Effects of exogenous ascorbic acid and ferulic acid on the yellowing of fresh-cut Chinese water chestnut

Yellowing of the cut surface is one of the main causes of quality loss in fresh-cut Chinese water chestnut (CWC). However, the mechanism underlying this phenomenon remains unclear. In this study, the peeled corms of CWC were treated with ascorbic acid (AsA) and ferulic acid (FA) and stored at 10 °C for 6 d. Changes in color, flavonoid content, activity levels of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), and peroxidase (POD), and the expression of key enzyme-coding genes in the phenylpropanoid pathway were measured. FA was significantly effective in inhibiting the yellowing of fresh-cut CWC, while AsA did not inhibit yellowing. Both AsA and FA suppressed the activity of POD and PPO during storage. Only with FA treatment, PAL activity and eriodictyol and naringenin levels were suppressed. However, in the in vitro test, FA did not significantly inhibit PAL activity, indicating that the inhibitory effect of FA on PAL was indirect. Furthermore, the analysis of key enzyme-coding genes in the phenylpropanoid pathway showed that in the control and AsA treatment, the expression levels of all the phenylpropanoid pathway genes were significantly upregulated after peeling, while eight genes (CwPAL, CwC4H, Cw4CL1, Cw4CL2, CwCHI, CwCHS1, CwCHS2, and CwF3′H) were down-regulated in CWC tissues treated with FA. To the best of our knowledge, this is the first study to report the effect of FA on the inhibition of CWC yellowing and the transcriptional regulation of genes encoding key enzymes in the phenylpropanoid pathway.