Browning is the major physiological cause of quality loss in lotus root. This study explored the effects of temperature (4 °C, 25 °C, 35 °C) or ethylene (ET) on quality, especially browning, as well as polyphenol and starch metabolism in lotus root. Low temperature (4 °C) reduced browning and color changes (L*, a*), while retaining water and vitamin C (Vc) content. ET maintained Vc and soluble protein, while high temperature (35 °C) promoted total soluble solids (TSS) and soluble sugar accumulation. ET or 35 °C upregulated polyphenol metabolism-related genes including NnPAL1/4, NnCHS1, NnF3H and NnANR, increased total phenolic and flavonoid content, and enhanced antioxidant capacity. Moreover, 35 °C increased PAL activity, and ET also upregulated NnUGT88B1. Furthermore, 4 °C downregulated NnGBE1-1/2, promoted starch accumulation, while ET upregulated NnSSI, downregulated NnGBE1-1/2, and delayed starch decline. Meanwhile, ET elevated NnETR and NnEBF1-2 and mediated ethylene signaling transduction. In conclusion, 4 °C storage was optimal for delaying browning and starch metabolism of lotus root. Meanwhile, ET treatment or 35 °C were more beneficial to obtain more phenolics and flavonoids.
Lu et al. (Thu,) studied this question.