Glutamate induction of whole potatoes alleviated the browning of fresh cuts: Jasmonate signalling may play a key role

Abstract

Enzymatic browning is one of the most troublesome issues for fresh-cut fruits and vegetables, as it not only reduces product quality and shelf life but also causes great waste and economic loss. Although many antibrowning technologies have been explored, few noncontact methods have been reported. In particular, the effect of using glutamate (Glu) is unknown. This study revealed that Glu treatment of whole tubers significantly reduced browning in fresh-cut potatoes. This whole-tuber Glu induction under optimal conditions (1 % Glu for 12 h) produced a brighter colour and better sensory quality than soaking slices in solutions of Glu or ascorbic acid. Notably, Glu induction led to increased jasmonic acid (JA) and jasmonate-isoleucine (JA-Ile) accumulation. The activities of 12-oxophytodienoic acid reductase 3 (OPR3), jasmonate-resistant 1 (JAR1), and coronatine-insensitive 1 (COI1) in the jasmonate synthesis pathway and the expression of their corresponding genes also increased. Additionally, phenylpropane metabolism was upregulated, as evidenced by increased levels of phenylalanine ammonia-lyase (PAL), 4-coumaric acid coenzyme a ligase (4CL), phenolic compounds and flavonoids. Moreover, the reactive oxygen species (ROS)–redox balance improved, the contents of hydrogen peroxide and malondialdehyde (MDA) decreased, and the catalase (CAT) activity and 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH) scavenging capacity increased. Finally, Glu induction increased microbiological safety, resulting in a lower total bacterial count. Thus, Glu induction may modulate jasmonic acid synthesis and signalling, regulate phenylpropane metabolism and the reactive oxygen species (ROS)–redox balance, and ultimately slow browning and improve storage quality in fresh-cut potatoes. This is the first report of a noncontact browning control technique involving Glu, which provides new ideas for the fresh-cut industry.