except hardened stone or seeds and were expressed by numbers of milligram-equivalent on 100g fresh weight or per fruit.
The results showed that all the kinds of fruits except Japanese pear were alike in the pattern of changes of acidities on 100g fresh weight. The titratable acidity was low at bloom. But soon it began to increase and reached a peak about in the middle stage of growth, then decreased afterwards.
Total acidity, comparatively high at bloom, decreased for a certain period and then increased rapidly on grapes and oranges, gradually on peach. It began to decrease after it had a peak about in the middle or later stage of growth. Combined acidity was the highest at bloom and decreased rapidly at the start and gradually later. Ratio of total acidity to combined acidity, increased sharply after a certain period of low value. It reached the highest value about in the middle stage and decreased afterwards.
On Japanese pear, however, titratable, total, and combined acidities were the highest at bloom and continued to decrease over the entire growth period.
It was suggested from above results that on Satsuma oranges, grapes, and peach, the growth period can be divided into three in respect of changes of acidities, as previously reported on tomato fruits.
Patterns of changes in acididies per fruit were different among fruits. Titratable, total, and combined acidities of peach and Japanese pear fruits continued to increase from bloom to harvest. On Satsuma orages the titratable and total acidities. increased until about the middle stage of growth and afterwards the former decreased slowly and the latter showed no distinct change. The combined acidity continued to increase from the start of growth to harvest. On grapes titratable and total acidities increased sharply until the peak in the middle stage, and then decreased rapidly. Combined acidity continued to increase over the entire growth period.