Changes in Polyphenol Content and Coloration of Apple Fruits over Time

Abstract

The object of this study was to clarify the effect of experimental hydroponics (water culture : WC) on browning reaction of apple fruits. The changes in total polyphenol (TPP) content and coloration over time after crushing of apple fruits were investigated. The polyphenoloxidase (PPO) activity and property were analysed also. In this study, ripe conventional soil cultured fruits (SCF) and water cultured fruits (WCF) of two cultivars (Fuji and Hokuto) were used. The results were as follows. 1) Regardless of the cultivar, the absorbance of 450nm (OD45o) in SCF increased rapidly as time elapsed, but that in WCF increased to half degree of SCF until 60 minutes elapsed gradually. Especially, the OD45o in WCF of Hokuto was inhibited significantly. 2) The reflectance in SCF and WCF (Fuji and Hokuto) showed a similar tendency at OD450, which was measured with a spectro color meter. 3) Before browning reaction, there was no difference in the TPP content between WCF and SCF in Fuji. But in Hokuto, the TPP content in WCF was larger than that in SCF. Regardless of the cultivar, the TPP content in SCF decreased over time, especially quickly in the early stage. However the TPP content in WCF decreased slightly. 4) The decrease in the content of TPP due to browning showed a good negative correlation with the degree of enzymatic browning. After all, the TPP content was closely related to the browning degree. 5) The PPO activity was significantly lower in WCF than that in SCF. Isozyme patterns of PPO showed no difference between WCF and SCF. In conclusion, the low browning degree of WCF resulted from the revelation of PPO activity that was inhibited by WC. The browning degree was not affected by the PPO property.