Effect of cutting on ascorbic acid oxidation and recycling in fresh-cut baby spinach (Spinacia oleracea L.) leaves

Abstract

Fresh-cut spinach during processing undergoes several mechanical procedures such as cutting, which may induce stress responses. These stresses may trigger the accumulation of harmful reactive oxygen species (ROS). Plants respond through a wide range of mechanisms and ascorbic acid (AsA) has an important role. The combined effect of cutting, temperature and storage time on AsA recycling route in spinach fresh-cut leaves was studied. AsA, gene expression and activities of the enzymes involved in the AsA oxidation and recycling were considered. Spinach leaves were cut in six pieces and stored at 4°C or 20°C. AsA content and enzymes activities were measured over six days of storage, while gene expression analyses were performed in a time-point experiment within 24h after cutting. Results showed that AsA decreased after cutting (from 19.41mg/100g FW to 15mg/100g FW) and generally was higher in samples stored at 4°C. After six days, AsA was 10mg/100g in control and 5mg/100g FW in cut leaves. The expression of genes and activities of the enzymes involved in the AsA oxidation and recycling route were, for some enzymes, in accordance with AsA levels. The APX (EC 1.11.1.11) activity after cutting increased up to 290nmolAsAmg−1protmin−1 compared to the control with 190nmolAsAmg−1protmin−1. AsA reduction is firstly affected by temperature and aggravated by cutting procedures. AsA represents a valuable postharvest quality indicator of freshness in spinach leaves.