Phosphate fertilization as a modulator of enzymatic browning in minimally processed cassava

Abstract

Cuts made during minimal processing trigger a cell signaling network initiated by ATP, stimulating the synthesis of phenolic compounds. In cassava, cutting also stimulates the polyphenoloxidase (PPO) and peroxidase (POD) activities, which leads to enzymatic browning. However, phosphate fertilization can also be a modulator of browning in minimally processed cassava. This study proposes to relate the increase in phosphorus (P) supply in the soil, via phosphate fertilization, to oxidative damage and protection, phenylpropanoid metabolism and enzymatic browning in minimally processed cassava roots. The roots were grown at three levels of P (0, 60 and 120 kg ha-1 P2O5). After nine months, the roots were harvested and yield and the P content in the root, stem and leaves were quantified. The roots were minimally processed and stored for 12 days at 5 ± 2 °C and 90 ± 5% relative humidity. The higher supply of P in the soil increased the P content of roots and stems, but commercial and agro-industrial yields remained significantly similar. Roots grown at 120 kg ha-1 P2O5 showed higher detection of hydrogen peroxide (H2O2) at the beginning and at 12 days of storage, which was accompanied by the peak activities of the enzymes superoxide dismutase, catalase and ascorbate peroxidase. In addition, phosphate fertilization increased total phenolic compounds; total soluble quinones; caffeic acid; the activity of the PPO and POD enzymes; and antioxidant capacity, by the DPPH and FRAP methods. The present study thus demonstrates another role of phosphorus application, in fertilization, in the quality of minimally processed cassava with browning potential.